Polar bears are intensely curious animals. That curiosity often brings them into contact with people and can put both species at risk from one another.

As the Arctic climate warms, some polar bears are spending more time on shore, away from the sea ice habitats they rely on to hunt seals. As the bears are under nutritional stress due to ice loss, some wonder if they're being forced to take more risks around people as they seek food, increasing interactions and conflicts between polar bears and people. But until now, there're been little research into this relationship.

Between 2011 and 2021, research colleagues and I placed trail cameras at three camps in Wapusk National Park in Manitoba and, later, at the nearby Churchill Northern Studies Centre (CNSC) to see how often polar bears visited these sites on the west coast of Hudson Bay.

The project began at the invitation of Parks Canada when their newly constructed field camps at Broad River and Owl River turned out to receive more bear visits than they expected. Those camps had been located away from the coast to reduce the likelihood of polar bear encounters, so answering this immediate question was a priority.

We investigated whether human activity, the length of the ice-free season — or both — were influencing polar bear visits. In approximately 80% of the bear visits, our photos showed enough of the animal that we could rate their body condition using an established fatness index.

We observed 580 bear visits with our cameras, mostly between July and November, when bears are well-known to be abundant in the area. What we found was that human presence at the camps and the CNSC didn't have any effect on the number of bear visits. The length of the ice-free season each year, however, had a notable effect.

It’s all about ice

The ice-free season can be longer if sea ice breaks up earlier in spring than normal, forms later in fall than normal, or both. During our study period, there was no long-term trend in the ice-free season's length, but it did vary a lot year to year. We found that the longer western Hudson Bay remained ice-free in a year, the more frequently bears visited our study sites.

Poor body condition is considered an indicator of nutritional stress, and a healthy body condition to survive on-shore fasting is critical for polar bear survival.

But rather than getting visits from hungrier bears that were detectably thinner — which is what we had expected — we found that the more time bears were off the ice, the more likely all bears were to approach our study sites, regardless of their nutritional health.

This result was unexpected since other research shows underweight polar bears are more likely to attack people, which has been taken to mean that those particular bears would take more chances to find food and so be more likely to approach or prey on people.

Instead, what we're seeing is that body condition may play a different role. Rather than influencing the bears to seek human interactions, body condition might instead influence whether interactions between people and polar bears escalate.

In other words, if polar bears are around people to begin with, a skinny bear might be more likely to aggressively try to obtain human food sources, or even prey on people, than a bear under less nutritional stress.

We were also surprised not to see many lone sub-adult bears in our photos. Those other studies have also shown that they're usually the ones most likely to come into conflict with people.

These observations, though, are consistent with other research on this sub-population. As the ice-free season has on average lengthened in western Hudson Bay, the production and survival of juvenile bears has dropped. Our unexpected results, then, are probably due to there simply not being many young bears in the population during our study.

Scientific and Indigenous observations

Our findings suggest that sea ice loss probably doesn't lead to more interactions with people just because polar bears are thinner or hungrier, so we need to better understand what can cause interactions to worsen into attacks.

What does this mean for current approaches to reducing the risk of polar bear-human conflicts? Bringing it back to the Parks Canada's original question, it appears that the likelihood of bear visits to their camps isn't affected by anything under human control, but the outcomes of any bear visits that do take place certainly are.

What we found may also help explain why scientific explanations and Indigenous and local observations of polar bear-human interactions have differed. Scientific literature has long maintained that poor body condition drives polar bears into northern communities.

However, documented observations from those communities themselves indicate bears who come into communities are not necessarily in poorer condition than would be expected.

Our findings align more closely with Indigenous observations, highlighting how untested assumptions can, through repetition in scientific literature, solidify into accepted wisdom.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

A bleak photograph shows a mother polar bear and her three cubs resting on bare ground and moss, their coats brown with mud.

The image is on the shortlist for this year's Wildlife Photographer of the Year Nuveen People's Choice Award — a contest in which members of the public vote for their favorite among 24 images that have been selected by the Natural History Museum, London, and a panel of photography and wildlife experts.

Photographer Christopher Paetkau captured the slumbering polar bears along the Hudson Bay coast in Canada as they traveled north toward the Arctic. The family paused in the summer heat to nap, the mother and one of the cubs falling asleep while the two other cubs kept watch with their heads resting on their mom's furry back.

The touching new photograph is a reminder that global warming endangers polar bears by shrinking their sea ice habitat, forcing them to find new sources of food elsewhere. Unlike other bears, polar bears (Ursus maritimus) do not hibernate. Previously, most polar bears spent the entire year on the ice hunting their favorite prey of ringed seals (Pusa hispida) and bearded seals (Erignathus barbatus). But with sea ice declining each year, polar bears now have to seek out more land-based prey, such as reindeer.

Another image of a polar bear is also shortlisted for this year's People's Choice Award. It captures a cub during a hunting trip on the Norwegian archipelago of Svalbard that ended in tragedy when the baby bear and its mother approached a human settlement. The mother bear was found dead shortly after, and police officers shot the cub because it seemed aggressive.

Voting for the Nuveen People's Choice Award is now open online until March 18 for anyone to select the winner of the people's choice award.

The winning image and four runners-up will be announced March 25.

"Whether showcasing fascinating behaviour or platforming a powerful story, this year's selection of images is truly exceptional, and we can't wait to see which one will be chosen as the public's favourite," Douglas Gurr, the director of the Natural History Museum, said in a statement shared with Live Science.

The winning image will be displayed along with 100 images from last year's Wildlife Photographer of the Year competition in an exhibition at the museum that's open until July 2026. Wildlife Photographer of the Year is developed and produced by the Natural History Museum.

You can see the images that made it onto the shortlist here.

Temperature stress may be driving genetic mutations in polar bears in southern Greenland, a new study reports.

The species is struggling in the face of a changing global climate. Global sea ice levels dropped to a record low in February, and the warming planet is pushing up sea levels. These changes threaten polar bears, which live and hunt on the shrinking ice sheets.

But a group of polar bears (Ursus maritimus) in southern Greenland may be evolving to cope with their challenging environment. Researchers have found a link between changes in polar bear DNA and rising temperatures.

The study, published Dec. 12 in the journal Mobile DNA, "shows, for the first time, that a unique group of polar bears in the warmest part of Greenland are using 'jumping genes' to rapidly rewrite their own DNA, which might be a desperate survival mechanism against melting sea ice," lead author Alice Godden, a senior research associate at the University of Anglia in the U.K., said in a statement.

Jumping genes, also known as transposons or transposable elements, are pieces of DNA that move from one location on the genome to another. Depending on where they insert themselves into the organism's genetic code, transposons can change how other genes are expressed. More than one-third of the polar bear genome is made up of transposable elements, while in plants it can be as much as 70%. By contrast, transposons make up about 45% of the human genome.

Transposons appear to be helping polar bears adapt to climate change, the authors of the new study argue.

A 2022 study published in journal Science described an isolated population of polar bears in southern Greenland that was less reliant on sea ice. The group split from a community of bears in northern Greenland about 200 years ago, and their DNA was different from that of bears in the North. The new research builds on these earlier findings.

The researchers analyzed the DNA of 17 adult polar bears in Greenland — 12 from the cooler northeast and five from the group in the warmer southeast. They compared transposon activity in the two populations, and then linked that with climate data.

In the Southeastern population, there were changes to genes linked to heat stress, aging, and metabolism, as well as fat processing, which is important when food is scarce. According to the study, this suggests the bears "might be adjusting to their warmer conditions."

"By comparing these bears' active genes to local climate data, we found that rising temperatures appear to be driving a dramatic increase in the activity of jumping genes within the southeastern Greenland bears' DNA," Godden said. "Essentially this means that different groups of bears are having different sections of their DNA changed at different rates, and this activity seems linked to their specific environment and climate."

Despite the bears' potential ability to adapt to warmer climates and less ice, Godden warned that climate change remains a real threat to polar bears.

"We cannot be complacent; this offers some hope but does not mean that polar bears are at any less risk of extinction," she said. "We still need to be doing everything we can to reduce global carbon emissions and slow temperature increases."

The battered skull of a brown bear discovered near a Roman amphitheater in Serbia reveals that the wild animal had been kept in captivity for years and was fighting off an infection when it died around 1,700 years ago.

The finding is the first direct evidence of the use of bears in the gladiatorial arena and attests to the barbarism of animal spectacles in the Roman Empire.

"We cannot say with certainty whether the bear died directly in the arena, but the evidence suggests the trauma occurred during spectacles and the subsequent infection likely contributed significantly to its death," study lead author Nemanja Marković, a senior research associate at the Institute of Archaeology in Belgrade, told Live Science in an email.

In a study published Monday (Sept. 1) in the journal Antiquity, Marković and colleagues detailed their analysis of the fragmented skull of a brown bear (Ursus arctos) excavated in 2016 near the amphitheater at Viminacium, a Roman frontier military base in present-day Serbia.

The amphitheater at Viminacium was built in the second century A.D. Oval-shaped with high walls, it could seat about 7,000 people. Archaeologists recovered the bear skull near the entrance to the amphitheater, along with a number of other animal bones, including those of a leopard, the researchers noted in the study.

"Previous research suggests animals killed in the arena were butchered nearby, their meat distributed, and bones discarded close to the amphitheatre — not buried in a formal animal graveyard," Marković said.

Bears forced to participate in these ancient spectacles had a variety of roles. They could be made to fight "venatores," gladiators who specialized in hunting; to brawl with other animals; to execute convicts; or to give trained performances.

Related: Lion mauled gladiator to death 1,800 years ago in Roman Britain, controversial study suggests

The researchers' analysis of the brown bear skull revealed just how brutal these spectacles were for the animals.

Using ancient DNA analysis, the researchers determined that the bear was male and was from the local area, and his teeth suggested he was about 6 years old when he died. Carbon dating of animal bones from the area where the bear was found gave a date range of A.D. 240 to 350, a time when the Viminacium amphitheater was regularly hosting gladiatorial games.

A large lesion on the front of the bear's skull showed signs of healing but also signs of infection, suggesting he was struggling with the injury at death. This traumatic injury could have been inflicted by a "venator" equipped with a spear, the researchers wrote in the study.

The animal's jaws also showed evidence of infection, and the researchers identified abnormal wear on his canine teeth. Captive bears are known to chew on the bars of their cages, the researchers noted, which can lead to the kinds of dental and jaw problems seen in this ancient bear.

"This bear was likely kept in captivity for years, not just weeks," Marković said, in which case he would have featured repeatedly in Roman spectacles at Viminacium.

Although historical records mention the use of brown bears in gladiatorial spectacles, "this study provides the first direct osteological evidence for the participation of brown bears in Roman spectacles," the researchers concluded, and offers a glimpse into the use and treatment of animals in the Roman Empire.

Roman emperor quiz: Test your knowledge on the rulers of the ancient empire

A brown bear has received the largest dental crown in history, representatives at the Lake Superior Zoo in Minnesota have revealed.

The bear, named Tundra, fractured one of his four major canine teeth and needed a first-of-its-kind metal crown for protection. A veterinary dentist fitted the specially designed silver-colored cap in a successful hour-long surgery at the zoo on June 23.

"Tundra the Brown Bear just made dental history!" a Lake Superior Zoo representative wrote in an Instagram post. "We're thrilled to share that Tundra has officially received the first-ever full metal crown placed on a bear — and it's also the largest veterinary crown ever created in the world!"

Tundra first fractured his right canine in 2023. The zoo's dentist initially treated the bear by giving him a root canal, but when Tundra later injured the same tooth, the zoo team decided he needed a full coverage crown, according to a statement released by the zoo.

Creature Crowns, a specialist veterinary dental company based in Idaho, created Tundra's new crown from a wax cast of the injured tooth, The Associated Press reported.

Related: Watch polar bear cubs emerge from their winter den for 1st time on Svalbard

The 6-year-old brown bear (Ursus arctos) weighs about 800 pounds (360 kilograms) and, when standing up on two legs, reaches a height of around 8 feet (2.4 meters). For the staff's protection, Tundra was sedated while the new crown was fitted. Lake Superior Zoo's armed response team also stood guard as the veterinary dentist worked, just in case Tundra woke up before his procedure was over — but he didn't, The Associated Press reported.

The surgery was successful, and Tundra is now eating normally again. His new silver full-coverage crown should protect the canine from further injury and bacterial infection.

"He's got a little glint in his smile now," Caroline Routley, the zoo's marketing manager, told The Associated Press.

Editor's note: This article was updated to correct the material used for the bear's crown, from titanium to talladium metal.

Together with its black-and-white fur, slothful behavior and cuddly demeanor, bamboo is a defining feature of the critically-endangered giant panda (Ailuropoda melanoleuca). A single panda can consume between 26 and 84 pounds (12 to 38 kilograms) of the vegetation each day, and may spend as much as 16 hours daily eating mouthful after mouthful of this fibrous, chewy plant.

These consumption patterns are so intense that Feng Li, a researcher at China West Normal University, describes the panda as a "mobile shredder of bamboo." But do panda bears ever expand their diets and eat anything besides this fast-growing plant?

Typically, the answer is no — although there are some rare exceptions. "There have been cases where wild giant pandas occasionally eat small animals," Li told Live Science in an email. Li mentioned rare instances documented in the Qinling Mountain region of China, where giant pandas were found gnawing the bones of a takin (Budorcas taxicolor), a goat-like wild ungulate. They have also been found occasionally preying on Chinese bamboo rats (Rhizomys sinensis).

John Speakman, the chair of zoology at the University of Aberdeen in the United Kingdom, confirms that these cases are opportunistic and unusual: "There is a picture online of [a panda] in a zoo that captured and ate a peacock. But as far as I know these are really chance encounters."

Aside from these rare lapses into carnivorism, pandas stick exclusively to bamboo. However, there's an interesting twist to this story, because there's plenty of evidence to show that pandas actually should have much more diverse diets. In fact, they're not especially well-suited to eating bamboo.

Research has shown that the bears have a gut architecture that's similar to carnivores, like their bear cousins, and that their stomachs lack the many-chambered structure that other herbivores use to process copious quantities of plants. What's more, the microbes that populate their gut flora are more like those of meat-eaters, and are capable of processing and extracting protein. Those microbes are unsuited to breaking down plants. Panda poop reveals this too: researchers on the study found it contained pieces of undigested bamboo.

Related: Why do chimpanzees throw poop?

The panda's evolutionary rise

These ill-fitted traits appear to be evolutionary hangovers from the giant panda's ancestral past. Clues from the fossil record show that the ancestors of modern giant pandas consumed not only meat but also vegetation. Then, about 7 million years ago, the fossil evidence suggests that one ancestor in particular, called Ailurarctos, began to sample a bit of bamboo.

This marked "the starting point of the transition from omnivorous to herbivorous," according to Li, which may have been accelerated by a change in the availability of food. "The currently popular view is that environmental changes in ancient times led to a sharp decline in food resources. The ancestors of giant pandas competed fiercely with other carnivores," Li said.

Having already started supplementing its diet with bamboo, Ailurarctos had an adaptive edge and was able survive the scarcity by inhabiting this ecological niche, researchers believe. "The evolutionary process of giant pandas changing from omnivorous to bamboo-exclusive is a classic case of 'survival of the fittest, but not necessarily the best' in evolutionary biology," Li noted.

However, while their evolutionary makeup may seem poorly matched to their bamboo-intensive diets, giant pandas have also developed several adaptations to suit their situation. For example, a gene that should enable them to taste the uniquely umami flavor of meat has been inactivated in their DNA, meaning they likely don't have a natural appetite for fresh meat, Li said. Pandas also have a very slow metabolism, which helps them to survive on their low-energy diet of bamboo. In fact, pandas expend just 38% of the daily energy of other land mammals of a similar size.

Speakman was involved in research that uncovered a possible root of this sluggish metabolic rate: a gene mutation that's unique to pandas and controls thyroid hormones, which are key in regulating metabolism.

"We all pretty much expected their metabolic rates would be low because otherwise they wouldn't be able to eat enough food to match their expenditure. The big insight was finding the genes that underlie that," Speakman told Live Science in an email. "Since then we built mice with the same mutation and confirmed those mice also have lowered metabolic rates."

Meanwhile, Li led a study that explored how bamboo itself might even play a key role in helping pandas adapt to their unusual diet. When Li examined blood samples taken from panda bears, he identified molecules called microRNAs, or miRNAs, circulating there. MiRNAs are molecules that occur in animals and plants, which cells use to control gene expression. These molecules also occur in bamboo, from where they enter the panda's body through diet, and can accumulate in its tissues over time.

When Li and colleagues examined several of the miRNAs occurring in panda blood, they found that they targeted specific genes that are variously involved in promoting appetite, regulating sense of smell and suppressing bitter flavors, among other things. So it's possible that these bamboo-derived molecules have helped develop and curate pandas' appetite for the plant. This could be essential for their survival, "ensuring that sufficient bamboo can be consumed every day to meet the energy intake requirements of the body," Li explained.

Elsewhere, studies have found that pandas' gut bacteria aren't completely at odds with their vegan diet. In fact, their gut flora changes during the season when bamboo shoots — a more nourishing part of the plant than the leaves — appear, allowing pandas to store more energy during this brief window, during which time they visibly gain weight.

Pandas have also evolved a "pseudo-thumb" that allows them to grip bamboo stems tightly. Their molars are broader than in other bears — essential for crushing hardy bamboo stems, as are pandas' uniquely powerful jaws: "Their big round faces are because they have these massive jaw muscles that give them a bigger bite force than a polar bear," Speakman said.

Pandas are adored, but equally mocked as poorly adapted, evolutionary dead-ends. But while it might seem like they just loll around and eat bamboo all day, as Li put it, "the 'laziness' of pandas is survival wisdom."

Bears are a type of mammal that can be found in many parts of the world. From the tiny, silly-looking sun bear to the iconic polar bear, these animals are specially adapted to different environments, including forests, mountains, icy tundra, deserts and swamps. Though there are different types of bear, all bear species have similarities. They all have stocky, fur-covered bodies; short legs; and a round head with a long snout. Whether the word "bear" makes you think of a fierce predator or a cuddly stuffed toy, there's plenty to discover about the science behind this diverse group of mammals.

5 fast facts about bears

• Panda bears poop 40 times per day.
• When they're first born, bear cubs weigh less than 2 pounds (0.9 kg).
• Bears that snack on honey have thick skin and fluffy fur that protects them against bee stings.
• Because polar bears spend so much time on the water, they're classified as marine mammals.
• Bears have a great sense of smell that helps them sniff out food.

Everything you need to know about bears

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—Polar bears: The largest land carnivores

—Black bears: The most common bear in North America

—Sun bear: The little carnivores that look so similar to humans they've been mistaken for people wearing costumes

Researchers have captured extremely rare footage of polar bear cubs leaving their snowy dens for the first time.

The footage, taken on the Norwegian archipelago Svalbard, shows a mother polar bear (Ursus maritimus) plodding through the Arctic island's frozen landscape and her three cubs emerging one after another from a hole in the ice, before slipping and sliding around the frozen terrain.

The scene is from one of 13 den sites on Svalbard that scientists have been monitoring for nearly a decade to shed light on denning behavior, which is notoriously difficult to study because polar bear moms build the dens underground in hard-to-access areas.

The researchers described new aspects of denning behavior in a paper published Thursday (Feb. 27) in The Journal of Wildlife Management.

"It's a pretty special thing to see polar bear cubs emerge into this vast, white landscape that appears so inhospitable," lead author Louise Archer, a Polar Bears International postdoctoral fellow at the University of Toronto Scarborough, told Live Science in an email.

Related: Polar bears are getting horrific injuries and huge 'ice balls' on their paws because of climate change, researchers say

"In Svalbard, polar bears build their dens on the slopes of steep mountainous areas, and it's hard to imagine how cubs could find their feet in this severe terrain," Archer said. "Watching them sliding, tumbling, and even climbing up on their mother was truly remarkable."

The new study offers a glimpse at one of the most vulnerable and critical periods of a polar bear's life, researchers said in a statement.

Polar bears spend the winter in their dens. Pregnant females give birth around early January and nurse their cubs through spring, when the family emerges to slowly make its way to the sea ice. Newborn polar bears are hairless and weigh just 1 pound (0.5 kilograms). However, they grow quickly thanks to their mother's fatty milk and reach 22 pounds (10 kg) by the time they emerge as cubs.

Maintaining healthy polar bear populations depends on cubs' survival, which is only around 50%, according to the statement. Cubs survive only if their dens remain undisturbed throughout the winter and they can roam the surrounding area after emerging. Human activity jeopardizes both of these requirements.

"Polar bear mothers are having increasing difficulties reproducing due to climate-driven changes, and are likely to face further challenges with the expansion of the human footprint in the Arctic," Archer said in the statement.

To assess human influence on polar bear reproduction, researchers need to better understand denning behaviors and timings. A decade ago, Archer and colleagues fitted 13 female bears with GPS collars that recorded the animals' locations, body temperatures and levels of activity. The researchers used this data to locate the bears' dens, before traveling to Svalbard to install camera traps outside them.

The study is the first to combine collar data with camera footage of polar bears. "Every den we monitored had its own story," Archer said.

Throughout the study period, the moms and cubs first emerged in early March, sometimes venturing out for just a few minutes before returning to their dens. The families abandoned their hideouts earlier than previously recorded on Svalbard, but more observations are needed to confirm if this is a new trend, according to the statement.

The bears remained near their dens for an average of 12 days before heading off toward the sea ice, where mothers teach their cubs to hunt. The cubs stayed with their moms 95% of the time, rarely leaving the den alone. On Svalbard, cubs remain with their mother for 2.5 years after birth, according to the statement.

The researchers couldn't follow the bears once they left the den site. "I would love to know how the polar bear families we monitored fared once they departed the den," Archer told Live Science by email. "How soon does the mother catch a seal, [and] do her cubs manage to survive those initial few weeks when they venture out on the sea ice?"

