They sleep on our beds, steal our food, and generally rule the house. Between them, cats and dogs make up two-thirds of pet ownership worldwide. But which of the two companion animals are we more closely related to?

The answer depends on how you look at the question.

"From an evolutionary perspective we are equally related to dogs and cats," Mark Springer, a professor emeritus of evolution, ecology and organismal biology at the University of California, Riverside, told Live Science in an email.

Cats, dogs and humans are all mammals. In the mammalian family tree, which maps out how different mammal species are related to one another, both cats and dogs belong to the order Carnivora, while humans are primates. These two groups split from a common ancestor about 90 million to 95 million years ago, Springer said. Meanwhile, cats and dogs split from each other much later, around 55 million years ago.

In terms of common ancestry, "dogs and cats are more closely related to mammals such as pangolins, horses, cows, whales, bats, shrews and moles than they are to humans," Springer said. And "humans are more closely related to colugos [flying lemurs], tree shrews, rabbits, rats, and mice than they are to cats and dogs."

Genetic ties

Another way of deciding which species we are more closely related to is through a genetic lens.

If you measure how much the DNA code has changed over time, humans are about equally related to cats and dogs, William Murphy, a comparative genomicist at Texas A&M University, told Live Science in an email.

However, scientists also compare how DNA strands are organized within chromosomes. Here, a difference emerges.

Murphy explained that the ancestors of modern-day dogs went through extensive chromosome rearrangements over evolutionary time. (Such rearrangements are not unique to dogs; they occur across different animal and plant species, though scientists don't fully understand why some lineages rearrange faster than others.) Cats, on the other hand, retained a genome organization that's closer to ours. "In terms of how genes are arranged within chromosomes, humans and cats are twice as similar to each other as humans are to dogs," he said.

Because the way DNA is organized affects how genes are switched on and off, cats may be a better model than dogs for understanding human gene regulation, Murphy said.

That also makes them useful for studying genetic diseases. For example, polycystic kidney disease occurs in both humans and cats, and treatments developed for cats could help inform therapies for people.

Cats may also provide clues about cancer. A recent study found that cancer-related genes in cats are strikingly similar to those in humans, both in number and variety. One notable example involves a gene called FBXW7, which was mutated in more than half of the feline mammary tumors studied. In humans, mutations in the same gene are linked to worse outcomes in breast cancer

That said, dogs are also used to model and analyze human illness, including Alzheimer’s disease, idiopathic epilepsy, eye disease and heart disease.

Although cats may share more similarities with humans in gene regulation, to date more research has focused on dogs. This may be due in part to the fact that the complete feline genome became available later than the canine genome, as well as historical bias — cats have long been perceived as less cooperative in research settings.

So, which are we more closely related to? From an evolutionary standpoint, it's a tie, but genetically, at least in terms of genome structure, we are closer to cats.

How much of a cat fan are you? Find out by taking our cat quiz!

Most cat owners are familiar with the funny head shake their pets do, often after eating, drinking or enjoying a nice cheek scratch ​​‪—‬ they flick their head back and forth a mile a minute. Dogs and other mammals are known to show similar behaviors.

So why do our furry friends shake like this, and does it mean something is wrong?

Usually, this head shaking is totally normal, experts told Live Science. However, the reasons for it can vary a bit between cats and dogs.

Why cats shake their heads

Cats shake their heads when the nerve endings on their heads are stimulated, Sarah Crowley, an anthrozoologist at the University of Exeter in England, told Live Science.

"The physiological driver for it is stimulation of the very sensitive hairs and nerve endings around the top of the head, particularly around the ears," she said.

These nerve endings can be stimulated by a satisfying scratch, prompting the kitty to shake it off. "If a caregiver has touched a sensitive area" ‪—‬ for example, around the ears or whiskers — "this may result in a head shake," said Amy Miele, a clinical animal behavior lecturer at The Royal (Dick) School of Veterinary Studies at the University of Edinburgh in Scotland.

This rapid swinging motion is very effective at dislodging obstructions, such as food or drink, from the cat's ears or whiskers. It can also help to resettle their fur, Crowley added.

"Often the head shake is followed by grooming of the face [or] ears," Miele told Live Science in an email.

The rapid head toss can also indicate annoyance. It's often a response to having their ear blown on — not something you should do on purpose, as they don't like it.

Thankfully, this erratic side-to-side motion doesn't usually cause dizziness. "Animals (including humans) are more likely to make themselves dizzy by spinning in circles," Miele said.

The full-body shake

Cats aren't the only animal with these silly shakes. "Lots of mammals have this head shake reflex to something in or around their ears," Crowley said. "You see mice and rats do it when they've been eating and drinking."

In dogs, breeds with upright ears, like German shepherds, are more likely to shake their heads than floppy-eared pups such as King Charles spaniels because it's easier to get something (like a grass seed or insect) stuck in an open ear.

Dog owners might recognize other types of shakes: the predatory shake (when your pooch tries to playfully "kill" its toys by whipping its head from side to side while its "prey" is in its mouth) and the full-body shake, sometimes called the "wet dog shake." "It starts at the head and then rolls down the whole body and ends at the tail," Crowley said. This is the kind of post-bath shake that soaks everything in your bathroom before you've had a chance to dry Fido with a fluffy towel.

The full-body shake can also indicate a transition between places or behavioral states ‪—‬ for example, if the pup just experienced something stressful or exciting. "This 'shake off' is a way of helping the animal to relieve tension and reset emotionally and physically," Miele said.

"It could be after quite an intense play session with another dog that was really fun," Crowley added. "You often see both dogs will finish playing, and then they'll both shake, and then they'll go do something else."

When to be concerned about your pet shaking its head

Although head shaking can be normal, if your pet starts doing it more often, in unusual circumstances, or while scratching or tilting their head, it might indicate a medical issue, such as an infection, parasite, irritation, neurological problem or something lodged in their ear.

"It's painful and uncomfortable, and that's the only thing that they can do, apart from stick their foot in it," Crowley said.

If you're concerned about your pet's head shaking, consult your vet. "If ear infections are left untreated, then this can result in hearing loss and risks the infection spreading beyond the tympanic membrane (ear drum) and into the middle ear, causing problems with balance and resulting in the animal becoming very unwell," Miele said.

For the most part, though, head shaking is just an adorably normal behavior that helps your pet stay clean and comfortable.

This article is for informational purposes only and is not meant to offer medical advice.

How much do you know about cats? Test your knowledge with our cat quiz!

Today's top story

Doomed scroll?

The social media giants Meta and Google have been held liable in a landmark California legal case that found the companies deliberately designed addictive social media products that caused harm to a young woman's mental health.

The ruling, which came with compensatory damages of $3 million to be awarded to the plaintiff, is the first of its kind, opening up social media companies to penalties across thousands of pending civil claims filed across the U.S.

Central to the young woman's claim was that the addictive nature of social media products led to her having anxiety, depression and body dysmorphia. The case was preceded by another one in New Mexico on March 24, which ruled that Meta failed to protect children from exploitation on its platforms, for which the company was ordered to pay $375 million in damages.

It's still unclear whether these rulings, which the companies plan to appeal, will lead to long-term structural changes to how social media sites and other online forums operate. Previously, companies used Section 230 of the 1996 Communications Decency Act to shield themselves from responsibility for what is said on their platforms.

With this defense circumvented, some analysts suggest the rulings pave the way for broader online censorship and privacy invasions, whereas the plaintiff's lawyers argued the case was not about content but about addictive design features built into platforms.

Meanwhile, the clinical evidence for the addictive nature of these features — particularly whether being glued to your phone constitutes genuine addiction or just "problematic usage" — remains inconclusive.

The trend

Fur-ever friends

A new analysis has found the oldest genetic evidence of the bond between humans and dogs, dating to 15,800 years ago — 5,000 years older than previous finds.

The researchers discovered this long interspecies bond by examining the genomes of various dog-like remains from archaeological sites around Europe, as well as the oldest take from Turkey's Central Anatolian Plateau. The latest findings suggest that humans became pals with domesticated wolves before the invention of agriculture.

Three to read

1. Chinese lander reveals giant 'cavity' of radiation between Earth and the moon — and it could change how lunar exploration is done [Live Science]
2. Landmark experiment reveals a big unexpected problem with cloning [New Scientist]
3. Scientists are racing to save Australia's 'zombie tree' from a fast-spreading fungal disease [Live Science]

Photo of the day

Roman leopard fighting was for women too

This drawing is the first visual evidence that women battled beasts in the arenas of the Roman Empire, a new study has revealed.

Found in Reims, France, in 1860, the original mosaic depicting this scene was destroyed during bombing in World War 1. But not before Jean Charles Loriquet, a French archaeologist, discovered it and preserved it in a sketch.

Say it, said it

Word of the day

Momoztli — Nahuatl for "stone altar". A recent excavation revealed one of these three-layer stone constructions that was used for human sacrifices.

Quote of the day

"A lot of people already feel overwhelmed by digital life. Asking them to strap a gadget to their face for casual interaction is a big ask."

Lik-Hang Lee, assistant professor of augmented reality and virtual reality at the Hong Kong Polytechnic University, on why the Metaverse spluttered to a halt.

Fun and games

All that reading got you looking for a break? Why not give our chain word puzzle a go.

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Cut marks on dozens of canine skeletons found at archaeological sites in Bulgaria suggest that people were eating dog meat 2,500 years ago — and not just because they had no other options.

"Dog meat was not a necessity eaten out of poverty, as these sites are rich in livestock, which was the main source of protein," Stella Nikolova, a zooarchaeologist at the National Archaeological Institute with Museum of the Bulgarian Academy of Sciences and author of a study published in December in the International Journal of Osteoarchaeology, told Live Science. "Evidence shows that dog meat was associated with some tradition involving communal feasting."

Although consuming dog meat — a practice sometimes called cynophagy — is considered taboo in contemporary European societies, this hasn't always been the case. Historical accounts mention that the ancient Greeks sometimes ate dog meat, and archaeological analysis of dog skeletons from Greece has confirmed those stories.

During the Iron Age (fifth to first centuries B.C.), a cultural group known as the Thracians lived to the northeast of the Greeks, in what is now Bulgaria. The Greeks and Romans considered the Thracians to be uncivilized and warlike, and in the middle of the first century A.D., Thrace became a province of the Roman Empire. Like the Greeks, the Thracians were said to have consumed dog meat.

To look into the question of whether the Thracians ate dogs, Nikolova examined skeletons and previously published data from 10 Iron Age archaeological sites spread throughout Bulgaria. She discovered that most of the dogs had medium-sized snouts and medium-to-large withers heights, making them roughly the size of modern German shepherds.

But the large number of butchery marks on many of the bones revealed the dogs were not man's best friend. "It is most probable they were kept as guard dogs, as the sites have a lot of livestock," Nikolova said. "I don't believe they were viewed as pets in the modern sense."

At the site of Emporion Pistiros, an Iron Age trade center in inland Thrace, archaeologists found more than 80,000 animal bones — and dogs made up 2% of the total. When Nikolova looked closely at the dog bones from Pistiros, she found that nearly 20% of them had butchery marks made by metal tools. Two lower dog jaws also had burned teeth, possibly the result of someone removing hair and fur with fire prior to butchering and cooking the animals.

"The highest number of cuts and fragmentation is observed in the parts with the densest muscle tissue — the upper quarter of the hind limbs," Nikolova said. "There are also cuts on ribs, although in dogs they would yield little meat." The cuts Nikolova noticed on the dogs followed roughly the same pattern as those on sheep and cattle at the site, suggesting all of the animals were being butchered in a similar manner.

Because the Thracians had many other animals more traditionally associated with meat consumption, such as pigs, birds, fish and wild mammals, Nikolova does not think the Thracians were eating dogs as a last resort.

At Pistiros, butchered dog bones were discovered within the discarded remains of feasts and in general domestic trash heaps, Nikolova said, meaning dog flesh may have been consumed in different ways. "So, while linked to a certain tradition, it was not confined to that title and was an occasional 'delicacy,'" she said.

Several other Bulgarian archaeological sites Nikolova investigated had evidence of cut and burned dog bones, as did sites in Greece and Romania, meaning "we cannot label dog meat consumption as unique to Ancient Thrace, but a somewhat regular practice that was carried out in the 1st millennium BC in the North-East Mediterranean," Nikolova wrote in her study.

Nikolova plans to further investigate the role of dogs at Pistiros as part of the Corpus Animalium Thracicorum project. She noted that the butchered dogs at Pistiros are from the first part of the Iron Age, but later on the people there began burying intact dogs, so she hopes to determine whether there was a change in people's attitude over time that made dogs a less acceptable source of food.

Animal quiz: Test yourself on these fun animal trivia questions

Most modern dog breeds have small amounts of wolf ancestry from long after dogs were domesticated, according to a new study.

The wolf DNA isn't left over from when dogs and wolves diverged; instead, it most likely came from interbreeding in the past few thousand years. That wolfish influence may be linked to certain characteristics, such as size and personality traits, in different dog breeds, researchers reported Nov. 24 in the journal PNAS.

"Dogs are our buddies, but apparently wolves have been a big part of shaping them into the companions we know and love today," study co-author Logan Kistler, curator of archaeobotany and archaeogenomics at the Smithsonian National Museum of Natural History in Washington, D.C., said in a statement.

Wolves and dogs genetically split more than 20,000 years ago. Since then, there has been some gene flow between dogs and wolves, thanks to their genetic compatibility. To measure the extent of intermixing and its effects on both animals, researchers studied the previously published genomes of nearly 2,700 dogs and wolves from the Late Pleistocene (the last ice age) to the present. This group included 146 ancient dogs and wolves, 1,872 modern dogs and about 300 "village dogs" that lived around humans but weren't pets.

At least 264 modern dog breeds have wolf ancestry passed on from mating that occurred an average of 900 dog generations ago, which equates to about 2,600 years ago — long after dogs became domesticated at least 20,000 years ago, the team found. The most wolfish dogs had up to 40% wolf ancestry in their genomes, but most had between zero and 5% wolf ancestry.

"Prior to this study, the leading science seemed to suggest that in order for a dog to be a dog, there can't be very much wolf DNA present, if any," study co-author Audrey Lin, an evolutionary biologist at the American Museum of Natural History in New York City, said in the statement. "But we found if you look very closely in modern dog genomes, wolf is there. This suggests that dog genomes can "tolerate" wolf DNA up to an unknown level and still remain the dogs we know and love."

Czechoslovakian and Saarloos wolfdogs had the highest degree of wolf ancestry, which is perhaps unsurprising, since they were intentionally bred by crossing domestic dogs with wolves in the 20th century. Larger dogs and certain working breeds — such as Arctic sled dogs, hunting dogs and certain guardian dog breeds from west and Central Asia, such as Anatolian shepherds — tended to have higher levels of wolf ancestry.

But plenty of breeds didn't fit these patterns. Some large guardian dogs, such as bullmastiffs and Saint Bernards, didn't have any detectable wolf ancestry. And some smaller dogs had small amounts of wolfish DNA. For instance, 0.2% of the Chihuahua's genome can be traced back to wolves, the team found.

"This completely makes sense to anyone who owns a Chihuahua," Lin said in the statement. "And what we've found is that this is the norm — most dogs are a little bit wolfy."

Meanwhile, every tested "village dog" had wolf DNA in its genome, the scientists found. And the reason why might be related to their survival. "The stretches of wolf DNA we found in village dog genomes contained genes related to olfactory receptors," Lin and Kistler wrote in The Conversation. "We imagine that olfactory abilities influenced by wolf genes may have helped these free-living dogs survive in harsh, volatile environments."

Some personality traits that kennel clubs use to describe certain breeds also tracked with the amount of wolfish influence. Breeds with lower wolf ancestry were frequently described as "friendly," "easy to train" or "lively," while breeds with more wolf DNA were pegged as "suspicious of strangers," "independent" and "dignified." It's not yet clear if wolf genes are directly responsible for these traits.

Footage of a hungry wolf performing a complex sequence of behaviors on the coast of British Columbia could potentially mark the first case of tool use in wild canids.

The wolf swam into deep water to retrieve a floating buoy attached to a submerged crab trap. It couldn't see the crab trap, but seemed to know the trap was there and how the human tool worked — once back on shore, the wolf began to reel in the line that led to the trap, scientists explained in a new research paper. Finally, when the trap emerged from the water, the wolf broke it open and devoured the bait inside.

Wolves (Canis lupus) have been recorded interacting with human objects before, but this behavior was much more sophisticated than anything previously documented in these animals, according to the study, which was published Nov. 17 in the journal Ecology and Evolution.

"This is a new dimension of wolf behaviour we had not seen before," study lead author Kyle Artelle, an assistant professor at the State University of New York College of Environmental Science and Forestry, told Live Science in an email. "It shows how we have likely only scratched the surface of what the other species we share this world with can do, what and how they think, and what they can teach us."

The bait-snatching wolf lives within the Indigenous Haíɫzaqv Nation Territory on the central coast of British Columbia. These wolves spend a lot of time on the coast, with many relying on the sea for their food, according to the Haíɫzaqv Wolf and Biodiversity Project, which was responsible for the new research and which Artelle helps coordinate.

The new behavior was spotted because Haíɫzaqv Guardians, Indigenous people who conduct research and monitoring on behalf of their nation and the project, kept finding their crab traps damaged by an unknown predator. The crab traps are part of an attempt to eradicate invasive European green crabs (Carcinus maenas), which outcompete native crabs and generally disrupt Canada's marine ecosystems, so it's important for the traps to remain intact.

Initially, it was suspected that seals, sea lions or otters may have been responsible for the damage. A lot of the traps are placed in deep water and don't get exposed even at low tide, so it seemed likely that the culprit was a marine animal. However, within a day of the researchers deploying camera traps in May 2024 in attempts to identify the culprit, the wolf was caught red-pawed.

Wolves have long had a reputation for being smart, but this footage could be the best example yet of their cognitive prowess, the researchers said.

"We realized this was important on the first watching," Artelle said. "Folks who know wolves well have always recognized how intelligent they are, but here is a video that really speaks for itself, that really highlights this clever behaviour, and shows us another aspect of the kinds of behaviours they can exhibit that we had not seen before."

The wolf's seemingly advanced intellect might not come as a surprise to owners of their domesticated pet cousins. Sophisticated behavior is well documented in dogs (Canis lupus familiaris), helped by the fact that we spend so much time with them. Researchers have even compared some dog behaviors, like learning the meaning of human words and gestures, to those of our famously quick-witted relatives, chimpanzees (Pan troglodytes), according to the study.

Researchers have also considered that dogs may be tool users, evidenced by behaviors such as moving chairs to [then jump on to in order to] access food. The same is potentially true for dingos, which have similarly been observed manipulating furniture in captivity. However, the authors couldn't find any reported tool use by a canid (member of the dog and wolf family) in the wild, which could make the wolf's clever feat the first case of wolf tool use captured on camera.

Tool use was once considered a unique trait of human intelligence. However, scientists have steadily dismantled this idea by documenting various nonhuman animals — including chimpanzees, capuchin monkeys and New Caledonian crows (Corvus moneduloides) — using tools. Of course, plenty of animals don't need to use tools, so the behavior is not necessarily the most reliable indicator of superior intelligence.

Precisely what constitutes tool use is debated among scientists, which muddies the new findings. Researchers generally accept that tool use involves the manipulation of an external object to achieve a specific goal with intent. However, some behaviors, like the pulling of a rope, can be excluded from definitions when the animals aren't deemed responsible for the rope's orientation, according to the study.

The wolf's use of a line to retrieve crab traps might be complex enough to be an exception to some researchers' rope exclusion rule. The problem is that the authors of the new study aren't sure what mechanisms are driving this newly observed behavior.

While the wolf appeared to have a sophisticated understanding of the unseen trap and its connection to the floating buoy above — potentially stemming from watching the Haíɫzaqv Guardians interact with the traps — the study doesn't rule out that the animals used a much simpler cognitive process: trial and error.

The camera traps, which are now a permanent feature in the Haíɫzaqv crab-hunting areas, have yet to capture a second incident of a wolf hauling up submerged bait. However, the researchers did retrieve some earlier clips that suggest one camera got tantalizingly close. The camera's footage opens with a dark wolf walking toward an exposed crab line that disappears off-screen. Once the wolf is out of shot, the line wobbles, and the next time the camera is triggered, the wolf is seen investigating the bait cups of two traps that have somehow made it to shore.

You may have noticed that your dog or cat tends to munch on grass from time to time. This may seem like an unusual choice for a snack, especially for cats, which are carnivores. So why do our pets eat grass?

"There's quite a few theories," said Dr. Jamie Lovejoy, a veterinarian at Stack Veterinary Hospital in Syracuse, New York. "We do see grass-eating behavior in both dogs and cats, and these are two species that technically really don't have the equipment to digest a lot of grass." For instance, grass-eating species tend to have special gut bacteria that helps break down grasses' tough cellulose, and many herbivores have multiple stomach chambers and a longer digestive tract to break down plant material.

One commonly repeated theory is that pets eat grass to settle an upset stomach, Lovejoy said. "Most of the time when it comes out, it comes out kind of unchanged, either by vomiting or defecation," she told Live Science. "And so I think it inspires a lot of old wives' tales."

