If you spot a small, long-tailed amphibian near a forested pond, you are likely looking at a salamander or a newt.

But what's the difference between a salamander and a newt? And how do you tell them apart?

"It's one of those things where all newts are salamanders, but all salamanders aren't newts," Nick Burgmeier, a research biologist at Purdue University, told Live Science.

Within the tree of life, salamanders are a large and diverse group of tailed amphibians. "They are the order Caudata, which literally means 'tailed' in Latin," said Karen Kiemnec-Tyburczy, an associate professor at California State Polytechnic University, Humboldt who specializes in salamanders. There are a total of 10 families of salamanders, she said. Newts are a subfamily called Pleurodelinae, within the Salamandridae family.

Since all newts are salamanders, there isn't really a distinct characteristic that separates one from the other. However, some species in the newt subfamily possess a few interesting traits, Burgmeier said. For example, a number of newts have warty, bumpy-looking skin. "They tend to have rougher skin," Burgmeier said, as opposed to salamanders' smooth, slimy skin.

This is likely because newts are the most toxic salamanders; their skin contains many poison glands. For instance, the skin of a rough-skinned newt (Taricha granulosa), a species found in western North America, has bacteria that secrete tetrodotoxin. It's the same toxin found in Japanese pufferfish and can be fatal if ingested.

"It would be pretty catastrophic if you happen to throw one in your mouth," Burgmeier said.

Further, salamanders in general have a "biphasic" lifestyle, Burgmeier noted, which means they often start the beginning of their life in water and then move on to land. With some newts, this life cycle can be "triphasic," which means they start their life in the water, have a juvenile "eft" phase in which they go onto land, and then end adulthood back in the water.

An example of this is the eastern newt (Notophthalmus viridescens), a common species in the eastern U.S. The newt has a characteristic bright orange juvenile that roams the forest floors (called a red eft). The efts live on land for around two to three years, equipped with developed lungs and toxins to ward off predators, before eventually metamorphosing into an aquatic adult.

However, interestingly, some coastal populations of eastern newts will skip their eft stage completely, spending their entire life underwater. And variations in lifecycles are common among newts and salamanders. Many newts in Europe and Asia have a more traditional biphasic lifestyle rather than the triphasic, Burgmeier said.

Similarly, not all newts have bumpy, toxic skin. Many, like the smooth newt (Lissotriton vulgaris), have smooth skin.

One reason for the lack of unifying newt traits is likely that when herpetology began, naming wasn't standardized.

"The term 'newt,' historically, was used informally as a common name for these sort of warty, bumpy [salamanders]," Kiemnec-Tyburczy told Live Science. "But it turns out that they are not each other's closest relatives. As salamander taxonomy became clearer throughout the 20th century, scientists classified the warty, bumpy salamanders and their closest relatives as newts. As a result today's subfamily hosts a hodgepodge of characteristics.

Diversity also abounds in the salamander order. There are lungless salamanders that have no larval stage at all; they develop inside the egg. Some salamanders, axolotls, never develop past their tadpole stage. Around the world, salamander species can also range from an inch (2.5 centimeters) to up to 6 feet (1.8 meters) long.

Salamanders are “just super cool," Burgmeier said. He studies the eastern hellbender (Cryptobranchus alleganiensis alleganiensis), the largest salamander in North America. Their presence and health can tell scientists a lot about water quality. For the smaller newts and salamanders, they can be a key part of the food web, eating invertebrates and supporting aquatic and terrestrial ecosystems alike, Burgmeier added.

"Salamanders have a ton of different things going on," Kiemnec-Tyburczy said. "Newts are just a small subset of all of the diversity within salamanders."

Animal quiz: Test yourself on these fun animal trivia questions

Scientists have identified three new toad species that give birth to live "toadlets" rather than laying eggs.

All three species are part of the Nectophrynoides genus, also known as "tree toads," which is a group known for birthing live baby toads that skip the tadpole stage. Previously thought to be one species with a large population and habitat range, these smaller, more fragmented species may require additional conservation measures, researchers wrote in a new study.

"Live-bearing is exceptionally rare among frogs and toads, practiced by less than 1% of frogs species, making these new species exceptionally interesting," study co-author H. Christoph Liedtke, a researcher who studies amphibian evolution at the Spanish National Research Council, said in a statement.

Just 17 of over 7,000 known species of frogs and toads were known to give birth to live young prior to this study, with 13 of them being part of the Nectophrynoides genus. The new study, published Nov. 6 in the journal Vertebrate Zoology, adds the three newly identified species to each of those totals.

Researchers first identified a species called Nectophrynoides viviparus in 1905 and classified it within the Nectophrynoides genus in 1926. Since then, scientists have found specimens of N. viviparus across the Eastern Arc Mountains and Southern Highlands of Tanzania. But a 2016 study suggested that many of those toads were genetically distinct enough that they might be from multiple similar-but-distinct species.

In the new study, researchers looked more closely at Nectophrynoides toads from the Eastern Arc Mountains. They studied hundreds of toad specimens preserved in museums, as well as recordings of some of the toads' calls in the wild. Using methods collectively known as museomics, they also sampled mitochondrial DNA from some of the museum specimens.

Together, the research revealed that the toads in that region were in fact from four separate species, three of which had not been identified before. These species — Nectophrynoides saliensis, Nectophrynoides luhomeroensis and Nectophrynoides uhehe — look similar to N. viviparus. However, slight differences in their genetics, their head shapes, and the shape and positioning of the glands on their shoulders distinguish them. Other toads from farther north in the mountains might constitute even more new species, the scientists noted.

"Some of these specimens were collected over 120 years ago," study co-author Alice Petzold, an evolutionary scientist at the University of Potsdam in Germany, said in the statement. "Our museomics work was able to reveal exactly which populations those old specimens belonged to, giving us a lot more confidence for future work on these toads."

Researchers previously thought N. viviparus was widespread across the Eastern Arc Mountains and Southern Highlands and that it wasn't vulnerable or endangered. But the discovery that the four distinct species have much smaller and more fragmented habitats could change their conservation statuses, since each individual species might be more at risk than expected. One related species, Nectophrynoides asperginis, went extinct in the wild in 2009 following the construction of a nearby dam and a fungal disease outbreak.

"The forests where these toads are known to occur are disappearing quickly," study co-author John Lyakurwa, a biologist at the University of Dar es Salaam in Tanzania, said in the statement. These habitats are vulnerable to both human uses and climate change.

Future studies could help scientists determine how threatened each species is and inform possible conservation strategies, the researchers wrote in the study.

In 2022, the U.S. National Park Service posted a blurry photo of a toad, snapped by a night-vision wildlife camera and accompanied by a tongue-in-cheek warning:

As we say with most things you come across in a national park, whether it be a banana slug, unfamiliar mushroom, or a large toad with glowing eyes in the dead of night, please refrain from licking. Thank you.

The message alludes to the urban legend that licking a toad can get you high. But do toads really have psychedelic properties?

It is true that a certain toad found across the southwestern United States and northwestern Mexico secretes a potent psychoactive chemical on its skin — but licking these toads is more likely to send you to the hospital than on a psychedelic trip.

The Colorado River toad (Incilius alvarius), also called the Sonoran Desert toad, has poison glands on its head that release the chemical 5-MeO-DMT.

"I think it's one of the most potent psychedelics that there is," said David E. Nichols, a professor emeritus of pharmacology at Purdue University and the first to create a synthetic analogue of 5-MeO-DMT.

5-MeO-DMT is a chemical that exerts its effects by binding to serotonin receptors in the brain. The drug lasts for about 15 to 30 minutes and can cause euphoria, a sense of nothingness, near-death-like experiences, and amnesia. According to Nichols, the drug can even cause complete dissolution of a person's sense of self, to the point where a user no longer remembers that they even used a drug.

However, 5-MeO-DMT doesn't have any psychedelic effects when ingested orally, so licking the chemical off of a toad wouldn't get you high — it requires more complicated methods such as smoking. What's more, it can be very dangerous to lick these toads, experts warn.