Polar bears are currently snuggled up their dens, but it won't be long before they emerge again. Archer and colleagues are in Svalbard now, collecting information that may help them fill these gaps.

"We're excited to introduce new tools to monitor bears during this vulnerable time and to gain insight into their behavior across the Arctic," Archer said in the statement.

There are eight species of bear living around the world today, and many more in the fossil record. "Prehistoric" mummified bears have even been found preserved in permafrost thousands of years after they died. At Live Science, our expert writers and editors bring you the latest news, features and articles about bears, whether it's American black bears evolving cinnamon-colored coats, the breeding habits of giant pandas, ferocious fights between grizzly bears, or mighty polar bears that are being forced to dine on "batteries and dirty nappies" because of climate change.

Discover more about bears

—Bears: Facts about the furry omnivores that live in many parts of the world

—Why aren't there polar bears in Antarctica?

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Polar bears are developing horrific wounds on their paws due to changing ice conditions in the Arctic, a new study reports.

In the most severe cases, researchers describe two bears with crippling, dinner plate-size balls of ice stuck to their feet. Beneath the ice balls, the bears' paw pads were covered in deep, bleeding cuts.

"I'd never seen that before," study lead author Kristin Laidre, a marine ecologist and associate professor at the University of Washington, said in a statement. "The two most-affected bears couldn't run — they couldn't even walk very easily."

This is the first time scientists observe such injuries in polar bears, according to the study, published Oct. 22 in the journal Ecology.

The debilitating ice balls likely formed due to slushy snow sticking between bumps on the pads that provide the grip polar bears need to walk on slippery surfaces. Snow accumulated on the pads and then froze solid, the researchers suggest, forming blocks of ice measuring 12 inches (30 centimeters) across.

Related: Bleak photo of polar bear with plastic in its jaws in the remote Arctic shows pollution's 'pervasive grip'

"The chunks of ice weren't just caught up in the hair," Laidre said. "They were sealed to the skin, and when you palpated the feet it was apparent that the bears were in pain."

Researchers say roughly one in four polar bears (Ursus maritimus) from two populations in northern Greenland whose feet they examined suffered from ice-related injuries. Affected bears were mostly adult males, which tend to travel longer distances and are much heavier than females or cubs.

Laidre and study co-author Stephen Atkinson, a wildlife biologist and veterinarian, examined polar bears from populations in East Greenland and Kane Basin — a waterway between Greenland and Canada's northernmost island, called Ellesmere Island — between 2012 and 2022. They captured the animals as part of standard population assessments, sedating them before conducting routine health checks.

Thirty-one of 61 bears in the Kane Basin population had laceration, skin ulceration, hair loss or ice buildup on their paws. Between 2012 and 2013, 73% of adult males in this population were affected, according to the study. In the East Greenland population, between 2018 and 2022, 15 of 124 polar bears displayed similar injuries.

The researchers proposed several explanations for the wounds and interviewed Indigenous hunters to identify potential causes. Ice buildup and lacerations may result from rising temperatures in the Arctic, with warm spells leading to wet snow and freeze-thaw cycles that create brittle ice on which polar bears cut their feet, the scientists suggested.

Climate change is leading to more frequent rainfall in the Arctic, turning snow into slush that becomes lodged in polar bears' paws, where it freezes, they wrote in the study. Warmer temperatures also cause the surface snow to melt and then refreeze into a hard crust, which heavy polar bears break when they trample over it, injuring themselves.

Indigenous hunters in Kane Basin knew about the lesions on polar bears' feet and attributed them to increased movement during the mating and hunting season. But the hunters also recognized these injuries as a recent phenomenon. They mentioned that wet snow conditions negatively impact sled dogs, too. According to the study, the hunters noted they now have to trim the hairs between their dogs' pads to prevent ice buildup and lameness.

John Whiteman, an assistant professor of biology at Old Dominion University in Virginia and chief research scientist at the non-profit organization Polar Bears International, said he has never seen or heard about these types of injuries before.

"This report is definitely surprising," Whiteman, who was not involved in the new study, told Live Science in an email. "If the conditions that encourage ice clumps become a common occurrence across a large area, more bears would be at risk for foot damage."

William Housty's grandparents taught him the sacred duty of preparing for the salmon's arrival each year. Before the first silver flashes appeared in the creek, his grandfather — following the wisdom passed down from his own elders — would clear woody debris, chase away seals, and maybe even fell a few trees to ensure a waterway was ready.

"They saw it as their responsibility to roll out a red carpet for the salmon because of their immense importance to us," said Dúqva̓ísḷa William Housty, a member of the Heiltsuk Nation of British Columbia's central coast.

This practice ensured that the salmon, the ecosystem and their community could thrive together, said Housty, who is director of the Heiltsuk Integrated Resource Management Department (HIRMD), which manages resources in their traditional territory.

Welcoming the salmon is just one example of the way the Heiltsuk's ancestral laws, or "Ǧvi̓ḷás — a set of principles centered on respect, responsibility, reciprocity and stewardship for all sentient beings — have shaped their interaction with their environment.

Now, the Heiltsuk are using traditional knowledge in concert with modern scientific approaches to monitor wildlife, count salmon, and maintain the health of waterways in their traditional territory. From the outset, the HIRMD stewards decided that Ǧvi̓ḷás would guide how they managed their resources, as well as influence how they would work with other government offices, industry or other outside parties.

This has led the Heiltsuk to braid relatively new techniques, like DNA analysis, with ancient ones, like the use of traditional fish weirs, so they can study — but not impact — the ecosystem. Their work has revealed shifting bear habitats and climate change impacts on salmon. Both have led to increased protections for creatures that are critical to the ecosystem.

"We're going back to the value system that our ancestors implemented for thousands of years," Housty told Live Science. "In our eyes, it is for the betterment of everything."

A symbiotic relationship

The Heiltsuk have lived in the diverse coastal rainforests, islands and marine areas of their traditional territory for more than 14,000 years. Over that time, they passed on ancestral knowledge of how to care for and enhance the natural resources they depended on.

In the mid-1800s, however, the British colonial government asserted control over Indigenous lands. In the following decades, deforestation, overfishing and pollution led to a marked decline in the richness of life.

"Take a look out there — it's beautiful," Housty said, pointing to the shimmering ocean water west of Bella Bella, the central community of the Heiltsuk Nation. "But when you go underwater, it's a different story — so many resources have been depleted to the extent that some of them have gone extinct."

For instance, commercial fishing has led to drastic declines in Pacific herring (Clupea pallasii), eulachon (Thaleichthys pacificus) and Northern abalone (Haliotis kamtschatkana). Some salmon that once thrived in the rivers and streams around Bella Bella have disappeared.

Government officials, forest companies and academia have their own agendas, said Q̓íx̌itasu Elroy White, an archaeologist who works part time for HIRMD. "It was often based on greed, commercial enterprise, and academic privilege and perspective," White said.

This contradicted the Heiltsuk way of living in harmony with the environment, in which they take only what they need to ensure a sustainable supply of resources for future generations.

Protecting the bears

For many decades after colonization, federal and provincial agencies controlled fishing quotas, logging operations and other resource management decisions that directly affected the Heiltsuk. However, that started to change in the 1990s, and a small team of Heiltsuk began doing field assessments on the health of the streams and salmon in the Koeye watershed, 34 miles (55 kilometers) southeast of Bella Bella. The team presented data to the Heiltsuk land use committee, which would use that information to craft conservation management plans. One key goal was to protect grizzly bear (Ursus arctos horribilis) habitat.

If "you protect grizzly bear habitat, you're protecting black bear habitat, wolf habitat, deer habitat and many other species," Housty said. "When you have lots of bears, it means you have a healthy ecosystem."

The Heiltsuk began monitoring bears directly in the Koeye watershed in the early 2000s.

The number of Heiltsuk researchers grew, and in 2010, the Heiltsuk formed HIRMD. That same year, they partnered with University of Victoria wildlife scientist Chris Darimont, who is also the science director at the Raincoast Conservation Foundation, and his graduate students. The academic team expanded the monitoring across a larger region of the Heiltsuk territory in a way that aligned with Heiltsuk values.

"A lot of the concepts were relational in that they were about how wildlife were like relatives to the Heiltsuk," Darimont said, "and ought to be treated accordingly."

Instead of catching grizzlies, sedating them and attaching tracking collars to them, which eventually fall off, the researchers took an entirely different approach: They created knee-high salmon-scented bear snares — barbed wire corrals around trees — and set 30 in the Koeye and more than 100 throughout the larger study area. Lured to the smell, the bears left hair samples, and the Heiltsuk used their DNA to track their movements. The noninvasive method didn't disrupt the bears' usual habits; the bait provided no rewards to the bears, so the grizzlies didn't become dependent on the snares for food.

Monitoring the bears, collecting scientific data and collaborating with academic scientists are proving critical to the Heiltsuk's involvement in management decisions, Housty said. Historically, when they didn't have the scientific resources, government organizations controlled the management of natural resources. "It is our partnerships and the science that has really given us the legs to stand on for joint management," Housty said.

The collaborations have helped the Heiltsuk identify bears on islands outside their traditional range and have pinpointed crucial corridors the bears use to move between feeding areas, according to new research that is under review for publication. Such findings have led to greater protection for bear habitats and will continue to do so, Darimont said.

The Heiltsuk stewardship principles often contrast with dominant government-led conservation approaches, which may suggest that hunting grizzly populations is acceptable when the numbers are sustainable. Seeing wildlife as a natural resource to be managed by humans is incorrect and unethical, Housty said. Even a single individual killed by trophy hunters is unacceptable, he said. "It violates our law regarding respect and reciprocity to the bears," Housty said.

In 2017, after gauging the broader public's views and listening to Indigenous perspectives, the British Columbia government ended trophy hunting of all grizzlies throughout the province.

Grizzlies feed on salmon during the spawning season, leaving the carcasses, skin, bones and leftover flesh to enrich forest soils and feed aquatic invertebrates, which, in turn, support juvenile salmon during their early life stages. Therefore, the ban on trophy hunting did more than benefit the bears; it strengthened the territory's salmon systems, Housty said.

Salmon stewardship

Each fall, Howard Humchitt and Lenard Stewart visit some of the many rivers on their territory, walking upstream to check salmon spawning habitats. They are Heiltsuk Coastal Guardian Watchmen, employed by HIRMD to take on many roles, from preparing for the salmon's return to monitoring the populations of chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha).

Over the years, the watchmen have seen certain types of salmon diminish. Last year, the watchmen counted 7,000 salmon returning to a particular river system where they used to count tens of thousands. "When our fathers were kids, that same river probably had 100,000 salmon in it," Humchitt told Live Science.

The Heiltsuk historically used ancestral technologies such as fish weirs. These traps were made of wooden stakes driven into a river, which created a semipermeable barrier that directed salmon into a holding area as they swam upstream. The Heiltsuk also used stone fish traps — miniature stone walls that stretch across tidal inlets. Fish swam through high gaps in the walls and, when the tide receded, were trapped. However, the Canadian government outlawed such practices in the late 19th and early 20th centuries because officials believed the traps harmed fish stocks. But both technologies allowed the Heiltsuk to selectively harvest fish, so the best fish for breeding could go upstream and spawn. Having reliable fish counts can also prevent over-harvesting.

These systems have historically kept fish stocks stable, said William Atlas, a salmon watershed scientist at the Wild Salmon Center in Portland, Oregon. "Prior to the arrival of European colonists, there's probably about 7,000 or 8,000 years of successful stewardship of salmon harvesting," Atlas said.

In the mid-19th century, however, the colonial government of Canada took over fisheries management. Since then, overfishing, habitat destruction and nonlocal management have led to crashes in catches of salmon and herring in British Columbia. Several Chinook salmon (Oncorhynchus tshawytscha) populations in the province are at risk of extinction, and many coho salmon (Oncorhynchus kisutch) runs — migratory populations of a specific river system — are endangered. Atlas, along with Indigenous colleagues, has called for the revitalization of Indigenous fisheries by supporting the sustainable management practices of coastal First Nations.

In recent years, some coastal First Nations, including the Heiltsuk, have regained a stake in the management of their fisheries. Collecting data on their marine resources continues to be important to the Heiltsuk.

"Knowledge is power when it comes to ecosystems," Atlas said. "Having numerical values and abundance estimates of how many salmon are returning gives them authority when it comes to co-governance and decision-making."

To this end, the Heiltsuk have been monitoring and researching the current state of salmon systems in the territory to learn what it takes to sustain them. They also collaborate with scientists to collect data when necessary. It's logistically challenging to count sockeye salmon (Oncorhynchus nerka), as they spawn high up in river systems, typically above a lake. So the HIRMD researchers partnered with Atlas and his colleagues to monitor these populations, using an approach that braids Heiltsuk traditions in salmon stewardship with modern science.

Starting in 2013, the collaborators began using a fish weir made from locally harvested cedar logs to help them capture and tag around 500 sockeye salmon each year in the Koeye watershed. The researchers count the outgoing smolts — the young salmon swimming downstream on their way to the sea — and then install the weir, now made of aluminum, at the beginning of June and begin counting the incoming adults. During the salmon's brief capture, the team takes genetic samples from the fish so that when they are caught in the ocean, scientists can identify the salmon's population of origin.

Each year, the collaborators report sockeye numbers for five or more populations in the territory. The Heiltsuk can then share this information with Fisheries and Oceans Canada (DFO), the government agency that has historically set fishing quotas for commercial, recreational and Indigenous fishing in British Columbia.

"That creates a bit of a reversal in the power dynamic that we've historically seen, where the DFO is the broker of the truth," Atlas said.

Planning for the future

Looking out for future generations and acknowledging humans' role in ecosystems are core principles of the Heiltsuk's Ǧvi̓ḷás. Early in their conservation efforts, the Heiltsuk devised a 1,000-year natural resources management plan.

"Our goal is to live sustainably, so we can ensure an abundance of resources not only for my generation but for those to follow," Housty said. "We've been here since the beginning, and the long-term plan is to stay until the end — if there is ever an end."

Ǧvi̓ḷás also emphasize that humans are as responsible for caring for their territory as they are for their own homes. To uphold their stewardship practices, the Heiltsuk educate their children on their culture, fostering a connection with the natural world from an early age. The Qqs Projects Society, a Heiltsuk nonprofit in Bella Bella, supports youth, culture and the environment, offering programs to strengthen bonds with Heiltsuk lands and waters.

"We want our youth to feel connected to their territory because it's an intrinsic part of their identity," said Cúagilákv Jess Housty, executive director of the Qqs Projects Society. "And we want them to love it, because we know if they love it, they will protect it."

One goal is to demonstrate how humans can contribute positively to ecosystems. This requires embracing the Heiltsuk understanding that humans are not separate from their environment. Elders would tell Housty that the Heiltsuk didn't own their territory; it belonged to the animals and fish. That means that the Heiltsuk have a responsibility to take care of the creatures in their territory, William Housty said. "That's a far different mindset from viewing the land in terms of how much we can take," he said.

Reporting and travel for this story was supported by the Sitka Foundation and the Science Media Centre of Canada.

An image capturing a polar bear with plastic hanging from its jaws has been shortlisted for the Ocean Photographer of the Year 2024 award. The image, taken on Kiepert Island in the Svalbard archipelago off Norway, by photonaturalist Celia Kujala serves as a "a stark reminder that even the uninhabited reaches of the Arctic are not exempt from the pervasive grip of plastic pollution," competition representatives wrote in a statement emailed to Live Science.

The photograph is shortlisted in the Ocean Conservation Photographer of the Year (Impact) category, which also includes a photo of a dead fin whale waiting to be butchered at a facility in Iceland, shark fins drying on a roof in Indonesia and a gannet, a large white seabird with a yellowish head, trapped in discarded fishing gear hanging from a cliff.

The polar bear (Ursus maritimus) photograph highlights the scale of plastic pollution in the Arctic and the impact it has on regional species. Considered vulnerable by the International Union for Conservation of Nature Red List of Threatened Species, polar bears face multiple threats. A 2016 study predicts their numbers will fall by 30% by the middle of the century.

Climate change is the primary threat, reducing the sea ice on which they hunt. However, plastic is compounding the problem. Polar bears are increasingly turning to landfills for food. An analysis of polar bear stomach contents from the population in the Southern Beaufort Sea off Alaska and Canada found 28% contained plastic. Half of the bears that had eaten plastic also had acute gastritis, potentially leading to painful blockages in their digestive system.

Related: Polar bear sleeping on tiny iceberg drifting in Arctic sea captured in heartbreaking photo

"There are not enough data to get a clear picture, but it is probable that bears are more likely to ingest plastic when they find human trash as they seek food on shore," John Whiteman, chief research scientist at Polar Bears International and assistant professor of biology at Old Dominion University in Virginia, told Live Science in an email.

"Sea ice loss, and the resulting increase in time spent on land, is making it ever more important to find safe, long-term ways to manage trash — an issue that multiple Arctic communities have tackled with success," he added.

The winners of the Ocean Photographer of the Year 2024, presented by Oceanographic Magazine and Blancpain, will be announced on Sept. 12. Shortlisted images for the Ocean Conservation Photographer of the Year (Impact) category can be seen below.

Name: Sun bear (Helarctos malayanus)

Where it lives: Southeast Asia

What it eats: Ants, bees, beetles, honey, termites, fruit, plants, small mammals and birds

Why it's awesome: Sun bears often stand on their hind legs and can look so similar to humans they've been mistaken for people wearing costumes.

Sun bears are the smallest bears in the world. While grizzly bears (Ursus arctos horribilis) can weigh more than 700 pounds (320 kilograms), sun bears weigh between 60 and 150 pounds (30 to 70 kg) and are between 4 and 5 feet (1.2 to 1.5 meters) long.

Related: Qinling panda: The shrunken pandas that diverged 300,000 years ago and sometimes come out brown

Found in Malaysia, China, Thailand, Laos, Cambodia, India, Bangladesh and Myanmar, sun bears take their name from the golden or white patch on their chests, which resembles the rising sun. Although they've been nicknamed "dog bears" because of their stocky build and short muzzles, these tree-dwelling mammals are best known for their human-like behavior. They often stand on their hind legs and have even been seen waving.

In the wild, standing frees up their front paws so they can reach for food such as fruit and dig into beehives and termite nests for honey and insects. They also have a 12-inch (30 centimeters) tongue to help them get their food — the longest tongue of any bear.

Sun bears also stand to check out their surroundings and to scare away other animals such as tigers, as it enables them to display their colorful chest patch as a warning sign. Standing upright also helps them to smell over longer distances.

Female sun bears have even been spotted walking around on their hind legs while carrying their babies in their arms. This may help mother bears, called sows, to spot predators and safely move their offspring around.

Recently, a captive sun bear named Angela became an internet sensation after she stood up and waved to visitors at Hangzhou Zoo in China. Her build, posture and behavior seemed so human that people thought she was a performer in costume.

Exactly why these bears appear to wave is unknown, but it could be to communicate.

A study published in the journal Nature in 2019 found that captive sun bears are excellent communicators and can mimic each other's facial expressions to build bonds — a behavior that humans do too. Biologists at Arizona State University and the University of Arizona suggest sun bears have evolved to be skilled tree climbers and because of this dexterity, may wave simply because they can.

Sun bears are classified as vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species because of habitat loss and hunting. They are poached for bile from their gall bladders, which is used in traditional medicine, and for their paws, which are eaten.

Name: Qinling panda (Ailuropoda melanoleuca qinlingensis)

Where it lives: Qinling Mountains in the Shaanxi province, China

What it eats: Bamboo

Why it's awesome: When we think of pandas, we tend to picture the famous bears in monochrome — but not all pandas are so black and white. 

A subspecies of giant pandas called Qinling pandas can sometimes be a mix of dark and light brown. These brown pandas are so rare, only a dozen or so have ever been documented.

The first officially recorded brown Qinling panda — a female named Dandan — was found in 1985  in Foping County in Shaanxi province by a local ranger and taken to Qinling Wildlife Zoo. She remained in captivity until her death in 2000.

Qinling pandas were officially recognized as a subspecies in 2005. Their habitat, diet and behavior are very similar to giant pandas. However, Qinling pandas are slightly smaller. They also have brown eye spots underneath their eyes, whereas giant pandas have patches around their eyes.

Research suggests Qinling pandas may have genetically separated from giant pandas from the Sichuan region around 300,000 years ago. And while most Qinling pandas are black and white, scientists were baffled as to why some of the subspecies have brown fur.

Related: World's oldest male panda dies at 35 after weeks of 'deteriorating health'

But in 2024, scientists published a study in PNAS revealing brown Qinling pandas exist thanks to a genetic quirk.

The team sequenced the genome of a captive brown panda known as Qi Zai, who was captured in the wild in 2009 and taken to Foping Nature Reserve in Shaanxi, along with his mother. In total, they sequenced the genomes of 35 giant pandas, including two brown ones.

They discovered that brown pandas get their unusual coloring because of a missing sequence in their DNA. Specifically, Qinling pandas have a mutation in a gene called Bace2, which is related to pigmentation. Further tests on another 192 black-and-white pandas showed none had this version of Bace2.

Interestingly, although Qi Zai is brown, his mother is black and white. The researchers believe this is because Qinling pandas have a dominant gene for black-and-white coloration and a recessive gene for brown-and-light-brown colors. For a brown Qinling panda to be born, both parents — who can be black-and-white — must carry the recessive "brown" gene.

However, there is a very low probability that both parents will have the recessive gene for brown-and-light-brown coloration, which is why brown Qinling pandas are so rare.

Additionally, the scientists analyzed preserved tissue from Dandan and concluded she had the same recessive trait as Qi Zai. The missing sequence represented a major breakthrough in genetics, as it was the first time that an absent genetic segment has been linked to a change in color.

Qinling pandas' brown fur is likely the result of inbreeding. The population lives exclusively in the mountainous region the subspecies is named after and is genetically isolated, which has enabled the brown color variation to persist.

A heart-wrenching image captures a young polar bear napping on the melting scraps of a tiny, drifting iceberg.