However, research suggests that sickness may account for only a small percentage of times cats and dogs eat grass.

In 2008, researchers asked several groups of dog owners about their pets' grass-eating behavior. Of 1,571 owner responses to a web survey, 68% reported that their dogs ingested plants daily or weekly, yet only 8% said their dogs frequently showed signs of illness before eating the plants. Two similar surveys of cat owners published in the journal Animals in 2021 found that only 6% of cats in the first survey and 9% in the second survey appeared ill before eating grass, although 27% and 37% vomited frequently afterward. In the second survey, 71% of owners witnessed their cats eating plants at least six times.

The 2021 study also tested the idea that cats eat grass to help expel hair balls. Previous research had suggested that long-haired cats vomit up hair balls more often than short-haired felines do. Yet the study found "no evident difference" in the frequency of grass-eating behavior between the two groups.

Related: Why do cats throw up so much?

Researchers have observed grass eating in wild canines and felines too, which suggests it may be an innate behavior. Scientists have hypothesized that wild cats and wolves eat grass to clear their intestines of parasites, so perhaps domestic animals do the same.

"I think it's a little bit of a hard theory to test, at least in the United States … because most of our pets really don't have these high worm burdens," Lovejoy said. "So it'd be hard to see."

Despite grass having "no apparent nutritional value," according to the author of the 2008 study, some scientists have posited that perhaps dogs and cats consume grass for micronutrients like B vitamins, said Dr. Lori Teller, a clinical professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences.

However, this likely isn't the case for most pets on a well-balanced diet, unless the dog or cat has underlying health issues.

"If you have a healthy pet who is getting a well-balanced diet and occasionally decides to go eat some grass, nibble on catnip, things like that, then [there's] absolutely nothing to worry about," Teller told Live Science. "If they're ravenous for these plants, or constantly eating them, or constantly eating them and then throwing up, then I would certainly be looking for an underlying problem."

Scientific studies on grass eating in cats and dogs are relatively scant, due to a lack of funding, Lovejoy explained. Pets rarely have major health issues from eating a lot of grass, and veterinary research tends to focus on how to treat more serious problems.

"I think a lot of these questions are kind of technically unanswered," she said.

But Lovejoy's current theory is simple: Mostly, our pets eat grass because they want to — maybe they like the taste, want some stimulation or are exploring their environments.

"There is no one reason why cats and dogs want to or choose to eat grass," Teller said. "There are probably as many reasons as there are different types of grass out there. Some dogs and cats just like it."

While grass-eating behavior is mostly harmless, pet owners should know that certain plants are poisonous. Lovejoy recommends checking the American Society for the Prevention of Cruelty to Animals' list of plants toxic to pets. Plants treated with certain chemicals may also be dangerous, so people should be cognizant of their use of pesticides and fertilizers. If pets are vomiting frequently or having abnormal stools, Teller recommends taking a trip to the vet.

Cat quiz: Can you get a purr-fect score?

Archaeologists in Germany have discovered the remains of three Copper Age women who were buried with what may have been blinged-out "baby carriers" — large pouches decorated with hundreds of dog and wolf teeth.

The pouches' fabric or leather is long gone, but pierced animal teeth unearthed from the three separate graves suggest the pouches were sewn onto the bags in a staggered pattern similar to roof tiles, the researchers said.

The pouches are from the Corded Ware culture, whose people lived across Europe — from Scandinavia, to the Alps, to what is now Ukraine — between 2900 and 2350 B.C.

"The arrangement of the teeth in the graves is a rare hint at a usually completely perished find category," Oliver Dietrich, an archaeologist and spokesperson for the State Office for Heritage Management and Archaeology of Saxony-Anhalt in Germany who was not involved in the find, told Live Science in an email. It would have been challenging to procure the dog teeth and make the pouches, so these decorated bags were "most likely markers of a high social status," he said.

Archaeologists think the pouches were about 12 inches (30 centimeters) wide and 8 inches (20 cm) deep. Each was covered in nearly 350 dog teeth, specifically the canines and incisors of medium-size dogs similar to modern small Münsterlanders that were bred for this purpose and were killed at a young age, according to a translated statement.

The elite women likely carried the pouches on a wide strap decorated with wolf teeth. A handful of fox teeth and imitations carved out of bone suggest they were used to replace dog or wolf teeth if they were lost, the statement reported.

Related: Viking Age woman was buried with her dog in an elaborate 'boat grave,' excavations reveal

The dimensions of the pouches and the presence of infant bones inside one of them indicate that the pouches were used as baby carriers. A baby's head, arms and legs wouldn't have fit inside the pouch, but infants lying on their backs were likely covered with small blankets that were lined with dog molars, according to the statement. The blankets were sequined, but it's unclear what material these ornaments were made of.

The preciousness of the pouches may explain why they have been found in only a small number of burials from the Corded Ware culture, Dietrich said. The new excavations, which were conducted ahead of a planned power line near the village of Krauschwitz in Saxony-Anhalt, uncovered 10 female burials from the Corded Ware culture, but only two held pouches. A third burial with a pouch was unearthed in Nessa, a village a little more than 1 mile (1.7 kilometers) away from the main archaeological site.

"Similar pouches are known for some other sites in Saxony-Anhalt," meaning these aren't the first finds of their kind, Dietrich said.

At the burial in Nessa, the pouch contained the remains of a newborn. Researchers will analyze the woman's remains to determine her age at death. If enough of the newborn's DNA is preserved, they will also test the child's relationship to the woman, Dietrich said.

The burials near Krauschwitz were located near the much older 6,000-year-old burial mounds from the Baalberg culture, which existed between 4100 and 3600 B.C., during the Neolithic period. People from the Baalberg culture buried their dead beneath wooden structures, but these had gone out of style by the time the Corded Ware culture emerged in the Copper Age, also known as the Eneolithic.

"Each culture has a unique set of rules and norms along which social relations evolve," Dietrich said. "Unlike the earlier Middle Neolithic Cultures, the Eneolithic people intentionally emphasized the gender of the deceased in burials as well as certain social roles."

Men in the Corded Ware culture were buried lying on their right side, while women were typically buried lying on their left side. Grave goods such as axes were reserved for male warriors, while jewelry and ornaments were placed in female graves. Both sexes were almost always buried with their heads facing south, according to the statement.

While excavating near an old harbor in Oslo, archaeologists have uncovered thousands of pieces of preserved, waterlogged leather that are nearly 700 years old. The bags, purses, shoes and sword scabbards — all dated to around the 13th and 14th centuries — are revealing new information about everyday life in medieval Norway.

This past winter and spring, archaeologists with the Norwegian Maritime Museum and the Norwegian Institute for Cultural Heritage Research began digging at a site called D2 ahead of the planned construction of the Bjørvika School, a new primary and secondary school in Oslo.

In medieval times, the dig area was open water in the harbor at the mouth of the Alna River. But in the 19th century, the area was filled in to create more land — which ended up preserving the discarded items there and creating an archaeological treasure trove of leather goods.

Artifacts likely wound up in the harbor for various reasons. Traders lost goods they were transferring, children dropped bowls of porridge, and people tossed away their old shoes. Light items made of wood and leather may have been chucked further upstream and then floated down the river and settled in the harbor.

Wet clay at the old harbor has preserved myriad leather artifacts, which don't decompose in the oxygen-free environment. So far, the archaeologists have discovered more than 200 shoes. "We wouldn't be surprised if we reach well over 1,000 before we finish going through everything we found," they wrote in a translated blog post.

Many of the old shoes show signs of wear, suggesting they were purposefully pitched in the past. One shoe was quite large, corresponding to a men's U.S. size 13 or a 47 in European sizing. Some had decorations cut into the leather, but most were simple, hand-sewn shoes — a leather sole and plain leather upper boot.

Related: 8 ancient Roman shoes of 'exceptional size' discovered at Roman fort near Hadrian's Wall

"When we hold one of these shoes in our hands today, it is like being close to the person who walked in it," the researchers wrote. "It is like a footprint from the Middle Ages: concrete proof that a person has lived, walked and had a life in this city."

In addition to shoes, archaeologists have uncovered 15 medieval bags and purses from the Bjørvika School dig. Most of these bags were small enough to be worn on a belt and hidden under a tunic. Both women and men used bags as "practical accessories" in a time before pockets were sewn into clothing, the researchers wrote in a translated blog post.

"Bags contained what you needed during the day," the researchers wrote. This might have included coins, a comb, a needle and thread, or even a small cross or amulet. "Medieval people needed to carry things around, just like us," they wrote, and the leather bags "give us insight into how people organized their everyday lives — and what they valued."

Almost everyone in the Middle Ages carried around knives attached to their belts, the researchers wrote in a blog post. Archaeologists have also found the remains of several protective leather sheaths at the Bjørvika School site.

One of the last things archaeologists excavated at the site this spring was the skeleton of a dog. In a blog post, the researchers noted that most of the more than 3,000 bones they recovered were from food trash, but the partially complete skeleton of a medium-size dog was a surprise.

"The bones show no obvious signs of wear, disease or dismemberment," they wrote, "but are well-fused together, meaning the dog had a good life with access to food and probably cuddles."

While excavation of the archaeological material is now complete, the researchers have just begun studying the loads of finds they've recovered, hoping to gain new insight into medieval Oslo.

Archaeologists have unearthed what they think are the remains of a Viking Age woman buried with her dog in the far north of Norway.

The remains were found late last month in a well-preserved "boat grave" near the village of Sand on the island of Senja, which lies on the Arctic Circle, at a site first recorded by metal detectorists in 2023.

The archaeologists don't yet know whether ancient DNA or sex-determined proteins can be extracted from the remains. But they suspect it was the grave of a Viking Age woman because it also contained two distinctive brooches, oval in shape and trimmed with silver wire, that have never been found in graves of Viking Age men.

The style of the brooches indicates the grave dates to between 900 and 950, during the heart of the Viking Age. The researchers don't yet know how old the woman was when she died.

A small dog was placed in the grave at the woman's feet, perhaps indicating the strength of the bond between them.

Anja Roth Niemi, an archaeologist at the UiT The Arctic University of Norway who led the latest excavations, told Live Science that graves from this time throughout Europe often held the remains of dogs and horses. But while horse skeletons were often found in parts, suggesting the animals were sacrifices, dogs were usually buried whole. "This suggests that dogs and humans had a close and cherished relationship, even over 1000 years ago," she said in an email.

Related: 7 myths about the Vikings that are (almost) totally false

Boat grave

The researchers were surprised to find that the woman had been buried in a "boat grave" consisting of a "sewn boat" almost 18 feet (5.4 meters) long — the first such grave ever found on Senja.

In these primitive "sewn boats," the wooden planks of the hull were fixed with something other than iron nails, such as wooden plugs, plant fibers or animal sinew. The boat has now rotted away, and only its shape can be seen.

"So-called 'sewn boats' were, until a few years ago, very rare in northern Norway," Niemi said. "However, in recent decades, several such vessels have been found in Iron Age graves in the region." It's thus possible they were fairly common in the area, she added.

Two similar boat graves had recently been excavated on the Norwegian island of Hillesøy, about 10 miles (16 kilometers) north of Senja, she said. One of those burials was of a man, and the other was of a woman; both had lived a few generations before the woman in the Senja boat grave.

The elaborate burial at Senja and rich grave goods indicate the woman had belonged to the social elite. "We believe the woman buried here held significant status locally, and perhaps even across the region," Niemi said.

Making cloth

The body of the woman was placed in the middle of the boat, with her head facing north, and the dog's body was placed near the woman's feet, Niemi said.

The grave goods included the two brooches; an iron sickle; a slate "whetstone" for sharpening knives; a metal ring with bronze beads, which may have been for tying back hair; two disk-shaped beads, possibly made from amber; a spindle whorl; and what may have been a "sword" or batten used for weaving made from whalebone.

Niemi said the sickle and whetstone suggest arming and harvesting, while the spindle and batten suggest spinning and weaving; tools for making textiles were often found in women's graves in Norway and often indicated that the buried individual held high status.

It would have been important for the mistress of a house to ensure that high-quality textiles were produced. "Textiles were needed for clothing, blankets, and much more, but also for producing sails for boats and ships," she said.

In addition, the mistress of a house also would have been expected to create fine clothes and elaborate tapestries that could be displayed during feasts and other visits, emphasizing the hosts' status, Niemi added.

Viking quiz: How much do you know about these seaborne raiders, traders and explorers?

A pair of 14,000-year-old "puppies" found melting out of the permafrost in Siberia have undergone genetic testing, proving they were actually wolf cub sisters and not domesticated dogs as was previously assumed.

"Whilst many will be disappointed that these animals are almost certainly wolves and not early domesticated dogs, they have helped us get closer to understanding the environment at the time, how these animals lived, and how remarkably similar wolves from more than 14,000 years ago are to modern day wolves," Anne Kathrine Runge, an archaeologist at the University of York in the U.K., said in a statement.

Runge led an international team of researchers in analyzing the bones and DNA of the puppies. Their study, published Thursday (June 12) in the journal Quaternary Research, revealed that the mummified "puppies" were wolf littermates that died somewhere between 14,100 and 15,000 years ago.

The remarkably preserved and mummified animal carcasses were found in 2011 and 2015 near the rural settlement of Tumat in far northern Siberia. Along with the two canines, scientists discovered woolly mammoth (Mammuthus primigenius) bones that appeared to have been cut and burned by humans. This archaeological evidence suggested that the canines could have been very early domesticated dogs that were seeking food from humans — such as a piece of woolly rhino meat that was discovered in the belly of one of the animals.

Dogs and wolves are closely related, but they diverged genetically between 20,000 and 40,000 years ago. Humans then domesticated wild dogs around 15,000 years ago. But the title of the world's oldest domesticated dog has never been clearly claimed. One possibility is the Bonn-Oberkassel dog, found in Germany in a human burial dated to 14,200 years ago.

Because they were older than this, the ice age Tumat canines were previously assumed to be among the oldest domesticated dogs in the world. But DNA testing in 2019 showed that they likely belonged to a now-extinct wolf population unrelated to today's dogs.

Related: Frozen in time: 10 prehistoric animals found trapped in ice

In the new study, Runge and colleagues built on the 2019 study by analyzing genetic data from the animals' gut contents and investigated chemical "fingerprints" in their bones, teeth and tissue to learn more about the famous cubs.

The cubs — genetically determined to be sisters — were only a couple of months old when they died, but both were eating solid food, including meat from a woolly rhino (Coelodonta antiquitatis) and a small bird called a wagtail — but not from a mammoth, which may have indicated that ice age humans had fed them leftover scraps. Additionally, both were still being nursed by their mother, the researchers discovered.

"It was incredible to find two sisters from this era so well preserved, but even more incredible that we can now tell so much of their story, down to the last meal they ate," Runge said in the statement.

But there's no indication that the Tumat pups got this food directly from humans or even from scavenging humans' mammoth butchering sites, according to the researchers. The sisters "inhabited a diverse landscape that was also occupied by humans," they wrote, but "this study found no evidence that can conclusively link them to human activities."

How the cubs died remains a mystery, as well. Given the cubs' lack of injuries, they may have been resting in an underground den when it collapsed, trapping them inside, the researchers wrote in the study.

"Today, litters are often larger than two, and it is possible that the Tumat Puppies had siblings that escaped their fate," study co-author Nathan Wales, an ancient-DNA specialist at the University of York, said in the statement. "There may also be more cubs hidden in the permafrost."

Additional research on the Tumat cubs may yet produce more information about ancient wolves and their evolutionary line, Wales noted in the statement.

Last ice age quiz: How much do you know about Earth's frosty past?

Editor's note: Following Colossal Biosciences' announcement, described below, various scientists have said that the framing of the work is misleading and that it shouldn't be considered a "de-extinction."

Dire wolves went extinct around 12,500 years ago. Now, thanks to genetic engineering, they're back in what the scientists have described as the "world's first de-extinction."

Scientists at Colossal Biosciences, a biotech-based conservation company best known for trying to bring back woolly mammoths, say they have successfully produced three dire wolf (Aenocyon dirus) pups. They did this by reconstructing the wolf's genome from ancient DNA, identifying versions of genes seen only in dire wolves and not in the extinct carnivores' living relatives.

The team then tweaked DNA from modern-day gray wolves (Canis lupus) to include these unique gene variants. They inserted the DNA into denucleated gray wolf egg cells and allowed them to mature in the lab before introducing them into surrogate dogs' wombs, TIME reported. Three embryos successfully implanted in three surrogate dogs, leading to the births of snowy white pups named Romulus, Remus and Khaleesi, which are reminiscent of Ghost, Jon Snow's dire wolf in HBO's "Game of Thrones" television series.

Related: 'We didn't know they were going to be this cute': Scientists unveil genetically engineered 'woolly mice'

"Our team took DNA from a 13,000 year old tooth and a 72,000 year old skull and made healthy dire wolf puppies," Colossal CEO Ben Lamm said in a statement. "It was once said, 'any sufficiently advanced technology is indistinguishable from magic.' Today, our team gets to unveil some of the magic they are working on."

How to make a dire wolf

To "de-extinct" the dire wolf, the team used a process similar to the one that led to Dolly the sheep in 1996.

To produce a perfect clone with this method a single cell is removed from the cloning subject and its genetic material, held in the cell's nucleus, is extracted. This genetic information is then inserted into the egg of a donor animal from the same species whose own nucleus has been removed. The egg now contains all of the genetic information required to rebuild the original cloning subject and is transferred to a surrogate to carry to term.

However, because dire wolves went extinct at the end of the last ice age, Colossal had to approximate their own dire wolf cells by piecing together clues from the fossil record.

To reconstruct the animal's genome, they used genetic samples from dire wolf fossils and compared these to the genomes of their living relatives, including wolves, jackals and foxes. They selected gray wolves to be the egg donors, as these animals are the closest living cousins to dire wolves.

This genomic analysis enabled the scientists to identify 20 key differences in 14 genes that were responsible for the dire wolves' distinguishing characteristics, including their larger size, white coat, larger teeth and characteristic howling.

Next, they collected cells from blood samples of living gray wolves — a less invasive method than using a chunk of tissue, as was done for Dolly the sheep. Then, using CRISPR gene-editing technology, the team made 20 edits to the 14 identified genes so that they bore the same sequence as the wolves' ancient relatives.

Once these "dire wolf cells" were created, their nuclei were extracted and inserted into eggs from a living gray wolf. As with Dolly the sheep, these donor egg cells had their own nuclei removed to make space for the new DNA. Reproductive cells — like eggs and sperm — normally have just one copy of each chromosome; however, cells from the body carry two copies. So transferring the nucleus from a body cell into a reproductive cell provides it with all the genetic instructions needed to mature into an embryo.

The eggs were allowed to mature into embryos in the lab, resulting in 45 embryos that were transferred into the wombs of two domestic dogs, which are technically a subspecies of the gray wolf.

Only one embryo in each surrogate took hold. After 65 days of gestation, Romulus and Remus were born via cesarean section, on Oct. 1, 2024. The whole process was repeated again a few months later with a third surrogate dog, who birthed Khaleesi three months later.

Colossal has shared footage of Romulus and Remus as they take their first steps, make their first howls and develop from newborns into young cubs. They have described the dire wolves as "the world's first de-extinction."

However, there has been one other de-extinction: In 2003 scientists in Spain cloned an extinct wild goat species known as a bucardo, or a Pyrenean ibex (Capra pyrenaica pyrenaica). But the newborn goat died only minutes after birth, according to a 2009 study.

Colossal have also announced the birth of two litters of cloned red wolves, the most critically endangered wolf in the world, the company said in a statement.

The announcement comes just months after Colossal unveiled genetically engineered "woolly mice", which have fur similar to the thick hair of woolly mammoths, marking a major milestone in the company's project to bring back these ice age titans by 2028.

The domestic cat is one of the smallest members of the family Felidae — the group that includes lions, tigers, jaguars and cougars. It is also the only member of that family that has been domesticated.

Cats have lived among humans for thousands of years. They probably started hanging around human grain stores, attracted by mice and other vermin, and eventually spread around the world as sailors brought them aboard ships.

Today, cats still help humans control pests, as well as provide companionship. In the past few centuries, humans have bred some cats to display certain traits, like hairlessness, thereby establishing dozens of cat breeds. With their charming mix of aloofness and goofiness, cats continue to amuse and fascinate us.

Everything you need to know about domestic cats

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At the turn of the 20th century, a famous horse named Clever Hans toured Germany. The horse stunned crowds as his trainer demonstrated the animal's alleged ability to understand German, tell time and even solve math problems.

But when an independent team investigated Clever Hans, they concluded his act was a fraud. It turned out that the horse actually just responded to subconscious body-language cues from his trainer and couldn't really comprehend human language or perform arithmetic feats.

Today, researchers are still testing the limits of animals' ability to understand humans, but examples like Clever Hans show just how difficult that task can be. So do we know if any animals can actually understand human language?