"Licking a toad is a no-go," Haley Dourron, a postdoctoral researcher at Linköping University in Sweden, told Live Science in an email. "Even pets that have licked the toad have ended up needing emergency medical care."

That's because Colorado River toads also secrete chemicals called cardiac glycosides. These compounds increase the strength of heart muscle contractions, and their effects on heart function can quickly become dangerous, leading to potentially life-threatening cardiac arrhythmias.

Yet the potential health risks haven't stopped poachers from gathering Colorado River toads in an attempt to chemically process the 5-MeO-DMT on their skin for recreational use.

"Toads are being systematically removed by poachers to extract their secretions to be trafficked," Robert Villa, a community outreach assistant at the University of Arizona, told Live Science in an email. Colorado River toads are already being affected by changing rain patterns, habitat loss, fungal diseases and pollution, Villa said, and poachers only add to the threat of their conservation.

The potential of 5-MeO-DMT

While obtaining 5-MeO-DMT from wild toads is unsafe and illegal, researchers are interested in the potential of synthetic 5-MeO-DMT, which is related to the psychedelic drug DMT. Compared with more traditional psychedelics such as LSD or psilocybin, relatively little is known about 5-MeO-DMT and how it affects the brain.

"At this point, over 100 people have had their brains scanned during trips on typical psychedelics like LSD and psilocybin," Dourron explained. "There are no published brain scanning studies of how 5-MeO-DMT works."

Trip reports of 5-MeO-DMT are often quite distinct from subjective experiences with typical psychedelics. Rather than experiencing classic hallucinations such as fractal patterns, some 5-MeO-DMT users describe experiencing a total "white-out."

"They might feel as if they've entered a 'void' or experienced a sense of nothingness," Dourron explained.

The strange effects of the drug have led Dourron to investigate whether the effects of 5-MeO-DMT stem from similar brain pathways to those impaired in certain types of seizures. Other researchers are exploring the potential of 5-MeO-DMT as an antidepressant. Early data show that the drug improves depressive symptoms within a day, with improvements lasting at least a week after treatment. Compared with other psychedelic drugs being explored for their antidepressant properties, such as psilocybin, 5-MeO-DMT's duration is much shorter, meaning treatment sessions could be completed more quickly.

"5-MeO-DMT is a very interesting substance, but ultimately, I think it likely plays by a different set of rules than other, more studied psychedelic substances," Dourron said. "Only science will tell us just what this playbook is."

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

Unlike humans, frogs and other amphibians don't need to rely on their lungs to breathe; their unique skin helps them exchange oxygen and drink. But how do frogs breathe and drink through their skin?

Frog skin is complex: It's thin, covered in glands that produce mucus to keep the skin moist, and porous enough to allow air molecules to permeate.

"[Their skin] is designed to allow both oxygen to get into the skin, and water to be absorbed," Christopher Raxworthy, a curator and herpetologist at the American Museum of Natural History in New York, told Live Science.

A network of small blood vessels right underneath the skin absorbs oxygen directly from water or the air, and also allows carbon dioxide to be driven out of the body in a process called cutaneous respiration, explained Kurt Schwenk, an evolutionary biologist at the University of Connecticut who has studied the breathing mechanisms of frogs and tadpoles. "It's really almost identical to a lung system," Raxworthy added.

Although frogs can also breathe through their lungs and the lining of their mouth, cutaneous respiration allows frogs to survive underwater and through long hibernations. "Almost without trying, just having skin that's moist, and having some blood vessels in it, they're going to exchange gas and water through their skin, whether they like it or not," Schwenk said, although not all frogs depend on cutaneous respiration equally.

Meanwhile, tadpoles don't have developed gills yet, so they need to breathe in air from the surface to survive. But when they're hatchlings, they're too small to break water's surface tension. Instead, they create their own air bubbles. In a 2020 study, Schwenk and his colleague observed the tadpoles swim right below the surface, where they quickly suck in air, forming a bubble. Then, they push the air bubble into their lungs.

Related: Can turtles really breathe through their butts?

Frogs' porous skin is also how they drink. "That water is getting into all those spaces in the skin, and is then being absorbed across cell membranes into cells and into the bloodstream," Schwenk added. Many frogs even have a highly vascularized area on their skin called a "drinking patch," through which they can absorb a large amount of water.

Some frogs found in arid areas — like the trilling frog and the water-holding frogs living in Australian deserts — are especially adept at absorbing water during rainy seasons. "They store it, and then they go into burrows, into the ground, and sometimes they might even put an extra layer of mucus around them, and then they can survive on that water that they stored internally for months or even years until the next rains come," Raxworthy explained.

Although it's a handy tool, their skin's permeability also means frogs and other amphibians are especially vulnerable to pollutants and climate change, Schwenk said. Studies have shown that the permeability of frog skin routinely exposes the animals to commercial chemical products and microplastics. And because frogs need to keep their skin moist to survive, the increased droughts and warmer weather scientists predict from climate change could shrink frog habitats, especially in the Amazon rainforest and the Atlantic rainforest in Brazil, Argentina and Paraguay.

"Amphibians tend to be some of the first groups that you start seeing declining or disappearing, and that usually is an indication of a problem within the environment," Raxworthy said. Losing frogs, in turn, changes the balance of an ecosystem because of their position on the food chain: They keep insect populations under control and are prey for snakes and birds.

Time will tell if some frog species will adapt to a changing climate. "A question that runs through all climate change biology is whether any particular species is subject to climate change, which is all of us, can adapt fast enough," Schwenk said. "In most cases, climate change is happening much faster than animals can adapt."

Animal quiz: Test yourself on these fun animal trivia questions

The wandering salamander isn't an average amphibian. Instead of skulking under logs or swimming in swamps, it lives an arboreal lifestyle. Native to the redwood forests, these amphibians spend most of their lives in trees, residing in the deep bark fissures and devouring insects.

With their homes over 300 feet (90 meters) off the ground, wandering salamanders glide across trees for resources and foraging, so they need a veritable grip during landing — if not, they could plummet to the forest floor.

To stay safe, wandering salamanders possess a unique gliding mechanism: 18 blood-powered toes. These specialized appendages are key to the salamander's precise leaping and landing through the complex canopy.

According to a study published in the Journal of Morphology, the wandering salamander controls its grip on the tree bark by pumping and draining blood in the tips of their square-shaped toes.

Scientists had previously theorized that the bright blood flow beneath their translucent skin helped keep their feet oxygenated. However, no empirical evidence backed this claim.

While using high-resolution video trials, biologists led by Christian Brown, a researcher at Washington State University, discovered that wandering salamanders can finely control the blood flow to each side of the toe tip asymmetrically, to increase or decrease the contact area with the surface.

When the salamander prepares to jump over branches, it quickly fills the toe tip with blood. The increased blood pressure helps salamanders to detach from the tree, as the blood influx increases the pressure and causes the toe pads to expand momentarily. This slight lift reduces the contact area, making it easier to detach from the surface.

Equally vital is the reverse process; wandering salamanders swiftly drain the blood from their toe tips when they land. This softens the toes and increases surface contact, allowing them to conform better to the irregular and rough texture, providing a more secure and effective grip that prevents the salamander from slipping.

They regulate the pressure dynamically depending on whether they're stepping, gripping, or releasing.

"If you're climbing a redwood and have 18 toes gripping bark, being able to detach efficiently without damaging your toe tips makes a huge difference," Brown said in a statement.

Around 230 million years ago, at least 19 alligator-size amphibians expired together on an ancient floodplain in what is now Wyoming.

The animals' fossilized remains, uncovered across four excavations between 2014 and 2019, have been relatively undisturbed since then and feature preserved delicate small bones and parts of the creatures' overall skeletal structure. The well-preserved findings could provide insight into how these Triassic amphibians lived and grew up, researchers reported in a new study published Wednesday (April 2) in the journal PLOS One.