British amateur photographer Nima Sarikhani captured the scene off the Norwegian archipelago of Svalbard, which sits deep inside the Arctic Circle, around 500 miles (800 kilometers) from the North Pole. The image was crowned the winner of this year's Wildlife Photographer of the Year People's Choice Award.

After three days of desperately searching for polar bears (Ursus maritimus) through thick fog, the expedition vessel that Sarikhani was on changed course and sailed southeast toward some sea ice. There, the crew spotted two polar bears — a younger and an older male. Just before midnight, as the ship hovered close to the bears, the younger one climbed onto a small iceberg and carved out a bed with his paws before drifting off to sleep. 

"This photograph has stirred strong emotions in many of those who have seen it," Sarikhani said in a statement shared with Live Science.

Members of the public voted "Ice Bed" as the competition winner from a shortlist of 25 images curated by a panel of judges and the Natural History Museum in London.

"Nima's heartbreaking and poignant image allows us to see the beauty and fragility of our planet," Douglas Gurr, director of the Natural History Museum, said in the statement. "His thought-provoking image is a stark reminder of the integral bond between an animal and its habitat and serves as a visual representation of the detrimental impacts of climate warming and habitat loss."

Related: 'This is unlikely to be an isolated event': 1st polar bear death from bird flu spells trouble for species

Climate change is considered the biggest threat to the survival of polar bears in the wild, as rising temperatures melt away the sea ice these animals depend on. An estimated 26,000 polar bears remain in the wild, according to the International Union for Conservation of Nature Red List of Threatened Species, and they are considered vulnerable to extinction. 

"Whilst climate change is the biggest challenge we face, I hope that this photograph also inspires hope," Sarikhani said. "There is still time to fix the mess we have caused."

The winning photograph will be displayed alongside four other "highly commended" images both online and in the Wildlife Photographer of the Year exhibition at the Natural History Museum until June 30. The shortlisted photographs can be seen below.

Wildlife Photographer of the Year is developed and produced by the Natural History Museum, London.

Are bears to blame for Bigfoot sightings? A researcher has found there's a link between North America's black bear population and people seeing hairy mythical creatures in the forest.

The new study, published Jan. 13 in the Journal of Zoology, found that for every 5,000 black bears (Ursus americanus), there's an average of one Bigfoot, or Sasquatch, sighting. And if bear numbers go up, so do the number of Bigfoot sightings. 

Bears have long been tied to the Bigfoot phenomenon, and previous research already reported sightings of Bigfoot in the Pacific Northwest could be sightings of black bears. However, the new study has now established a correlation between bears and Bigfoot in many more states and provinces.

"Correlation doesn't mean causation but there might be so much correlation between black bears and Bigfoot sightings in most areas that the parsimonious [simplest] explanation is people misidentifying bears as sasquatches," Michael Hickerson, a professor of biology at the City College of New York who was not involved in the study, told Live Science in an email. 

Related: 'Yeti hair' found in Himalayas is actually from a horse, BBC series reveals

Black bears are the most common bear in North America and can be spotted in 32 U.S. states and almost every province in Canada. Websites like the Bigfoot Mapping Project, which hosts around 8,000 historical and modern Bigfoot sightings, show people have reported seeing Bigfoot all over the U.S., but they're most heavily concentrated near the West Coast and in the eastern half of the country.

Bigfoot is a popular legend, but there's no hard evidence it actually exists. Reports typically describe Bigfoot as a large bipedal ape-like creature that's often around the size of a bear standing on two legs — a black bear can stand up to 7 feet (2.1 meters) tall. 

Hickerson and his colleagues published a "tongue in cheek" study in the Journal of Biogeography in 2009 that used a computer model to predict the distribution of Bigfoot in the Pacific Northwest, which ended up looking very similar to their predicted black bear distribution, suggesting many Bigfoot sightings were misidentified bears.

Floe Foxon, a data science student at the University of Leeds in England and sole author of the new study, built on the previous study by investigating the potential correlation between Bigfoot sightings and black bears across the U.S. and Canada, factoring in human population size — more people to make sightings — and forest cover. 

Foxon's model, which is based on publicly available data from 2006 only, found that for every 1,000 additional bears in an area, there was a 4% increase in Bigfoot sightings. In other words, the more black bears present, the more people see Bigfoot. The forest area correlated with the black bear population, as expected, while the correlation between sightings and human presence was also high. Foxon speculated in the study that some Bigfoot sightings might be misidentified people.

Hickerson said the analysis was "well done" but felt Foxon should have used population densities instead of total numbers for bears and humans, as this would have accounted for states like New Jersey and Connecticut, which have very high bear densities. 

Another wrinkle in the new study is that there were Bigfoot sightings in areas with few or no black bears. For example, Florida had a relatively large human population and many Bigfoot sightings but few bears and relatively little forest cover. 

"Shouldn't less forest area predict fewer sasquatch sightings, not more?" Hickerson said. "And if there are more humans but very few bears, what are the mistaken identifications coming from? The author [Foxon] says 'other humans,' but I wonder if that explains it away."

Extinct California grizzly bears weren't the giant, blood-thirsty "hypercarnivores" humans made them out to be, new research has found.

It turns out that the once-abundant grizzly bears were mostly vegetarian and only occasionally indulged in livestock after European colonizers and American settlers began farming in California. Contrary to popular belief at the time, these grizzlies also didn't grow to monstrous proportions and rarely, if ever, tipped the scales at the oft-cited number of 2,000 pounds (900 kilograms).

The last reliable sighting of a California grizzly bear (Ursus arctos californicus) dates to 1924, and the subspecies of brown bear likely went extinct soon after. Historical sources consistently paint California grizzlies as murderous beasts — but these records are more accurate representations of prevailing attitudes toward wildlife at the time than they are of the bears themselves, according to a study published Wednesday (Jan. 10) in the journal Proceedings of the Royal Society B. 

"By the time the California grizzly went extinct, it had been featured in a vast archive of documents and images," which suggested the bears attacked people and decimated livestock, researchers wrote in the study. "While these things were true in some ways, it was certainly not the whole story," lead author Alexis Mychajliw, an assistant professor of biology and environmental studies at Middlebury College in Vermont, told Live Science in an email.

Farms mushroomed across the state during the Spanish Missions and Mexican Rancho period, between 1769 and 1848, driving grizzlies into shrinking pockets of habitat. The Gold Rush of 1849, followed by California's admission as a U.S. state in 1850, sparked waves of immigration that put further pressure on bears.

Related: Half-asleep bears are wandering around Siberia because it's too hot to hibernate

For the study, the researchers measured the abundance of stable versions, or isotopes, of nitrogen and carbon in California grizzly pelts and bones. Isotopes vary depending on the food source and are incorporated into an animal's tissue via its diet, meaning they can reveal what the creatures ate.

The results indicated that grizzly bears were largely veggie both before and after the first Europeans arrived in the state in 1542, which is consistent with the diet of modern brown bears.

But California grizzlies more than doubled their meat consumption after the first settlers arrived. Meat from livestock and wild terrestrial animals shot up from 9% of their diet before 1542 to 26% after Europeans set foot in California, according to the study. "The bears likely increased meat consumption due to landscape changes coupled with the arrival of a new source of protein — livestock," Mychajliw said. 

This dietary shift was inflated in contemporary accounts, which encouraged widespread persecution of California grizzly bears and eventually led to their extinction, according to the study.

Newspapers also wildly exaggerated the size of California grizzlies. When the researchers measured skulls and teeth from natural history collections, they found the extinct bears weren't any larger than grizzly bears (Ursus arctos horribilis) that live in North America today and the average one probably weighed around 440 pounds (200 kg). 

Historical overestimates could be due to hunters targeting the biggest bears. "The bears reported in newspaper clippings were often killed as trophies, as part of publicity stunts, or even sold for meat," the researchers wrote in the study. "Therefore, there were both monetary and reputational incentives to both capture the largest animals possible and to exaggerate the size and aggressiveness of captured animals."

The researchers highlighted the sad story of Monarch, a California grizzly bear captured north of Pasadena in 1889 as part of a publishing stunt. Convinced that grizzlies were voracious meat-eaters, zookeepers fed Monarch a rich diet of raw beef, apples and biscuits, which caused the bear to become obese and develop osteoarthritis. "When Monarch died he weighed 1,127 lbs (511.2 kg), more than twice the size of the average California grizzly in our sample," the researchers wrote.

Polar bears could be catching bird flu after feasting on bird carcasses infected with the deadly strain H5N1. The infections could add additional and potentially devastating pressure on an Arctic population already under extreme stress from climate change, experts say. 

The first case of a polar bear (Ursus maritimus) dying from highly pathogenic avian influenza (HPAI) was recently recorded in Alaska. Officials with the state's Division of Environmental Health confirmed the death in December after the carcass was found in the northernmost town of Utqiagvik in October. Experts believe the bear contracted the virus from infected birds it was scavenging on. 

It is likely other polar bears have been infected with bird flu, Robert Gerlach, Alaska's state veterinarian, told Live Science in an email. But how individuals respond to infection will depend on their overall health. 

The case was not unexpected — black bears (Ursus americanus) and brown bears (Ursus arctos) have previously been found with the deadly virus. However, polar bears are a vulnerable species because of the loss of their sea ice habitat, so any additional deaths from disease could serve another blow to the species. 

Related: 1st-known 'highly pathogenic' bird flu cases in Antarctic could threaten penguins

H5N1 was first identified in China in 1996, and since then outbreaks have been recorded across the planet. In 2020, a new variant emerged that caused an unprecedented number of deaths among birds. It spread to North America in 2021. 

Numerous mammals have also been impacted by the virus, leading to thousands of deaths worldwide. 

The wider significance of the polar bear case is unclear. A single death isn't necessarily relevant from a conservation perspective, Douglas A. Clark, associate professor at the University of Saskatchewan's School of Environment and Sustainability, told Live Science in an email. 

However, it shows the species is vulnerable. "This is unlikely to be an isolated event — it's just that this one led to an outcome that was detected," he said. 

Monitoring for the virus among polar bears is difficult due to the landscape they live in. Experts said the risk of bear-to-bear transmission is low as polar bears are a solitary species, but the big concern for several subpopulations is that reduced sea ice has pushed them to feed more on seabirds, potentially leading to greater virus exposure. 

"The challenge is to determine if eating birds is increasing or if it's just that we're getting more reports of polar bears eating birds as there are more people in the Arctic and they're more likely to document such events," Andrew Derocher, a professor in the Department of Biological Sciences at Canada's University of Alberta, told Live Science in an email. "Regardless, avian influenza is present in the Arctic and polar bears are likely to have been and will be exposed. How big a challenge it is [or] will be for the bears is hard to know."

Pollution could also make polar bears more vulnerable to bird flu. The species is highly impacted by anthropogenic chemicals because they accumulate in the animals' high-fat diets. When the bears are forced to shore, their fat stores deplete and the circulating pollutants stored away in the fat start to interfere with their immune systems. "A bear fasting for longer, nutritionally stressed, may have a weakened immune system," Derocher said. "Now expose a bear with a weakened immune system to avian influenza and the issue of surviving the exposure becomes more challenging."

What happens next is unclear. Among polar bears, cases are likely to be limited to those scavenging or killing birds infected with the virus. 

Clark said disease hasn't really been a major issue in polar bear conservation so far, but this could change, and bird flu could become a "cumulative stressor" on a population already facing sea ice loss. 

"Decreasing the population of animals will mean fewer for breeding and raising the next generation," Gerlach said. "This on top of the stressors for access to habitat, food sources and impact of climate change could have some devastating effects."

Bears in Siberia are wandering around "half-asleep" following abnormally high temperatures this fall, according to the Department for the Protection of Wildlife of the Amur Region.

The bears are ready to hibernate, having accumulated the fat reserves needed to sleep through the winter, but warm temperatures in November have kept them up past their bedtime, the government department said in a translated Telegram post on Nov. 21.

"In some areas, half-asleep bears still walk around the dens," representatives wrote in the post. Bears were spotted traipsing around in a daze a month past the time they usually enter hibernation — toward the end of October, according to the post.

The sleepless bears were mainly males, while females with cubs took to their dens "strictly on schedule," the post said.

Bears normally spend winter asleep in dens, emerging in the spring when food becomes available again. Unlike other hibernating animals, bears decide for themselves when to begin their long seasonal sleep based on a number of cues, including food supply and temperature. Research has linked warmer weather and shorter winters to a reduction in the time bears spend hibernating, with bears leaving their dens 3.5 days earlier with every rise in temperature of 1.8 degrees Fahrenheit (1 degree Celsius).

Related: Bear linked to multiple attacks in Japan found dead alongside its final victim 

This fall, the Amur region, which shares a border with China in the Russian Far East, experienced abnormally high and record-breaking temperatures in October and November, The Moscow Times reported. And this could be delaying the bears' hibernation.

Soggy dens could also be to blame, Oivind Toien, a zoophysiologist and research assistant professor at the Institute of Arctic Biology at the University of Alaska Fairbanks, told Live Science in an email. "Temperatures above freezing in wet snowy conditions could cause melt-water to enter dens [and] that could make it uncomfortable for bears to stay in," he said.

Hibernation timing problems appear to impact males more than females and cubs.

"The denning period in females with cubs serves the additional purpose to protect the cubs," Toien said. Bear cubs are more susceptible to frigid temperatures than adults due to their smaller size, as their bodies store less energy and lose heat more quickly, he said.

Cubs also have a higher base metabolism per unit of body mass than adults during both the summer and hibernation months, "so smaller bears might have to be extra careful in not spending extra energy on activity during this transition period into hibernation," Toien said.

Large adult bears, however, can maintain daytime activity during the early winter months by elevating their metabolism when they are on the move, then slowing it down again when they are resting, Toien said. Bears that are wandering around "half-asleep" may have already triggered the physiological transition to a hibernation state, and are thus going about their business with a suppressed metabolism, he added.

Bears in Alaska may also be losing sleep due to warm temperatures, Toien said. "Bears walking around in winter is well known for instance from coastal areas of Alaska," he said. "Both the size of the bears and the mild climate in those coastal areas and continued availability of some food sources might play a role here."

Sleepless bears are especially common in urban areas, where trash cans offer plentiful and accessible food throughout the winter, Toien said. Unlike the bears in the Amur region, those that habitually scavenge on human leftovers don't typically build up fat reserves in preparation for hibernation, he added.

The body of a missing student in Japan has been found alongside the corpse of a bear that likely killed him. The bear is linked to a string of other attacks in the area and follows a trend of increased bear attacks in the country this year.

On Nov. 2, police found human remains on Mount Daisengen near Fukushima in Hokkaido island. DNA analysis revealed that the remains belonged to 22-year-old university student Kanato Yanaike, who had gone missing while hiking on the mountain on Oct. 29, Japanese news site The Mainichi reported. The carcass of a brown bear (Ursus arctos) was also discovered near his body.

A postmortem of Yaniake's remains revealed that the cause of death was hemorrhagic shock from severe bleeding, which suggests that the bear likely killed him, The Mainichi Shimbun reported. 

It is currently unclear what killed the bear, but scientists from the Hokkaido Research Organization will investigate its stomach contents to see if they can learn more about its death, The Mainchini reported

The bodies were located close to a site where three other men were attacked by a brown bear on Oct. 31. Two of the men were seriously injured, but the trio managed to fight off the bear with a knife and chase it away, The Mainichi reported.

Local police are now investigating the possibility that the same bear is responsible for both attacks, as well as other recent attacks in the area.

Related: Watch as 2 male Alaskan grizzly bears fight in an epic battle 

Japan is currently suffering its worst year for bear attacks in more than a century. Since April, when the first attack was reported, at least 158 injuries and two deaths have been confirmed (not including the most recent attacks in Hokkaido mentioned at the start of this article), The Guardian recently reported. Before this year, no bear attack fatalities were recorded in the country for more than a decade.

There have been at least seven other non-fatal bear attacks in Hokkaido alone this year, according to the Japanese news site The Asahi Shimbun. 

And in April, a fisher was likely killed and beheaded by a brown bear at Lake Shumarinai, in Hokkaido, The Japan Times reported. The man's head was found in the lake, and a bear was later spotted with bloody waders hanging from its mouth, sparking a bear-hunt that resulted in a brown bear being shot and killed. It is not clear if the bear killed was responsible for the attack.

Experts believe that the uptick in attacks are the result of a decrease in the number of acorns and other foods that bears feed on. This is in stark contrast to last year, when the amount of bear food skyrocketed and resulted in a greater number of large young cubs. The combination of more large young bears and decreased food availability has likely made the situation worse.

Japan also has a rising bear population thanks to conservation efforts to revive the previously dwindling population. In Hokkaido, the number of brown bears stands at around 11,700, which is more than double the number from 1990, The Guardian reported.

This year has also seen several unusual bear attacks in other parts of the globe as well.

In January, the U.S. experienced its first fatal polar bear (Ursus maritimus) attack in more than 30 years when a mother and her infant child were mauled and killed outside of a school in Alaska. And in July, a grizzly bear (Ursus arctos horribilis) likely killed a woman on a popular hiking trail near Yellowstone National Park.

In April, a brown bear with three cubs was also suspected of killing a jogger in the Italian Alps — the first bear attack fatality in the country after wildlife officials successfully reintroduced the species to the area.

A grizzly bear mauling the lifeless body of a black bear on a roadside in Canada was captured on video last week. The rare footage  reveals what happens when the two predators collide. 

Videos showing the encounter were posted to Facebook on Aug. 30 by Susan Griffith from Dawson Creek in British Columbia, Canada. "This is definitely one of the craziest things we have seen on a drive home," she wrote in the post. 

The Canadian Rocky Mountains, which straddle Alberta and British Columbia, are home to both black bears (Ursus americanus) and grizzly bears (Ursus arctos horribilis), which is one of the largest subspecies of brown bears (Ursus arctos). 

Grizzly bears are apex predators but are also prolific scavengers and will eat whatever they find, including other bears and members of their own species. They are known to kill and eat black bears in areas where the two species overlap. 

The footage posted by Griffith appears to show the grizzly bear biting the black bear's head, back and throat as it appears to be pulling the carcass up a hill. It is unclear if the grizzly killed the black bear, or if it was already dead when the grizzly bear found it. 

Frank T van Manen, an ecologist with the U.S. Geological Survey and team lead of the Interagency Grizzly Bear Study Team, said there are few estimates on how often grizzly and black bears interact, but it is not unusual for them to encounter one another. 

"Grizzly bears are formidable predators and sometimes pursue large prey such as elk and sometimes even bison, and occasionally that includes species like American black bears," he told Live Science in an email. "This looks to be a smaller black bear and it is no match for an adult grizzly. We have documented a number of instances like this in the Greater Yellowstone Ecosystem, including one male grizzly that pulled a black bear out of a den (i.e. this occurred in late fall), completely consumed it over the course of days and repeated the same pattern with another denned black bear about a week or two later. 

"This is the period of hyperphagia [extreme hunger] for bears when they fatten up for hibernation, and consuming a black bear that already has lots of fat storage makes sense from their life history perspective."

Related: Watch as 2 male Alaskan grizzly bears fight in an epic battle

While grizzly bears eating black bears in this part of Canada are known, footage of these encounters is rare. 

In August 2022, hikers in Banff National Park found a grizzly bear eating the carcass of a black bear. Steve Michel, a human-wildlife conflict specialist with Banff National Park, told CBC at the time that this was the fourth case of this kind he was aware of. "It may not be as rare as we think it is, but it is rare that we actually are able to document it," he told the broadcaster. "We tend not to know about it all." 

In 2018, a grizzly bear was filmed attacking a mother black bear and her cubs in a den in Alberta. The male grizzly was seen digging into the den before killing one of the cubs as the others fled. 

"Predators will always catch and consume another species," Chris Servheen, a former Grizzly Bear Recovery Coordinator for the U.S. Fish and Wildlife Service, told Field and Stream in 2022. "It's not for fun. It's not for profit. It's not out of anger or revenge. It's for the purpose of eating the animal it catches."

A Canadian city that was recently evacuated due to the threat of wildfires has been overrun by bears that swooped in to feed on the trash left behind when people abandoned their homes.

On Aug. 16, Yellowknife in Canada's Northwest Territories was evacuated as wildfires blazed through much of the surrounding area and came to within about 9 miles (15 kilometers) of the city's border. Around 95% of Yellowknife's roughly 20,000 residents left the city, while some key workers stayed behind, CBC News reported. 

Around a week after Yellowknife was evacuated, those who remained noticed an unusual number of black bears (Ursus americanus) wandering the streets, CTV News reported. Since then, the number of bear sightings has steadily increased, but there are no official statistics for how many bears are now in the city.

Video footage shared by BBC News shows bears exploring people's gardens, walking in the road, rummaging through landfill and chasing a man into a hotel. 

Related: 'Polar bear capital of the world' soon to be overrun with record number of bears due to shifting sea ice

The bears are likely being drawn to the city because most people left their trash cans full of waste, meaning there's lots of free food for the bears to eat, James Williams, a Northwest Territory wildlife officer who has been patrolling the city in search of the bears, told CTV News. However, the wildfires have also likely played a role in "pushing the bears" away from their natural territories and toward Yellowknife, he added.

The number of bears sighted in Yellowknife normally increases around this time of year. Earlier in August, two bears were shot and killed by wildlife officers in Yellowknife after posing a risk to residents' safety, after one of them tried to break into a house. And around the same time last year, people were warned to stay off trails around the city after residents encountered a number of bears, some of which showed little to no fear toward humans.

Wildfires may change how wildlife officers deal with the bears. Normally, officers use deterrents, such as bear spray and rubber bullets, to scare the bears out of town. When that fails, bears are captured and released far outside the city. But the wildfires will make it harder to release the bears back into the wild, Williams said. As a result, there is a chance that more bears may have to be euthanized.