Animal language studies with primates, birds, dolphins, and other animals flourished through the 1960s and 1970s, but skeptics went on to criticize this research, saying the animals were only mimicking their trainers like Clever Hans. Though many animals are adept at picking up on context clues like body language and tone of voice, it's less clear if they understand the meaning of words or more complex features of language like grammar. But today, research is beginning to suggest that, with training, some animals may understand certain features of human language, such as the sound and meaning of specific words.

"Humans are special in many ways, and certainly language is unique to humans," Simon W. Townsend, a professor of evolutionary anthropology at the University of Zurich, told Live Science. "But I think more and more, we're finding that there are really quite some similarities between the communication systems of animals and humans."

Related: Can animals learn another species' 'language?'

Can primates learn human language?

One of the most famous animal language experiments involves Koko, a female western lowland gorilla who learned modified American Sign Language (ASL). Koko, who died in 2018, could use about 1,000 signs and respond to over 2,000 words in spoken English.

However, experts warned that there's a big difference between learning some modified signs and actually mastering ASL, and Koko was never anywhere near fluent in sign language. Critics also pointed out that Koko sometimes signed nonsensically, and her trainers tended to lean on their own interpretations to make sense of Koko's signs.

According to comparative psychologist and linguist Michael Tomasello, the title for most advanced language skills in a primate goes to Kanzi, a male bonobo (Pan paniscus) who lived from 1980 to 2025. Kanzi communicated through a lexigram board, a keyboard of about 200 arbitrary symbols that corresponded to things in his environment.

Townsend, who worked with Kanzi, says the bonobo understood the symbols on his lexigram board well and could use them to communicate with his trainers. Kanzi used symbols for people's names, common objects, actions and locations, and he had vocalizations for "yes" and "no." He used his lexigram board to ask for objects or request certain actions.

"He's learned symbolic communication, which is a feature of another species' communication system," Townsend said. But, Townsend added, human language is more than just using symbols; it also involves combining those symbols into larger structures to create more complex meaning — a feature of language called syntax. If Kanzi grasped syntax, that would indicate a deeper understanding of our communication systems.

So far, studies have shown that Kanzi could order symbols at a rate better than random chance, but some critics doubt the bonobo's grammatical abilities. Townsend and other researchers studied Kanzi up until his death to learn the limits of his abilities to combine symbols. Their research is currently unpublished.

Kanzi understood some spoken English, too. In a 1993 study, researchers found that when the bonobo listened to brand-new sentences, like "Put on the monster mask and scare Linda," he could complete the requested task about three out of four times, outperforming a 2.5-year-old child.

Can dogs understand humans?

Most animals have no hardwired evolutionary reason to care about human language. But dogs, who've lived alongside humans for at least 14,000 years, have a special motivation to listen to their owners and respond appropriately.

Dogs are highly tuned in to the specific sounds and tones of voice that humans use to communicate. In fact, dogs show interest in human voices and gestures as early as 8 weeks old. Dogs are so used to human voices that they can tell when speech has been scrambled, and neuroscience research even suggests that dogs have their own mental representations of words, suggesting a deeper comprehension of language similar to humans'.

Related: Are dogs smarter than wolves?

Some prodigious dogs may even grasp basic grammar. One of them was Chaser, a highly trained border collie, known as the "smartest dog in the world," who learned over 1,000 words. According to a 2011 study, she could differentiate commands such as "bring the sock to the ball" and "bring the ball to the sock," indicating a basic understanding of syntax.

Federico Rossano, an associate professor of cognitive science at the University of California, San Diego, is using button boards — a series of buttons that play a recorded word when pressed — to investigate the linguistic capabilities of our canine companions.

In 2024, Rossano showed that dogs respond to the actual sounds of words and not just to their context, like their owner putting on their shoes while saying it's time to go outside. In a study of 59 dogs, the canines listened as a researcher pressed buttons with words related to "outside," "play" and "food," as well as a nonsensical word to serve as a comparison. The researcher wore headphones so their reactions and body language didn't affect the dogs' responses.

Even without these context clues, the team found that when dogs heard the recordings relating "outside" and "play," they tended to start exhibiting behaviors related to going outside or playing, respectively, such as running to the door or grabbing a toy.

The research is a promising step toward showing that dogs can understand human speech even without the context clues that come along with it. But other studies have found that dogs can't differentiate between words that differ by a single sound, such as "sit" and "set," so there may be a limit to how much they can understand.

Rossano emphasized that his studies are not meant to prove that dogs can "talk." Some Instagram-famous pets have gone viral for seemingly advanced communication through button boards, but these cases aren't the focus of his studies. For now, Rossano is focused on investigating the basics.

Like other animal language researchers, Rossano still has a lot of questions. He's currently investigating whether dogs use buttons to refer to people or objects that aren't currently present, and whether they combine buttons to refer to things they don't know the names of. Both of these feats would imply more complex cognitive processes.

Federico admits he began the research with some skepticism, but his view of dogs' language capabilities has "100%" changed since then.

"Maybe there's more of a mind there than we give them credit for," he said.

Animal quiz: Test yourself on these fun animal trivia questions

Posed as if leaping through the air, this carved ivory dog opens its mouth as a lever is pushed up and down, revealing two lower teeth and a red tongue. The dog, which was discovered in an ancient Egyptian tomb, is a reminder that these domesticated canines have been beloved pets for at least 3,400 years.

The small dog sculpture, now at The Metropolitan Museum of Art in New York City, is made from elephant ivory. It is 7.2 inches (18.2 centimeters) long from nose to toes and shows the very good boy in a flying gallop, legs extended in the air. According to The Met, the lever that works the dog's lower jaw, making it appear to bark, was originally held on by a piece of leather cord looped through small holes. At some point, the cord was replaced with a metal dowel secured in the dog's shoulder.

The Met obtained the dog sculpture from the personal collection of Howard Carter, the Egyptologist who famously discovered King Tut's tomb in the Valley of the Kings in 1922. It is unclear exactly where the dog was found, but The Met suggests it may have been placed in an elite tomb sometime during the reign of Amenhotep III, King Tut's grandfather, in the 14th century B.C. But its purpose is unclear; it may have been a toy or a magical ceremonial object.

Related: Onfim's doodle: A 13th-century kid's self-portrait on horseback, slaying an enemy

Ancient Egyptians were quite fond of their dogs. While some were used for hunting, shepherding or as watchdogs, many were pets. This sculpture definitely represents a domesticated dog because the incised lines around its neck form a collar, Met curator emerita Catharine Roehrig wrote in a publication of the artifact.

During Egypt's New Kingdom (1550 to 1070 B.C.), dog collars became increasingly ornate, often inscribed with the dog's name, such as those found in the Tomb of Maiherpri. This dog sculpture does not have a name attached to its collar, but The Met notes that some common Egyptian dog names translate to Blackie, Son of the Moon and Good-for-Nothing.

The breed of this sculpted dog is also unclear. Ancient Egyptians tended to prefer energetic dog breeds, and the ones often represented in their art include the ancestors of the hunting dog basenji, the Ibizan hound and the pharaoh hound.

Dogs were also linked with the god Anubis and with the afterlife in Egyptian mythology; they were sometimes seen as a kind of intermediary between the worlds of the living and the dead. Killing a dog — particularly a collared one — was a severe crime, and a family would have mourned the death of their dog as they would a human relative: by shaving their eyebrows. However, Egyptians believed that they would meet their dogs again in the afterlife, which is likely the reason they mummified them and buried them in special pet cemeteries.

Scientists don't know exactly how wolves were domesticated into early dogs, but it's possible that they domesticated themselves by choosing to coexist with humans so that, a new study finds, they could be fed consistently. Then, these snackish canines likely selected mates that did the same.

While the theory is nothing new, the new research shows it's statistically possible for the wolves to have driven their own domestication into dogs through natural selection.

Archaeological and genetic evidence suggests that dogs (Canis familiaris) are descended from gray wolves (Canis lupus) and became domesticated over two historical periods: between about 30,000 and 15,000 years ago when wild wolves were domesticated into early dogs, then from around 15,000 years ago to the modern era when these dogs became differentiated into breeds. These periods of domestication were driven by different evolutionary forces, according to a new study published Feb. 12 in the journal Proceedings of the Royal Society B.

The second domestication period is thought to have been mostly driven by artificial selection: humans chose more tame wolves to accompany them for hunting and companionship, and purposely bred the least-wild animals together, which ultimately produced the tame species we know as the domestic dog.

But the selective forces that drove the first domestication period are less clear. According to one hypothesis, wolves underwent "self-domestication": after prehistoric animals started coming to human settlements to scavenge for food scraps, they grew more accustomed to living near people. These more-tolerant wolves preferred a steady food supply over inconsistent sources in the wild, and their descendants gave rise to the first domestic dogs.

Related: Smarter dogs have smaller brains, surprising study reveals

A similar process is believed to have occurred with cat domestication, as research found that the ancestors of house cats spent time near farming communities around 10,000 years ago, before settling into a mutually-beneficial relationship in which they hunted and ate rodents in exchange for food.

Dog domestication debate

Scientists have long debated the dog self-domestication hypothesis. One criticism is that natural selection may not be able to work quickly enough to turn wild wolves into domestic dogs over thousands of years — without selective breeding by humans to speed the process up.

In the new study, researchers addressed this question of time constraint by using a statistical model that considered potential timelines of dog domestication and gave its computerized canines some agency over choosing their lifestyle and mates.

The model showed that over 15,000 years, natural selection could potentially drive dog self-domestication. But for this to happen, two conditions had to be met: Wolves had to choose to stay near humans to eat food scraps, and they had to select mates with a similar temperament.

"When females were selecting mates, they also had to select males that had a similar tameness to themselves," study co-author Alex Capaldi, a mathematician and statistician at James Madison University in Virginia, told Live Science. "So if both of those processes are in play, then it is possible for the self-domestication hypothesis to beat the time constraint critique."

The scientists pointed out that while the model doesn't show exactly how wolves became domesticated, the model's results do mean self-domestication is a possibility.

Dogs are the earliest animal to be domesticated, so studying their evolution can help scientists better understand how domestication may work in other species. And since the process of dog domestication was so closely linked to the development of early human societies — dogs herded cattle in early human settlements, and migrated with early humans to the Americas — understanding its timeline can illuminate our history, and how we ourselves evolved to communicate and bond with dogs.

Canine hookworms are becoming an increasing threat to pets and people, researchers say, after finding that the parasites have developed widespread drug resistance in both North America and Australia.

Researchers behind a new study found widespread resistance to benzimidazole-based dewormers in Australia, which are commonly used to treat dogs with parasites that can also spread to humans. The study, published Dec. 22, 2024 in the International Journal for Parasitology, builds on previous studies that identified widespread drug resistance in canine hookworms (Ancylostoma caninum) across North America.

Like in North America, the Australian parasites have developed genetic mutations, which give the hookworms resistance to treatments that would usually kill them.

"This is a big problem, as hookworm infections can be dangerous for both humans and animals," study first author Swaid Abdullah, a senior lecturer in veterinary parasitology at the University of Queensland in Australia, said in a statement.

Canine hookworms cause anemia, diarrhea and malnutrition in dogs, which can be fatal. Infected dogs also leave hookworm eggs in their feces, which then hatch out into the environment and can spread to humans through skin contact.

"In people, hookworms from dogs can cause cutaneous larva migrans (CLM) disease — or 'creeping eruption' — which is a winding, snake-like rash with blisters and itching," Abdullah said.

The disease usually goes away in a few weeks to months without treatment, but doctors may prescribe antiparasitic drugs to help kill the hookworms and antibiotics to treat infections, according to the CDC.

Antoinette Marsh, a professor of veterinary parasitology at The Ohio State University who wasn't involved in the study, told Live Science that she wasn't surprised by the new research in Australia because North America has the same problem.

"My biggest concern is cutaneous larva migrans that occurs in human beings," Marsh said. "If people aren't picking up the feces and [are] allowing it to develop in the environment, then it becomes a problem for us to actually treat humans."

Related: Parasitic worms cause terrible diseases — could the viruses they carry be to blame?

How parasitic hookworms became drug-resistant

Scientists first reported drug-resistant canine hookworms in racing greyhounds in the 1980s and have since found them in different breeds in the U.S. and Canada. In the new study, researchers looked for genetic markers tied to benzimidazole resistance in hookworms sampled in Australia and New Zealand.

The scientists discovered that drug resistance was common in canine hookworms across Australia but wasn't present in the New Zealand samples. They also found drug resistance in northern hookworms (Uncinaria stenocephala), which were previously believed to have no drug resistance, according to the statement.

Marsh noted that it's unclear whether drug resistance in Australia evolved independently or spread between North America and Australia with the movement of pet dogs. Hookworms breed quickly, so they could have developed resistance independently in different regions.

"Occasionally, you'll get a genetic change, and the ones that survive better are going to then take off in the population," Marsh said.

The study authors called for a change in how deworming drugs are used, with a move towards targeted, risk-based treatment and ongoing monitoring to slow the spread of drug-resistant hookworms.

"As resistance spreads, we need ongoing monitoring and the development of new control strategies to protect animal and human health," study co-author Dr. Jan Šlapeta, a professor of veterinary and molecular parasitology at the University of Sydney, said in the statement.

"This study is a wake-up call for both pet owners and veterinarians alike — the era of effortless parasite control may be coming to an end," Šlapeta added.

Compared with other animals, human babies start out with a lot to learn. Whereas some animals walk within hours of being born or hatching, human babies take months or years to master even the most basic functions. If you've ever had a baby and a pet at the same time, you might have wondered which one is smarter.

So what does science say about how the intelligence of human children compares with that of our fur babies? It's a complex question, and the answer depends on the dimension of intelligence, the animal, and the person you ask.

How smart are dogs compared with babies?

Stanley Coren, a professor emeritus of psychology at the University of British Columbia, has spent his career investigating dog intelligence. He adapted a psychological measure called mental age to test dogs' cognitive abilities.

While it's not possible to draw an exact comparison between dog and human intelligence, Coren said dogs do have some cognitive skills, such as vocabulary and counting, that roughly correspond to those of young toddlers. For example, the average dog can understand about 165 words and signals. In exceptional cases, some dogs can learn significantly more. For example, Chaser the border collie, who was specially trained by a retired psychology professor, was reported to understand over 1,000 words.

Most dogs can also "count" up to three, Coren said. If the idea of a dog being able to count sounds unlikely to you, try this: Show your dog three treats, hide them all in your hand, and then give the dog only two. Most dogs will know one treat is still missing and nuzzle your hand to try finding it. And in the lab, studies show that dogs' brains light up similarly to humans' as they see the number of dots on a screen change, suggesting they recognize when a quantity goes up or down.

Coren added that trained retrievers, which are bred to fetch downed birds or other game, often keep track of five or more objects in order while hunting. So, even though dogs can't recite "one, two, three," like a preschooler might, these sorts of behaviors show that many dogs have some intrinsic understanding of basic counting. In comparison, research shows that 14- and 18-month old human infants are already able to distinguish between two and four objects when an adult counts them.

By analyzing these sorts of cognitive functions, you can estimate the "mental age" of dogs on a human scale, Coren said. "We basically found out that the average dog has a mental age which is about the equivalent of a 2-and-a-half-year-old child," at least when it comes to certain cognitive skills such as vocabulary, counting and emotional awareness, he told Live Science. He said for different dogs, the number can range from about age 2 to 3.

Related: Are dogs smarter than wolves?

Keeping that mental age in mind can help dog owners understand their dogs' capabilities, Coren said. For example, just as 2-year-olds aren't yet fully capable of experiencing and comprehending guilt, dogs aren't, either; the shy behavior exhibited by dogs after misbehaving is actually just the fear of punishment, Coren said.

It's important to note that dogs' intelligence is highly dependent on their breed, experience and training. For example, border collies and poodles generally rank as more intelligent than Chihuahuas and bulldogs. There's also the caveat that these tests don't account for different breeds' unique, instinctive skills, such as herding or scent tracking, which are their own forms of intelligence but are difficult to compare to human cognition.

"Dogs are not four-footed people in fur coats," Coren said.

How smart are cats versus babies?

The research on domestic cat intelligence is less plentiful, but some studies have probed the cognitive abilities of cats. "We might look at things like problem-solving or innovation/behavioral flexibility as kind of a substitute for an intelligence test," Jennifer Vonk, a professor of psychology at Oakland University in Michigan, told Live Science in an email.

The landmark research on cat intelligence, conducted by Edward Thorndike in 1898, examined cats' ability to free themselves from a box by pulling a door open. Although the cats were able to open the door only through trial and error at first, the time it took them to escape the boxes generally decreased as Thorndike repeated the trials, showing that the cats were able to learn. Subsequent studies that used treats in puzzle boxes found that cats could learn new solutions when the puzzle box changed, which demonstrated cats' ability to adapt flexibly to new learning environments, Vonk said. And while it would be unethical to put human babies in a puzzle box, kids can begin escaping cribs as young as 16 months of age.

Other research has evaluated cats' memory, which is another important dimension of cognition. Studies have found that cats strategically search for food based on just a single memory, for example. Studies also show that cats grasp the concept of object permanence — the understanding that an object still exists even if it is no longer visible. Human babies usually learn object permanence between 4 and 10 months of age. And a recent study found that cats may even be better at associating words with pictures than human toddlers are.

But even though it's possible to quantify aspects of cat intelligence with these tests, Vonk doesn't think it makes sense to view cat intelligence through the lens of human development.

"I don't think it is relevant to compare animal abilities to those of human children because other species are not just developmentally delayed humans," she said. "They have evolved to solve different problems because they evolved in different ecological contexts and live in different environments."

These different evolutionary pressures have made cats excel at skills such as hunting and differentiating scents. "They are probably far more efficient hunters than most humans will ever be," Vonk said.

Ultimately, cats' unique adaptations also mean they simply may not be motivated to perform well on intelligence measures the way humans are. Over history, human survival has been dependent on tasks such as tool building and language development. Other animals haven't had the same evolutionary pressures — for example, cats rely on their sense of smell and physical coordination to hunt, rather than their ability to communicate or build tools — so Vonk believes it just doesn't work to compare cats with young humans.

"I think you cannot think about animals as being comparable to humans at different stages of development," Vonk said. "That's a comparison I try very hard to never make. We have to think about what abilities make sense for cats to have and understand why cats do well at the things they do well at, and worry less about comparing them to humans."

Dogs with bigger brains relative to their bodies aren't necessarily smarter, a new study finds.

The research, published Nov. 13 in the journal Biology Letters, suggests that while working dogs may have more complex abilities compared with other breeds, they're organized into a more compact space in the brain. This differs from what's seen in evolutionary history in wild mammals, where as brains get bigger relative to body size, cognitive skills tend to become more complex.

"In other groups [of species] relative brain size is indicative of higher cognitive abilities — here we see the opposite," said Ana Balcarcel, lead author of the new study and an evolutionary biologist at the Montpellier Institute of Evolutionary Sciences in France.

The study compared the ratios of dogs' brain size to body size by measuring 1,682 skulls of adult dogs covering 172 breeds housed at the Natural History Museum Bern in Switzerland. The researchers calculated the dogs' "relative endocranial volume" — their brain size relative to their body size. Scores for 14 behavioral traits were also taken from the Canine Behavioral Assessment and Research Questionnaire, a standardized behavioral evaluation of dog breeds that measures trainability, attention-seeking behaviors, aggression and other traits.

"Working" breeds, like Siberian huskies bred to perform complex skills to assist humans, had the smallest brains relative to their body size. "Companion" breeds, like Chihuahuas bred primarily to be pets, had the largest relative brain size.

Related: Why do dogs look like their owners?

Relative brain size was smaller in dogs that were more trainable — typically, working breeds like Siberian huskies, Great Pyrenees and rottweilers. Working breeds perform human-assistance roles such as search-and-rescue, guiding and policing, and previous research has shown that they have better executive function — meaning greater behavioral control and short-term memory — than other dog breeds. Bigger dogs have a different composition of internal brain tissues than smaller dogs, said Balcarcel.

Previous research has suggested that bigger brains tend to correlate with higher survival odds, better decision-making and higher information processing capacity, so the findings of the new study were surprising, Balcarcel said.

"The key difference here is that dogs are not in a natural environment,” Balcarcel said. "They are a function of artificial selection… a very directed selection, evolution under human hands."

The study also found that dog breeds with larger relative brain size — mostly toy breeds, like Chihuahuas, Pomeranians and Yorkshire terriers Pomeranians — tended to show higher levels of fear and aggression, separation anxiety and more attention-seeking behaviors.

These toy dogs are bred mainly as human companions, making affection and attention-seeking favorable traits for breeding and passing on through artificial selection. Fear and aggression may not have been as disadvantageous to these breeds as they would have been for working dogs, which have been bred to be more trainable, Balcarcel speculated.

"We can say that we have really altered the brains — not just the body sizes and the proportions of different dogs, but it looks like we have also changed their brains in a significant way," Balcarcel said.

Next, the team plans to compare different breeds' brain form and function. Variation in the shape of the neocortex — a part of the brain responsible for higher-level functions — across dog breeds could shed light on the senses and functions that are important for different types of dogs, Balcarcel said.