Study first author Aaron Kufner, a geologist at the University of Wisconsin-Madison, and colleagues uncovered fossils of Buettnererpeton bakeri in a Wyoming fossil bed called Nobby Knob. These alligator-size creatures belong to an ancient amphibian group known as metoposaurids, a family of large, primitive four-legged amphibians. B. bakeri is the oldest known North American metoposaurid. It lived during the Triassic period (252 million to 201 million years ago) and may have frequented freshwater lakes and rivers as breeding grounds.

It's fairly common to find large piles of bones, known as bone beds, in the fossil record. Typically, bone beds occur when flowing water deposits bones in the same place over many years. Other times, bone beds happen when a group of animals die at the same time and place — which appears to be the case at Nobby Knob.

"This assemblage is a snapshot of a single population rather than an accumulation over time," Kufner said in a statement. The discovery "more than doubles the number of known Buettnererpeton bakeri individuals." Alongside the B. bakeri fossils, the team also found fossilized plants, bivalves and fossilized poop, called coprolites.

The amphibian bones didn't show any signs of having been moved by flowing water, suggesting these creatures came to rest in or near calm waters and were slowly buried by fine sediments during repeated floods. This left some of the fossils in the same shape and arrangement as the animals' actual skeletons. The researchers found B. bakeri fossils of various sizes, which could help explain how the animals grew and aged.

Because the closely grouped bones weren't carried to the site by currents, the researchers suspect the animals perished around the same time. They may have been part of a breeding colony or died because they were somehow prevented from leaving a drying body of water they needed to survive, the team suggested. It's still unclear whether mass metoposaurid die-offs like the one at Nobby Knob were common during the Triassic or whether the site represents an isolated event.

The B. bakeri fossils could help scientists date other metoposaurid fossils, the researchers wrote in the study. The Buettnererpeton fossils were buried deeper than fossils of Anaschisma browni, another metoposaurid, in the Popo Agie Formation — a Triassic formation that spans parts of Wyoming, Colorado and Utah. The finding that the Buettnererpeton fossils were likely older than Anaschisma correlates with other fossil beds that preserve both species and help date the regions and depths at which those fossils were found.

The Nobby Knob bone bed "preserves a wide size range of individuals from a single site that can provide insight into the [development] of metoposaurids," the scientists wrote in the study.

All over the world, frogs are being wiped out by the chytrid fungus. At least 500 species have declined, including as many as 90 species now presumed extinct.

This catastrophic and ongoing biodiversity loss surpasses the devastation wrought by other notorious invasive species such as cats, rats and even cane toads. Short of removing species from the wild and treating them in captivity, few strategies exist to deal with the chytrid threat.

Our new research, published in the journal Nature, offers a promising option.

Outbreaks of chytrid (pronounced "KY-trid") are more common in cold winter months — just like seasonal human flu. We found a way to combat these winter outbreaks using heat. Our purpose-built "frog saunas" allow affected amphibians to warm up and bake off their infections. They are so simple you can build a frog sauna using supplies from the hardware store.

Why should we care about frogs?

If frogs' good looks are not enough for you to care about their welfare, perhaps learning how they contribute to the environment or human health will pique your interest.

Frogs eat insects that carry and spread human diseases. Their skin is also a rich source of new medicines that could help us combat antibiotic-resistant "superbugs" or curb the startling increase in opioid addiction.

The frogs themselves are food for many predators, including humans.

Often starting life as a tadpole eating algae, before morphing into a carnivorous adult, frogs carry energy from aquatic ecosystems onto land — where it can be transferred throughout the food web. So losing a single frog species can have serious flow-on effects.

The origin and spread of chytrid

It's likely the chytrid fungus originated in Asia, where the pathogen seems to coexist with native amphibians. But chytrid is deadly elsewhere, possibly because other frogs have no natural defenses.

Chytrid harms frogs by disrupting the integrity of their skin, depleting electrolytes needed for heart function. Infected frogs can die of cardiac arrest.

Chytrid has spread worldwide through the trade of amphibians, becoming a seemingly permanent part of ecosystems. As eradicating chytrid from the wild is not possible, we need a way to help frogs battle infection.

Related: New fungal infection discovered in China

Introducing frog saunas

Research has shown chytrid is worse in winter. My colleagues and I wondered whether, if frogs had access to warmth during winter, could they fight off infection?

The fungus can't tolerate high temperatures, so if we gave frogs a place to stay warm — even for a few hours a day — perhaps they could survive and recover.

We tested this idea, both in the laboratory and in outdoor experiments.

First we established that endangered green and golden bell frogs will select temperatures that reduce or eliminate chytrid infections, when given the opportunity.

Then we conducted experiments in the lab, with 66 infected frogs. The group given the option of choosing the temperature they liked best rapidly cleared their infection. The group placed in a set, warm temperature also cleared their infection, but it took longer. The low-temperature control group remained infected.

Next, we wanted to see what would happen if frogs that cured infections with heat would still get sick. Or were they immune? The group of 23 heat-cured frogs were 22 times more likely to survive the second infection than the 23 frogs that were heat-treated but not previously infected. So frogs cured with heat acquire resistance to future infections.

Finally, we wanted to see if this could work in a natural setting. We ran outdoor experiments with 239 frogs. Half were infected with chytrid one week before the experiment began. Then they were placed in enclosures with artificial structures that heat up in the sun, called "frog saunas". But the frogs could choose from shaded and unshaded areas, with or without saunas.

We found frogs flocked to the sunny saunas, heated up their little bodies, and quickly fought off infection. Think of frog saunas as little factories that pump out healthy, chytrid-resistant frogs.

The frog saunas could be used on a wider scale. We believe they would be best suited to supporting populations of Australian green and golden bell frogs, but they could be useful for other species too.

The saunas are made of inexpensive materials that can be found at your local hardware store, making them accessible to the general public and wildlife managers alike.

We are already building shelters at Sydney Olympic Park, working with Macquarie University and the Sydney Olympic Park Authority. The park is home to one of the largest remaining populations of green and golden bell frogs.

Want to get involved?

You can become a citizen scientist and help save frogs from extinction. Start by downloading the FrogID app to learn how frogs are faring. Record frog calls with the app for scientists to identify them. This helps provide valuable data for frog conservation.

Build a frog sauna for your backyard, to help keep them healthy through winter.

It's essentially a brick-filled greenhouse, warmed by sunlight. All you need is some common clay ten-hole masonry bricks, black paint and cable ties — and a little greenhouse to put the sauna inside.

Changing the fate of frogs

Since the discovery of chytrid more than 25 years ago, the pathogen has been a seemingly insurmountable challenge to endangered frog conservation. Now, we have developed a promising, inexpensive and widely applicable strategy to combat chytrid.

Amphibians are such a diverse group that no single approach will be suitable for all species. So this is no silver bullet. But a useful tool for even one threatened or endangered species is cause for optimism.

The concept could also be applied to other wildlife diseases, where differences between the physiology of the host and pathogen can be exploited.

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

Breeding seasons can be dangerous for male frogs that attempt to impress a potential mate: They can quickly find themselves being dragged off and eaten by an unimpressed female, researchers have discovered.

For the first time, scientists in Kooragang Island in New South Wales, Australia have observed adult female green and golden bell frogs (Litoria aurea) preying on their male counterparts during breeding season. They detailed their findings in a study published June 12 in the journal Ecology and Evolution.

The researchers first observed this behavior during a survey when they heard a high-pitched squeal.

"You hear it sometimes in the field, and it's often a frog that's being predated upon," study lead author John Gould, a postdoctoral researcher in population ecology at the University of Newcastle, Australia, told Live Science.

After following the screams, Gould discovered the distress noises were coming from a male with its thigh almost completely ingested by a larger female. She was dragging him into a hole by the bank of a pond.

"The male frog really did try to stop this from occurring, so it was grabbing onto anything around it, like sticks in the ground, to stop itself from being dragged in," Gould said.

The male eventually managed to escape. The observation prompted Gould and his team to compare their nocturnal field observations of three consecutive breeding seasons with other studies that reported instances of sexual cannibalism.