"Our number one priority is to protect life and property of the people and city of Yellowknife and as a territory as a whole, and when it comes down to it, sometimes we do have to dispatch some of these animals," Williams said. But if they do end up having to kill some of the bears, it will be "in a most respectful way as possible," he added. 

The world's unofficial polar bear capital, could see a record number of the white-furred visitors this year. Residents of Churchill, Canada, have already spotted an unusually high number of the bears in and around  town, likely because of low sea ice.

Around 900 people live in the Manitoba town. But every year, between July and November, several hundred polar bears (Ursus maritimus) descend on the town and the surrounding Hudson Bay area, which also brings in thousands of tourists hoping to catch a glimpse of the Arctic predators. 

Conservation officers from the town's government-funded Polar Bear Alert Program (PBAP) respond to calls from people who spot bears by either shooing the bears away or capturing them and holding them in Churchill's polar bear holding facility, commonly referred to as the "polar bear jail," before later releasing them into the wild.

As of Aug. 16, PBAP officers had received 76 calls from residents about polar bears, which have led to three bear detentions. By comparison, the officers had received only 18 calls and captured zero bears by the same time last year, CBC News reported.

"There are so many polar bears in and around the town of Churchill," Chantal Maclean, a Manitoba conservation officer with the PBAR, told CBC News. It's going to be a "very busy bear season," she added. "We are [potentially] looking at record numbers this year."

Related: In 'extremely rare' attack, polar bear killed mother and child in Alaska. Now we know why.

On average, officers receive around 250 calls from residents and detain around 50 bears every year, according to statistics provided to Live Science by the Manitoba government. The record number of bears captured in a single year was 176, in 2003. Most sightings occur in October and November, which means the number of sightings this year could easily surpass the average if the current trend continues.

Two people in Churchill have been killed by polar bears — one in 1968 and another in 1983. The last polar bear attack was in 2013, when two people were severely injured but survived. The rise in polar bear numbers does not necessarily mean chances of attacks increase, especially if people follow polar bear guidelines, officers said.

Rising numbers

Polar bears spend the winter hunting for seals on Hudson Bay's frozen surface. When the ice melts during spring, the bears head inland to mate and search for alternative food sources. In the fall, the bears head back out to sea. Normally, around half of the roughly 600 bears that live along Hudson Bay's western coastline pass through Manitoba as they return to the frozen waters in fall — and a majority of those make a pit stop in Churchill to look for food. The rest pass through Ontario and Nunavut.

But this year, almost all of the Hudson Bay bears that conservation officers monitor are in Manitoba, which may be why so many bears are being spotted in Churchill.

The likely cause of the change in behavior is the way sea ice is forming and melting, which has been impacted by human-caused climate change. Experts believe that the sea ice near Churchill is now freezing earlier than other parts of Hudson Bay, which makes it the best place to start hunting when winter arrives, CBC News reported.

Polar bear numbers in Churchill may be on the rise, but in general polar bear numbers are declining. The species is currently listed as vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Studies have predicted that polar bears could be wiped out by the end of the 21st century if current warming trends continue.

Over the last five years, Hudson Bay's population of polar bears has declined by around 27% after falling by around 11% in the five years before that, according to Polar Bears International. 

A black bear has been caught napping in an unlikely spot: the nest of a bald eagle. Researchers came across the sleeping bear while surveying eagle nests on a military base in Alaska. 

Black bears (Ursus americanus) are known to occasionally take advantage of eagles' architectural work — and these invasions spell trouble for the birds and their young, according to the U.S. Fish and Wildlife Service (FWS).

"In the past, a few eagle nests have been raided by black bears with predictably bad results for the nesting eagles," FWS staff wrote in a Facebook post on July 21, adding that these incidents often result in young birds going missing.

Bears occasionally eat eagles' eggs and nestlings, said Stephen B. Lewis, a FWS wildlife biologist who led the nest surveys on Joint Base Elmendorf-Richardson (JBER) military base in southern Alaska. "It's hard to say how much bears invade eagle nests because we don't (can't) spend that much time monitoring to see it happen or have cameras to witness it," Lewis told Live Science in an email.

Related: Grizzly bear believed to have killed woman on Buttermilk Trail near Yellowstone National Park 

During a helicopter survey in May, researchers spotted a female bald eagle (Haliaeetus leucocephalus) incubating an egg on the nest later occupied by the sleepy bear. A week later, the egg had been left out in the cold while both the female eagle and her mate busied themselves nearby.

"It wasn't clear if the nesting attempt had failed or if the female was just taking a break from incubating," Lewis said, adding that males would usually take over from females to keep the egg toasty, especially in cool places like Alaska. For that reason, Lewis suspects the nest "failed" in the spring, long before the bear crawled into it.

Bald eagles are Alaska's largest resident birds of prey and have wingspans of around 7.5 feet (2.3 meters), according to the ADFG. These raptors build the largest nests of any North American bird, with some nests measuring 8 feet (2.4 m) across and weighing more than two tons (1.8 metric tons).

These huge nests may also provide safe resting places for black bears that usually make "beds" on very steep slopes where other animals can't disturb them, Lewis said. "This nest isn't that far off from such a bear bed. It could have just happened to climb the tree and decided to take a nap."

Fishy smells wafting down from the nest may also have lured the bear. Eagle nests can be "rather smelly," because the fish adults catch for their young sometimes go uneaten. "Often that food isn't entirely consumed and ends up getting stomped into the nest or laying on the side and rotting," Lewis said. "Bears have incredible senses of smell so perhaps a bear is attracted to the smelly nest."

Bald eagles were listed as an endangered species across the U.S. in 1978, after their numbers plummeted due to habitat destruction, illegal shooting, pesticides and poisoning, according to the Alaska Department of Fish and Game (ADFG). Stronger protections have allowed populations to recover and monitoring is ongoing to assess the impact of other human disturbances, such as tourism and oil spills. 

A woman has died from a suspected grizzly bear attack near Yellowstone National Park, less than a week after officials warned that the animals had been spotted in areas they aren't normally found.  

The remains of the woman, who has not been named, were discovered on the morning of July 22 on the Buttermilk Trail, a popular route west of Yellowstone in Gallatin National Forest, Montana. Investigators discovered grizzly bear (Ursus arctos horribilis) tracks in the area, which suggest that a bear attack was the most likely cause of death — although investigations are still ongoing, representatives from the Montana Fish, Wildlife and Parks (MFWP) department wrote in a Facebook post.

The area around the trail has been closed to visitors until park officials conclude their investigation. Normally, in situations like this, park rangers attempt to kill the bear responsible if they can track it down, before reopening the area to ensure public safety.

On July 17, MFWP representatives revealed that grizzly bears had been "sighted in several places where grizzlies haven’t been seen in recent years, and in some cases more than a century." These include parts of the Elkhorn Mountains, the Pryor Mountains and Helena, the state's capital, as well as other areas surrounding the greater Yellowstone area.

Related: Watch as 2 male Alaskan grizzly bears fight in an epic battle

The unusual grizzly bear sightings are likely tied to their growing population in Montana. Thanks to a successful recovery program, the state now has around 2,000 grizzly bears, which is second only to Alaska and almost four times more than neighboring Wyoming, according to MFWP.

The growing number of grizzlies has previously sparked debate about whether or not people should be allowed to hunt the bears again in the region, with proponents saying that the population is large enough to sustain hunting. Those opposed argue hunting was one of the factors that previously drove the population to collapse in the first half of the 20th century.

In July 2021, another woman was killed by a grizzly while camping near Ovando, Montana, after the bear repeatedly entered the campsite, possibly in search of food. In April the same year, a man was fatally wounded by a grizzly while fishing near Yellowstone, USA Today reported at the time. And in March 2022, a grizzly mauled a man to death inside Yellowstone National Park while hiking in the Six Mile Creek area. Before these recent encounters, the last fatal grizzly attack in the state was in 2016. 

MFWP has warned everyone visiting the state's rural areas to remain "bear aware," by carrying bear spray, traveling in groups, avoiding dead animals, looking for tracks, making lots of noise in areas where a bear may struggle to see them coming and, most importantly, not approaching a bear.

A wildlife photographer in Alaska caught two massive male grizzly bears on video in what he said was "the longest, most intense bear interaction I have ever witnessed."

On May 8, Brad Josephs was visiting Lake Clark National Park and Preserve in southern Alaska when he caught the two grizzly bears (Ursus arctos horribilis) going head-to-head in a show of dominance during mating season, according to Outside magazine. The fight wasn't between equals, either; one male was larger and older while the other was smaller and younger, according to PetaPixel. 

Josephs uploaded the video to his YouTube channel, where it has already received more than 252,000 views.

"It just kept going and going,” Josephs told Outside magazine. “I was astounded by the determination and stamina of both bears as they battled for mating season dominance rights."

Related: Hungry grizzly bear photo-bombs camera trap in award-winning photo

The heart-pounding video, which lasts nearly nine minutes, begins with the two males posturing on all fours before eventually standing on their hind legs and wrestling each other. At one point, the bears can be seen catching their breath before going in for round two.

On average, grizzly bears stand at 3 to 5 feet (0.9 to 1.5 meters) tall at the shoulder when on all fours, but can reach a height of nearly 9 feet (2.7 m) on their hind legs. Male grizzly bears can weigh up to 860 pounds (390 kilograms). 

Mating season for the bears usually runs from May through July and it's not uncommon for larger males to chase away smaller males, while "evenly-matched" males will fight for dominance as seen in this video, according to the North American Bear Center. 

At the end of the video, one of the bears admits defeat and backs down by bowing his head in submission. 

"He's got his head down, he's basically saying, 'I'm sorry, I lost,'" Josephs said in the clip. "And the winner walks away."

Alaska has the highest population of grizzly bears in any state or province. Of the 60,000 wild grizzly bears located throughout North America, around 30,000 are found in Alaska, according to PetaPixel. 

Italian authorities are deciding what to do with a brown bear that mauled a jogger to death in the northeastern province of Trento. The case has shone a light on the country's successful — but problematic — rewilding program. 

On the evening of April 5, 26-year-old Andrea Papi was jogging on a woodland path near the village of Caldes. When he failed to return home, his family reported him missing. His mauled body was found at 3 a.m. the following morning. 

On April 8, provincial president Maurizio Fugatti, issued an order to kill the Alpine bear, but a court suspended that order following an appeal from animal rights group the Anti-Vivisection League (LAV), ANSA news agency reported. The bear, a female known as “JJ4,” was captured on April 17 accompanied by three cubs.

This is the second time JJ4 has had a kill order overturned, having previously attacked a father and son in 2020, Reuters reported. The victims of the 2020 encounter survived.

Claudio Groff coordinates the large carnivores sector within the provincial government's wildlife department. He told Live Science that Papi's death is even harder to accept because of what happened in 2020. "We tried to remove this dangerous bear," Groff said. "We didn't manage it, unfortunately, because of the decision of the court." 

Papi's death marks the first fatal bear attack in Italy, according to the Italian daily newspaper Corriere della Sera. However, bear-related incidents like this fuel a long-running debate about the presence of bears in the region.  

 How many bears are there in the Trentino-Alto Adige? 

Brown bears (Ursus arctos) were on the brink of extinction in the Alps in 1999, with only a handful surviving in the Trentino-Alto Adige region of Italy. The European Union-funded Life Ursus project brought bears from Slovenia to the region as part of conservation efforts to establish a minimum viable population of around 40 to 60 individuals. Today, there are around 100 bears in Trentino-Alto Adige. 

Related: 'Prehistoric' mummified bear discovered in Siberian permafrost isn't what we thought   

"Italy is a great success story," said Lana Ciarniello, an independent researcher in Canada and co-chair of the International Union for Conservation of Nature’s (IUCN) Human-Bear Conflicts Expert Team, of which Groff is also a member. "The bears were reintroduced, and they've done very well."

The bear program has worked so well that the animals have made a remarkable recovery — but now the region is adapting to once again becoming, as Ciarniello puts it, "bear country." 

What causes bear attacks?

Tom Smith, a professor at Brigham Young University in Utah whose research focuses on human-bear conflicts, told Live Science that the most common cause of brown bear attacks is people unintentionally surprising them. Smith has studied more than 2,000 bear attacks in North America. He said all bears, regardless of whether they have cubs, can attack if approached. 

"Anytime you intentionally or unintentionally run into a bear, you're going to unleash a natural instinct in them, which is to defend themselves," Smith said.   

Bears typically avoid humans and run away if they hear people coming. Smith noted that certain human behaviors increase the chances of attacks, including trying to get close to bears, feeding them, leaving food around, mountain biking, walking alone or having a dog off the leash — bears don't like dogs. However, according to Smith, solo runners are at greatest risk.  

"That's the worst thing you can do," Smith said. "Runners are single, they move fast, they don't make noise; it's the perfect storm of bad variables."

What has gone wrong in Italy, and what's the solution? 

Groff said there are hundreds of signs telling people how to behave, including where the fatal attack happened, "but it's not enough." 

He claims there are two things that would help that are out of his hands. The first is for people to carry bear spray — an effective bear deterrent in North America that is currently illegal in Italy. Ciarniello and Smith also advocated for the use of bear spray. 

The second is to be able to "shoot dangerous bears as soon as possible," Groff said. "There are very few," Groff added. "But we have to be fast to remove them, and as we can see, we are not."

 Related: Woman killed in unusual grizzly bear attack 

The decision to increase the number of bears in Italy was controversial, with fears from local communities that bears threaten livestock and people. The revival of the bear population also brought about the revival of poaching, according to a 2015 article in the journal Arcadia.

With the people living alongside bears being forced to make concessions, Ciarniello said that removing a bear perceived as a threat can help them feel more secure, helping to alleviate human-bear conflict.

"If it continues to foster positive attitudes for the [bear] population as a whole, then that individual should be removed, whether that individual needs to be removed or not," Ciarniello said.

A spokesperson for WWF Italy told Live Science in an email that the province can do more to promote coexistence. "Unfortunately these have not yet been adopted by the Province of Trento," the spokesperson said.

WWF Italy recommended more preventative action to avoid bears gaining access to human food and livestock, increased bear education and awareness, the use of bear spray for hikers and residents, and measures to allow the population to expand.

"The brown bear population in the Italian Alps has not been able to expand into other territories due to severe habitat fragmentation," the spokesperson said. "It is crucial to intervene by restoring habitats and providing wildlife corridors to allow the population to expand into other suitable areas outside western Trentino."

Are there too many bears in Italy?  

Italy's environment minister, Gilberto Pichetto Fratin, told Italy's Mediaset television that he has set up a committee to address the possible excess number of bears in the region, ANSA news agency reported. If there are deemed to be too many, some could be removed. 

Ciarniello noted that on every landscape, there's an ecological carrying capacity — how many individuals of a species an environment can support — and a social carrying capacity — how many of those animals a human population will tolerate.   

She said Italy now needs to decide when the social carrying capacity for bears will be reached and how to manage it — for example, by removing bears or hunting. 

What will happen to the bear that killed the jogger? 

At the time of writing, it is unknown what will happen to JJ4. She is being held at the Casteller wildlife center near Trento. A final court ruling on her future is expected on May 11. JJ4's cubs were mature enough to survive independently and allowed to go free, according to a statement released by the Trento provincial government. 

Polar bear twins have been reunited in a zoo after more than two years apart. The siblings were separated shortly after birth when one of them developed severe health problems and was later rejected by their mother.

The female polar bears (Ursus maritimus), named Astra and Laerke, were born at Detroit Zoo on Nov. 17, 2020 to mother Suka and father Nuka. But two days later, Laerke was separated from the den she shared with her mother and sister due to a medical emergency, which required keepers to hand-feed her and monitor her around the clock. After making a full recovery, zoo staff attempted to slowly reintegrate Laerke with Suka and Astra — but it did not go to plan. 

"Suka was very protective of her cub, Astra, and acted aggressively toward the cub she no longer recognized as her own," Detroit Zoo representatives told Live Science in an email. Laerke remained in a separate enclosure during the reintegration process and "was never at risk of being injured" by the mother, they added.

Astra and Suka were moved into separate enclosures in January this year after Astra reached the age when polar bears leave their mothers in the wild. This gave zoo staff the opportunity to reunite Astra with her twin, who grew up alongside an abandoned grizzly bear named Jebbie.

Related: Secret population of polar bears found living in seemingly impossible habitat

After a brief period of reintegration, where the pair met and interacted with one another in adjoining cages, zoo keepers let Laerke into Astra's new enclosure on April 11. The reintroduction went extremely well and "the sisters appear to enjoy sharing a space," the zoo representatives said. They hope the pair can remain together full-time, the representatives added. 

On April 17, the zoo shared heartwarming images of Astra and Laerke playing together on Facebook along with the caption "sister, sister — never knew how much I missed ya."

Keepers will continue to closely monitor the pair in the coming weeks. They expect that after becoming familiar with one another, the twins may spend less time together, which is normal because adult polar bears tend to keep to themselves in the wild.

Laerke's story is quite a common one in zoos. 

On Feb. 27, Born Free — a U.K.-based charity that advocates for relocating captive animals to the wild, as well as improving their quality of life — released a report into the issues associated with keeping polar bears in captivity. Along with concerns about reduced lifespans, improper diets and a lack of space to roam, the report said captive cubs are more likely to die or develop health complications in captivity, with less than half surviving past 30 days. 

When humans step in to save them, mothers can end up rejecting their babies. This is likely because mothers are more stressed when giving birth in captivity than in the wild, according to the report.

However, Polar Bears International, a non-profit conservation organization, says zoos and aquariums also play an important role in conserving polar bears. 

Captivity will also play an important role in preserving the species for future generations to appreciate because climate change is expected to wipe out most wild populations, potentially as early as the end of this century. 

A perfectly preserved, mummified bear found entombed in the Siberian permafrost in 2020 isn't what scientists thought it was, a new analysis reveals. It turns out that the eerily intact carcass is much younger than first assumed and belongs to an entirely different species. 

Reindeer herders unearthed the remains, which include the bear's intact skin, fur, teeth, nose, claws, body fat and internal organs, on Bolshoy Lyakhovsky Island, a remote Russian island located in the East Siberian Sea. Researchers named it the Etherican bear, after the nearby Bolshoy Etherican River. 

When the Etherican bear was first uncovered, researchers at the Lazarev Mammoth Museum Laboratory at North-Eastern Federal University (NEFU) in Yakutsk, who have led the analysis of the remains, thought that the mummy was an extinct cave bear (Ursus spelaeus). Fossils of this long-lost species suggest that the enormous ancient bears, which are closely related to brown bears (Ursus arctos) and polar bears (Ursus maritimus), grew to around 11.5 feet (3.5 meters) tall and weighed a whopping 3,300 pounds (1,500 kilograms). U. spelaeus went extinct around 22,000 years ago, toward the end of the Last Glacial Maximum, the coldest part of the last ice age, so the researchers believed that the mummy was at least this old.

However, subsequent analysis revealed that their assumptions about the Etherican bear were way off: In reality, the beast was a brown bear that dated to around 3,460 years ago, the NEFU team said in a statement in December 2022. 

Related: 10 stunning fossils from 2022 that didn't come from dinosaurs 

The NEFU team recently conducted a full necropsy, or animal autopsy, on the Etherican bear, which has revealed even more about the mysterious mummy, Reuters reported.

The bear was a female that was 5.2 feet (1.6 m) tall and weighed around 172 pounds (78 kg), suggesting it was likely around 2 to 3 years old when it died. It is unclear how the bear perished, but its mummy showed signs of significant spinal injuries that likely contributed to its demise.

The Etherican bear was so well preserved that its stomach contents were still partly intact, which revealed that the bear had been dining on a mix of unidentified plants and birds, some of whose feathers were still inside the bear's belly. This fits with what we know about living brown bears that are omnivores, meaning they have a mixed diet of plants and animals.

The researchers also removed the bear's brain after cutting through its skull, which they hope to study in the future. 

One of the biggest remaining mysteries about the Etherican bear is how it ended up on Bolshoy Lyakhovsky Island. 

The island is currently separated from the mainland by around 31 miles (50 kilometers) of water, so the most likely explanation is that brown bears moved to the island when it was still connected by sea ice during the Last Glacial Maximum, according to Reuters. But if this was the case, then researchers would have expected to find many more brown bear remains on the island, which is a hotspot for paleontological treasures, including mammoth remains.

Last month, a polar bear killed a woman and her 1-year-old child in Alaska. It was the first fatal polar bear attack recorded in the U.S. in more than 30 years. Now, a new report sheds light on what may have caused the tragic event. 

Experts analyzed the animal's tissues, which revealed that the male bear was in poor physical shape and likely elderly. However, it's unknown exactly what triggered the polar bear's (Ursus maritimus) aggressive behavior. 

Summer Myomick, 24, and her infant son, Clyde Ongtowasruk, were mauled to death Jan. 17 in the coastal town of Wales, the westernmost city on the mainland of North America. The pair were leaving a school when a polar bear attacked them in the middle of the street: A heavy snowstorm at the time meant that Myomick did not see the bear coming until it was too late. School staff attempted to stop the bear by hitting it with shovels, but the bear turned on the staff and forced them to retreat back into the school, which was full of pupils at the time. The school remained in lockdown until a village resident arrived with a gun and shot the polar bear dead, AP News reported.

"Polar bear attacks on people are extremely rare," Lindsey Mangipane, a wildlife biologist with the U.S. Fish and Wildlife Service's Polar Bear Program in Alaska, told Live Science in an email. The last U.S. attack happened in 1993, and the last fatality occurred in 1990, in Point Lay, Alaska, she added. 

So what caused the rare attack?

Dr. Kimberlee Beckmen, a vet with the Alaska Department of Fish and Game's Division of Wildlife Conservation (DWC), conducted tests on tissue samples collected from the dead polar bear to learn more about why the animal behaved so aggressively. The results were released Feb. 3 in a statement by the DWC.

Related: Move over polar bears, there's another top predator along the Arctic coast

At the time of the attack, there was speculation in the media that the bear may have had a brain-altering disease, such as rabies, toxoplasmosis, distemper or bird flu. "These conditions could impact bear behavior," Mangipane said, "but because we don't generally encounter affected bears in [the] wild, we are unsure how symptoms would impact the way bears interact with people."