Studying brain form in dogs could also answer questions about evolution and domestication. The brains of domesticated dogs (Canis lupus familiaris) are about 20% smaller than those of wild gray wolves (Canis lupus) relative to body size, yet compared with wild gray wolves, domesticated dogs are more specialized for complex social skills cooperating with humans: following humans’ gaze and interpreting human pointing gestures, for example.

Balcarcel reminded dog owners that, no matter your dog's brain-to-body size ratio, the findings don't necessarily translate directly to your dog's intelligence. "Dogs have been bred for different cognitive abilities," Balcarcel said, "so even if your dog is on the small-brained end of things, they are special and specialized in their own way."

If you've ever known a dog, you've probably had this experience: You're sitting out by a pool on a hot day, throwing a stick for your canine companion. Fido fetches it, then comes right up to you, gives you a doggy grin and shakes cold water all over your dry clothes.

Scientists have finally figured out why dogs do this shake. According to new research, the "wet dog shake" is the fault of a receptor in mammal skin called C-LTMR. And it causes furry animals of all sorts, from dogs to cats to mice, to perform a surprisingly consistent shake when stimulated by droplets of liquid on the back of the neck.

"It's a complicated behavior," said Dawei Zhang, who co-authored the research as a doctoral student at the Howard Hughes Medical Institute of Harvard Medical School. The study was published today (Nov. 7) in the journal Science. Across individuals and species, Zhang told Live Science, animals tend to shake at the same frequency and with a similar pattern of turns — usually three back-and-forth shakes at a time — and no one knew what receptors and nerves were responsible.

New genetic tools enabled Zhang and colleagues to find out, but identifying the culprit for the shake took a bit of detective work. First, the researchers created genetic mutations in mice that would knock out either the channels in skin receptors that detect mechanical forces, or the receptors that detect temperature change. They found that mice without the ability to detect temperature change still shook when droplets of oil were sprinkled on the backs of their necks (the most reliable way to trigger a "wet dog" shake). But mice without mechanoreceptor channels didn't shake.

So Zhang and his team focused on mechanoreceptors, tracking their activity in response to oil droplets. They narrowed down their focus to three receptors, all of which react to very light touch. Next, they used a technique called optogenetics to activate specific receptors on the skin with light. With this technique, they could trigger the individual nerve types without any liquid stimulus.

The results were clear: When the researchers stimulated a type of nerve called C-fiber low-threshold mechanoreceptors (C-LTMRs), the mice shook as if they'd been given a sudden shower. To double-check, the researchers engineered mice without C-LTMRs and found that they shook 58% less than normal mice when drizzled with water.

C-LTMRs have long been something of a mystery, Zhang said. They were suspected of creating ticklish sensations in animals based on research conducted 80 years ago, he said, but it wasn't clear how animals experienced the stimulus. In humans, related mechanoreceptors called C-mechanoreceptors have been associated with pleasurable, brushing touches on the skin.

C-LTMRs carry signals from the follicles of the undercoat of furry animals, so the new study suggests they're specialized for detecting tiny, annoying stimuli like crawling parasites or drops of water, Zhang said: "Essentially, it's a defensive system to get rid of potentially harmful stimuli that's on their fur."

Whether humans, with their fur-free skin, have any vestiges of this shaking response is an open question. "I used to give the answer that humans use a towel to dry themselves," Zhang said. But there is a common shiver reaction to light touch on the back of the neck in humans — it's just not clear whether that shiver is related to what a wet dog might feel before it shakes.

"It's difficult to correlate whether this is an evolutionary product of the rodent or furry animal 'wet dog' shake," Zhang said. "Maybe it is, maybe it's not."

Another outstanding mystery: Why do dogs have to come right up to you to shake themselves dry? That one may prove more difficult to solve.

If you have a dog, you may have noticed that its paws smell disturbingly similar to a popular snack food: Fritos.

In fact, even the corn chip brand acknowledged the stinky similarity, tweeting in 2022, "Stop saying we smell like dog paws, we're trying to sell corn chips here." 

So what causes dogs' paws to smell like this salty snack? And is it cause for concern?

Dr. Jerry Klein, chief veterinary officer at the American Kennel Club (AKC), told Live Science that the cause comes down to a shift toward higher levels of certain types of skin bacteria.

"It's just like in humans, our feet tend to not smell badly unless we are either grungy, dirty or sweaty," Klein said. "Our feet should not smell that way under normal circumstances."

Related: 'Puppy eyes' didn't evolve just for humans, study of wild dogs finds

But when the skin's flora changes, that's when feet can tread into smellier territory. 

"Every animal and person has normal skin flora that protects us and has a certain balance of different microbes and bacteria," Klein said. "But when things get disrupted, then things start to change."

But smellier paws don't necessarily imply the dog is unhealthy — especially if it displays no other signs of distress, Klein said.

Unlike humans, who protect their feet with shoes before venturing outside, dogs' bare paws are regularly exposed to different surfaces that can contain a menagerie of bacteria and fungi.

Ultimately, Frito feet result from two types of bacteria, Pseudomonas and Proteus, both of which can give off a yeasty odor akin to corn chips, according to the AKC. 

The fix for Frito feet is fairly simple. First, you can just accept that your dog smells like corn chips. "If your dog isn't being bothered by its paws, then it's probably not an issue," Klein said.

But if you are bothered by the smell, "you can always dilute some mild dish soap with water and wash their feet and dry them thoroughly," he added. "Then take a good look at the paws and make sure there's no lesions or ulcerations or infections, which could be a sign of something bigger."

If the dog is constantly licking or biting its paws or acting differently, that may be a sign of something more serious, Klein added.

"If you notice an overwhelming smell from the paws or even on the body, then maybe it's something that needs to be addressed," Klein said. "It's not necessarily an emergency, but it might be something that you want to mention the next time you go to the vet." 

Humans and dogs have been close companions for perhaps 30,000 years, according to anthropological and DNA evidence. So it would make sense that dogs would be uniquely qualified to interpret human emotion. They have evolved to read verbal and visual cues from their owners, and previous research has shown that with their acute sense of smell, they can even detect the odor of stress in human sweat. Now researchers have found that not only can dogs smell stress—in this case represented by higher levels of the hormone cortisol—they also react to it emotionally.

For the new study, published Monday in Scientific Reports, scientists at the University of Bristol in England recruited 18 dogs of varying breeds, along with their owners. Eleven volunteers who were unfamiliar to the dogs were put through a stress test involving public speaking and arithmetic while samples of their underarm sweat were gathered on pieces of cloth. Next, the human participants underwent a relaxation exercise that included watching a nature video on a beanbag chair under dim lighting, after which new sweat samples were taken. Sweat samples from three of these volunteers were used in the study.

Participating canines were put into three groups and smelled sweat samples from one of the three volunteers. Prior to doing so, the dogs were trained to know that a food bowl at one location contained a treat and that a bowl at another location did not. During testing, bowls that did not contain a treat were sometimes placed in one of three "ambiguous" locations. In one testing session, when the dogs smelled the sample from a stressed volunteer, compared with the scent of a cloth without a sample, they were less likely to approach the bowl in one of the ambiguous locations, suggesting that they thought this bowl did not contain a treat. Previous research has shown that an expectation of a negative outcome reflects a down mood in dogs.

RELATED: Could dogs survive without humans?

The results imply that when dogs are around stressed individuals, they're more pessimistic about uncertain situations, whereas proximity to people with the relaxed odor does not have this effect, says Zoe Parr-Cortes, lead study author and a Ph.D. student at Bristol Veterinary School at the University of Bristol. "For thousands of years, dogs have learned to live with us, and a lot of their evolution has been alongside us. Both humans and dogs are social animals, and there's an emotional contagion between us," she says. "Being able to sense stress from another member of the pack was likely beneficial because it alerted them of a threat that another member of the group had already detected."

The fact that the odor came from an individual who was unfamiliar to the dogs speaks to the importance of smell for the animals and to the way it affects emotions in such practical situations, says Katherine A. Houpt, a professor emeritus of behavioral medicine at Cornell University's College of Veterinary Medicine. Houpt, who was not involved in the new study, suggests that the smell of stress may have reduced the dogs' hunger because it's known to impact appetite. "It might not be that it's changing their decision-making but more that it's changing their motivation for food," she says. "It makes sense because when you're super stressed, you're not quite as interested in that candy bar."

This research, Houpt adds, shows that dogs have empathy based on smell in addition to visual and verbal cues. And when you're stressed, that could translate into behaviors that your dog doesn't normally display, she says. What's more, it leaves us to wonder how stress impacts the animals under the more intense weight of an anxious owner. "If the dogs are responding to more mild stress like this, I'd be interested to see how they responded to something more serious like an impending tornado, losing your job or failing a test," Houpt says. "One would expect the dog to be even more attuned to an actual threat."

Visit any dog park, and you're bound to see matching pairs of dogs and humans. But do dogs really tend to look like their owners? And, if so, what's responsible for this resemblance? 

"Whilst not a universal phenomenon amongst all owners and dogs, there is some evidence that purebred dogs and owners tend to resemble each other at some level," Katrina Holland, a research officer on the human behavior team at Dogs Trust, an animal welfare charity in the U.K., told Live Science in an email. 

Several studies have found that people can successfully match pictures of purebred dogs with pictures of their owners at levels above random chance. In one study, participants were able to match dogs with their owners regardless of whether they were told to choose the real dog-owner pairs or just choose pairs that looked alike. This finding suggests that it's physical appearance, and not some other element, that people are using to make these judgments.

Certain aspects of physical appearance are more important than others. Facial features, especially the eyes, are more integral to the perception of resemblance than qualities such as size, hairstyle and physical fitness, a different 2015 study found. When a researcher showed participants real and fake dog-owner pairs while masking different parts of the dogs' and owners' facial features, the participants were equally successful at matching when they saw only the eye region as when they saw the full face or the face with the mouth covered. But when they masked the eye region, the participants' success rate dropped to 50-50.

So if it's true that dogs tend to look like their owners, why is this? Do we choose dogs that look like us, or do our dogs start to look more like us over time?

Related: Could dogs survive without humans?

Research suggests it's probably the former, Holland said.

For example, a 2004 study found that how long a person had owned their dog wasn't correlated with their resemblance; participants were just as successful at picking out the dog-owner pairs regardless of how long those pairs had been together. That suggests that people are choosing dogs that look like them at the outset.

One hypothesis is that people tend to seek out people, including mates, who look like them, Holland said. Researchers have suggested that the same thing happens when people choose their pets. 

"Alternatively, it may be that we prefer dogs who look somewhat similar to us due to the 'mere exposure effect,' in which people prefer familiar items (i.e., their own faces, seen frequently through mirror exposure) over those they have not seen before or seen less often," Holland said. 

A familiar example of the mere exposure effect happens with music: A song that you didn't like much the first time you heard it becomes irresistible after it's on the radio all summer. People see their own face constantly, so that repeated exposure leads them to prefer faces that look like their own, including in dogs.

It's not just appearance, either. "Findings from a recent study indicate that dogs and their owners resemble each other in the 'Big Five' personality dimensions": extraversion, agreeableness, openness, conscientiousness and neuroticism, Holland said. These findings also support the idea that we select pets that are similar to us, she said — not just those that look like us, but those that act like us, too. 

Of course, a dog's similarity to us isn't the only thing to think about when choosing a pet. "Taking your time to fully consider all aspects of dog ownership and being prepared will help set you up for a lifelong, successful relationship with your new dog, Holland said." But after those considerations, there's nothing wrong with picking out a cute canine twin to hit the dog park with.

When a dog stares at you with big, sad, puppy dog eyes, it's easy to imagine that this adorable look is meant specifically to melt your heart (and score some treats). But new research shows that other species in the canid family tree are just as capable of making sorrowful eyes as your pooch.

The new finding, published April 10 in the journal The Anatomical Record, dispels the belief that puppy dog eyes are the product of domestication. And it debunks a 2019 study hypothesizing that pooches evolved a highly expressive face due to their long history with humans.

The 2019 study found that domestic dogs had highly developed muscles around their eyes compared with wolves (Canis lupus), which enabled them to make a wider range of facial expressions. The researchers concluded that these muscles may have developed as dogs began living more closely with humans so they could mimic our own facial expressions as a way to encourage us to take care of them. 

"We were curious to see, is that true? Or do these muscles also exist in other highly social canids?" Heather Smith, an anatomist at Midwestern University in Illinois and first author of the new paper, told Live Science.

To find out, Smith's team performed a detailed dissection on a deceased African wild dog (Lycaon pictus) specimen donated by a zoo. The researchers found that not only do African wild dogs have the same "puppy-dog eye" muscles as domestic dogs, but these muscles are just as developed as those in domestic canines. "So it kind of debunks the idea that domestic dogs are the only canids that have this, and that they evolved specifically for us," Smith said.

Related: Are dogs smarter than wolves?

The researchers believe these eye muscles developed to help African wild dogs coordinate and communicate as they hunt on the open savanna. Like wolves and their domestic cousins, African wild dogs are highly social, living in groups of around five to nine individuals. Their highly expressive faces may enable them to make silent visual signals across the grassy plane.

"This study affirms that not only are [wild dogs] very social, but a lot of those social cues are probably linked to visual signals," Adam Hartstone-Rose, a comparative morphologist at North Carolina State University who was not involved in the new research, told Live Science.

Despite also living in tightly knit social groups, wolves' facial muscles probably did not evolve to be as strong as those of domestic and African wild dogs because they rely less on visual communication. Wolves hunt in a variety of landscapes, including in dense forests and mountains, where each individual is much more likely to be obscured by rocks or trees when pursuing prey. As a result, they may have evolved to coordinate using more complex vocalizations or scent signals rather than visual cues, according to Hartstone-Rose. 

In the future, Smith and her team hope to examine the facial anatomy of other wild canid species, such as foxes, Asian wolves and dholes (Cuon alpinus), to see how well-developed their puppy dog eye muscles are. This will give them better insight into how these species communicate and hunt, and should help the researchers determine whether the trait exists in species that are both social and visually oriented.

For Hartstone-Rose, this research highlights the ways in which evolutionary pressures work to emphasize or de-emphasize different traits in similar species. "It's not really that these muscles either exist or don't exist," he said. "This is a really elegant example of how all species of mammals have these basic building blocks."

When two dogs meet, they often go straight for a whiff of each other's behind. And anyone living in a multicat household will tell you that cats regularly put their nose under their fellow felines' tails.

So why do dogs sniff each other's butts? It turns out, there's a good reason behind this bottom-sniffing obsession.

"Dogs can tell [another dog's] health and reproductive status, identify what they have eaten, and generally catch up on the 'news' from smelling each other's rear ends," said Ellen Furlong, an associate professor of psychology who specializes in animal cognition at Transylvania University in Lexington, Kentucky.

Mating also plays a role. "Male (particularly unaltered) dogs may also spend more time sniffing females for information about their reproductive status," Furlong told Live Science in an email. 

But how is it possible for dogs to glean all of this information from a simple butt sniff? One of the first clues for unraveling this mystery came in 1976, when a study on dogs and coyotes was published. The study found that two small pouches, one on each side of a dog's anus — known as anal sacs — release a cocktail of smelly chemicals, including fishy-smelling trimethylamine and pungent propionic acid and butyric acid. These anal sac secretions probably serve as chemical communication signals between dogs, according to a study published in 2021.

Related: Why do cats' claws retract but dogs' claws don't?

Each chemical released by a dog is likely to relay specific information to another dog, but scientists have yet to crack this scent code. A study published in 2023 made some headway in decoding this chemical language by comparing the anal sac secretions of male and female dogs. It found that certain chemicals were released only by females and others only by males. 

The researchers also recorded a lot of variation in the chemicals released and their concentrations among individuals of the same sex. This suggests that parameters besides gender influence a dog's odor profile, the researchers said.

So a dog sniffs out a mixture of chemicals in another dog. Thanks to their far superior noses, dogs can identify individual smells in a mixture and detect them at significantly smaller concentrations than humans can. "A dog's sense of smell is 10,000 to 100,000 times better than ours. Dogs can smell 1 part per TRILLION, which is truly astounding," Furlong said.

Cats do it, too

A cat's sense of smell also far exceeds a human's. Research suggests that scent detection is central to cats' behavior and overall cat welfare, Kristyn Vitale, an assistant professor of animal health and behavior at Unity Environmental University in Maine told Live Science in an email.

Like dogs, cats have small glands that produce chemicals with distinct odors. "From smelling another cat's rear end, a cat can identify whether that individual is familiar or unfamiliar to them, as well as the cat's sex and even possibly their reproductive status," Vitale said.

"Both male and female cats utilize scent to identify social partners and communicate with them," she added.

In 2023, researchers at the University of California, Davis, unveiled another piece of the bottom-sniffing puzzle through a study of 23 domestic cats. They found that a cat's anal glands are home to a bustling community of bacteria, which are probably involved in the production of smelly anal gland secretions. Different cats had different bacteria in their anal glands, and the types of bacteria varied with a cat's age and weight status.

More research is required, but the study authors believe that these bacteria help cats communicate. Other carnivores, including dogs, are also thought to communicate via the secretions of gland-inhabiting bacteria. Supporting this hypothesis, a study in hyenas found that bacteria living in their scent glands produce components of chemical signals that hyenas use to communicate.

Imagine the sound of a dog walking across a tile floor, the "click, click, click" of its claws tapping against the ground. Now, imagine a cat padding across the same floor — the difference is the cat moves in total silence. Cats can fully retract their claws, giving them superior sneaking ability.

But why do cats have retractable claws, whereas dogs do not?

It all comes down to how cats and dogs use their claws. Cats use their claws primarily to attack their prey, said Anthony Russell, an evolutionary biologist at the University of Calgary in Alberta, Canada. They use their front claws to grab and hold on to their quarry and their back claws to rake open the prey's belly.

Cats need to keep their claws sharp to secure that next meal. If their claws were extended all the time, they would wear down as they scraped the ground, much like how a nail file wears down sharp points on a human fingernail.

"So the reason for this type of retraction is to keep them really sharp," Russell said. "Keeping these very sharp tips means that [cats] can use them when they're needed, then store them away for the next time."

Related: Why do cats wiggle their butts before they pounce?

To keep those tiny toe weapons in prime slicing condition, cats' claws are retracted by default, Russell told Live Science. "It would be like having the end of the finger on a rubber band," he said. "It costs energy to actually extend those claws, and once you relax those muscles, the claws flip back on their own."

Because cats are solitary hunters, sharp, hidden claws help them take down prey by themselves. "Having a retractable claw is a vital piece of equipment to really be able to single-handedly handle the prey," said Xiaoming Wang, a vertebrate paleontologist at the Natural History Museum of Los Angeles County. Their sharp claws prevent prey animals from wiggling out of the felines' grasp, allowing cats to ambush and wrangle prey two to three times larger than themselves, Wang told Live Science.

Dogs, on the other hand, are social hunters. They work in groups to take down larger animals, wearing their prey out over longer distances. For dogs, "if you're hunting a moose or something, you wander along for kilometers and nip at it and worry [at] it until it is exhausted, and then you all jump on it," Russell said. "Whereas cats essentially have a short burst, and then it's over. Either the prey got away, or the prey is captured."

With more predators working together, it's less important for dogs to be able to grip and hold onto their prey, so they don't have to keep their claws as sharp. Sheer numbers are enough to give them the advantage.

But dogs' claws aren't completely useless; they are important for maintaining traction and maneuverability while running, Wang said. Dogs' claws help them grip the earth and change directions quickly — a useful adaptation for pursuing prey over long distances.

Most cats get by without using their claws while running, but cheetahs are an exception. "A cheetah just runs too fast to not use its claws" for traction, Wang said. Cheetah claws have evolved to be less retractile and more dog-like than other cats' claws so that cheetahs can chase their prey faster and over longer distances.

It's worth noting that all carnivores can pull back their claws to some extent, Russell said. Cats' claws are "hyper-retractile" — they fold all the way back against their finger bones when not in use, and cats don't need to expend effort to keep them there. But while most other carnivores don't have retractable claws in the colloquial sense, all carnivores can lift their claws at least a little by flexing their fingers or toes. Imagine flexing your hand to point your fingernails just a bit backward. "It's a small amount of movement," Russell said, "but it is retraction."

The discovery of a lynx buried with four dogs at an early-medieval settlement in Hungary is confounding archaeologists, as these wild cats are rarely found in archaeological digs.

The fifth-to-sixth-century pit, which was about 4.6 feet (1.4 meters) deep, contained a complete lynx skeleton at the bottom and the skeletons of four dogs — the size of present-day pointers or German shepherds — layered on top of it. Possible interpretations of the unique find, such as a hunting accident and a lynx cult, are detailed in a new study published March 21 in the International Journal of Osteoarchaeology.

Found all over the Northern Hemisphere, the lynx — better known as a bobcat in North America — is a large carnivore that typically preys on small mammals and birds. While the Eurasian lynx has all but disappeared in continental Europe due to human encroachment on their forest habitats, the species was widespread before modern times.