Cannibalism is well-documented in amphibians, but most reported cases involve either adults cannibalizing juveniles that were emerging from the water or tadpoles cannibalizing each other, Gould said.

Amphibian cannibalism typically occurs when large numbers of the animals congregate in the same area, such as when tadpoles emerge from eggs, and when there are notable size differences between predator and prey.

Many species of frogs are sexually dimorphic — adult females are often significantly larger than males.

"There’s a very good opportunity that females can exploit their male counterparts, not only as breeding partners, but potentially as prey," Gould said.

The researchers speculated that this cannibalism may act as a natural selection process.

Females may differentiate between potential mates or prey depending on the quality of their calls during breeding season. Larger males with deeper calls may be seen as better breeding partners, leaving smaller, inferior males as potential meals.

However, Gould suggested that the superior mates may not escape predation either. Instead, once females have dumped all their eggs after breeding, they may choose to eat their mate — similar to female praying mantises, which decapitate and eat their mates during or after mating.

"It's risky for male frogs out there. They're calling their little hearts out to find a mate, but they just have to take on this extra risk of maybe being used as prey," Gould said.

Scientists still don't know for sure what influences these cannibalistic behaviors. Observations of sexual cannibalism are rare because they occur quickly. However, this may not mean that they are infrequent, Gould said.

Gould points out that field observations of amplexus — when a male frog mounts a female to fertilize her eggs — are also relatively rare, even though scientists know it is necessary for breeding.

Further research is needed to establish how frequent these cannibalistic events are and how they impact the local populations of green and golden bell frogs, the team said.

Scientists in Australia have discovered a tree frog with bright blue skin instead of the usual green color, new pictures show.

The blue pigmentation is due to a rare genetic mutation, experts say.

Land managers in a wildlife sanctuary in Kimberley, Western Australia, spotted the mutant amphibian when it hopped into their workshop and sat on a bench gazing at them, ABC News reported Friday (July 12). Scientists later identified the animal as a magnificent tree frog (Litoria splendida).

The land managers sent pictures of the blue frog to Jake Barker, a conservation and ecology intern with the Australian Wildlife Conservancy (AWC). "Seeing the picture of the frog, it definitely elevated my heart rate," Barker told ABC News. "It was so cool, it was a really exciting and special thing."

Related: Paradoxical frog: The giant tadpole that turns into a little frog

Magnificent tree frogs are usually green with white spots on their backs, according to AWC. They grow to around 4 inches (10 centimeters) long and have a characteristic poison gland on the top of their heads. The poison tastes extremely bitter and serves as a defense mechanism against predators, such as larger amphibians, reptiles, birds and mammals.

The frogs can live for 20 years and inhabit areas of low rainfall across the northern Kimberley region and nearby Northern Territory.

This is the first time researchers have ever seen a blue-skinned magnificent tree frog, according to AWC. The mutant frog had an olive-green poison gland on its head, a few white spots on its back and yellow toe pads, the pictures showed.

Most frog species are green thanks to a combination of blue and yellow pigments in their skin, Barker told ABC News. The blue coloration in this individual was caused by a rare mutation called axanthism, where the yellow pigments are suppressed, he said.

"It's just a lovely freak of nature," Jodi Rowley, a herpetologist and curator of amphibian and reptile conservation biology at the Australian Museum, told Yahoo News.

Rowley has only ever seen one other blue frog in real life, possibly because these frogs are not well camouflaged in nature and get picked out by predators, she said. The newly discovered magnificent frog was 4.7 inches (12 cm) long, which is "really big" and indicates that "he's a few years of age," she said.

"It's a very healthy frog," Rowley said. "It's definitely a showy frog. It's one of the most beautiful frogs I've ever seen."

A newly described species of proto-amphibian that lived 270 million years ago has been named after Kermit the Frog.

Paleontologists at the Smithsonian National Museum of Natural History rediscovered the ancient amphibian ancestor's fossilized skull while looking through the museum's archives, according to a statement.

The "creature’s cartoonishly wide-eyed face" immediately reminded the researchers of the "Muppets" character Kermit the Frog, so the scientists named the species Kermitops gratus. They described the animal in a study published Wednesday (March 21) in the Zoological Journal.

"Using the name Kermit has significant implications for how we can bridge the science that is done by paleontologists in museums to the general public," lead study author Calvin So, a doctoral student of biological sciences at The George Washington University, said in the statement. "Because this animal is a distant relative of today's amphibians, and Kermit is a modern-day amphibian icon, it was the perfect name for it."

Related: World's tiniest fanged frog with males that 'hug' their babies discovered

The skull, which measures roughly an inch (2.5 centimeters) long and has "oval-shaped eye sockets" was first unearthed by Nicholas Hotton III, a paleontologist and curator at the Smithsonian. Hotton discovered the skull while exploring the Red Beds, a fossil-rich rock outcrop in Texas. During that field season, Hotton and his team discovered so many fossils that "they were not able to study them all in detail," according to the statement.

Then, in 2021, Arjan Mann, a postdoctoral paleontologist at the museum, and the study's co-author, found the skull in the archives.

"One fossil immediately jumped out at me — this really well preserved, mostly prepared skull," Mann said in the statement.

The paleontologists noticed that the skull contained unique physical traits that set it apart from other tetrapods, the ancient ancestors of amphibians. For example, the part of the skull with the animal's eye sockets "was much shorter than its elongated snout." Scientists think that the animal likely "resembled a stout salamander" and used its longer snout to "snap up tiny grub-like insects," according to the statement. 

The researchers determined that the animal is not a frog but rather from the order temnospondyls, which are thought to be the common ancestors of Lissamphibia, the group that includes all modern amphibians, such as frogs, salamanders and caecilians.

The new find could help researchers better understand how these groups evolved and fit together on the evolutionary tree.

"Kermitops offers us clues to bridge this huge fossil gap and start to see how frogs and salamanders developed these really specialized traits," So said in the statement.

In incredible new footage, a worm-like creature feeds its babies with a milk-like substance similar to what mammals give their newborns. It is the first time this behavior has been documented in caecilians.

In the first-of-its-kind video, a female Brazilian ringed caecilian (Siphonops annulatus), an egg-laying amphibian, produces a transparent liquid to feed its offspring. The female's brood communicates with physical touch and high-pitched sounds to encourage the mother to secrete the viscous liquid from its anus so they can feed.

This maternal behavior was documented in a study published March 4 in the journal Science.

Amongst vertebrates that produce eggs, offspring depend on obtaining nutrition from the embryonic yolk sac, the external organ of an embryo.

Related: Watch translucent cockroach babies burst from their egg cases in skin-crawling footage

But some species have developed parental care behaviors and specialized food for their offspring. Other than in mammals, different types of maternal care have been observed in spiders, cockroaches, fish and birds — and now in this egg-laying amphibian.

Brazilian caecilians are a group of strange, legless amphibians that move like worms. Some species give birth to live young; others, like S. annulatus, lay eggs.

Using their teeth, the offspring nibble and touch the mother's behind with their snouts to encourage her to expose her cloaca — the opening of the rectum, urinary ducts and genital ducts known as a vent — to release the milk-like substance. This method of communication from the offspring is considered a type of begging behavior, according to the study.

The mother fed her offspring the "milk" daily for the first two months after they hatched. During this time, the mother did not leave her brood, not even to feed.

Further analysis of the milk showed its composition of long chain fatty acids — similar to the secretions of mammals where fats are the primary source of energy provided during parental care.

The research team collected the caecilians during fieldwork in the Brazilian state of Bahia and kept the critters in captivity with their broods. All of the babies had light-pink, semi transparent bodies which indicated that they were in the initial or medium stage of development after hatching.

Aside from this milk-like substance, caecilians are known to provide their young with another nutritional meal — their skin. Brooding mothers lose their dark coloration and appear pale. Glandular secretions transform the outer layer of the skin into a nutrient-packed food source that's rich in fats. After hatching, the offspring use their teeth to scrape away the mothers fleshy skin.