However, the tests carried out by Beckmen came back negative for any brain-altering pathogens. Instead, the bear's sex and physical condition were likely to be the "key factors" that influenced the attack, Mangipane said.

The bear in the Wales attack was an adult male in "poor body condition" and was likely elderly, according to DWC. (A tooth was sent for a separate analysis to determine the bear's age, but the results haven't been released at the time of publication.)

In a 2017 study, published in the journal Wildlife Society Bulletin, researchers analyzed data from 73 polar bear attacks between 1870 and 2014 across Canada, Greenland, Norway, Russia and the U.S. and found that "nutritionally stressed adult male polar bears were the most likely to pose threats to human safety." This latest attack is consistent with these findings, Mangipane said.

There was "no definitive explanation as to why the bear was in poor body condition," DWC representatives wrote in the statement. But it is possible that human-caused climate change played a role. 

"Sea ice loss is resulting in polar bears having less access to their primary prey," such as seals, Mangipane said. "This means that polar bears may increasingly be in poor body condition, especially when encountered on land." 

Climate change could also be elevating the risk of attacks occurring in other places.

"Historically, polar bears spent most of their time on the sea ice which resulted in minimal spatial overlap with people," Mangipane said. "As the open-water season becomes longer [due to increased melting], some areas are experiencing more bears on land for longer periods of time, increasing the probability of human-bear interactions."

In coastal ecosystems around the Arctic peninsula, polar bears have long been considered the top predators. But a new study suggests that sea stars could be surprising contenders to rival the famous white bears at the summit of the local food web.

A food web is a sprawling map of ecological connections that combines all the different food chains within an ecosystem. Individual food chains contain primary producers, which derive energy from the sun or by recycling dead organic material; primary consumers that graze upon the primary consumers; and then secondary or tertiary consumers that prey upon all the consumers beneath them. But the organisms in one food chain can also have a place in another, or multiple others, so the best way to see how an ecosystem functions is to link these chains together.

In marine food webs, researchers often focus on pelagic, or open water, food chains that contain tiny, surface-dwelling plankton all the way up to large predators such as polar bears (Ursus maritimus), which often sit at the top of multiple food chains. But the seafloor, or benthic, realm is often overlooked in marine food webs because scientists believed it has no real top predators of its own. 

But in a new study, published Dec. 27, 2022, in the journal Ecology, researchers took a more in-depth look at a coastal marine ecosystem in the Canadian Arctic and found that the benthic component of the region’s food web had been majorly underappreciated. The research team created a detailed map of the various food chains surrounding Southampton Island, in the mouth of Hudson Bay in Canada's Nunavut territory, and found that the benthic part of the web had just as many connections as its pelagic counterpart, as well as its own equivalent of the polar bear — predatory sea stars.

Related: Swarm of rainbow-colored starfish devour sea lion corpse on seafloor 

"It’s a shift in our view of how the coastal Arctic marine food web works," study lead author Rémi Amiraux, a marine ecologist at Laval University in Canada who was with the University of Manitoba when the study was conducted, said in a statement. "We proved that the wildlife inhabiting the seawater and those inhabiting the sediment form two distinct but interconnected subwebs."

The researchers analyzed data on 1,580 individual animals living in the Southampton Island coastal ecosystem to create the new food web. They found that the benthic and pelagic components each had a similar number of steps, or trophic levels, in their respective food chains. 

Sea stars were a key part of the benthic food web, occupying various trophic levels, but one family,  Pterasteridae, was consistently at the top of most individual food chains. The researchers discovered that these sea stars feed on a range of secondary consumers including bivalves, a group of mollusks whose bodies are protected by a hinged shell, sea cucumbers and sponges. This means Pterastidae sea stars were hunting on an equivalent scale to polar bears, which preyed upon walruses, gulls, beluga whales (Delphinapterus leucas) and ringed seals (Pusa hispida). The key difference between the polar bears and sea stars was the size of their prey. 

In addition to being among the most successful predators in the entire ecosystem, the Pterasteridae sea stars and polar bears also shared the ability and willingness to scavenge, which researchers believe has enabled both groups to thrive in the Arctic. 

The sea stars opportunistically fed on dead pelagic organisms that sank to the seafloor, meaning they had to hunt less often. Similarly, polar bears can scavenge on whales that wash up dead, which can sustain them for weeks or even months, researchers wrote in the study.

The team believes that the new findings highlight the importance of seafloor food chains in many other marine food webs. Pterasteridae sea stars are found in almost all marine ecosystems, and if they are as successful elsewhere as they are in the Arctic, they could turn out to be one of the ocean's most successful predators, researchers wrote.

Some American black bears in the western United States have evolved to have cinnamon-colored fur. The new hue is likely due to a genetic variant similar to one that causes albinism in humans, a new study finds.

Researchers from the United States and Japan analyzed DNA samples from 151 American black bears (Ursus americanus) across the United States and Canada and found that those residing in western states such as Nevada, Arizona and Idaho were more likely to exhibit reddish-colored coats than the black fur for which the medium-size bears are named.

The researchers identified a mutation known as R153C in a gene called tyrosinase-related protein 1 (TYRP1), which causes an alteration in the coat's pigmentation that makes its fur the same color as a copper penny.

"TYRP1 is a known pigmentation gene in the pathway in the precursor molecules that ultimately produces either eumelanin (black or brown pigment) or pheomelanin (red or yellow pigment)," Emily Puckett, the study's lead author and an assistant professor in biological sciences at The University of Memphis in Tennessee told Live Science. "What it's doing is changing the amino-acid sequence of that gene."

This "cinnamon variant," which Puckett calls "a young mutation," came about approximately 9,360 years ago, according to the study, and has gradually spread through the population.

Related: Scientists extract ancient DNA from 32,000-year-old bear skull

Black bears elsewhere in the United States, including along the Great Lakes and in the Northeast, are less likely to exhibit red-hued fur because this young mutation "hasn't had enough time for natural migration," Puckett said.

"Geography definitely plays a part," she said. "Our demographic modeling identified that the most likely place where the mutation arose was somewhere in the western region, very likely in the Southwest. From there, it expanded through gene flow throughout populations."

But even that is a slow process, with the majority of black bears on the East Coast still sporting jet-black fur.

"The bears don't pass through the Great Plains," Puckett said. "If they wanted to go east, they would have to go up north to Canada, across the Canadian [Prairies], around the Great Lakes and then drop back down into the eastern populations. That would take a long time. We do see that it's happening and is moving [eastward], but it's a process that takes time."

The researchers also examined whether or not the development of this gene in western American black bears had anything to do with thermoregulation, a mechanism that helps mammals regulate their body temperatures, or competition with another cinnamon-colored bear species: brown bears (Ursus arctos), also known as grizzly bears.

"Our modeling suggests that yes, [the gene is] adaptive in some way, but we're not 100% sure what it's adapted to," Puckett said. "We tested for both thermoregulation and competition with brown bears, and neither were strongly supported. Our new hypothesis is that it's a mechanism for selective advantage."

Interestingly, the variant is similar to one in humans known as oculocutaneous albinism type 3 (OCA3) that causes lighter colored hair and skin, two hallmarks of albinism. In some cases, it can also lead to poor eyesight.

"What is fascinating is that the bears aren't showing signs of visual problems," Puckett said, "since it would be hard for them to survive."

The findings were published Dec. 16 in the journal Current Biology.

As climate change diminishes Arctic sea ice, polar bears (Ursus maritimus) are being forced to ransack towns and garbage dumps in ever greater numbers, a new study in the journal Oryx finds. 

While bears eating human garbage is not a new phenomenon, the frequency and severity of human-bear interactions in the Arctic are increasing steadily, the study authors wrote, with some encounters ending in polar bears being shot and killed.

"What we have seen is an increase in intensity (of encounters) and increased occurrences in places where polar bears don't normally occur," study co-author Geoff York, a researcher with Polar Bears International, told The Globe and Mail.

In the new study, the researchers described six case studies that showed above-average (and occasionally deadly) polar bear encounters with Arctic communities in the United States, Canada and Russia. In each town or community, the number of polar bear sightings has increased steadily over the past several years or decades, leading to some dicey situations.

In 2019 in Russia, for example, ravenous bears overran garbage dumps in two Arctic villages. The town of Belushya Guba (population roughly 2,000) reported a "mass invasion" of 52 polar bears beginning near the town's open landfill, with some of the bears later venturing further into town and attempting to access buildings. Meanwhile, in the village of Ryrkaypiy (population 600), 60 polar bears took over the town's garbage dump for several weeks. 

In Arctic Canada, two polar bears were shot and killed — one in 2015 and one in 2016 — after venturing too close to human settlements, the study added.

It's likely that human-made climate change is at least partially responsible for the increase in human-polar bear interactions, the study authors wrote. 

All six case study communities are located near coasts where sea ice forms in late autumn, which gives polar bears a platform from which to hunt prey like seals and walruses, according to the study. As warming temperatures diminish the available sea ice each year, bears may be forced to venture inland and seek alternate food sources from towns and landfills, the researchers wrote.

It doesn't matter that the nutritional value of human garbage is less than ideal — or that dumpster-diving bears may be ingesting everything from batteries to dirty diapers to ceramic containers coated with food, York told The Globe and Mail.

"Polar bears will come a long distance if they can smell food," York said. "If they can find a reliable source of calories, they will go to extraordinary measures to come back."

One solution to the problem is to replace open landfills with composters or incinerators to dispose of organic waste, thereby minimizing opportunities for polar bears to come into contact with humans, York added. However, even with landfills closed, polar bears will likely continue venturing into Arctic towns in search of food so long as sea ice diminishes. This challenge is just one more unforeseen consequence of climate change, and underscores the importance of taking meaningful global action.

Originally published on Live Science.

An An, the oldest-ever male panda in captivity, has died at the age of 35 in a Hong Kong amusement park. The giant panda was euthanized after his health deteriorated over the course of several weeks, according to a statement from the Ocean Park theme park, where An An lived since 1999.

"An An lived a full life that ended at the respectable age of 35 — the equivalent of 105 years in human age," the statement added. "An An has brought us fond memories with numerous heart-warming moments. His cleverness and playfulness will be dearly missed." 

The male giant panda was gifted in 1999 to Hong Kong along with a female, named Jia Jia. The two pandas were provided by Chinese officials as part of a "panda diplomacy" program, where giant pandas (exclusively found in China) are leased to other nations, according to the Associated Press (AP).

Jia Jia died in 2016 at age 38, making her the single oldest panda ever kept in captivity. In the wild, pandas typically live 14 to 20 years, according to the World Wide Fund for Nature (WWF). Once captive pandas reach their 20s, they typically stop breeding, at which point they are considered to be "geriatric."

Geriatric pandas are susceptible to a host of health issues, including high blood pressure — an ailment that afflicted An An in his final weeks. According to Ocean Park, An An's food intake steadily declined, while his nap time steadily increased. By July 17, An An had stopped taking solid foods altogether and only drank water infused with electrolytes.

Several weeks after An An was taken off display due to his poor health, a team of vets and panda conservation experts opted to euthanize the giant panda, to prevent further suffering. 

Ocean Park is home to two more giant pandas — Ying Ying, a female, and Le Le, a male. The panda pair was gifted to the park in 2007, to celebrate the 10th anniversary of Hong Kong's return to China, according to the AP. Both pandas are 16 years old.

Originally published on Live Science.

A secret population of polar bears in Greenland has been discovered in a seemingly impossible habitat — one that, for most of the year, lacks the floating platforms of sea ice the beasts use to hunt. The unusual group, which scientists previously thought was part of another nearby population, has been hiding in plain sight for hundreds of years.

The bears live on the steep slopes around fjords — long and narrow coastal inlets, where glaciers meet the ocean — and hunt on a patchwork of glacial ice that breaks up in these inlets. The new discovery suggests that some polar bears, at least, may be able to adapt to sea ice disappearing as climate change worsens, the study suggests.

Still, that's no silver bullet for the species at large.

"Glacier ice may help small numbers of polar bears survive for longer periods under climate warming, but it is not available for the vast majority of polar bears," lead researcher Kristin Laidre, a wildlife scientist at Polar Science Center at the University of Washington, told Live Science in an email. That's because this type of glacier ice is only found near a small fraction of other polar bear populations.

Related: Why aren't there polar bears in Antarctica?

Until recently, scientists had identified 19 known subpopulations of polar bears (Ursus maritimus) living in the Arctic Circle. One of those populations spans a 1,988-mile (3,200 kilometers) stretch of the eastern coast of Greenland. But when researchers took a detailed look at this group to monitor their numbers, they realized the bears actually comprised two completely separate populations. 

Researchers analyzed 36 years' worth of tracking data from bears tagged with GPS collars and found that bears from southeast Greenland did not pass above a latitude of 64 degrees north, and bears from the northeast did not pass the same line in the other direction. Genetic sampling from individual bears confirmed that the southeastern bears were distinct from their northeastern neighbors. 

"We present the first evidence for a genetically distinct and functionally isolated group of polar bears in southeast Greenland, which meet [the] criteria for recognition as the world’s 20th polar bear subpopulation," the researchers wrote in their new study, which was published June 16 in the journal Science.

The new southeastern population contains around 300 individuals, although determining an exact number is tricky, the researchers said. The newfound group is the most genetically diverse out of all 20 populations in the Arctic, and genetic comparisons suggest that they have been isolated from the northeastern population for around 200 years, the researchers said.

Polar bears are listed as vulnerable to extinction, according to the International Union for Conservation of Nature (IUCN) Red List, and there are around 36,000 individuals left in the wild. But some studies have suggested that the species could vanish by the end of the century due to the effects of climate change.

Despite being the world's largest land predator, polar bears are actually listed as marine mammals because they rely on a predominantly aquatic diet, consisting mainly of seals. But in order to hunt for food, the snow-white bears rely on sea ice as a platform to stalk their prey from above. Unfortunately, rising temperatures caused by climate change are reducing the amount of sea ice available, shrinking their natural habitat.  

Sea-ice extent waxes and wanes in the Arctic. The temporary ice sheets form on the ocean's surface during autumn and then melt away in spring. Polar bears normally survive for between 100 and 180 days without food as the sea ice disappears over the summer. But warming temperatures in the Arctic mean that sea ice is melting sooner and freezing later, pushing polar bears to the brink of starvation.

The fjords that are home to the southeastern polar bears lie at the southern edge of the Arctic Circle and, as a result, the region is sea ice-free for more than 250 days a year. These sea ice conditions mimic those predicted for the rest of the Arctic by the end of the 21st century, based on previous studies, which should make the fjords unlivable for polar bears, the researchers said. But the southeastern bears seem to be managing surprisingly well without the sea ice.  

The researchers think that the bears are taking advantage of glacial mélange, or the bits of ice that break off the fjords' glaciers and into the sea. The bears likely use these freshwater ice patches in the same way they use sea ice to hunt, which allows them to feed themselves during the long spells when sea ice is absent from the region. "This suggests that marine-terminating glaciers may serve as previously unrecognized climate refugia," the researchers wrote.

The southeastern population also lives nowhere near any human populations, and the area is believed to be too hard to reach for most hunters, which adds an extra layer of security for the bears. However, the steep slopes of the fjords can also be quite tricky for the polar bears to traverse, which may limit their movements. The birth rate among the new population is also very low compared with other populations, which researchers suspect is because potential mates struggle to reach one another.

In the new study, the researchers used genetic data to identify two individuals that could be immigrants from the northeastern population. These immigrant bears appear to have adapted very well to hunting on glacial mélange, which suggests that other populations might be able to follow suit as sea ice conditions deteriorate in other areas. The researchers identified other similar locations where glacial conditions could support polar bears in northern Greenland and Svalbard. However, moving to these locations may not be possible for a majority of bears. 

Although the study does provide a glimmer of hope for some polar bears, the researchers insist that this does not make climate change any less of a threat to the Arctic predators. "Loss of Arctic sea ice is still the primary threat to all polar bears," Laidre said. "This study does not change that." Sea ice will continue to decline across the Arctic, which will decrease the survival odds for most polar bears, she added.

Originally published on Live Science.

A California family unexpectedly discovered that they had been sharing their home with a family of five bears — an adult female and four cubs. The bears recently emerged from underneath a home in Lake Tahoe, where they had been hibernating for the winter.

The BEAR League — a volunteer-led bear conservation organization and rescue service — described the bear's emergence on April 19 in a Facebook post. 

In the post, the group mentioned that the female bear had three 9-month-old cubs of her own, and had "adopted" an orphaned bear cub that was about the same age. Before the winter began last year, the now five-member bear family found an "unsecured crawl space opening" beneath a home in Lake Tahoe, California, where they hibernated for the season.  

Related: Mysterious brain infection makes bears act 'like friendly dogs'

Throughout the winter, the home's human residents heard "some odd rumbling and snoring-like noises" beneath their floors, but were unable to identify the source of the sounds — until the bear family awoke and "prepared to exit" from the crawl space, according to the post,

The residents promptly called the BEAR League for assistance. That was when the organization's volunteers discovered that there were multiple bears under the house, BEAR League Executive Director Ann Bryant told the Huffington Post. 

Upon arrival, BEAR League volunteers entered the crawl space and created a lot of noise to "encourage" the bear family to vacate, according to KTVU FOX 2. 

BEAR League volunteers are trained to handle such interactions safely, as they are frequently contacted in the spring to assist homeowners who acquired bear "roommates" over the winter, KTVU reported. 

"They were just waking up," Bryant told KTVU. "We got the mother out, and she called to the babies, and they came."

Three species of bears are native to North America, but the Tahoe bears were black bears (Ursus americanus) — the only wild species in California, and there are approximately 25,000 to 35,000 bears in the state, according to the California Department of Fish and Widlife. 

Black bears can weigh up to 500 pounds (227 kilograms) and during the summer months they spend almost 20 hours each day eating vast quantities of  nuts, fruits, insects, and small mammals, fueling up for the coming winter months, according to the Conservation Society of California. 

According to the North American Bear Center, a bear and wildlife education facility in Ely, Minnesota, black bears begin seeking or building dark, cozy winter dens from September to October. They look for rock crevices, caves and hollow trees — and in some rare cases,a home's crawl space. Once in the den, as the bear prepares to hibernate, its body temperature decreases and its active heart rate falls from 80 to 100 beats per minute to 50 to 60 beats per minute. 

Black bears will hibernate for several months before reemerging in the spring. In March 2022, the Lake Tahoe Interagency Bear Team, a partnership between the California Department of Fish and Wildlife, California State Parks, Nevada Department of Wildlife, Tahoe Regional Planning Agency, and the USDA Forest Service, asked Lake Tahoe residents to anticipate increased bear activity as the animals emerged from their winter dens, according to the Tahoe Daily Tribune. 

The Lake Tahoe Interagency Bear Team advises that Tahoe residents and visitors should  never approach a wild bear, and if a bear is in the vicinity people should increase their distance from the animal — but you should never run or act aggressively towards the bear. 

"People really need to make sure their crawl space openings are closed and secured before bears go inside," Bryant told the Huffington Post. "especially in the fall, when they are looking for hibernation dens." 

Originally published on Live Science.

Grizzly bears are a type of brown bear that live in North America. The name "grizzly bear" is typically given to members of the subspecies Ursus arctos horribilis, but the scientific classification of American brown bears is not settled, and some people use "grizzly bear" and "brown bear" interchangeably. 

Grizzly bears are named after their grizzled hair, which can be streaked with strands of gray or silver. However, people commonly believe the word "grizzly" comes from "grisly," which means to cause horror, according to the Center for Biological Diversity. Despite their imposing size and appearance, grizzly bears rarely attack humans. 

Are grizzly bears and brown bears the same?

Brown bears (Ursus arctos) are the most widely distributed bears in the world and can be found in North America, Europe and northern Asia, according to the International Union for Conservation of Nature (IUCN). North America's brown bears are split into two main groups; grizzly bears and Kodiak bears (Ursus arctos middendorffi). While Kodiak bears are only found on the Kodiak Archipelago in Alaska, grizzly bears live across the rest of their North American range, according to the National Wildlife Federation (NWF). This includes mainland Alaska, three other U.S. states and Canada. 

Grizzly bears can be grouped together under the subspecies Ursus arctos horribilis, but some sources recognize multiple subspecies. For example, the Integrated Taxonomic Information System (ITIS) recognizes eight brown bear subspecies in North America, including extinct California grizzly bears (Ursus arctos californicus). These grizzlies inhabited California until humans wiped them out in the 1920s, according to the Pacific Grove Museum of Natural History in California. 

"Grizzly bear" is a common (rather than a scientific) name, so it doesn’t necessarily correspond to a specific subspecies. According to the NWF, many North Americans use "grizzly bear" to describe smaller and lighter-colored bears that live in interior areas, and "brown bear" for larger and darker bears in coastal areas. Regardless of how the name is used, all grizzly bears are members of the only brown bear species. 

Related: Mountain goat kills grizzly bear by stabbing it with razor-sharp horns

What do grizzly bears look like?

Grizzly bears are typically 3 to 5 feet (0.9 to 1.5 meters) tall at the shoulder when standing on all fours and can reach almost 9 feet (2.7 m) tall when standing on their hind legs. Males are heavier than females and weigh up to 860 pounds (390 kilograms), while females weigh up to 455 pounds (205 kg). Grizzlies are smaller than Kodiak bears and polar bears, which can both stand more than 10 feet (3 m) tall.  

Grizzly bears’ coat color can be anything from blond to black, according to the National Park Service. This wide variation in size and coat color means that these two features alone aren't surefire ways to tell grizzly bears apart from American black bears (Ursus americanus), which are typically smaller and darker — but not always.  