Yet remains of lynxes have been found at only a couple dozen archaeological sites in Europe and Asia. "Archaeologically, lynx skeletons are extremely rare, as lynx meat is usually not consumed," study co-author Lászlo Bartosiewicz, an archaeologist at Stockholm University, told Live Science in an email. Sometimes, lynx claws end up in human graves, likely because their pelts were buried there and decayed, Bartosiewicz said, but intact skeletons are rarely encountered.

Related: Ancient Romans sacrificed birds to the goddess Isis, burnt bones in Pompeii reveal

The pit of animals was found at the site of Zamárdi-Kútvölgyi-dűlő in west-central Hungary, an area known as Pannonia under Roman rule. The last phase of occupation of the site dates to the early Middle Ages, not long after the fall of the Western Roman Empire. Zamárdi appears to have been a small settlement at that time, and archaeologists have previously discovered dozens of buildings, pits, wells and ovens there. The people likely obtained their food from domesticated animals and crops rather than from hunted wild game.

At the bottom of the beehive-shaped pit, the male lynx skeleton was found fully stretched out. Four adult dogs — two females and two males — were buried on their right sides, above the lynx; each animal was separated by an 8-to-16-inch (20 to 40 centimeters) layer of dirt.

"It is hard to summarize our interpretation of the lynx/dogs burial as no parallels (archaeological or ethnographic) are known," Bartosiewicz said.

It's possible that the burial is the end result of a deadly confrontation, in which the dogs may have been killed by a cornered lynx, the researchers said. Or, perhaps it was a purposeful animal burial with ritual significance. But if this were the case, the researchers noted in their study, it's surprising that more care wasn't taken in the placement of the lynx and dogs.

"Unfortunately, the Migration Period population of a former Roman province may have represented almost any ideology given the chaotic history of the period," Bartosiewicz said.

Victoria Moses, a zooarchaeologist at Harvard University who was not involved in the study, told Live Science in an email that "the authors are wise not to over-interpret what burying lynx and dogs meant to the inhabitants of the site at the time." But given the presence of such a unique animal in an atypical burial made within a short time frame, "the likelihood of ritual is high," Moses said.

Given the dynamic multicultural setting of Zamárdi, it is currently impossible to make an  unambiguous interpretation of the animal pit without further evidence, the researchers concluded.

In the absence of additional written or ethnographic material on the perception of this large carnivore in the early Middle Ages, "our rather special find is indeed the 'missing lynx' in this story," Bartosiewicz said.

Editor's note: Updated at 1:18 p.m. on April 9 to note that the dogs would have been the size of a modern pointer or German shepherd and that while lynx pelts don't preserve in ancient burials, their claws often do.

Sleeping with your dog in the same room could be negatively affecting your sleep quality, according to my team's recently published research in Scientific Reports.

We recruited a nationally representative sample of more than 1,500 American adults who completed questionnaires assessing their sleep habits. Overall, about half of the participants reported co-sleeping with pets — defined in our study as sleeping in the same room with your pet for at least part of the night.

Next, our research team compared the sleep habits of people who did and didn't co-sleep with pets. Our analyses revealed that participants who co-slept with pets had poorer sleep quality and more insomnia symptoms than those who did not. These findings persisted even after accounting for demographic differences between these groups. When considering pet type, we found evidence for a negative effect on sleep when co-sleeping with dogs but no evidence for a negative effect on sleep when co-sleeping with cats.

Surprisingly, 93% of people in our study who co-slept with their pets believed that their pets had either a positive or neutral overall effect on their sleep. Although more research is needed, these findings could suggest that most people are unaware of the potential negative effects their pets may have on their sleep.

Why it matters

Most pet owners report that their pets have a generally positive effect on their mental health. Pets can improve their owners' health in numerous ways during the day, such as by encouraging physical activity, promoting a daily routine and providing love and companionship.

However, our study fills an important knowledge gap by indicating that co-sleeping with pets can affect sleep quality. Good sleep is a pillar of health and wellness. Even though pets may have an overall positive effect on mental health, it is possible that some of this benefit may be undermined if they are also causing you to lose sleep at night.

Although some people report that co-sleeping with their pets can provide them with a sense of comfort or intimacy, it is important for people sharing a bedroom with their pets to be aware of their potential to serve as a source of nighttime noise, heat or movement that can disrupt your ability to fall or stay asleep.

What still isn't known

Survey-based studies like ours are unable to prove that co-sleeping with pets causes disrupted sleep, although there is some evidence suggesting that this could be the case.

One important factor that our study did not assess was whether participants were also co-sleeping with other people like a spouse or child. Previous research suggests that sharing a bed with other people can also affect our sleep and that the mental health benefits of pet ownership could be stronger for people with a romantic partner.

What's next

It probably isn’t realistic for most people to just stop co-sleeping with their pets. So, what should someone do to improve their sleep if they already share a bed with their pets?

Some expert tips include choosing a mattress that is large enough for you and your pets, washing and changing your bedding regularly, and establishing and maintaining a consistent bedtime routine with your pets. Further research is needed to identify more specific habits and routines that pet owners can adopt to ensure a good night's sleep when sharing the bedroom with their pets.

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

Retrievers are known to be food-motivated dogs, but a gene mutation found in some of these pups causes them to have not only an insatiable appetite but also lower metabolism, a combination that can lead to obesity, a new study finds.

This "double whammy" is caused by a mutation in the POMC gene, which plays a role in satiety by alerting the brain of hunger, according to a statement.

This genetic anomaly affects 25% of Labrador retrievers and 66% of flat-coated retrievers, and can cause the dogs to feel hungry even when their stomachs are full, according to a study published Wednesday (March 6) in the journal Science Advances.

"We found that a mutation in the POMC gene seems to make dogs hungrier," Eleanor Raffan, an assistant professor in systems physiology at the University of Cambridge in the U.K., said in the statement. "Affected dogs tend to overeat because they get hungry between meals more quickly than dogs without the mutation."

In the study, researchers analyzed 87 adult pet Labrador retrievers that were either a healthy weight or were slightly overweight. The researchers fed each dog a can of food every 20 minutes until the canines were stuffed. All of the dogs "ate huge amounts of food," but those with the POMC mutation ate the same amount as those without it, showing "they all feel full with a similar amount of food," according to the statement.

Related: How long do dogs live?

However, on a separate day, the researchers conducted what they called the "sausage in a box test." Three hours after feeding the dogs a basic breakfast, they tempted them with a meaty tidbit inside a clear plastic box with a partly cut open lid, so that the dogs could smell but not access the delectable treat. 

The dogs with the mutation "tried significantly harder" to nab the sausage versus those without it, indicating that they were more motivated to snag the snack due to higher hunger.

After the test, dogs slept in chambers that measured the gases they exhaled, as an approximate measure of their metabolic activity. This revealed that the POMC canines burned about 25% fewer calories than the other dogs when at rest.

The team also found that the POMC mutation changes a pathway in the dogs' brains that is linked to body-weight regulation. In effect, the mutation drives a starvation signal that tells the body to eat more food and to conserve energy by slowing down the metabolic rate even though the dogs are not actually starving.

Interestingly, the POMC gene and its effect on brain pathways is similar in humans, and mutations in the gene can also lead to obesity.

"People are often rude about the owners of fat dogs, blaming them for not properly managing their dogs' diet and exercise," Raffan said. "But we've shown that Labradors with this genetic mutation are looking for food all the time, trying to increase their energy intake."

She recommended that retriever owners space out food rations, for instance, by putting their dog's food in a puzzle feeder or by spreading it around a yard so it takes the dogs longer to eat it.

"It's very difficult to keep these dogs slim, but it can be done," Raffan said.

It has long been debated whether animals can smell fear in humans. Unfortunately, answering this age-old question isn't as simple as pulling Fluffy or Fido aside and asking them what they're sensing.

So what does the research say? Can animals actually smell fear? To get to the root of this question, researchers have largely taken human presence out of the equation, as animals such as dogs are known to respond to our expressions and body posture. Instead, investigators have focused on how animals, including horses and dogs, respond to various smells emitted by humans watching happy versus fear-inducing videos.

In a horse study, published in 2023 in the journal Scientific Reports, researchers had participants watch clips from a comedy one day and a horror movie the next.

After the participants watched each video, the researchers collected sweat samples from the viewers' armpits using cotton pads and asked the participants to report how much joy or fear they felt while watching each clip. Then, the researchers presented the two swab samples from the same human to an assigned horse to see if it could discriminate between odors produced by humans during times of happiness and distress. 

"At first we weren't sure if the horses could differentiate between the odors," lead study author Plotine Jardat, a doctoral student at the University of Tours in France, told Live Science.

Related: Do dogs love us?

But the horses reacted differently depending on which cotton pad they were presented with.

"When the horses smelled the joy samples, they used only their left nostrils," Jardat said. "That indicates which part of the brain they are using to analyze the odor. In all mammals, the two brain hemispheres have different functions, and in an emotional context, it seems like the odor from the joy samples were perceived as positive by the horses."

But when the horses were given the samples swiped during the horror film, the animals reacted much differently and not only sniffed the sample longer but also "used both nostrils" to catch a whiff, Jardat said.

However, Jardat was quick to point out that this doesn't necessarily mean that horses know what fear is. "It's not like when the horses smell another animal that they have the word 'fear' cross their minds," she said. "But now we do know that [horses] can differentiate odors from different emotional states in humans."

This raises a question: What specific compounds do humans produce in their sweat that causes a shift in the horses' behavior?

Researchers propose that chemosignals, which are chemicals produced by animals that can affect the behavior of another animal, could be behind the horses' reactions. In humans, there are several compounds in sweat, such as adrenaline or androstadienone (a pheromone-like protein) that could be causing a shift in odor during moments of fear. These compounds could also be carrying "emotional information" from one species to the other, the researchers wrote in the study.

In a future study, scientists plan to examine whether smelling fear could cause a fearful reaction in the horses and what kind of impact this could have on the animals emotionally by having them perform a range of tests after smelling the samples.

"We want to see if fear will modify their reactions to the tests," Jardat said.

Meanwhile, in a 2018 study in the journal Animal Cognition, scientists tasked Labrador retrievers to sniff samples swiped from male participants' underarms after watching either a scary or happy video clip. The researchers placed the sample inside a box with an opening and placed the box inside a closed room with two people: a stranger and the dog's owner. 

Similar to the horse study, researchers found that the dogs reacted differently depending on whether they smelled the scent of a fearful or a happy human. 

"When the dogs smelled the odor of a happy person, they increased their interactions with the stranger in the room," study lead author Biagio D'Aniello, a professor of zoology at the University of Naples Federico II in Italy, told Live Science.

But when they sniffed a sample from someone who was fearful, the dogs had a completely different reaction.

"When they smelled fear, they would either go to their owner or they would go to the door and try to leave the room," study co-author Anna Scandurra, a postdoctoral researcher at the University of Naples Federico II, told Live Science. 

The researchers came to a similar conclusion as the scientists in the horse study: The dogs' reactions were likely due to chemosignals, suggesting that "interspecies emotional communication" was at play, the authors wrote in their study. 

A puppy has spontaneously regrown his jawbone after part of it was surgically removed because of a cancerous tumor. It is believed to be the first reported case of a dog regenerating its mandible.

Veterinarians at Cornell University College of Veterinary Medicine's Dentistry and Oral Surgery Service first diagnosed Tyson, a 3-month-old French bulldog, with cancer when he was scheduled for surgery on a cleft palate in spring 2023. The tumor was an oral papillary squamous cell carcinoma, a rare type of malignant skin cancer in dogs.

The cancer had not spread to the rest of Tyson's body, so the vets decided to remove the left side of his jaw, which was the affected area. 

Astonishingly, when Tyson was examined eight weeks later, veterinarians found that his jaw had begun to regrow. Although this phenomenon has previously been recorded in human children, this is the first time it has been documented in a dog.

Related: Could dogs survive without humans?

According to the case report, published Oct. 11 in the journal Frontiers in Veterinary Science, the regrowth may have occurred because the vets managed to preserve a significant amount of periosteum — a thin membrane that covers the surface of bones — during the operation. Periosteum contains blood vessels, nerves and cells that help bones grow and heal.

"This was likely imperative to the regeneration of new bone," report lead author Alexandra Wright, a dentistry and oral surgery resident who led Tyson's care, said in a statement.The early detection of the tumor likely also played a vital role in the regrowth. If a larger part of the jaw had had to have been removed, it may not have grown back, the authors wrote.

Tyson's new jawbone is functional but it is missing certain features, such as teeth and the mandibular canal, which normally contains blood vessels and nerves. However, it is the same length as the bone on the right, which should prevent mandibular drift. This is a common issue after part of the jaw is removed, causing the unaffected side to be pulled towards the center. There is also no sign that the cancer has returned.

After the tumor was removed, Tyson underwent another surgery to address his cleft palate — an opening between the mouth and the nose that happens when the tissues separating these two cavities do not grow together properly. Although he isn't yet able to chew on hard toys, he enjoys playing with soft toys, his owner Melissa Forsythe said in the statement. "We had no idea his jaw would grow back," she added. "He was the best patient."

The report authors said spontaneous regeneration is unpredictable and that more research is needed to understand the process.

"More has to be done to understand the likelihood of this occurring in other dogs and if a specific age range makes a difference," Wright said. "But this case documents a very positive surgical outcome in a life-threatening situation."

Mick Moloney was walking on the banks of the Murray River in northwestern Victoria, Australia, when he noticed his dog Hutchy was missing. He glanced toward the water and saw a kangaroo standing waist-deep in the river with its arms submerged.

"Next thing you know, Hutchy came up gasping for air, water spilling out of his mouth and screaming his head off," Moloney told the Australian broadcaster 7News.

Moloney waded through the water to retrieve his dog, which the kangaroo was gripping from behind, and took a swing at the offender, a video that has since gone viral showed. The kangaroo retaliated with a punch, but both Moloney and Hutchy eventually made it safely back to the riverbank.

The bizarre run-in, which occurred on Oct. 12, is the latest recorded duel between a kangaroo and a pet dog, where it appears the kangaroo is trying to drown the dog.

Related: Mammals with pouches are 'more evolved' than humans — sort of

In 2020, a small dog nearly met its fate after clashing with a 5 foot (1.5 meter) tall kangaroo in Brisbane River in Queensland, 7News Sydney reported. And in 2014, a kangaroo tried to drown two staffies after the dogs cornered it in a dam in New South Wales. But why do the marsupials behave in this way? 

Kangaroos perceive dogs as a threat because dogs closely resemble dingoes — one of their deadliest predators, said Euan Ritchie, a professor of wildlife ecology and conservation at Deakin University in Australia.

"This behavior is one way that kangaroos have learnt to survive attacks by dingoes, a native top predator they've coexisted with for many thousands of years," Ritchie told Live Science in an email.

Dingoes (Canis dingo) are Australia's largest land predators and genetically sit somewhere between a wolf and a modern domestic dog. Humans likely brought the ancestors of modern dingoes to the mainland between 5,000 and 8,500 years ago, and the canines gradually settled for a diet of marsupials and reptiles. Modern dogs weren't introduced to Australia until 1788, when the first ships carrying British and Irish convicts arrived on the continent. 

Dingoes hunt kangaroos in large packs, relaying each other to chase their prey until exhaustion. To kill them, dingoes either bite at their hind legs to slow them down before going for the throat, or approach kangaroos from the side to bite at the neck directly.

Kangaroos seek refuge from dingoes by hopping into the nearest body of water — an escape strategy that "works well for domestic and farm dogs too," Ritchie said. Should a dingo or dog chase after them, the kangaroo might attempt to drown it.

"It's an instinctive behavior that has evolved as a defense against predators," said Graeme Coulson, an honorary principal fellow at the University of Melbourne in Australia specializing in kangaroo behavior and ecology. "Males are strong enough to stand up and handle a four-legged dog-paddling adversary," he told Live Science in an email.

Male eastern gray kangaroos (Macropus giganteus) — one of Australia's four species of kangaroos, to which the kangaroo that tried to drown Hutchy belonged — can weigh up to 150 pounds (70 kilograms), Ritchie said. "The males have long, very powerful, muscular arms, and long, sharp claws, and they'll use these to hold a dog and push it under the water in an attempt to drown it," he said. 

The largest living species of kangaroo is the red kangaroo (Osphranter rufus), with the males weighing up to 202 pounds (92 kg).

Dog owners should also beware of kangaroos, as they can sometimes attack people, Ritchie said. "A powerful kick or scratch can do serious harm," he said. "Dog owners should ensure kangaroos aren't being harassed or harmed, which also ensures their dogs are kept safe too."

Dogs across the U.S. are getting sick with an unexplained respiratory illness. 

As of Monday (Nov. 27), at least 14 states, including Oregon, New Hampshire, Colorado and Massachusetts, have reported cases of pet dogs of different breeds developing symptoms including cough, runny nose, lethargy and a loss of appetite. In Oregon, for example, more than 200 cases have been reported since mid-August. However, the first cases of the outbreak are believed to have been reported in New Hampshire as early as last year, an expert told Live Science. 

The mystery illness' symptoms resemble those of common respiratory diseases that affect dogs, such as kennel cough and canine influenza. However, the infection appears to last longer than those diseases typically do and seems resistant to treatment with antibiotics, vets say. 

Here's what we know so far about the outbreak. 

Related: 2 Salmonella outbreaks linked to pet foods hit US and Canada

What are the symptoms of the new dog illness?

The unexplained dog disease is similar to common respiratory illnesses that affect canines. It typically starts with a cough that moves on to a fever, sneezing, a runny nose and watery eyes. However, not all the affected dogs have shown the same combination of symptoms. 

Normally, dogs recover from respiratory illnesses fairly easily, either on their own or with the help of antibiotics in the case of bacterial infections, Dr. Kurt Williams, director of the Oregon Veterinary Diagnostic Laboratory at Oregon State University, told The New York Times. Usually dogs recover from kennel cough, for example, within seven to 10 days. However, this outbreak is different. 

"In these dogs, either it lingered for longer or it took a downward spiral and led to very serious outcomes, including death," Williams said. It seems that serious outcomes are more likely to happen in older dogs or those with existing health issues, The New York Times reported.

What is causing the dog respiratory infection?

The cause of the outbreak among U.S. dogs is still unknown. However, some scientists think the culprit is a type of "funky bacterium" that has never been seen before, based on samples gathered from dogs in three states. 

"It’s smaller than a normal bacterium in its size and in the size of its genome," Dr. David Needle, a senior veterinary pathologist at the University of New Hampshire, told NBC News. "Long story short, it's a weird bacterium that can be tough to find and sequence," he said. (Sequence refers to analyzing an organism's DNA code.) 

Needle and his team have been tracking the outbreak since last year. So far, they have genetically sequenced 30 clinical samples from dogs that fell ill in New Hampshire last year, as well as 40 dogs from Rhode Island and Massachusetts that got sick this year. Twenty-one of the 30 New Hampshire samples were identified as the same unusual bacterial species, NBC reported. And 7% of the Rhode Island and Massachusetts samples also contained the microbe, Needle told Live Science in an email. 

Related: Why do dogs have cold noses?

The researchers have yet to publish their findings in a peer-reviewed journal, but they're sharing what they've found so that vets are kept as informed as possible. Needle's team hasn't been able to grow the bacteria in lab dishes yet, so they haven't had the opportunity to directly test how antibiotics affect it, Needle told NBC News. However, they can pull some clues from its structure and genetic code.

The specific pathogen behind the ongoing outbreak hasn't been identified, Needle stressed, and it's still unclear whether the one they've found is the same one infecting dogs across the country. Needle thinks the newfound bacterium may have evolved from a microbe normally found in the dog microbiome — the collection of microbes and viruses that live inside and on the surface of their body. 

Whatever its cause, the disease currently appears to be specific to dogs. There have been no reported cases in humans, Mike Stepien, a spokesperson for the the United States Department of Agriculture Animal and Plant Health Inspection Service, told NBC News.

Where has the new dog disease been reported?

Potential cases of the new dog respiratory illness have been reported in at least 14 states, American Veterinary Medical Association (AVMA) president Dr. Rena Carlson told USA Today on Nov. 27. The affected states include California, Colorado, Florida, Georgia, Idaho, Illinois, Indiana, Maryland, Massachusetts, New Hampshire, Oregon, Rhode Island, Vermont and Washington.

As far as we know, New Hampshire was the first state to report cases, Needle told Live Science. 

There is no official count of the total number of infections nationwide, so a lot of our understanding of the outbreak is down to anecdotal reports from vets. 

It's also difficult to get a full picture of how many infections there have been because scientists still don't know what is causing the disease, so vets can't accurately diagnose or test for it, Williams told The Associated Press.

Related: 1st suspected case of human-to-dog monkeypox transmission reported in France

What advice do vets have for dog owners about the new illness?

As the holiday season approaches, people are more likely to put their dogs in kennels or send them to doggy daycare, Dr. Lindsey Ganzer, a veterinarian and chief executive at North Springs Veterinary Referral Center in Colorado, told The New York Times. This could trigger an increase in infections as dogs are likely to come in closer contact with one another. 

"We're really hoping just with getting the word out there that people are less inclined to do that," Ganzer said. Since late October, she's treated about 35 dogs with the disease and all of them had recently spent time in boarding facilities, doggy day care or dog parks. Four dogs died or had to be euthanized. "The veterinary community as a whole is kind of scared," she said. 