Because most caecilian species are terrestrial and live underground in burrows, they are very difficult to find and thus are little understood. "The study by Mailho-Fontana et al. opens new areas of research for caecilians and for amphibian biology in general," Marvalee Wake, a biologist at the University of California, Berkeley, who was not involved in the study, said in a statement. "It also provides an expanded approach to investigate the evolution of derived modes of reproduction in the broadest sense, and to better understand key aspects of evolutionary biology." 

In a bizarre, never-before-seen case, a live frog was found in India with a mushroom growing from its skin, leaving scientists puzzled.

The frog — identified as Rao's intermediate golden-backed frog (Hylarana intermedia) — was spotted sitting among 40 other individuals from the same species, perched on a twig with a white stalk and gray cap protruding out of its left flank.

The discovery was made by Lohit Y.T., a river and wetlands specialist at World Wildlife Fund (WWF) India during an expedition with friends to find reptiles and amphibians in the foothills of the Kudremukh ranges in India.

After the team shared photos of the frog, mycologists said the mushroom could be from the genus Mycena. Lohit and his co-author Chinmay C Maliye documented their discovery in a new study, published Jan. 28 in the journal Reptiles and Amphibians.

The group didn't collect the frog, and it is not known whether the fungus grew from within the frog's body or on the skin surface. Some mycologists suspect the amphibian picked up the fungus following an infection or wound — leaving a pitted area that the fungus could cling to.

Related: Paradoxical frog: The giant tadpole that turns into a little frog

"I would guess that this is a purely superficial skin infection with Mycena, those can be sustained over a long time, [the same] as most fungal skin infections in humans," Christoffer Bugge Harder, a researcher in the University of Copenhagen's Department of Biology, who was not involved in the study, told Forbes about the new finding.

The fungus did not seem to be harming the frog, according to the study, and it had no other visible injuries.

This is not the first time amphibians have encountered fungi. Previous research revealed that amphibians are vulnerable to a pathogenic fungi called Batrachochytrium dendrobatidis, which causes the lethal skin disease chytridiomycosis. The disease is responsible for mass mortalities of amphibians across the world. Because of this, scientists wonder whether this new discovery of fungal infection could be a cause for concern.

Rao's intermediate golden-backed frogs are around the size of a thumb and are native to the Western Ghats, a mountain range running parallel to India's west coast. 

Species in the genus Mycena, meanwhile, are commonly called bonnet mushrooms. Most of these species thrive on nutrients from dead or decaying organic matter and are usually found growing in clusters on decayed wood.

Mushrooms develop in nutrient-rich places from fungal spores. The spores reproduce into thin, branching filaments, and mushrooms then grow if nutrients are available. Although most Mycena species are found on dead materials, a study published in 2023 reported growth of a Mycena species on live plants. 

Harder, who was lead author of the 2023 study, said this study suggests these mushrooms are in the process of an evolutionary development and can be invaders of living plants under favorable conditions, but that live frogs are definitely not ordinary terrain.

A fossilized frog that lived alongside the dinosaurs 100 million years ago has been discovered with a belly full of eggs — the oldest such frog ever found, scientists have announced.

Researchers believe the frog was likely killed during mating, when the female may have been drowned by a male that was gripping her.

Frogs do not get pregnant. Instead, female frogs develop a batch of eggs that they are ready to lay, in what is known as a "gravid" state. The eggs are eventually laid and fertilized by a male.

The gravid frog, from the species Gansubatrachus qilianensis, was found in a fossil bed in northwest China and dates from the Cretaceous period (145 million to 66 million years ago), researchers revealed in a study published Feb. 6 in the journal Royal Society B: Biological Sciences.

Fossilized frogs from this period are  exceedingly scarce, and those that have preserved soft tissues are even rarer. This specimen is more extraordinary still, as it's the earliest documented record of a gravid frog, the researchers noted.

Related: These female frogs fake their own deaths to get out of sex

The scientists compared the fossilized gravid frog with other previously discovered specimens. They built  a high-resolution model of its skeleton using computed tomography (CT) scans of the fossils, and analyzed the composition of its eggs using X-rays.

Their analysis suggested that the frog was still skeletally immature, meaning she was able to sexually reproduce before being physically fully developed. Though this is common in many modern animals, there was previously no direct fossil evidence that this was the case for ancient frogs and toads.

"The evolution of reproduction, especially reproductive strategies, is a very important part of biological evolution," lead author Baoxia Du, a paleontologist at Lanzhou University in China, told Live Science.

Understanding the reproductive strategies employed by early frogs could offer valuable insights into their complete reproductive history, he added.

As the frog was skeletally immature, the researchers ruled out old age as her cause of death. Environmental factors, such as abrupt changes in water conditions or algae blooms, were also unlikely, as evidence of this would've been apparent in the deposits studied, Du said.

Few other frog fossils were found in the deposits, suggesting that some disastrous event was not the culprit as it would have led to a mass death and numerous frog fossils nearby.

"We currently believe that the most likely cause of death is weakness or even suffocation after 'amplexus behavior,' which is quite common among existing frogs,” Du said.

Amplexus, which means embrace in Latin, describes the behavior when males mount and grip onto females with their front legs for hours or days at a time until her eggs are fertilized. In doing this, the female may have died from drowning or exhaustion, according to the study.

While more fossil records are required to substantiate the findings that early frogs were sexually mature before adulthood, the discovery provides a tantalizing glimpse into the development of ancient frogs. "The fact that [early frogs] thrived during the dinosaur era and endured multiple mass extinctions makes studying their survival strategies highly valuable," Du said.

Australia is about to embark on a massive annual cane toad killing spree — known as the Great Cane Toad Bust — to put a dent in the numbers of this invasive pest. Now, scientists are proposing a humane method to purge the toxic toads.

Instead of bludgeoning cane toads (Rhinella marina, formerly Bufo marinus) with cricket bats and golf clubs, or poisoning them with harsh chemicals, scientists advise bagging the toads and sticking them in the fridge. The cold puts the amphibians into a state of torpor and shuts their pain receptors off. People can then transfer the toads to the freezer to finish them off humanely, said Rick Shine, a professor of biology at Macquarie University in Sydney, Australia.

"As a toad cools, its metabolism slows down and it becomes very inactive," Shine told Live Science in an email. "Even its brain shuts down. So a cold toad doesn't feel pain, and the toad never knows what is going on — it just falls asleep and never wakes up."

Cane toads naturally experience temperatures dropping at night, so their bodies don't go into shock when they are initially put in the fridge, Shine said. In a 2015 study, Shine and his colleagues found that the toad's brain activity declined smoothly during freezing and produced no detectable pain signals. By the time ice crystals start to form in a toad's tissues, "it's not aware of anything," he said.

Scientists introduced cane toads from Hawaii to Queensland, Australia, in 1935 to exterminate cane beetles (Dermolepida albohirtum) that were ravaging newly planted sugarcane crops. However, this effort backfired, because cane toads showed no interest in the beetles and multiplied uncontrollably. The toads, which secrete venom that can kill animals that eat them, spread to coastal New South Wales, the Northern Territory and parts of northwestern Australia. Everywhere they went, they triggered declines in native predators and caused damage to ecosystems.

Related: 'Monster cane toad' dubbed 'Toadzilla' found in Australia

Cane toads still wreak havoc today, prompting the environmental non-profit Watergum to organize the Great Cane Toad Bust, an annual campaign to kill as many toads as possible in a week. This year's kill-athon — the third nationwide bust and the first to target tadpoles as well as adult toads — will take place between Jan. 13 and Jan. 21.

"The Great Cane Toad Bust is Australia's biggest toad bust," Nikki Tomsett, Watergum's invasive species project officer, told Live Science in an email. "It's all about taking collective action to effectively and humanely control cane toads, which are an invasive pest species in Australia." 

The campaign has been successful so far, with people removing over 50,000 cane toads from their local environment in a single week, Tomsett said. "This year we're aiming to beat that record," she said.

Cane toads can live for more than 10 years in the wild, Tomsett said. Female toads produce as many as 35,000 eggs every time they breed, which means every toad matters when it comes to toad busting.