A more reliable method to distinguish grizzly bears from black bears is to look at a bear's body shape and tracks. All brown bears, including grizzly bears, have a pronounced shoulder hump that is higher than their rump. Black bears lack a hump, and their rumps are higher than their shoulders. Furthermore, grizzly bears have dish-shaped faces and short, round ears, while black bears have straight faces and taller, more oval-shaped ears, according to the NPS. Brown bears also have longer and straighter claws that leave marks in tracks more often than black bear claws do. 

Are grizzly bears dangerous?

Grizzly bears typically avoid people unless they perceive them as a threat to their cubs, food or territory. However, bears do sometimes attack and kill humans. Brown bears have killed 84 people in the U.S. and Canada since 1900, according to the Florida Museum of Natural History. The same records show that black bears have killed 78 people and polar bears have killed 11 people during the same period. 

The NPS recommends that people keep their distance from bears, make an effort to be noticeable when in a bear's environment and avoid surprising them. Bear behavior can be unpredictable, and there isn't a strategy to deal with bear attacks that will work in every situation.

According to the NPS, if attacked by a grizzly or brown bear, you should leave your backpack on (if you have one) and play dead by lying flat on your stomach with your hands clasped on the back of your neck and legs spread — this makes it harder for the bear to turn you over. Grizzlies usually attack with greater intensity if you fight back, so it's best to stay still until the bear leaves you alone. However, you should fight back vigorously if the attack persists by striking the bear in the face with anything available to you, according to the NPS. The NPS advice differs for black bear attacks: During a black bear attack, it is never advisable to play dead. Victims of black bear attacks should try to escape or fight back if no escape is possible. 

People who are in a tent when attacked by any bear, or stalked and then attacked, should not play dead and should instead immediately fight back. In this scenario, the bear sees humans as prey, the NPS says. 

Related: Woman killed in unusual grizzly bear attack

Where do grizzly bears live?

The vast majority of North American brown bears, which includes most grizzly bears, live in Alaska. The state is home to an estimated 30,000 brown bears, or about 95% of the total population, according to the Pacific Grove Museum of Natural History. Grizzly bears also live in Canada and the U.S. states of Washington, Idaho, Montana and Wyoming, according to the International Association for Bear Research and Management. 

Grizzly bears are adaptable and occupy different habitats across their range, including coastal areas, mixed-conifer forests, grasslands, mountainous forests and Arctic tundra, according to the Center for Biological Diversity. Individual bears live within home ranges that cover 50 to 150 square miles (130 to 390 square kilometers) for females and up to 600 square miles (1,555 square km) for males, and their ranges can overlap with other bears’ territories, according to the University of Montana's Grizzly Bear Recovery Program. 

Grizzlies are solitary but do sometimes interact with other bears. When grizzly bears rub trees with their backs, they're not trying to scratch an unbearable itch. Rather, they are communicating with one another by leaving their scent. They also use urine to mark their territory, and they communicate with other bears using sounds and movement, according to the Pacific Grove Museum of Natural History.

Grizzlies can be diurnal (active during the day) or nocturnal (active during the night), and they may switch their activity patterns if disturbed by humans. A 2013 study of bears in Yellowstone National Park, published in the Journal of Mammalogy, found that grizzly bears' peak period of activity varied from midday to evening depending on the season, suggesting that they also change their activity patterns based on food availability.  

What do grizzly bears eat?

Grizzlies are omnivores, which means they eat a mixed diet of vegetation and meat. A grizzly bear's diet can consist of fruit, nuts, leaves, roots or animals, which can be as small as insects or as large as ungulates, such as moose. 

The 2013 study of Yellowstone bears found that 70% of the bears’ elk calf kills took place at dusk or night, when the calves were likely easier to catch; the bears were therefore nocturnal during the calving season in late spring and early summer and became diurnal during the summer and early fall, when their diet shifted to roots, berries and nuts. A 2006 study into grizzly bear diet published in the Canadian Journal of Zoology found that grizzly bears eat more meat in areas where ungulates and spawning salmon are more abundant. 

Grizzly bears eat as much food as they can in the summer and fall to build up fat reserves before they enter dens and hibernate over winter. Grizzlies are excellent diggers and use their front claws to dig dens into hillsides, or they make their dens in rock caves, tree hollows or brush piles, according to San Diego Zoo. During hibernation, a grizzly's heart rate slows from 70 beats per minute to only 10 beats per minute;  metabolic activity also decreases, and the bear stops defecating. Hibernation time varies with the length of winter across the grizzlies' range, but they can stay in their dens for up to seven months living off their fat reserves. Captive grizzly bears that have access to food all year round, such as the bears in San Diego Zoo, may not hibernate at all. 

How do grizzly bears reproduce?

Grizzly bear mating season takes place from May to July, according to the University of Michigan's Animal Diversity Web (ADW). During that time, fertilized eggs start to develop in females, but implantation in the uterus is usually delayed until November when the female is hibernating. After a gestation period of six to eight weeks, a mother gives birth to between one and four grizzly bear cubs. Newborn cubs weigh between 12 and 24 ounces (340 and 680 grams) and are cared for by their mother in the den. 

Mothers stay with their cubs for at least two years before separating. Most grizzly bears live for up to 25 years in the wild, according to the NWF. However, some bears may live beyond 30 years. In 2020, a 34-year-old male grizzly bear monitored by scientists was caught in the Yellowstone region — although it was subsequently euthanized as it was in extremely poor physical condition and had begun attacking cattle, the Jackson Hole News & Guide, a newspaper in Wyoming, reported. 

Related: During Fat Bear Week, bears compete in a battle of the bulge

Are grizzly bears endangered?

The IUCN doesn’t consider brown bears to be an endangered species, and they are listed as Least Concern. However, this assessment covers all brown bears around the world and not grizzly bears in North America specifically. 

There were an estimated 50,000 grizzly bears spread across what is now the western U.S. until they were annihilated en masse in the 1800s by settlers, who tried to eradicate the bears. Thousands of grizzlies were shot, poisoned and trapped, and by the 1930s they were restricted to about 2% of their former range, according to the U.S. Fish & Wildlife Service. 

Grizzly bears became protected as a threatened species in the Lower 48 states in 1975, and it is illegal to kill them unless a person is defending themselves or another person. Grizzly bear hunting is legal but regulated in Alaska, where licensed hunters are permitted to kill bears with certain restrictions, such as not being allowed to target bears with cubs, according to the Alaska Department of Fish and Game. Today, it is estimated there are between 20,000 and 26,000 grizzly bears in Canada. There are about 30,000 grizzly bears in Alaska and an estimated 1,900 in the lower 48 states.  

Additional resources

To learn more about where the "grizzly bear" name came from, read parts 1 and 2 of "A Bear by Any Other Name: The Many Monikers of Ursus arctos" on the Alaska Department of Fish and Game website. For more information about bear attacks, check out "Bear Attacks: Their Causes and Avoidance" (Lyons Press, 2018), available to buy at Amazon. To see grizzly bears catching salmon, watch this short YouTube video by BBC Earth.  

Bibliography

Alaska Department of Fish and Game, "Black Bear Hunting in Alaska," 2021. https://www.adfg.alaska.gov/index.cfm%3Fadfg%3Dblackbearhunting.blackbrown

Dewey, T, and Ballenger, L. Animal Diversity Web, "Ursus arctos," 2002. https://animaldiversity.org/accounts/Ursus_arctos/

Center for Biological Diversity, "Grizzly bear." https://www.biologicaldiversity.org/species/mammals/grizzly_bear/natural_history.html

Fortin et al. "Temporal niche switching by grizzly bears but not American black bears in Yellowstone National Park," Journal of Mammalogy, Volume 94, Aug. 16, 2013. https://academic.oup.com/jmammal/article/94/4/833/895215

Florida Museum of Natural History, "International Shark Attack File: Bear Attacks," updated Feb. 11, 2021. https://www.floridamuseum.ufl.edu/shark-attacks/odds/compare-risk/bears/

Grizzly Bear Recovery Program, University of Montana, "Grizzly bear biology." https://www.cfc.umt.edu/grizzlybearrecovery/grizzly-bears/biology.php

Integrated Taxonomic Information System, "Ursus arctos Linnaeus, 1758," reviewed 1993. https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=180543

International Association for Bear Research and Management, "Brown bear." https://www.bearbiology.org/bear-species/brown-bear/

McLellan et al. "Ursus arctos," The IUCN Red List of Threatened Species, 2017. https://www.iucnredlist.org/species/41688/121229971

Koshmrl, M., Jackson Hole News & Guide, "Grizzly 168 brushes up against longevity records for North American bears," Jan 20, 2021. https://www.jhnewsandguide.com/news/environmental/grizzly-168-brushes-up-against-longevity-records-for-north-american-bears/article_d1786f9b-cd62-5ef4-ad53-7d0b3efdee5b.html

Mowat, G., and Heard, D. C. "Major components of grizzly bear diet across North America," Canadian Journal of Zoology, Volume 84, March 28, 2006. https://www.researchgate.net/publication/237973703_Major_components_of_grizzly_bear_diet_across_North_America

National Park Service, "Bear Identification," updated Oct. 26, 2021. https://www.nps.gov/articles/bear-identification.htm

National Park Service, "Grizzly Bear," updated Nov. 1, 2021. https://www.nps.gov/yell/learn/nature/grizzlybear.htm 

National Park Service, "Staying Safe Around Bears," updated April 13, 2018. https://www.nps.gov/subjects/bears/safety.htm

National Wildlife Federation, "Grizzly Bear." https://www.nwf.org/Educational-Resources/Wildlife-Guide/Mammals/Grizzly-Bear

Pacific Grove Museum of Natural History, "Brown Bears." https://www.pgmuseum.org/brownbear

San Diego Zoo, "Brown Bear," 2022. https://animals.sandiegozoo.org/animals/brown-bear

U.S. Fish & Wildlife Service, "Ursus arctos horribilis," 2021. https://www.fws.gov/species/brown-bear-ursus-arctos-horribilis

This article was originally written by Live Science contributor Alina Bradford and has since been updated.   

Editor's note: The numbers of grizzly bears in the U.S. and Canada was corrected at 3.26 a.m. on May 21, 2024.

The Arctic and Antarctica, while similar habitats in some ways, are home to very different creatures. Both poles host a variety of seal and whale species, but only the Arctic is home to Earth's largest bear, the polar bear.

Polar bears (Ursus maritimus) and their tumbly cubs can be found around the Arctic Circle in Alaska, Canada, Greenland (part of Denmark), Norway, Russia and, occasionally, Iceland. A polar bear's fur is specially suited for temperatures that can dip below minus 22 degrees Fahrenheit (minus 30 degrees Celsius). They live on ice for most of their lives, feeding on fat-rich seals that keep them energized for long periods between meals.

Antarctica also has sea ice, cold temperatures and seals. So why aren't there any polar bears on the southernmost continent?

The answer has to do with evolution and the geologic history of Earth.

Related: How do emperor penguin dads stop their eggs from freezing?

"Bears are largely a Northern Hemisphere phenomenon," said Andrew Derocher, a professor of biological sciences at the University of Alberta in Canada who has studied polar bears for nearly 40 years. Aside from the Andean bear (Tremarctos ornatus) of South America, bears appear only in the Northern Hemisphere. There's no specific reason for this, just that some species evolve in some places and some don't. "Biogeography is full of oddities," Derocher said. "Some species made it to new places and some didn't."

For polar bears specifically, there was never a time in their evolutionary history when the North and South poles were connected by ice (or land, for that matter). People say polar bears are the "biggest terrestrial carnivore in the world, and yet they're not a terrestrial species at all," Derocher told Live Science. The big, white bears live on sea ice for almost their entire lives, only occasionally coming ashore to breed.

Polar bears are, evolutionarily, a relatively young species. They evolved from a common ancestor of the brown bear (Ursus arctos) sometime between 5 million and 500,000 years ago, Derocher said. But even 5 million years ago, the continents were in similar positions to where they are today, so polar bears never got the opportunity to travel from pole to pole. The closest landmass to Antarctica is the southern tip of South America, which includes Chile and Argentina. To get to Antarctica, polar bears would have to cross the treacherous Drake Passage. The area is also known for powerful storms and rough seas as cold water from the south runs into warm water from the north.

But if polar bears got the opportunity, would they survive on the South Pole?

To Derocher, the answer is simple: "They would have so much fun in Antarctica."

In the Arctic, polar bears feed on seals and the occasional bird or egg. Antarctica is abundant in all three, with six seal species and five penguin species. Plus, none of those animals have evolved to be wary of large, land-roving predators. The Antarctic landscape would be a free-for-all buffet for a polar bear — which is why no one should ever bring polar bears there. Their voracious appetite, combined with the local faunas' ignorance of large land predators, would likely lead to ecological collapse. It's probably best for the great white bear to remain in the north.

Originally published on Live Science.

Dozens of polar bears have been making themselves at home in abandoned buildings on an Arctic island, and a Russian photographer recently captured remarkable photos of the bears peering through windows and standing on porches.

When photographer Dmitry Kokh traveled to the remote Russian region of northern Chukotka in late summer 2021, he was hoping to find polar bears to photograph on Wrangel Island, a natural reserve and World Heritage site that's protected by the United Nations Educational Scientific and Cultural Organization and is located above the Arctic Circle. 

What he found instead was a strange and unexpected sight: On the smaller Kolyuchin Island to the south of Wrangel Island, more than 20 polar bears had taken up residence in buildings that were once part of a Soviet weather station. Kokh photographed the polar bears in their dilapidated homes and shared the photos on his website and on Instagram, alongside other examples of his dramatic marine wildlife photography, and the images struck a chord with viewers and quickly went viral, Kokh told Live Science.

Related: Polar bear photos: Stunning shots capture Earth's icons of climate change 

As Kokh sailed 1,200 miles (2,000 kilometers) north to the islands from his starting point at Anadyr, the capital of Chukotka, he noticed that there was far more sea ice than is typical for Chukotka's northern coastline during the summer months. Abundant sea ice could explain why the bears were visiting Kolyuchin Island instead of sticking to their usual summer territories farther north, as polar bears use sea ice for hunting their seal prey, he said. 

Kolyuchin is so small, "you can see almost the whole island from your boat," he said, and while there was once a Russian weather station on the island, it was abandoned in 1991 after the Soviet Union collapsed. Shortly after Kokh's boat docked near Kolyuchin to wait out a storm, "we saw some movement in the window of this weather station — and then we saw that it was a bear," Kokh said. "We saw one, then we saw another one, then 20 of them. And they all were inside this building."

To capture the photos, Kokh used a camera mounted on an aerial drone that had been modified with low-noise propellers, making it quiet enough to slowly approach the bears without disturbing them. In the photos, the bears appear unconcerned about the camera and photographer — but when it comes to polar bears, looks can be deceiving, Kokh warned.

"Polar bears are very clever — and sometimes tricky — hunters," he said. "Sometimes they pretend they are not looking at you, and they are relaxed; at this moment, they are ready to attack." 

A nature reserve employee was with the group at all times, carrying a rifle and flares as precautionary measures to ensure the team's protection. Polar bears weigh up to 1,700 pounds (770 kilograms), but for all that bulk, they are surprisingly quick, capable of galloping up to 24 mph (40 km/h), according to McGill University.

Polar bears usually inhabit remote parts of the Arctic that are far from humans, but climate change is reshaping their habitat and has even driven bears to invade towns in the Russian Arctic in search of food. Since 1979, the sea ice that the bears depend on for hunting has shrunk and grown thinner, and researchers predict that summer sea ice could vanish from the Arctic by the end of the century, Live Science previously reported.

Though polar bears face an uncertain future, these images of the bears peering out from ramshackle buildings are a reminder that life on Earth can persist even as human-made objects and structures break down, Kokh told Live Science.

"But life will exist forever only if we care about it," he added.

Originally published on Live Science.

A "highly predatory" brown bear woke up from hibernation and killed 38 reindeer calves in a single month, then 18 young moose the next month, according to a new study.  

The unnamed 13-year-old female was one of 15 brown bears researchers tracked in northern Sweden to understand how the bears use their landscape. They found that the bears change habitats to target reindeer and moose calves in spring. The exact spaces bears occupied varied depending on how many calves they hunted, with some bears like the unnamed female killing more than others. 

Why are some bears more predatory? "It must be a combination of different factors," study co-author Antonio Uzal Fernandez, a senior lecturer in wildlife conservation at Nottingham Trent University in the U.K., told Live Science in an email, "such as innate behaviour related to personality (for instance, some people are more aggressive than others)." 

The researchers don't indicate these "highly predatory" bears pose anymore of a threat to humans. 

Related: 6 surprising facts about reindeer

Brown bears (Ursus arctos) are the most widely distributed bears on Earth; they can be found in 45 countries across North America, Europe and Asia, according to the International Union for Conservation of Nature. The new paper is part of a long-term project to study the lives of brown bears in Norway and Sweden. 

In the new study, researchers tracked bears with GPS collars between 2010 and 2012 and recorded the bears' kills. As the reindeer calving period begins, brown bears in Sweden move to the high-elevation, rugged terrain preferred by reindeer with young, and then on to habitats used by calving moose, such as near deciduous forests, according to a statement released by Nottingham Trent University. This allows them to hunt vulnerable calves. 

The team mapped the habitats different bears used and compared individual kill rates. Bears were called "high predatory" if they killed more than the average kill rate across all of the bears — 0.4 kill per day, and "low predatory" if they killed at a lower rate than that, according to the study. The team found some differences between where high- and low-predatory bears went. For example, high-predatory bears favored forested areas occupied by more reindeer than the more open areas low -predatory bears selected.  

Eight of the 15 bears were deemed to be highly predatory and regularly killed more than 20 reindeer calves and 5 moose calves in a calving period, according to the statement. Bears are not as effective at hunting larger adult prey and so they focus on hunting calves until July, after which the calving period ends and they rely on berries for the rest of the year until re-entering hibernation, according to the study. 

"Our study shows the differences between individual bears' predatory behaviour and how this helps to explain individual variation in their habitat selection," Fernandez said. "Differences among individuals are also important from a management perspective; for instance, mere predator removal, without targeting specific individuals, may not necessarily reduce conflict." That's because some bears are more aggressive and bolder than others.

Reindeer are semidomesticated in Sweden and herded by the Indigenous Sámi people. Every year, people kill bears in response to reindeer being attacked. The new findings may help researchers develop forecasts for potential bear-reindeer hotspots to help reduce this conflict, according to the study. The hotspots could inform livestock owners about where bears are most likely to attack during calving season and help them take preventative actions to reduce losses, such as increased vigilance in those areas, the researchers said. 

The findings were published Dec. 17 in the journal Diversity.

Originally published on Live Science.

People have smuggled hundreds of bear body parts — including polar bear parts — into Australia and New Zealand, a new study reveals. 

Enforcement agencies seized bear teeth, rugs, bile and embryos suspended in honey from passengers arriving in Australia and New Zealand from 2007 to 2018.

Most of the bear parts and derivatives, such as gallbladder bile, were ingredients in traditional medicines. The goods were most often seized from people traveling into Australia and New Zealand from China, but they also came from other countries such as the U.S. and Canada. 

"We knew we would find some records, but we never expected them to be in the hundreds or the diversity of products and number of countries from which they were being sourced/transported," lead author Phill Cassey, head of ecology and evolutionary biology at the University of Adelaide in Australia, told Live Science in an email. 

Related: Polar bear photos: Stunning shots capture Earth's icons of climate change 

Trade in wildlife threatens many species around the world, according to World Wildlife Fund (WWF). Bears are traded for their gallbladder bile, which is used in traditional Asian medicines, as well as their meat and body parts, such as those used as hunting trophies, according to the study. 

To gain a greater understanding of the bear trade, the researchers looked at countries that don't have their own wild bears. "We were intrigued to know how much of a role countries without native bears were playing in this trade," Cassey said. 

The research team found records of 781 seizures; 369 in Australia and 412 in New Zealand. They involved five of the eight bear species and all seizures were declared for "personal use." The number of seizures declined in Australia during the study period, from a peak of 74 in 2011 to 12 in 2018. There was no such decline in New Zealand. Though  2009 was a peak for seizures with 52 and 2018 was a low point with 13 seizures, the overall trend was more variable than Australia, with more than 40 seizures in 2017 for example.   

The items seized came from 33 countries spread around the world, with China being the reported origin of 37.7% of seizures in Australia and of 71.2% of seizures made in New Zealand, according to the study. The most common items seized were traditional medicines made out of bear bile, the researchers reported in the study published Nov. 4 in the journal Pacific Conservation Biology. 

Humans obtain bear bile by killing bears or by keeping them alive in cages in bear farms, where handlers regularly extract the bile, such as through a catheter inserted in their gallbladder, according to Animals Asia, a nonprofit working to end bear bile farming. 

Bear bile contains ursodeoxycholic acid, which can be used to reduce the absorption of cholesterol and  dissolve gallbladder stones in people, according to the Chemical Entities of Biological Interest (ChEBI) database. However, herbal and synthetic alternatives exist with the same properties and bear bile is used to treat many conditions that it does not benefit, such as hangovers, according to Animals Asia. 

The U.S. and Canada were the biggest source of bear body parts, such as teeth, claws and trophy heads. "North America is popular with trophy hunters," Cassey said. "Some legal hunting is still permitted in North America and Europe, and clearly Australians and New Zealanders are partaking in these activities." 

Travelers had legally procured some of these seized items, which were returned to them. That was the case far more often for trophies than it was for medicines, teeth and claws, the majority of which were illegal. The study highlights the demand for bear parts and their derivatives in countries without wild bears.

"The illegal wildlife trade is a global problem, which needs global solutions," Cassey said. "Just because Australia and New Zealand don't have any native bears doesn't mean they aren't part of the problem.

Originally published on Live Science.

A grizzly bear attacked a photographer's camera and ended up starring in a grisly photo that has won the photographer an award.

Zack Clothier, a professional photographer based in Montana, set up a camera trap pointing at an elk carcass hoping to get some shots of scavenging wildlife. He returned to find his camera setup trashed and one clear picture of the culprit: a large grizzly bear (Ursus arctos horribilis). 