However, other vets think that dog owners should be cautious but not worried about the infection. In Oregon, for example, the number of dogs with the mysterious infection represents only a small fraction of the total number of dogs in the state, Dr. Stephen Kochis, chief medical officer for the Oregon Humane Society, told The New York Times. 

Although the current outbreak is being caused by an unknown pathogen, similar respiratory diseases, such as kennel cough, also cause periodic outbreaks of infection, the ODA said. 

To help keep dogs healthy, Williams said that owners should make sure dogs' vaccinations are up to date, but don't panic, he told the AP. Vaccinations may include those for canine influenza, Bordetella (a common cause of kennel cough) and parainfluenza. 

If a dog is sick, people should keep it at home and avoid using communal water bowls or toys, as well as report any symptoms to their vet, the ODA said. 

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

Around and around they go — dogs are often seen spinning in endless pursuit of their own rears. But why do dogs chase their tails?

There are several possible reasons for this behavior, as well as ways to thwart it, experts told Live Science.

Puppies and younger dogs may simply chase their own tails for fun. Puppies, especially, may not yet realize their tails are actually part of their own bodies, according to Schertz Animal Hospital in Texas.

Boredom may be another reason, especially when dogs are left alone for a long time. "Anytime a dog is not enriched or exercised fully, they have the potential to be bored and to self-soothe," Russell Hartstein, a dog behavioral consultant and founder of Fun Paw Care in Los Angeles, told Live Science.

For dogs that run in circles because they are bored, a simple solution may be to play fetch or take a walk. Most dogs would rather chase a ball than their own tails, the VCA Animal Hospitals in Los Angeles notes.

Another reason dogs may chase their tails is to seek attention. A dog's owner may have rewarded this behavior by laughing or saying "good boy" or "good girl," Hartstein said. Even scolding a dog for tail chasing may draw attention that reinforces this behavior, according to VCA Animal Hospitals. To curb tail chasing, ignore the behavior while otherwise supplying the dog with a healthy amount of attention, Schertz Animal Hospital says.

Related: Why do dogs bury bones?

Certain dog breeds are prone to tail chasing. For instance, bull terriers and German shepherds "are well known for susceptibility to compulsive behaviors such as tail chasing," Hannes Lohi, a geneticist at the University of Helsinki, told Live Science.

Unfortunately, a number of physical ailments are linked with tail chasing. An injury to the tail, itching due to intestinal parasites or fleas; impacted anal glands; or food allergies may cause a dog to lick, bite or chase their tail, according to Schertz Animal Hospital. If dogs suddenly start chasing or biting their tails, their owners should schedule a visit with their vet, VCA Animal Hospitals noted.

Finally, tail chasing may be linked with neurological disorders, such as canine compulsive disorder, the dog version of obsessive-compulsive disorder.

In a 2012 study, Lohi and his colleagues investigated 368 dogs from four breeds known for tail chasing. The behavior typically began at 3 to 6 months of age, with nearly half of the tail-chasing dogs displaying other types of compulsions, such as pacing in repetitive patterns, more than regular dogs did.

"Interestingly, dogs that received dietary supplements, especially vitamins and minerals, expressed less tail chasing compared to dogs that did not receive any supplements," Lohi said. "Neutered females had less tail chasing, suggesting an influence of ovarian hormones on tail chasing." In addition, compared with dogs that didn't chase their tails, tail chasers were often shier and had separated earlier from their mothers, he said.

If a dog is otherwise healthy, "practicing dog training and engaging their mental and emotional aspects of their lives will help stop tail chasing," Hartstein said. "There's no downside to training more with your dog and making sure they are fulfilled and enriched in every way possible."

Getting dogs to practice behaviors that are incompatible with tail chasing can help curb the behavior. "For example, if a dog is heeling next to you, or if they're sitting or in a down position, or they're waiting for your guidance, then they will not be looking to chase their tail," Hartstein said.

Two separate outbreaks of Salmonella in people in the U.S. and Canada have both been linked to pet food.

In the U.S., seven cases of Salmonella infection in seven states have been connected to the outbreak so far. These illnesses occurred between January and August of this year, and one case required hospitalization, the Centers for Disease Control and Prevention (CDC) reported. No deaths have been reported.

It can take several weeks for symptoms of Salmonella infection — such as diarrhea, fever and stomach cramps — to emerge, and it takes time to link cases to an ongoing outbreak. So the true number of people who got sick may be much higher than currently reported, the CDC noted. Six of the seven people affected were infants, and the other was over 65.

Officials conducted five interviews with individuals who tested positive for Salmonella or their families. They found that all five had contact with a dog or had a dog in their household. Three of the five people interviewed fed their dogs Victor brand dog food, and one remembered purchasing the Hi-Pro Plus product.

Related: Will eating pet food kill you?

Researchers sampled DNA from the Salmonella bacteria that sickened each person and found that the microbes were very closely related. "This suggests that people in this outbreak got sick from the same product," the CDC reported. Salmonella uncovered in a specific batch of Victor brand Hi-Pro Plus dog food also closely matched the outbreak strain.

"This means that people likely got sick by touching this dog food, touching things like dog bowls that contained this dog food, or touching the poop or saliva of dogs that were fed this dog food," the CDC said. (Note that most pets don't get sick from Salmonella and show no symptoms, but they can spread the bacteria.)

Mid America Pet Food, the manufacturer of the Victor brand dog food, has voluntarily recalled all brands of dog and cat foods it has manufactured with a "best by" date before Oct. 31, 2023. The full recall list can be found on the Food and Drug Administration website.

Meanwhile, in Canada, officials are investigating an outbreak of "extensively drug-resistant" Salmonella that has affected at least 40 people across six provinces, according to a statement from the Public Health Agency of Canada (PHAC). As in the U.S. outbreak, many of the reported illnesses have occurred in children under age 5. Thirteen people have been hospitalized, and no deaths have been reported.

Cases in the Canadian outbreak occurred between July 2020 and September 2023, with 13 of the cases happening within the past year. The investigation was initially prompted by an unusual uptick in drug-resistant Salmonella in multiple provinces. "Using a laboratory method called whole genome sequencing, it was determined that some Salmonella illnesses dating back to 2020 were caused by the same outbreak strain as the illnesses that occurred in 2023," the PHAC reported.

Two likely sources of infection have been identified so far: exposure to raw meat prepared for pets (raw pet food), and contact with cattle, particularly calves. A common supplier of the raw pet food has not yet been identified, and additional sources of infection may turn up as the investigation continues.

"The outbreak is a reminder that Salmonella bacteria can be found in raw pet food and in many species of animals, including dogs and cattle," the PHAC advised. "Always use safe food handling practices when preparing, cooking, or storing raw pet food to prevent illness. Practice good hand hygiene and frequent handwashing after contact with dogs fed raw pet food, cattle, and their environments."

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

At least 15,000 years ago, dogs evolved from groups of gray wolves, leading theories suggest. But does that mean modern-day pooches are smarter than their canine ancestors?

According to experts, the answer is no. But that doesn't mean wolves are smarter than dogs, either.

"You would never say dogs or wolves [are smarter] because we would always say they are both adapted to their environment," Juliane Bräuer, an associate researcher at the Max Planck Institute for Human Development in Germany, told Live Science.

Animal cognition is measured by a range of skills that typically fall into two categories: social cognition, or the skills an individual has with other animals, and nonsocial cognition, or how animals process and manipulate the physical world around them. Wolves and dogs have different cognitive skills that suit their specific lifestyles, according to Bräuer.

"You should just consider those cognitive skills separately," she said. "I always compare this [to] subjects in school."

Related: Do wolves wag their tails?

One of the most common experiments used to measure cognition in dogs and wolves is the pointing test. In a 2021 study, researchers put two cups upside down on a table, with food hidden under one of them. Then, they tasked 44 puppies with finding the food by giving them cues, such as pointing or gazing at the cup or placing a block next to it. After repeating the exercise with 28 wolf pups, the team found that the dogs were twice as likely to find the food as their canine cousins were.

This shows that "there does seem to be something that's more innate about dog cognition that primes them to be able to understand these kinds of pointing tasks and understand the intention behind people's gestures," Hannah Salomons, a postdoctoral evolutionary anthropologist at Duke University and a co-author of the study, told Live Science.

In a 2017 study, a different group of researchers, including Bräuer, set up an experiment in which they shook a cup with food in it. Both the dogs and the wolves identified the cup with the food. But when the researchers shook an empty cup, the wolves stayed put, while the dogs still went for it. This suggests that wolves have a better understanding of cause and effect than dogs do, Bräuer said.

"The wolves are adapted to their environment [and] to the forest where they have to hunt," she said. "They are responsible for their food; they don't get it just by humans. And so it's very adaptive for them to understand something about causality, which they showed in that study."

These are just a few of many tests to measure cognitive skills in wolves and dogs, according to Friederike Range, an animal researcher and founder of the Wolf Science Center in Vienna. At this center, researchers frequently test social and physical skills in dogs and wolves. They have found that overall, wolves are more adept at working with each other, while dogs are typically better at performing tasks with humans because "for dogs, domestication brought a very different picture," Range told Live Science. "They're not so dependent anymore on cooperation with each other."

In any case, these tests aren't used to rank whether dogs are smarter than wolves but rather to better understand the various ways they navigate the world, experts say.

"It's not really meaningful, I guess, to try to rank intelligence, because even within humans, it's hard to define," Salomons said. "It would be hard for us to say, 'Oh, who was smarter, Van Gogh or Einstein,' right? There's just totally different skill sets that those people had. And just the same thing with animals."

While dogs may be man's best friend, it's hard to avoid judging Fido when he gets into his own feces.

A 2018 study published in the Journal of Veterinary Medicine and Science surveyed about 1,400 dog owners in the United States and found that 23% of dogs had eaten poop at least once and 16% were "frequent" poop eaters who ate poop at least six times over the course of the study.

But why do dogs eat poop, and is it harmful to them?

Dogs eating their own poop — a condition called coprophagia — is considered a natural behavior. It's not a form of attention seeking or a result of nutritional deficiencies. Instead, veterinarians think coprophagia in dogs stems from their evolutionary connection to wolves, as wolf mothers eat their pups' poop to avoid exposing them to intestinal parasites.

Wolves will eat the feces of their young during the first three years of life, veterinarian Dr. Nicholas Dodman, president of the nonprofit Center for Canine Behavior Studies and a professor emeritus at Tufts University Cummings School of Veterinary Medicine, told Live Science. In fresh poop, the eggs of various parasites are not yet infectious. If let to sit, the parasites can grow and infect the pups if ingested.

"You're more likely to survive if you're healthy than if you're … ridden with worms," he said.

Related: Could dogs survive without humans?

Even though domesticated dogs have come a long way from the wolf den, "I think the important takeaway is that it's no risk; it's just disgusting to us because of our upbringing," Dodman said.

Which dogs eat poop?

Certain dog breeds might be more prone to coprophagy, the 2018 study found. Shetland sheepdogs had the highest rate of coprophagia (41%), while no poodles were reported as poop-eating. A dog's sex is also linked to its tendency to eat poop. A 2019 study conducted by Dodman and colleagues and published in the Journal of Veterinary Behavior looked at the behavior of over 4,000 dogs. They found 11% of male dogs engaged in poop eating, while 16% of female dogs did. Interestingly, coprographia was twice as common in dogs that were neutered than in dogs that were not neutered.

As for why dogs eat the poop of other animals, like cats and rabbits … it's just tasty, Melissa Bain, a veterinary behaviorist at UC Davis Veterinary Medicine and co-author of the 2018 study, told Live Science. Cats eat a high-protein diet, so their stool might be particularly delectable to dogs, she said.

How do I get my dog to stop eating poop?

Even if it's not harmful to your pooch, there's no denying that people are repulsed by poop eating. So is there anything you can do to get your dog to stop?

Several commercial products are marketed for getting dogs to stop eating poop, but these have not been proved effective. Bain's 2018 study looked at 11 food additives marketed for coprophagia and found that the effectiveness of these products ranged from zero to 2%. "Don't waste your money," she said.

The internet is full of home remedies to stop coprophagia, like adding breath mints or pineapple to a dog's food. But there's no evidence that this works for most dogs, either. "You'll probably find someone who says they think it worked in their dog," Dodman said. "But basically, it's not a strategy that you can rely on."

In his veterinary practice, Dodman has tried diet changes that alter the consistency of a dog's poop and stop coprophagia. Brands like Hills RD or Purina OM have between about 14% and 16% fiber, according to their websites, which is much higher than in commercial dog kibble, Dodman said. The result is a dog stool that's more like cardboard, he said.

"If you change it to be less palatable, if you can imagine that, and more … dry and cardboardy, that seems to work," Dodman said, although he has not tested this in clinical trials.

What does work? "Clean it up," Bain said, and give the dog no time to munch on its feces. Some owners may try sprinkling Tabasco sauce or cayenne pepper on a dog's poop to deter them from eating it. "But if you're going to do that," Dodman said, "you might as well pick it up."

Scientists have developed a new device inspired by octopus suckers that can deliver drugs without requiring needles or pills. They've already tested it in humans in a small, short trial.

The 0.4 by 0.2 inch (1.1 by 0.6 centimeters) patch can stick to the inner lining of the cheek, stretch across it and increase the absorption of an attached drug.

When used in dogs for three hours, the patch efficiently delivered two drugs — desmopressin, which is used to treat excessive thirst and the urge to pee often, and semaglutide, the active ingredient in Ozempic and Wegovy, drugs that are respectively used to treat diabetes and obesity. A version of the patch without a drug attached was also safely used by 40 human volunteers for 30 minutes while they were able to talk, move around and rinse their mouths with water. 

Further development is needed. However, the patch could represent a less invasive and more comfortable approach to drug delivery, especially for larger drugs that are poorly absorbed by the digestive system so can normally only be injected using needles. 

Related: DeepMind's AI used to develop tiny 'syringe' for injecting gene therapy and tumor-killing drugs

"This is an interesting and well-designed series of studies expanding the range of drug delivery systems inspired by nature," Adrian Williams, a professor of pharmaceutics at the University of Reading in the U.K., who was not involved in the research, told Live Science in an email. "Stretching is known to increase the permeability of mucosal membranes [the protective layer that lines your organs and cavities like the mouth], and is particularly promising for large biological drugs, such as peptides and proteins, which tend to be poorly absorbed and so are usually given by injection." 

Other ways of delivering large drugs to the body, for example via the nose or using microneedles applied to the skin or in capsules, can be inefficient and difficult to make, the study authors wrote. 

"Compared to nasal delivery systems, we would offer something which is much more straightforward to use because you have the drug dose contained in the suction patch, you apply it on your mucosa and then you press. That's it," Jean-Christophe Leroux, senior study author and professor of drug formulation and delivery at ETH Zurich, told Live Science. "If you compare it to microneedles, it is less invasive," he said.

The authors only tested the patch for a short time so would need to find out what would happen if it was used repeatedly. They'd also need to determine which drugs would work with the technology: the target is large molecules, such as those used to treat obesity or osteoporosis, but they can't be too large to fit in the cup, Leroux said.

Chris McConville, an associate professor in pharmaceutics, drug formulation and delivery at the University of Birmingham in the U.K. who was not involved in the research, told Live Science in an email that although the device is interesting, it may not be very practical. The authors tried to mitigate the risk of accidental swallowing of the patch by using dental floss to link it to the volunteer's shirts, for example, but this needs to be further explored.

The authors also used a compound that increases the absorption of drugs called a permeation enhancer with the patch, which could mask any benefits of using it. 

"I am not sure what the device offers over buccal tablets [drugs that stick to the inside of the mouth and dissolve] as it seems that it is the permeation enhancers that increase absorption," McConville said. 

The findings were published Wednesday (Sept. 27) in the journal Science Translational Medicine.

Scientists in India have observed mugger crocodiles engaging in some strange behaviors, including hunting in packs, using sticks as bait to lure herons and egrets within striking range, showing interest in flower garlands floating in the river and even saving a feral dog that had been chased by other dogs. 

The new study, published Aug. 26 in the Journal of Threatened Taxa, suggests that mugger crocodiles (Crocodylus palustris) inhabiting the Savitri River in Maharashtra, India are more cognitively advanced than scientists currently believe. 

As tantalizing as these observations are, though, an expert Live Science contacted is skeptical, noting that while the hunting behaviors have previously been reported — anecdotally — the latter two claims are almost certainly anthropomorphic conjecture. 

"Crocodilians do have a sophisticated suite of behaviors," said Duncan Leitch, a biologist specializing in the neurophysiology of reptiles at the University of California, Los Angeles, who was not involved in the research. "But some of these conclusions are using a human definition of intelligence and trying to find that in crocodilians."

Related: Crocodiles and gharials are getting bizarre orange 'tans' in Nepal. Here's why.

The new study recorded several instances in which groups of mugger crocodiles swam in circles around schools of fish, creating a vortex. Their movement was presumed to have corralled the fish, and the crocodiles were observed consuming them while engaging in this behavior. Similar behaviors have previously been observed in other crocodilians. 

The recent paper said mugger crocodiles appear to use sticks to lure wading birds such as cattle egrets (Bubulcus ibis). These birds use sticks in constructing their nests, and competition for prime twigs can be intense. So, a branch positioned on a crocodile snout might seem a tempting option.

A 2013 paper also chronicled a series of anecdotal observations of crocodilians using sticks to entice wading birds. 

"Crocodilian sensory systems are incredibly sophisticated. They have a very good sense of vision. Their sense of touch is among the finest in the animal kingdom," Leitch said. "They're definitely tuned to picking up signals from their environment. Whether or not this is intelligence in the way that we see crows using tools — it's difficult to say."

He added that the anecdotal evidence cited is not widely accepted among crocodile researchers. 

The authors also said that mugger crocodiles appear to be attracted to  garlands of marigold (Tagetes erecta) flowers dropped into the river during funeral rites. The researchers suggested the crocodiles may be enticed by both the color of the flowers and their antibacterial properties. 

However, the crocodiles were not observed interacting with or consuming the flowers — they were simply found in proximity to them. Though the authors cited incidents in which captive crocodilians were observed playing with bougainvillea flowers, no such behavior was observed in the muggers. 

Crocodile empathy?

The researchers also reported an incident in which a young dog was chased into the river by a pack of adult feral dogs. Rather than eating the dog, three mugger crocodiles seemed to nudge it back to shore. 

"[The crocodiles] guided the dog away from the site where it would have been vulnerable to being attacked by the pack of feral dogs waiting on the river bank," they wrote. "These crocodiles were actually touching the dog with their snout and nudging it to move further for a safe ascent on the bank and eventually escape."

The authors interpreted this action as empathic — suggesting the crocodiles may have been concerned for the dog's safety. While it is certainly interesting that they did not consume an obvious prey item, there is little evidence that crocodilians are capable of empathy for other species, Leitch said.  

"They [the authors] may be coming from an anthropomorphic perspective and trying to ascribe abilities that they potentially might not have," Leitch said.

Anecdotal findings like the ones offered in this paper may offer prospects for additional investigation. But in the absence of more rigorous research they are just that: anecdotal, Leitch said.

A dingo recently attacked a 6-year-old girl while she was paddling in a shallow lagoon in Australia, holding her underwater and repeatedly biting her head.

The wild dog attacked the girl on K'gari, also known as Fraser Island, on April 3. The child is in stable condition, having suffered three puncture wounds around her ear. Rangers with the Queensland Parks and Wildlife Service (QPWS) believe the dingo responsible was an untagged male. 

"It's believed the young tourist was swimming in shallow water on the eastern side of the island when the dingo tried to grab onto her," LifeFlight rescuers said in a statement. "The animal repeatedly held her underwater for a few seconds before nearby family members were able to get the dingo off her."

Authorities reported a second dingo attack on a toddler on Friday (April 14) in Karijini National Park, in Western Australia, 932 miles (1,500 kilometers) north of Perth. The boy suffered serious but non life-threatening injuries before his mother managed to fight the animal off.

Dingoes (Canis dingo) are part dog, part wolf. They are Australia's largest carnivorous mammals and typically hunt rabbits, kangaroos, wallabies and wombats — but not humans. 

"Generally dingoes go about their lives and stay clear of people," representatives of QPWS, which is investigating the mauling, said on its website. "From time to time, dingoes may come close and some encounters can turn to tragedy."

Related: Humans are practically defenseless. Why don't wild animals attack us more?

K'gari is home to roughly 200 wild dingoes, according to the QPWS. They live in packs of up to 12 animals that patrol defined territories, but their curiosity occasionally draws them into tourist locations, where close encounters can turn nasty.

The QPWS urges visitors to clear away scraps of food and to never feed dingoes, as they may become increasingly habituated and emboldened in the presence of humans. Research suggests the availability of human food can reduce dingoes' aggression towards each other and lead to larger numbers of animals foraging together.

If they can regularly access human leftovers, dingoes may come to associate humans with food and try to steal items that they perceive as a meal. A survey of dingo attacks on K'gari between 2001 and 2015 found that more than half of the incidents involved a "chase," where a person was walking or running after a wild dog to retrieve a stolen possession. This may trigger a defensive response from dingoes and has led to aggressive group attacks, according to experts writing in The Conversation. 