The cool-and-freeze method "is currently considered best practice for the humane euthanasia of cane toads," Tomsett said. "Blunt force trauma and most chemical applications are not considered humane, and pose a threat to wildlife and pets, as cane toads euthanized in this way are typically left in the environment and are still toxic after death."

People who club the toads to death also risk hitting the poison glands, which can cause temporary blindness in humans if it gets into the eyes," ABC News reported.

Australians are encouraged to keep busting cane toads after Jan. 21, Tomsett added.

A team of researchers has identified a teeny new frog species that's no bigger than a quarter. But don't let its diminutive size fool you: This one has fangs.

The new species, Limnonectes phyllofolia, which the researchers described in a new study published Dec. 20 in the journal PLOS One, was found in the lush forests of Sulawesi, an Indonesian island renowned for its biodiversity — including fanged frogs.

The frogs use these teeth like weapons to tussle with their competitors for territory to lay their eggs. Researchers think the frogs may also use their fangs to pierce through the protective casings of prey such as insects and crabs. (Technically, the saber-like structures, which are situated in the frogs' lower jaws, are bony protrusions, not teeth.)

The fact that some frogs have teeth may come as a surprise. In fact many frog species have tiny teeth that line the upper jaw — though these are near-invisible in most. However the 70-plus species of the genus Limnonectes are known for the more notable fang-like protrusions on their lower jaws. These fanged amphibians are spread across East and Southeast Asia, and the dense rainforests of Sulawesi are a hotspot, home to 15 of those species. Some of the frogs in the genus are huge, such as the Blyth’s river frog (Limnonectes blythii) which can weigh over 2.2 pounds (1 kilogram). But the genus' newest member, L. phyllofolia, is just 1.2 inches (3 centimeters) long, meaning it's the smallest fanged frog in the world. 

Related: These female frogs fake their own deaths to get out of sex

But its minuscule size isn't this frog's only unusual trait. Researchers first discovered the new species when they noticed some strange nesting behavior in the Sulawesi rainforest. They spied unmistakable clusters of frog eggs spread across mossy boulders, fern fronds and the leaves of sapling trees, which surprised them because most frogs lay their delicate eggs in riverbanks and ponds to prevent the gel-like sacs that surround the developing tadpoles from drying out. 

What's more, when the researchers hung around to find out which animal these above-ground nesting sites belonged to, they noticed the tiny frogs that returned to their eggs were all male. "Male egg guarding behavior isn't totally unknown across all frogs, but it's rather uncommon," study lead author Jeff Frederick, a postdoctoral researcher at the Field Museum in Chicago, in a statement. Males are the primary caretakers in only one other fanged frog species, L. arathooni, which lays its eggs at ground level in stream banks and ponds. 

The unusually doting dads of L. phyllofolia — whose second name means "leaf-nester" — get around the threat of desiccating eggs by seemingly "hugging" their brood, coating the eggs in compounds that are excreted from their skin to keep their progeny moist and ward off bacterial and fungal infection, the researchers said in the statement. 

Whether laid on a leaf or a mossy rock, each nest had been positioned about 3 to 6.5 feet (1 to 2 meters) above a body of water. This means that when it comes to hatching time, the tadpoles can conveniently slither out of their eggs and plop directly into the water. 

The researchers think this unusual nesting behavior might help explain why the frogs evolved to be so small and have tiny pinprick fangs compared with their relatives' larger teeth. Choosing nest sites above ground and away from other competitors seems to work well enough at protecting the nest from competitors and predators that these frogs don't need a hefty body weight or impressive gnashers to do the job.

The researchers hope that the discovery of L. phyllofolia will provide extra motivation to study these creatures. Of the 15 species in Sulawesi, only five have been formally described, they noted. "Our findings also underscore the importance of conserving these very special tropical habitats," Frederick said. "Learning about animals like these frogs that are found nowhere else on Earth helps make the case for protecting these valuable ecosystems."

Name: Paradoxical frog (Pseudis paradoxa), also known as shrinking frog

Where it lives: Northern South America and Trinidad

What it eats: Invertebrates, mainly insects

Why it's awesome: This rather odd species is unusual because it gets smaller as it grows up — it is notably larger in the larval stage than in the adult stage. The paradoxical frog's substantial tadpole is three to four times larger than an adult and measures up to 9 inches (22 centimeters). In comparison, an adult measures up to 3 inches (8 cm) long.

Other species in the Pseudis genus also exhibit this unusual change in size, but the paradoxical frog holds the record for the longest tadpole. 

So how do these tadpoles get so big? A study published in 2009 in The Herpetological Journal found that the growth rate of the tadpoles is similar to other species, but the paradoxical tadpoles just keep on growing and developing.

By the time the tadpoles undergo metamorphosis into adults, the males have already begun to produce sperm and are "essentially mature," and the females have eggs in development — which normally happens in the juvenile frog stage of the life cycle.

Another paper, which looked at a different Pseudis species, studied the skeletal development of that species' tadpoles and found that it was well-advanced or complete by the end of metamorphosis. 

Much of the tadpole’s extraordinary size comes from its long and deep tail. Prior to metamorphosing into an adult, its snout-vent length (i.e. its body length) is comparable to the mature adult. 

In most other frogs, a post-metamorphosis frog starts small and then grows larger. However, because this tadpole grows for longer than other species, and is well-developed when it undergoes metamorphosis, the adult exhibits little to no growth. The loss of the tail that causes the frog to "shrink."

Paleontologists have discovered the earliest molecular evidence of the toxic pigment that causes red hair in the fossil record — in 10 million-year-old frog fossils.

The ancient amphibians had preserved fragments of pheomelanin (also spelled phaeomelanin), a yellowish-red pigment that produces ginger-colored hair in animals, including humans, according to a study published Oct. 6 in the journal Nature Communications.

"It's the exact same pigment that causes red hair in us," lead study author Tiffany Slater, a postdoctoral researcher of paleobiology at University College Cork in Ireland, told Live Science. "But that doesn't mean that the frogs were necessarily ginger colored when they were alive."

Pelophylax pueyoi is an extinct species of large frog that lived in what is now Spain during the Early Miocene (23 to 5.3 million years ago). Their fossilized remains are part of a museum collection and were loaned to the researchers, according to a statement.

Related: These female frogs fake their own deaths to get out of sex

To get a better understanding of how the pigments degrade during the fossilization process, the researchers examined liver tissues taken from the frog remains (the liver is known for containing high levels of pheomelanin) along with black, ginger and white bird feathers, which dovetailed with a previous study of theirs, according to the statement.

Their findings showed traces of pheomelanin contained within the liver tissues of the ancient frogs. 

"Fossils are invariably altered by the ravages of heat and pressure during burial, but that doesn't mean that we lose all original biomolecular information," study co-author Maria McNamara, a professor of paleobiology at University College Cork, said in the statement. "Our fossilization experiments were the key to understanding the chemistry of the fossils and prove that traces of biomolecules can survive being cooked during the fossilization process."

Slater said their experiments are "pushing the boundaries" of what they thought was possible regarding the information a fossil can contain. 

However, scientists are still learning how and why pheomelanin evolved in the first place, especially as it can be toxic to animals, Slater said. Pheomelanin is a type of melanin, a substance in the body that produces hair, eye and skin pigmentation. In humans, there are two types of melanin — eumelanin, which is responsible for dark colors, and pheomelanin, which produces blond and ginger hair colors and pale skin. While eumelanin helps protect from the sun's harmful UV rays, pheomelanin does not.

"It's toxic in the way that it interacts with sunlight, which can cause damage to certain cells," Slater said. 

The scientists hope that further study can lead to a better understanding of the evolution of different pigments within the fossil record, providing an insight into the colors of ancient animals.

"This is the first molecular record of pheomelanin in the fossil record, and we need to start looking for pigments in more and older fossils," Slater said. "Then we can start [to rebuild] what it says about evolution, and the big question of why ginger pigments evolve despite them being toxic to animals."

In the video above, the female frog in the top left tank fakes death to avoid sex with the male. 