The photo, called "Grizzly leftovers," captures the bear just before it lunges at the camera. Clothier found out his picture won the 2021 Wildlife Photographer of the Year prize for the Animals in their Environment category at an awards ceremony on Oct. 12. 

"I was in shock, I actually could not believe it," Clothier told Live Science. "I really like the image, it's definitely a unique image."

Related: Wow! Amazing undersea images

Clothier discovered the elk carcass near his home in Montana during the winter of 2019-2020. He set up a camera trap by sealing his camera in a case and placing it on a tripod by the carcass for about two months, until the beginning of spring, when bears start emerging from their winter dens. 

On his way back to the area where he left his camera, Clothier found bear tracks on the trail leading to the carcass. He checked another camera he'd set up to monitor the trail and saw footage of a large male grizzly bear making the tracks earlier that morning. 

"I hung around there for a little while just kind of making noise, just to spook anything off the carcass that may have been on it, especially that bear," Clothier said. When he didn't hear anything, he cautiously approached the carcass. 

Clothier found his camera case in rough shape at the base of a tree near the carcass. The camera had been ripped off its tripod and was pointing up in the air, with claw marks on the case and slobber all over the lens.

Fortunately, the camera survived the attack inside its case and Clothier retrieved the photos of the bear. Camera traps have an infrared sensor and take pictures when the sensor detects movement. Bears can be very protective of carcasses and the sound of the camera shutter may have startled the bear. 

"I think he just heard the sound and didn't like it, and decided to trash it," Clothier said. "I've had black bears do similar things. A lot of times it's more curiosity with them I think. They come up and inspect the camera and nose the lens and bite the case, and kind of bash it around a little bit. Bears definitely have something against camera traps."

"Grizzly leftovers" went on display with other photos from the 2021 Wildlife Photographer of the Year competition in London on Oct. 15. The exhibition will tour internationally, including to the U.S. 

Wildlife Photographer of the Year is developed and produced by the Natural History Museum, London. The museum is accepting entries for next year's competition starting Monday (Oct. 18) until 6:30 a.m. ET on Dec. 9.

Originally published on Live Science.

Arctic sea ice has been steadily decreasing since the beginning of satellite records in 1979, but a new study comes with a chilling (or perhaps, warming) prediction: By the end of this century, Arctic sea ice may disappear during the summer, which could drive polar bears and other ice-dependent species to extinction.

The "Last Ice Area" is a region containing the oldest, thickest Arctic ice. It spans an area of more than 380,000 square miles (1 million square kilometers) from the western coast of the Canadian Arctic Archipelago to Greenland's northern coast. When scientists named the 13-foot-thick (4 meters) ice region, they thought it would last for decades.

But now, under both the most optimistic and pessimistic scenarios for warming linked to climate change, the sea ice will dramatically thin by 2050. The most optimistic scenario, in which carbon emissions are immediately and drastically curbed to prevent the worst warming, could result in a limited portion of the ice surviving in the region. In the most pessimistic scenario, in which emissions continue at their current rate of increase, the summer ice — and the polar bears and seals that live on it — could disappear by 2100, researchers reported in a new study. 

Related: Images of melt: See Earth's vanishing ice

"Unfortunately, this is a massive experiment we're doing," study co-author Robert Newton, a senior research scientist at Columbia University's Lamont-Doherty Earth Observatory, said in a statement. "If the year-round ice goes away, entire ice-dependent ecosystems will collapse, and something new will begin."

Arctic sea-ice cover grows and shrinks each year, reaching its minimum extent at the end of the summer melt season in September before rebounding in the fall and winter to reach its maximum extent in March. But as carbon dioxide and other greenhouse gases increasingly contribute to the warming of the atmosphere, the span of the sea ice has yo-yoed between ever shrinking bounds — with the past 15 years bringing the lowest 15 sea-ice extents in the satellite record, according to the National Snow and Ice Data Center (NSIDC). 

Worse still, the NSIDC reports that the amount of older, thicker Arctic ice that has survived at least one melt season is at a record low, around a quarter of the total recorded by the first satellite surveys 40 years ago. 

A more dramatic decrease in ice coverage could have a crippling effect on the lives of the animals that dwell on, or under, the shifting ice network, including photosynthetic algae, tiny crustaceans, fish, seals, narwhals, bowhead whales and polar bears. 

"Ringed seals and polar bears, for example, have relied on their dens in the ridged and corrugated sea-ice surface to stay approximately in one place," the researchers wrote. 

Because they are specialized predators, polar bears (Ursus maritimus) would be especially vulnerable to extinction if the ice were to disappear. Adapted to lurk atop sea ice, the Arctic bears hunt by snatching unfortunate seals that come to the surface to breathe. Polar bears have jaws adapted for consuming soft blubber and meat; and though the bears have been seen shifting their diet to seabird eggs and caribou while on land, a 2015 study published in the journal Frontiers in Ecology and the Environment found that the calories they gain from these sources do not balance out those the bears burn from foraging for these animals, Live Science previously reported. 

This rapid habitat shift could cause polar bears to become extinct or lead to more extensive interbreeding with grizzly bears (Ursus arctos horribilis), whose ranges are expanding northward as the climate warms, Live Science previously reported. This process could eventually replace polar bears with hybrid "pizzly" bears. Nonetheless, in the more pessimistic, increasing-emission scenario, the researchers expect the summer ice and the ice-dependent ecosystem to disappear.

"This is not to say it will be a barren, lifeless environment," Newton said. "New things will emerge, but it may take some time for new creatures to invade." The researchers suggested that fish and photosynthetic algae may make their way northward from the North Atlantic, although they are uncertain if the new habitat would be stable enough to support those organisms year-round, especially during the long, sunless Arctic winter.

Even a partially melted Arctic could also create a positive feedback loop: The water's surface is darker and more efficient at absorbing sunlight, meaning the melt would accelerate the overall rate of warming, in a vicious cycle.

On Aug. 9, a landmark report from the U.N.'s Intergovernmental Panel on Climate Change (IPCC) issued a stark warning that Earth is expected to reach a critical threshold: a global temperature increase of 1.5 degrees Celsius (2.7 degrees Fahrenheit) due to climate change within the next 20 years. A draft third section of the IPCC report leaked to the Spanish publication CTXT warned that global greenhouse gas emissions must peak in the next four years if global heating is to remain within 1.5 C.

The researchers published their findings Sept. 2 in the journal Earth's Future.

Originally published on Live Science.

Picture a polar bear stalking an unsuspecting walrus in the frozen Arctic: The predator slowly inches closer, camouflaged by ice and snow, until it's close enough to pounce. And then it delivers the killing blow — by bopping the walrus on the head with a large rock.

That might sound like something you'd see in a cartoon, rather than in nature. But for centuries, Inuit people in the Arctic have shared such stories with non-Native explorers and naturalists, describing polar bears killing or stunning prey with stones and chunks of ice that the bears grasp in their paws (or throw off cliffs onto animals at the bottom, according to a memorable 19th-century engraving).

A new study looked at Inuit anecdotes describing this behavior — "from a diversity of locations and over a long period of time" — and found they were so widespread and consistent that they suggested that in rare cases, polar bears likely wield such objects as weapons. However, until scientific researchers actually catch the Arctic bears in the act of bludgeoning walruses, it's hard to say for sure.

Related: Polar bear photos: Stunning shots capture Earth's icons of climate change

"I have always been impressed with the accuracy and reliability of the observations of animals reported by experienced Inuit hunters, so I thought it was likely the accounts might not just be myths but the result of reporting of actual observations, even though the behavior itself is likely quite rare," study lead author Ian Stirling, a member of the Scientific Advisory Council for Polar Bears International and an adjunct professor in the Department of Biological Sciences at the University of Alberta, told Live Science in an email.

Inuit descriptions of polar bears (Ursus maritimus) hoisting — and sometimes hurling — hefty blocks of rock or ice date to the late 1700s, according to the study. In a description that naturalist Otto Fabricius wrote in 1780 in the book "Fauna Groenlandica," polar bears grab sizable ice chunks and launch them at walruses' heads.

"The bear makes it [the walrus] lose its balance (or 'stagger' is more literal) and thus kills it easily," the scientists wrote in the June issue of the journal Arctic.

An Inuit account from 1883 described another ice-chucking bear that "seized a mass of ice in his paws, reared himself on his hind legs, and threw the ice with great force on the head of a half-grown walrus." A 1925 record of another Inuit report noted that a polar bear "carefully selected a young walrus and threw the ice block down upon it with such a force that it became immobilized," the study authors wrote.

In one astonishing example, illustrated by the 19th-century Arctic explorer Charles Francis Hall, a polar bear allegedly threw a boulder onto a walrus's head from atop a tall cliff. Hall published an engraving of the scene in 1865, basing it on a description by his Inuk guide from Baffin Island.

"The bear mounts the cliff, and throws down upon the animal's head a large rock, calculating the distance and the curve with astonishing accuracy, and thus crushing the thick bullet-proof skull," Hall wrote in the book "Arctic researches, and life among the Esquimaux" (Harper & Brothers, 1865).

"If the walrus is not instantly killed — simply stunned — the bear rushes down to the walrus, seizes the rock, and hammers away at the head till the skull is broken," Hall concluded, according to the study. 

Tools in captivity

The scientists also reviewed more recent reports, by Inuit and non-Inuit witnesses, that suggested the bears used rocks and ice for hunting and for disabling human hunters' traps. But these conclusions were based on the placement of rocks and ice that the bears had left behind and did not reflect observations of the bears actually using the objects as tools, the scientists wrote.

However, in 2010, photos showed a captive male polar bear named GoGo at the Tennoji Zoological Gardens in Osaka, Japan, using "tools" in his enclosure to reach a piece of food. Caregivers had hung a piece of meat about 10 feet (3 meters) above GoGo's pool — too high for him to grab — "to provide stimulation and distract his attention" by challenging GoGo with solving this puzzle, according to the study. 

At first, GoGo tried jumping at the meat. But after a month of failure, he "invented" two tools: a piece of plastic pipe that he chucked at the food, and a branch measuring around 7 feet (2 m) that he used to smack the meat and knock it off its hook. Initially, GoGo took several hours to succeed, but he was soon able to knock down the meat in just 5 minutes, the researchers reported.

GoGo's example, together with centuries of anecdotes and other recent observations, hints that tool use for hunting among wild polar bears — though likely not a common occurrence — is certainly possible, according to the study. 

"An occasional adult polar bear might be capable of mentally conceptualizing a similar use of a piece of ice or a stone as a tool," the study authors reported. However, such extreme measures are probably used only for the biggest prey that polar bears hunt: walruses.

Polar bears prey on walruses and seals, but walruses are much more formidable targets. While an adult ringed seal (Pusa hispida) may weigh up to 165 pounds (75 kilograms), a 2-year-old walrus (Odobenus rosmarus) can weigh a whopping 750 pounds (340 kg) and full-grown adults may weigh as much as 2,000 pounds (907 kg), according to the Alaska Department of Fish and Game. What's more, walruses have long tusks to defend themselves during melee encounters, and their skulls are denser and harder to crack than seal skulls, Erica Hill, a professor of anthropology at the University of Alaska Southeast, reported in 2017 in the journal Études/Inuit/Studies. (Hill was not involved in the recent study.)

The targets of occasional boulder hurling by adult polar bears are therefore most likely to be walruses, the researchers concluded.

Originally published on Live Science.

DNA extracted from a 32,500-year-old bear skull hints that ice age brown bears migrated to Honshu, Japan's largest island and lived near present-day Tokyo before eventually dying out.

Today, Japan's only brown bears (Ursus arctos) live in Hokkaido, the northernmost island in the Japanese archipelago. Evidence suggests that the ancestors of these bears migrated to the island from Sakhalin, an island just north of Hokkaido that is now part of present-day Russia. The bears likely lumbered over a land bridge that connected Sakhalin and Hokkaido at various points in the Pleistocene, a time period that lasted from 2.6 million to about 11,700 years ago.

Although brown bears no longer traipse around Tokyo, their fossils — dated between 340,000 and 20,000 years old —have been discovered in several locations on Honshu Island, researchers noted in a new report, published Tuesday (Aug. 3) in the journal Royal Society Open Science. That raises the questions of when and how the Honshu bears first got to the island, but unfortunately, there's little fossil evidence of the beasts' migration.

Related: Genetics by the numbers: 10 tantalizing tales 

"The number of brown bear fossils excavated from the Pleistocene in Japan is scarce, with less than ten incomplete specimens," lead author Takahiro Segawa, a senior assistant professor at the University of Yamanashi's Center for Life Science Research in Japan, told Live Science in an email. 

But one unique specimen, excavated from a cave in the Gunma Prefecture, northwest of the Greater Tokyo area, includes the skull of a bear, complete with right and left petrosals — dense portions of the temporal bones that surround the inner ear. 

The dense structure of petrosals helps shield ancient DNA from degradation, so these bone fragments retain more DNA than other fossilized bones, according to a 2015 report in the journal PLOS One. Knowing this, the research team collected a tiny amount of powdered petrosal from the brown bear skull and brought it to their lab for DNA analysis.

The samples were roughly 32,700 to 32,200 years old, the team determined. The team then compared recovered genetic sequences from the petrosals with 95 near-complete genomes from other brown bears, including all those available from the nearby Hokkaido lineages. 

Based on this analysis, they concluded that the Honshu bear belonged to a "previously unknown lineage" that split off from its sister lineage, the so-called Southern Hokkaido brown bear clade, about 160,000 years ago. The authors theorize that the bears crossed the Tsugaru strait, which separates Hokkaido and Honshu, sometime around that split. 

Related: 10 amazing things you didn't know about animals

And in fact, fossil evidence suggests that other large mammals, including Naumann's elephants (Palaeoloxodon naumanni) and the giant deer (Sinomegaceros yabei), crossed from Hokkaido and Honshu a few thousand years later, around 140,000 years ago, during a glacial period when sea levels were low, according to a 2005 report in the journal Paleoceanography and Paleoclimatology. Brown bears may have taken advantage of the same shallow waters to reach Honshu, the authors suggested. 

The oldest brown bear fossil ever found in Honshu is estimated to be 340,000 years old, the authors noted. That fossil was uncovered in a limestone quarry at the northernmost point of Honshu, and the specimen predates both the Honshu bear skull and the Southern Hokkaido clade. This suggests that different lineages of brown bear ventured to Honshu at different times — once more than 340,000 years ago, and then again during the late Pleistocene. 

Whenever they reached the island, "for reasons unknown, the bears were extirpated by the end of the late Pleistocene in Honshu," along with the Naumann's elephants, giant deer and other large mammals, like bison (Bison priscus), the authors wrote in the study. The exact timing and reason for these animals' disappearance remains shrouded in mystery. 

Originally published on Live Science. 

Polar bears (Ursus maritimus) are the largest bear species and the biggest land carnivores in the world. The enormous bears live in the Arctic, where they prowl the icy expanse searching for seals, their preferred prey. 

Polar bears likely evolved within the last 500,000 years when a population of brown bears traveled north into the Arctic during a warm period and became isolated. When temperatures dropped again, the bears were forced to adapt to the colder environment, according to Aarhus University's Arctic Research Centre in Denmark. 

Polar bears have many adaptations for life in the frigid Arctic, including dense fur and a thick layer of fat to keep them warm, as well as small bumps under their paws to stop them from slipping on the ice, according to Polar Bears International. They are excellent swimmers, and their scientific name, Ursus maritimus, translates to "sea bear," according to the San Diego Zoo. Polar bears depend heavily on the ocean environment and are the only bears to be considered marine mammals. 

Related: Polar bear photos: Stunning shots capture Earth's icons of climate change 

Size & appearance

Polar bears are usually 3.5 to 5 feet (1 to 1.5 meters) tall at the shoulder on all fours, but an adult male may reach more than 10 feet (3 m) when standing on its hind legs, according to Polar Bears International. In 1960, a polar bear that was killed in Alaska stood 12 feet (3.7 m) tall on its hind legs, according to the National Wildlife Federation. 

Male polar bears usually weigh between 770 pounds and more than 1,300 pounds (350 to 600 kilograms). The 12-foot-tall Alaskan bear shot in 1960 is the heaviest recorded bear and weighed 2,210 pounds (1,000 kg). Females weigh half as much as their male counterparts, at 330 to 650 pounds (150 to 295 kg), according to Polar Bears International.

Polar bear fur appears to be white but it's actually transparent; the white appearance is due to visible light scattering and reflecting back off clear, hollow strands of hair, according to Polar Bears International. Their white appearance enables the bears to blend in with their snow-covered, icy environment. Polar bears can also appear yellowish or even brown and gray, depending on the season and light conditions. Polar bear skin is black and absorbs the heat of the sun, which helps keep the bears warm.

Polar bears vs. Kodiak bears

Polar bears are the biggest bear species, but Kodiak bears, a subspecies, or type of brown bear, can grow to about the same size as some polar bears. Kodiak bears live on islands in the Kodiak Archipelago off southern Alaska, where they have been isolated from other brown bears for about 12,000 years, according to the Alaska Department of Fish and Game. These brown bears can stand over 10 feet (3m) tall on their hind legs and weigh up to 1,500 pounds (680 kg), according to the Alaska Department of Fish and Game. 

Some sources, such as the Alaska Department of Fish and Game, claim that Kodiak bears are the largest bears on Earth. The confusion is partly due to the way that "largest" is defined, because the answer varies depending on whether bears are measured by length, weight, or by the largest individual ever recorded, according to the Library of Congress in Washington, D.C. Polar bears are heavier and taller on average, but individual Kodiak bears may be larger than average-size polar bears.  

Where do polar bears live?

Polar bears live on the ice-covered waters of the Arctic and countries around the Arctic Circle, including Canada, Alaska in the U.S., Greenland (part of Denmark), Norway, Russia and occasionally Iceland, according to the International Union for Conservation of Nature (IUCN). They are not found in Antarctica, where penguins live. 

Some polar bears stay on permanently frozen sea ice in the Arctic Basin, but most live on the annual sea ice that forms around the Arctic Basin. This annual sea ice melts in the summer, so polar bears are forced to spend several months on land while they wait for it to freeze over again, according to the IUCN.

Polar bears swim between sea ice and the shore, hunting down prey, searching for mates, or just cooling off. They paddle through the water with their big front paws and use their back legs as rudders, according to Sea World. They also have webbing between their toes, similar to ducks' feet, which helps them swim.

Polar bears have been recorded swimming for nearly 10 days at a time and traveling up to 427 miles (687 kilometers) in a single swim without stopping to rest, Live Science previously reported. Long swims like this put polar bears at risk of drowning, but they may be forced to undertake such great journeys more often as warming temperatures associated with climate change melt sea ice in the Arctic.

Related: Sweating the details: Polar bear hits the treadmill for science

What do polar bears eat?

Polar bears are the most carnivorous bear species and almost exclusively eat meat. Their primary prey are ringed seals (Pusa hispida), according to the National Wildlife Federation. Polar bears will sit by a seal breathing hole waiting for a seal to pop up so they can grab it. The bears will also sniff out seal dens, then crash through the roof and kill the seals inside.

If polar bears have a plentiful supply of seals and are in good health, they'll only eat the seal's blubber, according to Polar Bears International. This is the highest calorie meal available to polar bears and helps them build up fat reserves and stay healthy between feedings. Polar bears can consume 4.4 pounds (2 kg) of fat each day, according to the World Wildlife Fund (WWF). 

Polar bears will also hunt walruses, sea birds, fish and small mammals such as rodents; scavenge on whale carcasses and other dead animals; and eat small amounts of vegetation, according to the University of Michigan's Animal Diversity Web (ADW). However, these are alternative food sources when seals aren't plentiful; seals are crucial to sustaining a polar bear population. Polar bears are top of the food chain and have no natural predators other than humans. 

Related: Polar bears now eat dolphins, thanks to global warming 

Life in the cold

Polar bears are solitary except for when a mother is raising her cubs. However, unrelated bears will occasionally be seen together, such as when they share a large whale carcass or garbage dump, or when they are waiting on land for sea ice to re-form, according to Sea World. They do not defend territories, but polar bears may occasionally fight over a carcass, and males may fight over a female during the breeding season, between March and June. 

Male polar bears find females by following their scent, and the pair may spend a week or more with each other. After mating, fertilized eggs don't enter the female's uterus straight away, and this process is delayed until usually September or November, according to the San Diego Zoo. Polar bears have a gestation period of up to about seven months including this delayed implantation. Pregnant females will dig a cave in a snowbank to give birth in; called a maternity den. Polar bears do not hibernate in winter, unlike most brown bears and black bears, and will continue to hunt unless the weather is extremely harsh. 

A female polar bear gives birth in her den, typically to twins in December or January. Newborn polar bear cubs usually weigh just 1.3 pounds (0.6 kg), according to the San Diego Zoo. The cubs grow quickly on their mother's milk and will start exploring outside their den by spring, although they don't travel far for the first 12 days or more and still sleep inside the den at night, according to Sea World. Polar bear cubs stay with their mother for up to three years learning how to survive. Wild polar bears usually live for 15 to 18 years but can survive into their 30s, according to Polar Bears International. A captive polar bear called Debby lived to be 42 years old in Assiniboine Park Zoo in Canada. She was believed to be the world’s oldest polar bear when she died in 2008, according to Reuters.

Related: Polar bear body cam shows predator's POV

Are polar bears dangerous to humans?

Polar bears rarely attack humans. A 2017 study published in the journal Wildlife Society Bulletin cataloged 73 confirmed polar bear attacks between 1870 and 2014, including 20 fatalities. The researchers found that nutritionally stressed male bears were most likely to attack humans and that most attacks were predatory, meaning the bear was killing for food. Polar bear attacks increased over the study period, which is likely due to changes in their environment. 