Although uncommon, dingo attacks on children are often linked to food — if a baby is left sitting on a picnic rug and dogs try to pinch some food, for example — or due to defensive interactions sparked by toddlers playing or running around, according to the QPWS. Altogether, there have been 33 incidents of dingoes nipping, mouthing or biting people since 2018, according to the Queensland Department of Environment and Science.

In December 2022, a dingo repeatedly bit a 5-year-old boy on the head, arm and buttocks in a remote camping area on K'gari. The last fatal attack on the island was in 2001, when two dingoes mauled a 9-year-old boy to death after he and his brother happened upon the dogs and tried to run away.

In the iconic painting "His Master's Voice," a terrier cocks his head as he listens to his owner's voice coming from a gramophone. This gesture is one many dog owners will be familiar with, but why do dogs tilt their heads?

In a 2021 study in the journal Animal Cognition, researchers in Hungary conducted the first scientific investigation of head-tilting in pooches. They found that dogs may incline their heads as they are remembering details they find meaningful.

"Head tilts in dogs are a fairly known behavior, but the most surprising thing for me was that no one before us investigated it," study lead author Andrea Sommese, an ethologist (a scientist who studies natural animal behavior) at Eötvös Loránd University in Budapest, told Live Science. 

In an earlier 2021 study in the journal Scientific Reports, Sommese and his colleagues analyzed videos from around the globe in which dog owners asked their pets to fetch them a toy by saying its name. Although 33 pooches were not able to learn the names of any new toys after three months of practice, seven gifted dogs were able to learn more than 10 names during that time, with one female border collie, Whisky, correctly identifying 54 toys.

While conducting the study that appeared in Scientific Reports, the researchers noticed that all 40 of the dogs cocked their heads during the tests. The scientists next investigated when the canines performed these tilts.

Related: Why do dogs and cats run around in random bursts of speed?

In the following Animal Cognition study, the scientists found that the gifted dogs tilted their heads 43% of the time when asked to retrieve a toy by name. The other pooches tilted their heads in only 2% of these cases.

"We are not claiming that only gifted dogs tilt their heads while typical dogs never do it," Sommese said. "Typical dogs also do that, some more often than others, but in this specific situation, when the owner asks for a toy by its name, only the gifted dogs show a nice tilt."

These findings suggest that dog head-tilts are related to sounds the pets have learned to find important. 

"Dogs tilt their heads in a number of situations, but it seems that they do this only when they hear something that is very relevant to them," Sommese said. "It seems that this behavior is strongly associated with sound perception, and it might be something they do when they're trying to listen more closely, or maybe when they are a bit confused, just like humans do."

In addition, the researchers found the side of the tilt was consistent in the gifted dogs across 24 months of tests, but the favored side differed from canine to canine. This suggests one side of the brain of each dog may favor the mental activity underlying head-tilting, the scientists noted. Just as humans typically prefer using one hand over the other, many dog behaviors favor one side, such as the paw with which dogs reach for an item, the direction in which they favor wagging their tail and even the nostril they use more during sniffing, they explained. 

Future research can explore what other sounds or contexts might trigger canine head-tilting, said Monique Udell, a human-animal interaction researcher at Oregon State University, who did not take part in the studies.

"Studies like this one are important because they remind us that we, as humans, also have a lot to learn about what a dog's body language is communicating to us," Udell told Live Science.

It's easy to look into the adoring eyes of our pampered pups and think they'd be totally helpless without us. Even the thought of a pet dog living out in the wild is enough to make some owners despair. But imagine if humans suddenly disappeared and dogs had to fend for themselves. In such an apocalyptic scenario, could dogs survive in a world without people?

"I have no doubt that dogs would survive without us," Jessica Pierce, a faculty affiliate with the Center for Bioethics and Humanities at the University of Colorado Anschutz Medical Campus and author of "A Dog's World: Imagining the Lives of Dogs in a World without Humans" (Princeton University Press, 2021), told Live Science. "Dogs are descended from wolves and they still have much of the behavioral repertoire of wolves and other wild canids, so they know how to hunt and scavenge."

Without humans, our former pets would likely roll back the clock on their domestication and live as wild species do. Not all dogs would survive this transition, though. There's a great variety of dog breeds today, and some are less equipped for the wild than others. For example, flat-faced dogs such as pugs and bulldogs are prone to various health problems, including those that restrict their breathing, which would hinder their ability to hunt. They are also bred with short tails, which would hurt them socially when they interacted with wild dogs. 

"Tails are an important part of the communicative toolbox," Pierce said. "Even if you're slightly less skillful at communicating something like an aggressive feeling or a submissive feeling, you're more likely to wind up in a fight than if you're able to send clear signals."

Related: What if humans had tails? 

Dogs that are likely to wind up in a fight are more likely to get injured and less likely to survive. Fortunately for our barking buddies, humans wouldn't be around to dictate the canines' reproductive habits any longer. As a result, different breeds would mix, allowing natural selection to forge the fittest mutts.

These doomsday dogs would also interbreed with wolves to create hybrids where their ranges overlapped. Stray dogs and wolves already mix in Europe in countries such as Italy, according to a 2017 study published in the journal Global Ecology and Conservation. Friederike Range, an associate professor at the University of Veterinary Medicine Vienna who studies both dogs and wolves, told Live Science that the main thing that really separates the two is us. 

"While wolves are primarily hunters and dogs primarily scavengers, it's a continuum," Range said. "And wolves can also scavenge and dogs can go hunting." For example, wolves can be found living in human garbage dumps just like stray dogs do, and stray dogs can be found hunting wild prey just like wolves do.

But even if dogs could get by in a humanless world, wouldn't they be miserable without any morning fetch or evening fuss? Neither Pierce nor Range see the dogs suffering psychologically without owners. 

Pierce noted that, in a domestic setting, humans suppress a lot of dog behaviors — such as roaming, digging and peeing — because we find them annoying. Ownerless dogs don't have such restrictions, and while they also don't have the same home comforts as pet dogs do, they may be better off psychologically. "What they do have that pet dogs lack is freedom," Pierce said. 

Having studied dogs living independently from humans, Range has seen dogs form their own social groups and believes that food is a more important consideration than human companionship in these canines' well-being. 

"If we were to disappear, the food would be the main problem for the dogs, not losing the human as a social partner," Range said. "As long as they could find food, they would be perfectly happy without us." 

The feats that dogs undertake for their owners are the stuff of legend. News stories are filled with tales of pups leading rescue workers to injured owners and heroic dogs protecting children from animal attacks, but a question often arises in these remarkable situations: do dogs help because they love us, or because they see us as a meal ticket?

If the experts and studies are to be believed, dogs may actually love people more than food. 

"I am completely convinced that our dogs love us. There's no question in my mind," Clive Wynne, a professor of psychology at Arizona State University and the director of the university's Canine Science Collaboratory, told Live Science. 

Of course, it's one thing to have an opinion about a favorite pet. Proving love — a feat that still dogs humans — is another thing entirely. But studies of varying sophistication, all conducted by inquiring dog owners, appear to back him up. 

After the death of his beloved dog, Newton, Gregory Berns, a neurologist at Emory University in Georgia and author of the books "How Dogs Love Us: A Neuroscientist and His Adopted Dog Decode the Canine Brain" (New Harvest, 2013) and "What It's Like to Be a Dog: And Other Adventures in Animal Neuroscience," (Basic Books, 2017), said he became curious about what dogs felt and thought. So, he trained his dog, Callie, and other dogs to tolerate the noise inside the imaging chamber of an MRI and then analyzed their brain activity. He then subjected the dogs to a variety of scents from familiar and unfamiliar dogs and people. While the smell-region of the brain lit up for all 12 dogs regardless of who the person or dog was, only the familiar scents lit up the caudate nucleus, a region tied to higher-level mental processes such as emotion, motivation and reward and romantic feeling, according to a 2015 study published in the journal Behavioural Processes. 

In an additional study of 15 dogs, published in 2016 in the journal Social Cognitive and Affective Neuroscience, Berns found that 86% showed a similar or higher level of caudate activation in response to praise than they did from food. 

Related: How long do dogs live?

While it may not have used such sophisticated equipment, Wynne and colleagues also found that dogs may prefer their owners over food when they are left at home without food or human companionship for more than four hours, according to a 2022 study published in Peer J Life and Environment. Researchers set up the experiment simply enough; in most cases it was in a suburban home with an attached garage. After the dog's owner arrived home, an assistant placed a bowl of food in a small circle in the garage 6.5 feet (2 meters) and off at an angle from the door while the owner stood in a circle that was 6.5 feet away from the door and off at an opposite angle.

"Eight out of 10 times, the dogs chose their owner," Wynne said. 

Takefumi Kikusui, a researcher in the School of Veterinary Medicine at Azabu University in Japan and colleagues found that dogs will shed tears when reunited with an owner after a long absence, but will not show the same depth of response to the return of another human the animal recognizes, he reported in a 2022 study published in the journal Current Biology.

Wynne took the research one step further by seeing how far man's best friend might be willing to go to show their love. Inspired by stories of dogs digging up their owners after bombing raids in London during World War II, Wynne had the owners of 60 dogs climb into boxes and pretend they were in distress to see if their pets would rescue them. Roughly 1 out of 3 did so, according to a  2020 study published in the journal PLOS One. 

"That might sound superficially disappointing. What about the other two [out of three] dogs? Don't they care?" Wynne asked. They might, he said, but they couldn't figure out how to get into the boxes even when they knew their favorite foods had been placed there.

Before people go patting themselves on the back, however, Wynne was quick to point out that the love dogs feel isn't unique to humans. "Dogs are born with a remarkable capacity to form strong emotional connections with members of any species that they meet during the first three months of life," he said. So, if a puppy is born on a farm, it could have the same depth of emotion for a sheep, cow or even cat as it might for the farmer. 

MRIs and controlled experiments aren't the only way to determine how a dog feels about its owner, though, Wynne said. 

"I tell people, look at the everyday events" like when you come home at the end of the day. "If you have a dog, your dog will be there at the door and your dog will be wagging his tail. You're allowed to observe that behavior and believe what your dog is telling you. That is your dog expressing strong emotions at reuniting with you."

Archaeologists in Italy are uncovering a 1,600-year-old burial ground containing the remains of infants, children and sacrificed puppies. 

Some of the burials have unusual features — such as a child buried with a block in their mouth, which suggests that people were afraid that they could become "revenants" — corpses revived after death, archaeologists said. Analysis of the burials indicates that many of the dead suffered from malaria. 

In 2018, it was suggested by local individuals that this child may have been viewed as a vampire, but new research suggests that this is inaccurate. The idea of the child being a vampire started among locals who called it the "Vampire of Lugnano" and this idea was spread by the media. Since then, archaeologists have had more time to better understand what exactly the child may have been seen as: a possible revenant. 

The cemetery is located in the ruins of a Roman villa at the archaeological site of Poggio Gramignano, in central Italy, that dates to the fifth century A.D., a time when the Western Roman Empire was collapsing. By this time, many people in the Roman Empire had converted to Christianity.

Excavations at the site started in the 1980s and continue today. Since then, archaeologists have unearthed a large number of dog remains, many of them from puppies. Dog burials from this period "are often associated with children as tomb protectors and puppies would have been an especially lively and fresh sacrifice with perhaps more potency for remedy for the community," David Soren, a professor of anthropology at the University of Arizona who is one of the team leaders, told Live Science in an email. 

Related: Why an outlaw was stabbed to death and then buried face-down in medieval Sicily

Some of the children were buried in unusual ways. One child, for instance, had a piece of mortar in their mouth, and others seem to have been buried with their limbs weighed down with stones. "There was tremendous fear of revenants and of mysterious forces [such as witches] who might harness the spirits of the dead for their own devices," Soren said. Fear of the undead was common among both Christians and non-Christians from this period.

Analysis of the human remains indicate that many of them were suffering from malaria. This outbreak also may have influenced people to bury children in this way. "Stones in the mouth or over the body to weigh it down were seen as apotropaics [having the power to avert evil] to protect the as yet unaffected community," Soren said. 

Around this time, there was "a sense of a constant struggle with the supernatural and it is not surprising to see such things in a cemetery where people were facing a severe outbreak of malaria," William Bowden, a professor of classics and archaeology at the University of Nottingham in the U.K. who was not involved in the research, told Live Science in an email. 

An important aspect of this site is how carefully it was excavated, John Pearce, a senior lecturer of archaeology at King's College London, told Live Science in an email. This meticulousness allows for a detailed reconstruction of the rituals that were performed on the deceased, Pearce noted.

Dogs grow up much faster than humans, meaning these furry companions often do not live as long as their owners. But how long do dogs usually live?

A dog's life span may depend strongly on its breed, according to an April 2022 study in the journal Scientific Reports. By analyzing the ages of more than 30,000 dogs that died between 2016 and 2020, scientists calculated the average life expectancies of 18 breeds and crossbreeds in the United Kingdom.

The dogs had an overall average life expectancy of 11.2 years. However, the life span of these canine companions varied by breed. 

Related: Why do parrots live so long?

The creation of breeds about 150 years ago allowed dog breeders "to give flight to our whims and desires for how wild and extreme we could reshape the canine body," said study senior author Dr. Dan O'Neill, a veterinarian and epidemiologist at the Royal Veterinary College in Hertfordshire, England, told Live Science in an email. Given that many of these dogs no longer had a working function, such as herding or retrieving or guarding, "the requirement for good health was no longer a constraint" in creating new breeds, he noted.

The researchers found that small dogs had longer life expectancies than bigger canines.

"The life expectancy advantage for small dogs actually flies in the face of the basic rules of life expectancy across species in the natural world, where smaller species generally live shorter lives than larger species," O'Neill said. "A mouse might expect to live one to two years, whereas an elephant may expect to live 60 to 70 years." (Some other research suggests this general size-linked trend in longevity seen across species may not always hold within a species; for instance, while a 2019 study suggested larger women may live longer than smaller women, this may not hold true for men.)

One possible explanation is not that small dogs live longer, but that the larger breeds live shorter. Breeding may have resulted in large breeds that grow very rapidly compared with their predecessors, triggering early-onset diseases, such as osteoarthritis and cancer, O'Neill said.

In addition, the deaths of 90% of dogs in the United Kingdom involve euthanasia, so their life span "is heavily influenced by human decision-making," O'Neill said. It may be more difficult to care for larger breeds of dogs with mobility issues than smaller ones, or the financial costs of medical treatments may be greater for larger dogs than smaller ones as they age, he noted.

The scientists also found that the life expectancy of crossbred dogs was 11.8 years, about 6 months more than the average of the group as a whole. This matches previous research suggesting that hybrids are often healthier than purebreds, O'Neill said. Female dogs also generally lived longer than male canines, although whether this was true varied across breeds, he noted. Neutering was also generally linked with a longer life expectancy, potentially because it is often associated with stronger owner responsibility and better care, and perhaps because it may reduce or eliminate a number of health problems linked with reproductive organs and hormones, such as tumors.

All in all, the scientists found that Jack Russell terriers had the highest life expectancy, at 12.7 years, while French bulldogs had the lowest life expectancy, at 4.5 years.

"Sadly, while many breeds did retain a basic healthy body shape — for example, the Labrador retriever — several other breeds followed a pathway to extreme body shapes — for example, the English bulldog," O'Neill said. Soon after breeding created these major physical differences, "the serious health issues linked to these extreme body shapes started to become apparent," he said.

Jack Russell terriers may live longer than other breeds as part of the trend that smaller dogs live longer, O'Neill said. In addition, they were not bred to have an unusual body shape that might limit their overall health.

"These little dogs were bred to be hardy and benefited by not being constrained to fitting a pre-defined breed standard," O'Neill said. "Essentially, these are the archetypal healthy little family companion dog."

Other dogs with long life expectancies also have body shapes similar to closely related wild species such as wolves, coyotes and foxes, which evolutionary forces likely optimized for survival and health, O'Neill said. For instance, the average life expectancy was 12.5 years for Yorkshire terriers, 12.1 years for border collies and 11.9 years for springer spaniels.

In contrast, in addition to French bulldogs, similar breeds often have brief lives. The average life expectancy was 7.4 years for English bulldogs, 7.7 years for pugs and 7.8 years for American bulldogs.

Previous research found that these breeds are prone to a number of serious health disorders that are often linked with their physical characteristics, such as their short snouts or large heads. These conditions include skin fold dermatitis, breathing problems, eye ulceration, cherry eye, difficulty giving birth, slipping kneecaps, elbow joint disease and heatstroke. 

"Many of these disorders are life-limiting in that they either directly lead to early death in these dogs or that owners opt for euthanasia on welfare grounds," O'Neill said.

Although a common method for guessing the life span of dogs is to use "dog years" — that is, to multiply their age by seven to get an idea of how old they might be in human terms — the recent work from O'Neill and his colleagues suggests "that such a concept really is no longer that useful," he said. "Given the wide variation in life expectancy across breeds, an alternative approach would be to generate a concept of dog years within each breed. This is much more likely to be accurate."

Your dog's breed may not dictate its behavior, though genes do play a role, a study of the genomes of 4,000 purebred, mixed-breed and wild dogs has revealed. 

In comparing the DNA data of so many animals, researchers found that genetic variations appeared in clusters around different types of dogs. These clusters contained dog breeds that all had one thing in common: the role their ancestors played in human history. 

"Humans have employed dogs for thousands of years to perform tasks such as herding livestock, killing vermin, hunting, pulling loads, guarding, and companionship," the study authors wrote in their paper. "To produce dogs that will [perform these roles] reliably, humans have selectively bred toward a variety of behavioral ideals." 

This selective breeding began around 2,000 years ago, but humans began classifying dog breeds much more recently. The names we use for modern breeds are less than 160 years old, "a blink in evolutionary history compared with the origin of dogs more than 10,000 years ago," the authors wrote in the paper, published Dec. 8 in the journal Cell. 

Instead of grouping dogs by breed, the DNA analysis revealed 10 genetic lineages from which modern dogs descend: the scent hound, pointer-spaniel, retriever, terrier, herder, sled, African and Middle Eastern, Asian spitz, dingo and sight hound. Within these 10 groups, the researchers found distinct genes — and common behaviors. 

Related: Are dogs really smiling at us?

Terriers had more dog-directed aggression and a higher predatory drive. This makes sense in light of the history of the terrier breeds, which were generally used for hunting vermin and in the "sport" of dogfighting. Companion and toy dogs showed high levels of fear of dogs, humans and different situations. Scent hounds demonstrated anxiety-related behaviors, which the authors suggested could be caused by the hunting dogs' need for acute sensitivity to the movements of their targets. 

Herders, which include dogs that were bred for working with sheep and cattle, were some of the most easily trained, and they had decreased levels of aggression and predatory drive. Owners of these dogs commonly report the animals' tendency to herd, even if they've never been trained to work. Sheepdogs, for example, can take to rounding up their toys or even grouping small children. 

As well as a strong herding instinct, the original herders needed to have precise control over their movements, as subtle changes in position can drive a herd in a different direction. But whether these behaviors, shown in generations of herding dogs, had a basis in the dogs' DNA was of particular interest to study first author Emily Dutrow, a postdoctoral fellow at the National Human Genome Research Institute.

Dutrow and colleagues found specific genes in herding dogs' DNA that relate to brain activity. These included genes that link to motor control and vision, as well as one that has been associated with a mothering instinct in mice to gather their litter. 

The study also found genes relating to the heart, the digestive system and other parts of the dogs' physiology, as well as many bits of DNA that are inactive or non-coding, or "junk DNA." While some of these genes were found more commonly in some lineages than in others, the research doesn't directly prove a link between specific bits of DNA and certain behaviors, said Kathleen Morrill, a genomics researcher at the University of Massachusetts. 

Earlier this year, Morrill co-authored a paper on dog genetics that also found common behaviors across large groups of dog breeds. In showing that very few traits are breed-specific, Morrill's paper broke down many of the stereotypes about dog personalities. Behavior, Morrill told Live Science, emerges from a complicated interaction of genes and environment that we still don't understand. 

"It's not as simple as 'all retrievers have a retrieving gene,' or that broad behaviors, like aggression, are genetically ingrained into certain breeds," Morrill said; these studies illustrate the "genetic complexity of dogs."

Cats and dogs enrich their owners' lives, but even the most avid fans of these furry friends may not love all the hair they can shed. But shedding must serve the animals somehow, right? So why do they make fur if they are only going to shed it later? And are there times when shedding signifies a health problem? 

Shedding is a regular part of life for animals with hair, and not a waste of effort. Normally, shedding helps to remove dead hair and release natural oils in the skin, according to animal health company Zoetis. If dead hair does not get removed, skin irritation can result.

In addition, cats and dogs often seasonally undergo molting, or heavy shedding, about twice a year to help them control their body temperature, veterinarian Angela Martin, co-founder of Island Veterinary Group in Huntington Station, New York, told Live Science. This usually happens in the spring and the fall; spring shedding helps pets lose their heavy winter coats, whereas fall shedding helps them prepare to grow winter coats, Zoetis noted.