Female frogs have developed a number of ways to get out of sex, including rolling, grunting and even faking their own deaths, scientists have discovered.

European common frogs (Rana temporaria) are known as "explosive" breeders that gather in their dozens to mate in ponds. Usually, males outnumber females, which means six or more males may compete to mount a female at one time in what is known as a mating ball.

"In some cases, the female might be killed inside these mating balls," Carolin Dittrich, a researcher at the Natural History Museum in Berlin, told Live Science.

But the females have developed several techniques to avoid mating. "Rather than being passive and helpless, we find that females can use three key strategies for avoiding males they don’t want to mate with — either because they aren't ready to breed or do not want to mate with a certain male," Dittrich said.

Related: Female spiders play dead during sex so males don't have to worry about being eaten

The researchers collected male and female European common frogs from a pond during the breeding season and divided them into tanks filled with water, so each tank contained two females and one male. They then filmed the frogs for an hour. 

Of the 54 females that were grasped by a male, 83% of them rolled onto their back in response.

"This puts the male underwater, so the male lets go to avoid drowning," Dittrich said. 

The team also found that 48% of the females that were mounted by males emitted grunts and squeaks. The grunts mimicked "release calls" that male frogs usually make to ward off other males from mounting them, Dittrich said. "But it's unclear what the higher frequency squeaks are signaling," she added. 

The researchers also found that a third of females lay motionless with their limbs outstretched for around two minutes after being mounted by a male.

"To us, it appears as if the female is playing dead, although we can't prove it's a conscious behavior," Dittrich said. "It could just be an automatic response to stress."

Smaller female frogs, which are usually younger, were the most likely to use all three deterrence strategies, whereas larger, likely older, females were less likely to fake their own death, Dittrich said. As a result, smaller female frogs were generally better at escaping a male's advances than larger ones, she added.

It could be that younger females, which have lived through fewer breeding seasons, become more stressed upon being mounted by males, causing them to respond more strongly, Dittrich said. 

Overall, 46% of females who were mounted by a male successfully escaped.

Although the experiments are quite different to the real-world scenario, these strategies have been seen in the wild, Dittrich said. 

Faking death as a strategy to escape unwanted males has been documented in just a handful of other animals, including dragonflies, spiders and in one other amphibian species — sharp-ribbed newts (Pleurodeles waltl). 

Understanding mating behaviors like these could help support conservation efforts in the future, if we try to breed species back from the brink, Dittrich noted. "Although the European Common frog is more common than many other species, there has been a steady decrease in population numbers in the past 17 years due to the lack of rain and droughts," she said.

The study was published Wednesday (Oct. 11) in the journal Royal Society Open Science.

Name: Mexican salamander (Ambystoma mexicanum) also known as an axolotl

Where it lives: Lake Xochimilco and Lake Chalco, near Mexico City

What it eats: a variety of small invertebrates, along with some small fish

Why it's awesome: Despite its rarity, the axolotl's incredibly cute looks has made it one of the world's most famous amphibians, inspiring characters in Pokemon and Animal Crossing, making an appearance in Minecraft and even featuring as a Google Doodle. 

With a happy little face and frilly gills, it’s like the amphibian version of a puppy. This cuteness is caused by literally not growing up properly. Most salamanders undergo metamorphosis from their totally aquatic larval form to their mostly terrestrial adult forms. However, the axolotl is one of the salamander species that doesn’t. Instead it retains all of its larval features — external gills and a fin along its back — and remains completely aquatic, but is able to reproduce. This is called paedomorphosis or neoteny. 

Related: Meet the bizarre, grumpy-faced black rain frog that's terrible at jumping and swimming

It can also regenerate almost any part of its body, including its limbs, eyes and even parts of its brain, which makes it of great interest to scientists studying regenerative biology. 

The axolotl is so beloved it is the national amphibian of Mexico and appeared on a 50 peso bill released in 2021.

However, with just 50 to 1,000 remaining in the wild and a decreasing population, it is considered critically endangered on the International Union for Conservation of Nature (IUCN) Red List. Limited to just a couple of lakes in southern Mexico City, it faces habitat loss due to the introduction of invasive predators and pollution.

Raising the profile of the species goes some way to helping conserve the species, but work has also been undertaken to improve the water quality where it lives, and encouraging traditional farming that creates habitats for the species.

Name: Black rain frog (Breviceps fuscus)

Where it lives: The forested slopes of the southern Cape fold mountains, South Africa

What it eats: Small insects 

Why it's awesome: Move over grumpy cat — say hello to the grumpy frog. In addition to being a famous meme, black rain frogs have plenty of unusual traits that make them fascinating critters.

For starters, unlike most other frogs, their chonky round bodies and short, stubby legs make them terrible at swimming and jumping. They are, however, extraordinarily good at burrowing, and spend a large amount of time underground.

"They dig backwards into the ground using their hind feet, which have specialized digging tubercles," Jeanne Tarrant, manager of the Threatened Amphibian Programme at the Endangered Wildlife Trust told Live Science. Using their hindlimbs, they shift the soil by slowly rotating to "disappear below the surface," she said. 

Related: What's the difference between a frog and a toad?

Once there, they create tunnels to form an intricate underground system where females lay their eggs. This has led some to believe they don’t have a tadpole stage, but they do, it just takes place underground, sloshing around the soil rather than swimming in water before emerging from the burrows as froglets. 

Above ground, black rain frogs — which are about 1.6 to 2 inches (4 to 5 centimeters) long — run or walk, rather than hop: "Their legs are very short, and their bodies round," Tarrant said. "They will inflate their round bodies as a predation defense… They do this basically by inflating with air." These frogs also produce a milky substance that is slightly toxic to predators, she added.

So although they may appear grumpy — and have a high-pitched screech to go with their angry faces — we think black rain frogs are pretty cute, especially as the small bumps that cover their body make them look a bit like a tiny avocado.

While most frogs eat a diet rich in insects, one species in Brazil has its own method of nourishment: dunking itself headfirst into a flower's bulb to slurp up its sweet nectar. When the frog comes up for air, pollen grains stuck to its rust-colored body get dispersed as it hops from flower to flower in the forest.

Scientists think this could be the first time an amphibian has been observed pollinating flowering plants, according to a study published in the June issue of the journal Food Webs.

"We observed individuals entering large flowers and leaving covered in pollen without destroying the flower structures," lead author Carlos Henrique de-Oliveira-Nogueira, a graduate student at the Federal University of Mato Grosso do Sul in Brazil, told Live Science in an email. "This was the first time this behavior (actively seeking fruits and flowers) was seen and documented."

It's long been known that species other than bees, including bats and birds, can act as pollinators. But scientists were surprised to see an Izecksohn's Brazilian tree frog (Xenohyla truncata) performing a similar behavior on a Brazilian milk fruit tree (Cordia taguahyensis), known for its creamy-white flowers, according to the study.

One evening, the team watched as two frogs "lapp[ed] up nectar from inside the bell-shaped flowers" in eastern Brazil's Restinga forests and then spread the pollen around, The New York Times reported.

Related: Otherworldly 'Lord of the Rings' frog discovered in the mountains of Ecuador

Normally, frogs prefer to dine on moths and insects, which they capture by sticking out their long tongues. 

"Most frog species are carnivorous in their adult phase," de-Oliveira-Nogueira told Live Science. He said there are other frogs that are known to feed on plant parts. But in Brazil, X. truncata is the only one. "Here, we confirmed how opportunistic X. truncata seems to be. It feeds on both insects and plants — apparently anything that is available for consumption," he told Live Science.

However, he cautioned that more research needs to be done before this species can be classified as a bona fide pollinator. 

"This was amazing and left us with many questions that still need answers," he said. "The species meets some of the requirements to be a pollinator, but we still need further study to actually prove this."

Felipe Amorim, a pollination ecologist at São Paulo State University in Brazil who wasn't involved in the study, agreed.

"We cannot say that these frogs are actually pollinators," Amorim told The New York Times. "They are flower visitors, they are flower-visitor frogs. We have a lot to learn about this novel interaction."