"The danger is the proximity to people, coupled with an increasing number of polar bears in poor body condition spending more time on shore. Both people and bears are trying to adapt to rapid changes on the ground and at sea," Geoff York, study co-author and senior director of conservation at Polar Bears International, said in a statement at the time. As sea ice declines and moves further from the shore, more polar bears spend longer periods on land, such as in Hudson Bay in northeastern Canada. 

"Bears are now having to make a choice as the ice melts each year: Do they stay on the ice and retreat with it into deep Arctic waters or do they jump, come to shore, and take their chances on land?" York said. "Those who come ashore may come into conflict with human communities or activities. And as they get more desperate for food, they may well take higher risks."

Related: 52 polar bears 'invade' a Russian town to eat garbage instead of starve to death

Are polar bears endangered?

Polar bears are vulnerable to extinction, according to the IUCN Red List of Threatened Species. Climate change poses the biggest threat to their long-term survival as increasing temperatures cause the Arctic sea ice they depend on to shrink. They are also threatened by other human-related activities, such as oil and gas drilling in the Arctic, which increases the risk of negative human-bear interactions. 

There are only about 26,000 polar bears living in the wild, according to the IUCN. However, estimating the number of polar bears is difficult because they live in such remote habitats at low densities, and information about their subpopulations is often poor or outdated. Polar bears are listed on the U.S. Endangered Species List as threatened and are protected under the Marine Mammal Protection Act.

Inuit and Indigenous people still hunt polar bears for food and clothing as part of long-held cultural traditions, but this hunting is carefully regulated. The Inuit people have long believed that polar bears, which they call "Nanuq," are wise, powerful and almost human, according to Polar Bears International.  

Related: 'Pizzly' bear hybrids are spreading across the Arctic thanks to climate change

Additional resources

• The United States Geological Survey carries out long-term research on polar bears
• Polar Bears International has more information about polar bears and conservation efforts to save them.  
• Children's Book: "The Polar Bear" (Enchanted Lion Books, 2016). 

This article was originally written by Live Science contributor Alina Bradford and has since been updated.  

Early Tuesday morning (July 6), a bear attacked and killed a woman while she was camping in western Montana. Local authorities are still searching for the animal.

The attack took place near Ovando, about 70 miles (112 kilometers) northwest of the state capital Helena, according to KGVO News. A statement from Montana Fish, Wildlife and Parks (FWP) noted that, prior to the attack, a video camera at a local business caught footage of the animal, which appeared to be a grizzly bear. Grizzlies are common to Ovando and the surrounding Blackfoot Valley, according to the statement. 

As of late Wednesday (July 8), the bear had still not been found, The Washington Post reported. The camper has now been identified as Leah Davis Lokan, a 65-year-old resident of Chico, California, who was passing through the area on a long-distance biking trip. She was accompanied by her sister and a friend, who heard Lokan being attacked by the bear at about 3:30 a.m. local time and drove the animal away with bear spray. The bear initially passed by their campsite about a half-hour earlier, waking the campers and prompting them to secure their food before going back to bed.

"The bear basically came back into the campsite. It wandered into a campsite a couple different times," Powell County Sheriff Gavin Roselles told The Associated Press.

Based on an examination of the bear's footprints and the descriptions of its behavior, FWP determined the animal is likely male and weighs about 400 pounds (181 kilograms), the Post reported. DNA collected at the scene will be used to identify the bear should it get caught in one of the five traps the agency has set so far, according to The Daily Montanan. In addition, helicopters equipped with infrared sensors have already been deployed three times to search for the animal, the agency stated.  

Once caught, the bear will be killed, making it the second grizzly to be killed by FWP this summer for fatally injuring a human, FWP official Greg Lemon told the Daily Montanan. 

It's not clear why the bear sought out the campsite or attacked Lokan, but Tuesday's attack does not represent "normal bear behavior," Lemon said. "Usually, human and bear conflicts stem from bears protecting food, female bears protecting cubs or surprise encounters that result in the bear feeling threatened and attacking the person. … Going into a campground and attacking a person is not a natural instinct."

This is the second deadly bear attack to occur in the region in recent months. In April, backcountry guide Charles Mock sustained fatal injuries from a male grizzly outside West Yellowstone, The New York Times reported. After the April attack, FWP spokesperson Morgan Jacobsen told the Times that the likelihood of human-grizzly encounters will likely rise as the population of federally protected bears grows and the bears expand their territory. At the same time, the number of people living in the region continues to grow. 

In general, conflicts between grizzlies and humans have increased in the Northern Rockies over the past 10 years, as the local bear populations have slowly recovered, according to The Associated Press. Ovando sits at the southern edge of the Northern Continental Divide Ecosystem, where an estimated 1,000 grizzly bears live; in total, fewer than 1,500 grizzlies live in the U.S. south of Canada, according to the National Wildlife Federation. (About 31,000 live in Alaska.)

In the last 20 years, there have been about 20 incidents near the Continental Divide in which people required hospitalization after being injured by bears, the AP reported. And in the past 50 years, 11 fatal bear attacks have taken place in the region, making the occurrence fairly rare. Tuesday's attack counts among those 11, while the April attack took place in the nearby Greater Yellowstone Ecosystem, which hosts a separate population of bears, the Washington Post reported.

Originally published on Live Science.

American black bears (Ursus americanus), often simply called black bears, are the most common bears in North America. They live in northern Mexico, the U.S. and Canada. Black bears are smaller than brown bears (Ursus arctos) and polar bears (Ursus maritimus), making them the smallest of the three species of bears in North America.

Black bears are excellent climbers and use their curved claws to scale trees and access food, such as nuts and honeycombs. On the ground, they are powerful runners and can reach speeds of up to 35 mph (56 km/h), according to the U.S National Park Service (NPS). 

Black bears are usually black, as their name suggests, but their coats may also be brown, cinnamon-colored or even white, according to the International Association for Bear Research and Management (IBA). This coat variation means they're occasionally mistaken for brown bears, especially where the ranges of the two species overlap in the northwest of the U.S. and Canada. 

Related: Un-bear-ably cute: Black bear caught napping 

How to identify a black bear

Black bears are usually about 3 feet (0.9 meters) tall at the shoulder when standing on all fours, and up to 7 feet (2.1 m) tall when standing upright on two legs, according to the NPS. Brown bears are a bit bigger, typically 3 to 5 feet (0.9 to 1.5 m) tall at the shoulder and almost 9 feet (2.7 m) tall when standing upright. 

A black bear's size and weight vary depending on its age and the time of year. Male black bears are up to 60% bigger than females, weighing up to 660 pounds (300 kilograms), while females only reach 175 lbs. (80 kg), according to the IBA. In contrast, male brown bears can weigh up to 860 lbs. (390 kg) and females up to 455 lbs. (205 kg). 

Although brown bears are bigger than black bears and usually have lighter-colored coats, the NPS suggests that other characteristics, such as the shape of the bear's body and their tracks, are a more reliable way to identify each species. Black bears do not have a pronounced shoulder hump, and their shoulders are lower than their rump when standing on all fours. Brown bears, on the other hand, have a clear shoulder hump that is higher than their rump. 

Black bears also have straighter faces than brown bears when viewed from the side, and have taller, more oval-shaped ears, according to the NPS. Their front claws are less than 2 inches (5 centimeters) long and are shorter than brown bear claws, which are 2 to 4 inches (5 to 10 cm) long. Black bear claws are also more curved than brown bear claws and appear in bear tracks less often. Toe prints are more separated and arced in black bear tracks than brown bear tracks, and claw marks are closer to the foot pad (when they are visible).

Where do black bears live?

Black bears range from northern Mexico, through the U.S., to northern Canada. They are found in 32 U.S. states and every province in Canada except Prince Edward Island, according to the IBA. Black bears are usually found in coniferous and deciduous forests, but their broad diet enables them to also use other types of habitat, including open alpine areas, according to The National Wildlife Federation.

Brown bears live in the western region of the black bears' range, including western Canada and U.S. states such as Alaska, Washington and Idaho. Black bears also live so far north that their range overlaps with polar bears along the northern coastlines of Canada, such as in Ontario and Québec, according to the International Union for Conservation of Nature (IUCN).  

Are black bears dangerous?

Bears don't normally harm humans and often avoid encounters with people. However, bears occasionally attack to defend their cubs or food, and on extremely rare occasions kill humans to eat them. Seventy-eight people have been killed by black bears in the U.S. and Canada since 1900, compared to 84 killed by brown bears, according to the Florida Museum of Natural History. A 2011 study published in the Journal of Wildlife Management found that most fatal black bear attacks are caused by predatory male black bears. Predatory attacks occur when a bear attacks a human they see as prey. 

Related: Hiking in bear country? How to prevent an attack

The NPS recommends that people keep their distance from wild bears and avoid surprising them. If attacked by a black bear, a victim should fight back. Playing dead doesn't fool black bears (although it might work with brown bears), so if a victim is unable to escape to a car or another secure location, they should use whatever objects are available and strike the bear in its face and muzzle. 

What do black bears eat?

Black bears are omnivores and eat both plants and animals, with a wide diet that varies depending on their location and the time of year. Most of their diet is made up of insects, nuts, berries, grasses and other vegetation, according to the IBA.

Black bears are not active predators and only hunt when an opportunity for prey presents itself. Most of the vertebrates they eat are already dead, according to the University of Michigan's Animal Diversity Web (ADW). If they do decide to hunt, black bears will go after young, hoofed mammals, such as elk, moose and other deer species, according to The National Wildlife Federation. Black bears in Canada and Alaska also feed on salmon.

Breeding and hibernation

Black bears are usually solitary except for the breeding season and when a female is raising her cubs, according to the Kentucky Department of Fish & Wildlife Resources. Males will seek out females for mating during the breeding season in June and July. Once she's mated, a female black bear's fertilized eggs won't enter her uterus until the autumn, in a process called delayed implantation, according to ADW. This delay, followed by a 220-day gestation period, allows females to give birth in their winter dens, typically during hibernation. 

Bears usually fatten up in late summer and fall as they prepare to hibernate through the winter months, from about November to March. They may feed for up to 20 hours, consuming up to 20,000 calories per day during this period, according to the Pennsylvania Game Commission. 

Black bears create their dens in the ground, under a windfall or in a hollow tree or cave, or use a previously occupied animal den, according to the NPS. The hibernation length varies across the black bears' range. Black bears in Mexico, for example, may not need to hibernate at all as the climate is mild and food remains available through winter. In contrast, black bears living in the colder environment of northern Alaska hibernate for about 7 months, according to Alaska Department of Fish and Game.

During hibernation, black bears lower their body temperature and heart rate and suppress their metabolism by 75% to reduce their energy needs, Live Science previously reported. They survive off fat reserves built up in late summer and fall but maintain much of their muscle mass so they don't become weak.

Female black bears typically give birth to two or three offspring in February during hibernation. Baby black bears, called cubs, weigh just 7 to 11 ounces (200 to 310 grams) at birth, according to the Arizona-Sonora Desert Museum. Black bear cubs stay in the den with their mothers until spring. The cubs are weaned before they reach 8 months old, but they won't leave their mothers until they are about 17 months old, after hibernating with her during their second winter, according to ADW. 

Black bears can live more than 30 years in the wild. The oldest black bear on record was a female in Minnesota that reached 39, according to the Florida Fish and Wildlife Conservation Commission (FWC). However, most black bears only live to be about 10 years old and die well short of their maximum lifespan, according to ADW. The main causes of death for adult black bears are vehicle collisions, hunting and starvation due to a lack of available food, according to the Florida Fish and Wildlife Conservation Commission.

Types of black bear

American black bears only live in North America. Black bears in Asia are called Asiatic black bears (Ursus thibetanus), or moon bears, and are a separate species from American black bears. 

The Integrated Taxonomic Information System (ITIS) recognizes 16 different subspecies of American black bear, often named after the parts of North America they inhabit. For example, there are Florida black bears (Ursus americanus floridanus) and California black bears (Ursus americanus californiensis), although these bears are not just confined to these states. Cinnamon bears (Ursus americanus cinnamomum) get their name because they often have cinnamon-colored coats.  

kermode bears or spirit bears

Kermode bears (Ursus americanus kermodei) are a subspecies of black bear in British Columbia, Canada that are sometimes white. White Kermode bears are also known as spirit bears, although they are part of the Kermode population and are not a separate subspecies. The highest concentration of spirit bears is found on Gribbell Island, off the north coast of British Columbia, where one-third of the black bears on the island are born white, according to The National Wildlife Federation. 

Spirit bears' white coats are caused by a mutation in a gene called mc1r. The gene is recessive, which means a bear cub will only be white if both of its parents carry the gene, according to The National Wildlife Federation. If only one parent carries the recessive gene then the cub will have a normal, black coat. 

A 2009 study published in the Biological Journal of the Linnean Society found that white black bears are better at catching salmon than normal black bears during the day. This could be because the fish find it harder to see the white bears overhead as lighter coats blend in better with a bright sky background than black coats.  

Conservation status

American black bears are not endangered and are categorized as a species of least concern on the IUCN Red List of Threatened Species, which means the species is at low risk of extinction. The black bear population is estimated to be twice as large as all other bear populations around the world combined. In fact, while many bear species are in decline, such as Asiatic black bears, the American black bear population is increasing, overall. 

Related: Real-life 'teddy bear' is no longer endangered

However, black bears are threatened in some parts of their range. Black bears are considered nationally endangered in Mexico due to deforestation, hunting and other human activities. Hunting black bears was banned in Mexico in 1985, and the population is now recovering and expanding thanks to conservation efforts, according to the IUCN. 

Bears are regularly hunted and killed in the U.S. and Canada, but this is controlled and managed by state and provincial agencies. Other common threats to bears include residential and commercial development, agriculture, road building and high traffic densities.

Additional resources

• The IUCN Red List of Threatened Species website has a map showing where black bears live.  
• Book: "Bear Attacks: Their Causes and Avoidance" (Lyons Press, 2018). Available to buy at Amazon. 
• The Royal BC Museum website offers more information on Kermode spirit bears.  

Endangered polar bears are breeding with grizzly bears, creating hybrid “pizzly” bears, and it's being driven by climate change, scientists say. 

As the world warms and Arctic sea ice thins, starving polar bears are being driven ever further south, where they meet grizzlies, whose ranges are expanding northwards. And with that growing contact between the two species comes more mating, and therefore increased sightings of their hybrid offspring.

With features that could give them an edge in warming northern habitats, some scientists speculate that the pizzlies, or "grolars", could be here to stay.

Related: Polar bear photos: Stunning shots capture Earth's icons of climate change

"Usually hybrids aren't better suited to their environments than their parents, but there is a possibility that these hybrids might be able to forage for a broader range of food sources," Larisa DeSantis, a paleontologist and associate professor of biological sciences at Vanderbilt University in Tennessee, told Live Science. Polar bears have longer skulls, which makes them experts at grabbing seals out of the sea, DeSantis said. "But their molars are smaller than is typical for their body size because all they eat is blubber all day. Grizzlies, on the other hand, can eat whatever they want. We don't know yet, but perhaps the intermediate skull of the pizzly could confer a biomechanical advantage."

Grizzly bears and polar bears only diverged 500,000 to 600,000 years ago, so the two species can mate and produce viable offspring. Observations made in captivity and a study conducted in the wild also suggest that the hybrids are fertile and have themselves produced young.

Wild sightings of hybrid pizzly bears began in 2006, when a hunter shot what he thought was a polar bear in the Northwest Territories of the Canadian Arctic. 

When he took a closer look he found an altogether more unusual animal: A bear with the cream-white fur of a polar bear but the long claws, humped back, shallow face and brown patches of a grizzly. DNA tests confirmed that the animal was a hybrid — the first documented wild offspring of a polar bear and a grizzly bear.

Since then, sightings of the hybrids have been increasing, with a 2017 study in the journal Arctic showing eight hybrids springing from a single female polar bear who mated with two grizzly bears.

The rise of the pizzlies coincides with polar bears’ decline: their numbers are projected to decrease by more than 30% in the next 30 years, according to a 2016 study in the journal Biology Letters. This precipitous fall is linked partly to the encroachment of grizzly bears into polar bear ranges, where they outcompete them for alternative food sources, but also to polar bears' highly specialised diets, as DeSantis highlights in research published on April 1 in the journal Global Change Biology.

According to DeSantis, generalist animals such as coyotes and cougars are the best survivors of rapid change to their environment, not highly specialized apex predators like polar bears and saber-toothed cats. 

"Polar bears consumed soft foods even during the Medieval Warm Period, a previous period of rapid warming. Their diets haven't changed much at all." DeSantis said, referring to blubbery meals such as seals. "It's why what we're seeing now — all of these starving polar bears trying to find alternative food sources — could really represent a tipping point."

According to a statement from the National Snow and Ice Data Center (NSIDC), Arctic sea ice, which the bears use as their hunting grounds, decreased by about 336,000 square miles (870,000 square kilometres) this year from its 1981 to 2010 average maximum. That represents the loss of an area about twice the size of California. Although polar bears can adapt their diet to include sea bird eggs and caribou when on land, a 2015 study published in the journal Frontiers in Ecology and the Environment found that the calories they gain from these sources do not balance out those they burn from foraging for them, Live Science previously reported.

All of this could result in a habitat ready for the hybrids to move in and take over, leading to a loss in biodiversity if polar bears are replaced. 

"We're having massive impacts with climate change on loads of species right now," DeSantis said. "The polar bear is the canary in the coalmine telling us how bad things are."

In some sense, pizzly bears could be a sad but necessary compromise given current warming trends, DeSantis said.

"Apex predators help stabilize ecosystems, and looking forward I really hope the Arctic still has a polar bear. But, with that all being said, could the pizzly allow for bears to continue to exist in intermediate regions of the Arctic? Possibly, yes. That's why we need to continue to study them." 

 Originally published on Live Science. 

A mysterious neurological disease in young Californian black bears (Ursus americanus) is making them behave like pet dogs, cozying up to humans in a friendly manner.

Though it sounds cute, this abnormal behavior dramatically worsens the bears' chances of surviving in the wild.

The bears, which are all around 1 year old, appear to be suffering from a form of infectious encephalitis — inflammation of the brain tissue that can be caused by viruses, bacteria, fungi and parasites, as well as part of an autoimmune response. But veterinarians are unsure exactly what is causing the problem or how fast it is spreading among the population. 

Symptoms include a prominent head tilt, lethargic movements, muscle tremors, seizures, walking in circles and being significantly underweight, as well as a surprising fearlessness towards humans. 

Related: The 10 weirdest medical cases in the animal kingdom

"Infected bears come to our attention because they approach people in a peaceful, friendly and non-aggressive manner," said Ann Bryant, executive director of the BEAR (Bear Education Aversion Response) League who has been involved in rescuing infected bears. "Their behavior is similar to a dog, not a bear."

In the last year, four individuals have been found with the disease — the highest number of cases since it was first detected in 2014, according to the California Department of Fish and Wildlife (CDFW).

The black bear population in California has increased from between 10,000 to 15,000 individuals in 1982 to between 30,000 to 40,000 today, according to the CDFW. As a result, veterinarians aren't too worried about the impacts of the disease on the overall population. 

Fearless youngsters 

Although cases of encephalitis are rare, the symptoms have made it quite easy to spot infected bears.

"The first bear I personally rescued was diagnosed with encephalitis in March of 2018," Bryant told Live Science. "She walked into a school and entered a classroom where she sat down among the children, behaving very much like a friendly dog."

In 2019, another infected bear was caught on video trying to climb onto a snowboard alongside its rider. The young male was eventually rescued after the snowboarder and his friends played with him and fed him sandwiches. However, friendly behavior doesn't mean it's safe for humans to be around the bears.

"Bears approaching people who might then treat the animal as if they are tame could easily present a danger," Bryant said. "I would not be comfortable with a member of the public trying to handle one of these, or any, bears."

Instead, if anyone comes across bears displaying symptoms of encephalitis they should report it to the CDFW, Bryant said.

These two particular bears now reside in rescue centers, where they must receive constant medical care to keep the brain inflammation under control, but most other bears aren't so lucky.

The most recent bear found to have the disease, which was discovered in February lying in the back of a truck parked on a residential property, was majorly underweight and covered in fleas, and had to be put down because of its poor physical condition, according to the Sacramento Bee. 

Unfortunately, this sad fate has befallen the majority of infected bears, who are not able to take care of themselves and appear to have been abandoned by their mothers.

On the increase? 

Veterinarians with the Nevada Department of Wildlife (NDOW) first discovered the encephalitis in bears around Lake Tahoe on the Californian border in 2014, according to the CDFW. 

Since then the CDFW has recorded eight cases in California, although the actual number may be higher. Half of the confirmed cases have been detected in the last year, but this doesn't necessarily mean it is on the increase. 

"My opinion is that this is not on the increase," Bryant said. "But more studies are now finally being done so we are more aware of it." 

The disease also doesn't appear to be transmissible between individual bears, Bryant said. This is encouraging for the rest of the population but has left researchers confused as to what is causing it.

"The worst part about this threat to our bears is that we don't know for sure what causes it," Bryant said. "The unknown is troubling."

Unknown origin 

Infected bears are taken to the CDFW's Wildlife Investigations Laboratory, where they can either be treated or, more likely, euthanized due to their poor physical condition. 

"Bears that die or are euthanized are necropsied to determine the cause of death," Brandon Munk, senior wildlife veterinarian at the CDFW's Wildlife Investigations Laboratory, told Live Science. "Evaluation of the tissues can confirm whether an animal had encephalitis or not."

Although the vets can identify the disease, determining the cause of the encephalitis has proved much harder.

"The brain inflammation is likely what causes the symptoms," Munk said. "Beyond that, we do not know the specific mechanisms that may be at play."

Potential pathogens have been identified as the cause of the encephalitis, but none have been confirmed so far. 

"We have identified five new viruses from black bears, some of which are being pursued further as possible causes of the encephalitis," Munk said. "We are also working with a research lab to further evaluate whether a protozoan parasite might be the cause."

However, it is also possible that there is more than one pathogen responsible for the encephalitis, Munk said.

Originally published on Live Science.