This cycle of shedding may change depending on the amount of time a pet spends inside versus outside. Indoor pets are exposed to air conditioning in the summer and heating in the winter, as well as artificial lighting. This may confuse their internal clocks, which can result in relatively constant shedding across the year, according to Zoetis.

Related: Fur, wool, hair: What's the difference?

Shedding "is also a defense mechanism," Martin said. "If a bear is chasing the dog or cat and grabs the animal but comes away with a mouthful of fur, that dog or cat goes on to live another day. 

There are other reasons cats and dogs shed. One is stress: "You have probably noticed this at the vet's office," Martin said. Other common causes of shedding include parasites, such as fleas and mites; endocrine diseases, such as diabetes and thyroid disorders; poor nutrition; certain medications; and excessive grooming, she said.

Signs of unhealthy shedding include a thin coat or bald patches, Martin said. "When shedding accompanies itch, odor, inflammation of the skin, crusting of the skin, darkening of the skin, or gastrointestinal signs, allergies with secondary skin infections are often to blame," she said.

If a pet is losing hair while experiencing weight changes or other systemic symptoms, endocrine conditions may be a more likely explanation, Martin said. Immune system-linked conditions or cancer are less common explanations but are also possible, she said.

Some breeds of pets shed more than others. When it comes to cats, Maine coons, Persians and Ragdolls are known to shed a lot, Zoetis noted. In contrast, the sphynx, Siberian, Bengal, Cornish rex, Siamese and Bombay cat breeds shed the least, according to BondVet in New York. When it comes to dogs, Labrador retrievers, Newfoundlands and Pekingese tend to shed a lot, whereas dachshunds, poodles and border terriers seem almost shed-free, according to the American Kennel Club.

It’s a common misconception that shedding in dogs depends on their coat length, according to pet food company Hill’s. Similarly, in cats, American shorthair cats are among the biggest shedders, pet-sitting company Rover noted. There is no specific reason why one breed might shed more than another — some pets might be prolific shedders simply because of their natural genetic makeup, according to The Village Vets, an animal hospital network in Atlanta.

Regularly brushing or combing a pet can reduce the amount of hair they shed, according to the American Society for the Prevention of Cruelty to Animals. This can also help remove dead skin flakes and stimulate blood circulation, thus improving the overall condition of their skin.

It hardly seems like a dainty teacup poodle and a wrinkly Neapolitan mastiff could belong to the same species, much less the same subspecies. But both are Canis lupus familiaris, the beloved domestic dog.

A member of the family Canidae — along with wolves, foxes, coyotes and jackals — dogs have been human companions for at least 14,000 years (and possibly much longer than that). Much about how dogs and humans became inseparable remains a mystery, but research finds that the bond is very real. As many pet owners may already attest, there is evidence that dogs understand human distress and want to help their owners when they're sad.

Despite the diversity of domestic dogs, these animals share an evolutionary history and behavioral traits.

When were dogs domesticated?

The closest living relative to modern dogs is the gray wolf (Canis lupus). The ancestor of modern dogs and the ancestor of modern wolves probably split at some point in the late Pleistocene, the last ice age. Genetic studies put different dates on this split. One 2014 study based on the mutation rates found that the schism happened between 9,000 and 34,000 years ago, and that the wolf population dogs split from later went extinct. Another genetic study from 2017 put the window between 20,000 and 40,000 years ago.

The oldest fossil that scientists agree came from a dog, rather than a wolf, comes from a site in Germany called Bonn-Oberkassel and dates back about 14,200 years. But archaeologists have found fossil specimens that might be domesticated dogs dating back more than 30,000 years. It's difficult to confidently identify a Pleistocene fossil fragment as being from either a dog or a wolf, and because dogs and wolves interbred even after they diverged genetically, genomic studies are complicated. Researchers also debate whether dog domestication happened once or at multiple sites around the world.

"We don't know where in the world it happened," Anders Bergström, a postdoctoral fellow in ancient genomics at the Francis Crick Institute in London, told Live Science in 2022. "We don't know what human group was involved, and we don't know whether it happened once or multiple times."  

It is clear that humankind's bond with dogs goes way back. The 14,200-year-old dog from Bonn-Oberkassel was buried with two humans and had been nursed through several episodes of canine distemper before it died. In a 12,000-year-old cemetery in Israel, a woman was found buried with her hand on a small wolf or dog puppy. A Stone Age dog from what is now Sweden was buried with a human companion about 8,400 years ago, researchers reported in 2020.

What are dog breeds?

In the time since domestication, humans have shaped dogs like clay: Sometimes it seems like the only things different dog breeds have in common are four legs and a tail. The American Kennel Club (AKC) currently recognizes 200 breeds, and that list doesn't even begin to touch the diversity of hybrid breeds (Labradoodles, anyone?) and uncategorizable mutts (often the best kind).

The AKC isn't the final arbiter of what makes a dog breed. According to the organization, there are some 400 dog breeds registered around the world. AKC registration just means there are enough of a certain breed in the United States and enough interest from owners in documenting a breeding history and a "breed standard," which is a description of the ideal characteristics of a breed.

Picking dogs with certain traits and breeding to maximize those traits has led to dogs specialized for many different tasks. Labrador retrievers, for example — which often top the lists of most popular breeds in the United States — have webbed toes and a two-layered coat that is resistant to water. These are traits left over from the breed's original role of retrieving downed ducks for duck hunters. According to the AKC, Labradors were bred from the St. John's dog, a water-loving breed used in early Newfoundland fisheries to retrieve nets and lines.

The sausage-like dachshund, on the other hand, is a poor swimmer but a keen hunter. It was bred for its narrow body and digging acumen, all the better for burrowing into badger dens and killing the occupants, according to the AKC.

Though most official modern breeds date back to the Victorian era, a 2010 paper did find divergence between some breeds indicating that they emerged 500 or more years ago. These breeds were the basenji, Afghan hound, Samoyed, saluki, Canaan dog, New Guinea singing dog, dingo (a wild canine), chow chow, Chinese shar-pei, Akita, Alaskan malamute, Siberian husky and American Eskimo dog.

Do dogs see color? (And other dog senses)

Dogs can see yellow and green hues, but they can't distinguish red from green ​​— a similar situation to humans who are red-green color-blind. However, dogs may be more sensitive to ultraviolet light than humans are, according to 2014 research, in which case they would be better at sensing a wider ranges of blues than people are.

Dog vision is almost three times blurrier than human vision, according to a 2017 study. In that research, whippets, pugs and Shetland sheepdogs were trained with treats to distinguish lines that were different distances from one another. These lines were then used to give the dogs a visual test, not unlike the alphabet chart a human might see during a visit to the eye doctor. Dogs had about 20/50 vision, the study found, meaning that something a human could see clearly at a distance of 50 feet (15 meters), a dog could see clearly at 20 feet (6 m). Dogs, however, do see better than people in dim light, according to the Merck Manual for Veterinary Medicine, and can see movement better, too. One special feature that magnifies light to a dog's eye is the tapetum lucidum, a reflective layer that also gives dogs their characteristic eyeshine at night.

Hearing and smell are where dogs really shine. According to the Merck Manual, dogs hear about four times better than humans do. Incredibly, their sense of smell is a whopping thousand to ten thousand times better than ours. The olfactory center of a dog's brain is 40 times the size of the olfactory center in a human's brain. Because dogs can distinguish between smells with great sensitivity, they have been trained to sniff out human diseases: researchers discovered in the early 2000s that dogs can sniff out signs of early stage cancers, and in 2021 scientists found that dogs could identify COVID-19 in the scent of urine samples, Live Science previously reported.

Can dogs feel emotions?

Humans and dogs really do understand each other. A 2014 study found that emotional processing regions of dogs' brains respond to human emotional sounds, like laughing and crying, in the same way as these regions respond to dog emotional sounds, like whining or yipping. Humans, too, process dog emotional sounds in the same way they process human emotional sounds.

But what emotions do dogs feel? And what do they understand about others' emotions?

It's pretty clear that dogs experience basic emotions, like pleasure, sadness, anxiety and fear, said Julia Meyers-Manor, a psychologist at Ripon College in Wisconsin who studies animal emotions. Meyers-Manor led a 2018 study that found that dogs showed stress in response to their owners' crying noises and that dogs were more likely to attempt to comfort or help a crying owner compared with a laughing owner. Follow-up research that has not yet been published suggests that dogs attempt to comfort upset strangers, too, though not as readily as they comfort their owners, Meyers-Manor told Live Science.

"There's quite a bit of consistency in brain areas that process emotions across mammal species," she said. Dogs are social animals, so it's not surprising that they'd respond to the emotions of others. It is interesting, however, that dogs respond to emotions across species, she said. It's possible that crying is similar enough among species to elicit a response no matter what animal is crying and what animal is listening, she said. It's also possible that, because dogs have co-evolved with humans for so long, they're particularly good at interpreting human emotion. More research comparing different species' reactions is needed to clear up these questions, Meyers-Manor said.

Despite these similarities, one thing is certain: Your dog probably doesn't feel guilt when it digs up the flower beds and knocks over the trash. Though many dog owners take the pitiful, droopy-eyed look a dog gives when it senses trouble to mean that their dogs know exactly what they did wrong, a 2009 study found that the guilty look is simply a way to stay out of trouble. In that study, dogs were put into situations where they were framed for doing something wrong, like eating a forbidden treat. Even when the dogs had not eaten the treat, they looked guilty when their owners thought they had and scolded them.

In other words, the expression that humans interpret as guilt is nothing of the sort. It's just a reaction to a scolding human. "They've just learned, make this expression when there's a big mess in the house and owners won't kill you," Meyers-Manor said.

How smart are dogs?

Dogs are pretty smart, though not "exceptional," according to a 2018 study in the journal Learning & Behavior. The study compared dogs with other carnivores, with other social hunters, and with other domesticated animals, looking at definitions of intelligence that covered sensory cognition, physical cognition, spatial cognition, social cognition and self-awareness. These comparisons focused on other species for which intelligence studies had been conducted, which mainly included wolves, hyenas, African wild dogs, cats, bottlenose dolphins, chimpanzees, horses and pigeons.

On the whole, the researchers concluded, dogs have sensory abilities similar to those of other hunting carnivores. They're pretty bad at solving problems involving objects, such as pulling a string to get at a treat attached to the other end. Spatial cognition, which involves understanding places and navigation, was harder to compare, the researchers found, but there did not seem to be any evidence that dogs were standouts compared with other hunters. Dogs were impressive at using other animals' behavior to cue their own and did beat out many other similar animals at social learning, though dolphins and chimps might be better at imitation. Finally, unlike dolphins and chimpanzees, dogs don't show many signs of self-awareness, or the ability to project themselves mentally into the past or future by remembering events like a story or planning for future events.

Dog smarts are about what would be expected from a domesticated social carnivore and hunter, the researchers concluded in their paper. Dogs are socially savvy, paying attention to cues from other dogs and from humans, their evolutionary co-pilots. They have sensory abilities and spatial smarts sufficient to navigate the environment of a pack hunter. But they aren't as good at things that don't matter as much to their survival, such as figuring out how objects work or making detailed plans for the future.

How do dogs help people?

Humans and dogs have been working together for a long time. Though the earliest history of dogs is shrouded in mystery, there are hints that humans may have used dogs to help with hunts as long as 14,000 years ago, according to a 2019 study in the Journal of Anthropological Archaeology. In Saudi Arabia, rock art estimated to be about 8,000 years old shows humans hunting with dogs on leashes, killing ibex and gazelles, ScienceAlert reported.

Today, dogs still help hunters stalk quarry large and small. Labrador retrievers continue to be used to hunt ducks, while sprinters such as the Pharaoh hound are excellent at catching prey such as rabbits.

Dogs are also used by police and the military, often to sniff out drugs or explosives, to perform search and rescue operations, and to bite and hold suspects. According to the AKC, police dogs are usually breeds that have been bred to be highly trainable, including German shepherds, Labrador retrievers, and bloodhounds.

Modern dogs also play a huge role as service dogs, therapy dogs and emotional support animals. Guide Dogs or Seeing Eye Dogs help people with vision loss navigate obstacles. Therapy dogs are used to support and calm people with autism, post-traumatic stress disorder, anxiety and other conditions. There are even squads of good-natured dogs roaming airports (with their handlers, of course), calming nervous travelers with snuggles.

Additional resources

Check out the Humane Society of America for more on pet dog behavior and welfare. The American Kennel Club is an exhaustive reference on dog breeds, health, and training. For a deep and detailed dive into what scientists know (and don't) about how dogs were domesticated and came to the Americas, read the 2021 paper "Dog domestication and the dual dispersal of people and dogs into the Americas," which is freely available.

Originally published on Live Science.

Dingoes are Australia's largest land predator, but their evolutionary history has been shrouded in mystery and debated for decades. Now, a new study finds that they are genetically somewhere between a wolf and a modern domestic dog.

Researchers sequenced the genome of a "pure" dingo puppy that was discovered alive by a roadside in the central Australian desert, according to a statement released by La Trobe University in Melbourne. When compared with the DNA of domestic dogs (Canis lupus familiaris) and a wolf (Canis lupus), the dingo pup’s DNA identified dingoes as an "intermediary" between wolves and domestic dog breeds, researchers recently reported

“It gives us much clearer insight into how the dingo evolved, which is fascinating from a scientific point of view, but also opens up all sorts of new ways to monitor their health and ensure their long-term survival,” study co-author Bill Ballard, a professor of evolutionary genomics at La Trobe University, said in the statement. 

Scientists suggest that humans brought the ancestors of modern dingoes to Australia between 5,000 and 8,500 years ago, but it's not clear where these ancient dogs were in the domestication process when they first arrived. Modern dog breeds weren't introduced to Australia until 1788, so dingoes were also separated from other dogs for thousands of years.

Related: 11 weird desert animals

Dingoes are apex predators and have been top of the food chain in Australia since Tasmanian tigers (Thylacinus cynocephalus) disappeared from mainland Australia at least 2,000 years ago (Tasmanian tigers survived on the island of Tasmania until 1936, according to the International Union for Conservation of Nature). Dingoes may have contributed to the extinction of Tasmanian tigers by competing with them for food, according to the Australian Museum. 

After arriving in Australia, dingoes' ancestors adapted to eat marsupials, including kangaroos, as well as reptiles. One difference between dingoes and most domesticated dog breeds is that dingoes — like wolves — have only one copy of the amylase-producing gene AMY2B, which breaks down starch. This reduces dingoes' ability to digest starch and suggests that dingoes have a protein-rich diet, as wolves do. By comparison, most domestic dog breeds have multiple copies of AMY2B, so they can handle a starch-rich diet that is more similar to a human diet. 

Today, dingoes interbreed with feral dogs — domestic dogs living in the wild — further complicating their status. A 2015 study published in the journal Molecular Ecology found widespread hybridization between dingoes and domestic dogs, potentially threatening dingo survival and disrupting their role in the Australian ecosystem.

The study was published April 22 in the journal Science Advances.

Originally published on Live Science.

Veterinarians frown upon giving dogs any kind of "people food" but are especially adamant about keeping chocolate far away from our canine friends. During holidays such as Easter, when delicious chocolate may be more commonly found around the house, it's even more important to be vigilant about your pet gulping down this human treat. 

But why is chocolate — milk or dark — so toxic for dogs?

Chocolate contains the chemicals theobromine and caffeine, and these two stimulants — which dogs can't metabolize as easily as people can — accumulate in the animal's body, where they can rev up a dog's bodily functions and cause dangerous side effects, according to VCA Animal Hospitals. 

The severity of chocolate's negative impacts on a dog are determined by the levels of theobromine and caffeine in the chocolate product, how much of it the dog ate, and the dog's weight and sensitivity to chemical stimulants. Chocolate that is dark and bitter is more toxic to dogs, as it contains a higher concentration of theobromine per ounce than milk chocolate (130 to 450 milligrams per ounce, compared with milk chocolate's 45 to 58 mg per ounce). White chocolate, on the other hand, contains just 0.25 mg of theobromine per ounce, and therefore poses a much lower toxic threat to dogs, according to VCA Animal Hospitals.

What are symptoms of chocolate toxicity in dogs?

Initial symptoms of chocolate toxicity typically appear within 6 to 12 hours, and may include excessive drooling and panting, increased thirst and urination, and an upset stomach followed by vomiting and diarrhea, according to the American Kennel Club (AKC). The dog may experience an increased heart rate and become restless, nervous and excited, much like a caffeine-sensitive person who has downed too many cups of coffee. 

In severe cases, irregular heart rate from chocolate consumption can reduce circulation, resulting in a drop in body temperature. Extreme symptoms include lethargy, muscle spasms, seizures and coma, sometimes leading to death, according to VCA Animal Hospitals. And because theobromine has a long half-life, which means it takes longer for the body to break it down, symptoms of chocolate poisoning can persist for days.

In some cases, dogs consume chocolate but show no symptoms; that's because the dosage size of the toxins can affect an animal's response to being poisoned, according to the Office for Science and Society at McGill University in Ontario, Canada.

How do veterinarians treat chocolate poisoning?

Veterinarians typically treat chocolate toxicity by inducing vomiting or administering doses of activated charcoal,  which purges toxins from the dog's digestive system before they can be absorbed by the animal's bloodstream, according to the AKC. Depending on the severity of the poisoning, medication or fluids may be required to counteract the poisoning, the AKC says.

What might affect a dog's reaction to chocolate?

How a dog reacts to chocolate can depend on the animal's size, said veterinarian Dr. Greg Nelson, Director of Surgery and Director of Diagnostic Imaging at Central Veterinary Associates in Valley Stream, New York. A square of chocolate will therefore have a more pronounced effect on a Chihuahua, which typically weighs about 4 to 6 pounds (1.8 to 2.7 kilograms) than on a Saint Bernard, which can weigh as much as 180 pounds (81.6 kg).

"One hundred milligrams of theobromine and caffeine per each kilogram of a dog's weight is enough to be lethal," Nelson told Live Science. (A kilogram equals 2.2 pounds.) "Different chocolate products have varying levels of theobromine and caffeine, and the worst offender is baker's chocolate. In my experience, one ounce of baker's chocolate per kilogram [of the dog's body weight] can be lethal."

Milk chocolate is less dangerous than baking chocolate because it contains less stimulants, but Nelson warns that if your dog has ingested any type or amount of chocolate, you are always better off being safe than sorry.

"I advise clients to come in instead of second-guessing and possibly creating an emergency by not having the dog looked at right away," Nelson said. "At the very least, call your veterinarian or the national Animal Poison Control center for advice." (The American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center can be reached 365 days a year at 888- 426-4435.)

While chocolate poisoning may affect dogs at any time, pups are more likely to find and consume chocolate on holidays such as Christmas and Easter when plentiful chocolate is available as figurines (such as bunnies and Santa Claus), as well as in bars, eggs, liqueurs, cakes and decorations, researchers wrote in a 2017 paper in the journal Vet Record. In fact, during Christmastime, dogs are four times more likely to require a vet visit for chocolate poisoning than during non-holidays; and on Easter, dogs are twice as likely to be sickened by chocolate, compared with other times of the year, Live Science previously reported.

Additional resources

Read more from the ASPCA on their Toxicology and Poison Control web page, to learn about toxins, medications, hazards and resources that could help you save the life of your pet in the event of a toxic exposure. The Veterinary Emergency Group provides tips for identifying symptoms of chocolate toxicity in dogs, and recommends what to do in an emergency. The ASPCA also compiled a list of other human foods that are hazardous for pets to eat, such as avocados, coconuts, citrus and alcohol, among others.

This article is for informational purposes only, and is not meant to offer medical advice.

Originally published on Live Science.

Bibliography

"Chocolate Poisoning in Dogs." Chocolate Poisoning In Dogs | VCA Animal Hospitals, https://vcahospitals.com/know-your-pet/chocolate-poisoning-in-dogs. 

Staff, AKC. "What to Do If Your Dog Eats Chocolate." American Kennel Club, American Kennel Club, 28 Dec. 2021, https://www.akc.org/expert-advice/health/what-to-do-if-your-dog-ate-chocolate/. 

"My Dog Ate Chocolate and He Was Fine, so What's the Big Deal?" Office for Science and Society, 26 Aug. 2019, https://www.mcgill.ca/oss/article/health/my-dog-ate-chocolate-and-he-was-fine-so-whats-big-deal. 

Noble, Peter-John M, et al. "Heightened Risk of Canine Chocolate Exposure at Christmas and Easter." Veterinary Record, vol. 181, no. 25, 2017, pp. 684–684., https://doi.org/10.1136/vr.104762. 

"Toxicology & Poison Control." ASPCApro, 21 Mar. 2022, https://www.aspcapro.org/topics-animal-health/toxicology-poison-control. 

"Chocolate Toxicity in Dogs: Signs and What to Do." Veterinary Emergency Group, 21 Feb. 2022, https://veterinaryemergencygroup.com/blog/chocolate-toxicity-in-dogs/. 

"People Foods to Avoid Feeding Your Pets." ASPCA, https://www.aspca.org/pet-care/animal-poison-control/people-foods-avoid-feeding-your-pets.