Baby hellbender salamanders don't stand a chance against their fathers who have gone rogue and started cannibalizing their offspring.

For the past eight years, scientists from Virginia Tech have been studying the behavior of hellbender salamanders (Cryptobranchus alleganiensis), a species of giant amphibians that inhabit the frigid waters of southwestern Virginia rivers and are considered the largest salamanders in North America, growing about 2 feet (0.69 meters) long and weighing up to 5 pounds (2.3 kilograms).

The researchers noticed that male salamanders were more prone to eating their young if they resided in areas affected by deforestation.

In fact, in the past 50 years, hellbender salamander numbers have decreased across the United States, and the researchers cited disease, poaching, climate change and habitat loss due to deforestation as possible factors leading to this cannibalistic behavior, The New York Times reported. 

Related: World's oldest known case of cannibalism revealed in trilobite fossils

Typically, male salamanders are doting fathers that stick around for months after fertilizing the eggs to fend off possible predators, eating only around 14% of the offspring that have low chances for survival. However, in areas where deforestation is an issue, this tendency to chow down on their young tripled. Hopkins suspects that changes in water chemistry due to deforestation could be depleting the salamanders' food supply and thus causing this shift in behavior, according to The New York Times. 

Infanticide has become so commonplace among these jumbo salamanders that the researchers worry that the practice could lead to the species' extinction.

"If you have rates of cannibalism this high, then that alone is enough to explain many of the population declines we've seen across the species range," William Hopkins, an ecologist at Virginia Tech and lead author of a new paper describing the research, told The New York Times.

Male hellbender salamanders aren't unique in their hankering to eat their young. Filial cannibalism is also common in other species, like cane toads and Baltic comb jellies.

The research by Hopkins and his colleagues will be published in a forthcoming issue of the journal The American Naturalist.

Scientists in Ecuador have discovered a newfound species of stream frog with pale pink eyes and gold-speckled toes that looks like it came straight out of Middle-earth. That's why the researchers who discovered it named it Hyloscirtus tolkieni after J. R. R. Tolkien, the author of "The Hobbit'' and "The Lord of the Rings" books.

"The new species of frog has amazing colors, and it would seem that it lives in a universe of fantasies, like those created by Tolkien," Diego F. Cisneros-Heredia, director of the Museum of Zoology of the Universidad San Francisco de Quito (USFQ) and associate researcher of the National Institute of Biodiversity in Ecuador, said in a statement.

The researchers describe the "Lord of the Rings'' frog in a study published Jan. 19 in the journal ZooKeys. H. tolkieni is 2.6 inches long (6.5 centimeters) and grayish green in color. Black spots dot its golden-yellow throat, belly, flanks and the undersides of its legs. The frog's fingers and toes too, are covered in black specks and broad skin stripes. The creature boasts an arresting pair of dusty pink eyes with black irises, which reminded the researchers of the otherworldly animals in their beloved author’s fantasy worlds.

Related: Adorable 'chocolate frog' discovered in crocodile infested swamp

Scientists discovered H. tolkieni in the Río Negro-Sopladora National Park, a largely unstudied area of pristine páramo (alpine tundra) and cloud forest protected since 2018 and covering more than 185,000 acres (75,000 hectares). Like other species of stream frog, this critter lives in the clear mountain rivers and streams of the high Andes. Tadpoles mature near rocks in the rapids, while adult stream frogs prefer the protection of lush vegetation on the river banks.

"For weeks, we explored different areas of the Río Negro-Sopladora National Park, walking from páramo grasslands at 3,100 meters [10 thousand feet] elevation to forests at 1,000 m [3.3 thousand feet]. We found a single individual of this new species of frog, which we found impressive due to its coloration and large size," Juan Carlos Sánchez Nivicela, also an associate researcher at the Museum of Zoology at USFQ and the National Institute of Biodiversity, said in the statement. 

Scientific expeditions in this region of Ecuador have led to the discovery of a large number of new species since 2020.

"The tropical Andes are magical ecosystems where some of the most wonderful species of flora, funga, and fauna in the world are present," Cisneros-Heredia said. "Unfortunately, few areas are well protected from the negative impacts caused by humans. Deforestation, unsustainable agricultural expansion, mining, invasive species, and climate changes are seriously affecting Andean biodiversity."

As a result, 57% of amphibian species in Ecuador are at risk of extinction, according to the statement.

A jumbo-size cane toad (Rhinella marina) captured in Queensland, Australia, has tipped the scales at a whopping 6 pounds (2.7 kilograms), earning it the nickname "Toadzilla" and likely making it the largest example of the species on record.

Rangers stumbled upon the hefty amphibian on Jan. 19 in Conway National Park while they were conducting track work. They announced their discovery via a tweet, writing that they were "shocked to find a monster cane toad" that weighed as much as a rooster.

"I just couldn't believe it to be honest — I've never seen anything so big," Kylee Gray, a ranger for the Queensland Department of Environment and Science, told the Australian Broadcasting Corporation (ABC). "It flinched when I walked up to it and I yelled out to my supervisor to show him. [It looked] almost like a football with legs."

Related: What's the difference between a frog and a toad?

Gray described the find as "a big warty, brown, ugly cane toad just sitting in the dirt," and she and her colleagues think it was a female, "due to the size, and female cane toads do grow bigger than males."

The official largest known toad on record is a cane toad (also called a marine toad) found in 1991, also in Australia, that weighed 5 pounds, 13 ounces (2.65 kg), according to Guinness World Records. 

After weighing the portly toad found at the national park, rangers euthanized it "due to the environmental damage they cause," they wrote in the tweet.

"A cane toad that size will eat anything it can fit into its mouth," Gray told ABC, "and that includes insects, reptiles and small mammals."

CNN reported that the toad's remains have been sent to the Queensland Museum for further analysis.

When a glassfrog falls asleep, it vanishes. Nestled atop a lush leaf, the frog's bright green back blends right in, while its underbelly's reddish hue quickly grows transparent. 

Now, a new study in the journal Science reveals that the northern glassfrog (Hyalinobatrachium fleischmanni) pulls off this feat by removing almost 90% of its red blood cells from circulation and packing them into its liver. The findings reveal how one of the only transparent land animals hides its blood. 

"If you really want to be transparent, you need to hide your red blood cells," study co-author Sönke Johnsen, a professor of biology at Duke University in North Carolina, told Live Science. "These glassfrogs are — by some process; we don't know the details — filtering red blood cells out of their blood and cramming them into their livers so tightly that it should create a clot. But it doesn't."

Understanding why these clots never form could have implications for human diseases, the researchers said.

Northern glassfrogs seldom grow larger than 1 inch (2.54 centimeters) in length, and spend most of their adulthood perched on leaves in Central and South American forest canopies, high above the rapidly flowing streams where they lay their eggs. Their underbellies are translucent even when the frogs are awake, allowing an observer to easily see their hearts pumping red blood throughout their bodies. But scientists have long been fascinated by the way the frogs' bellies turn transparent when they fall asleep, rendering them all but invisible to predators.

Related: Why is the color blue so rare in nature?

To better understand this phenomenon, Johnsen and colleagues tracked the red blood cells circulating throughout glassfrogs' bodies. One of these methods, known as photoacoustic microscopy, is not unlike ringing a bell with a laser beam — scientists shine a bright light onto the frog's body and capture the sound waves produced whenever the light strikes hemoglobin, the protein in red blood cells that carries oxygen and gives blood its distinctive color. 

"Even with a transparent animal, seeing exactly what is going on inside can be difficult," Johnsen said. "We used sound, because it travels through tissue much better than light."

Once they had developed this technique, studying how glassfrogs turn transparent was a simple matter of repeatedly agitating the hapless amphibians. "We'd let the frog rest, then poke it a few times, and let it fall asleep again." Johnsen said. Following the hemoglobin revealed that glassfrogs pull 89% of their red blood cells from circulation and stash them in their livers. Since their skin reflects very little light and their blood, sans hemoglobin, does not absorb it, they become almost entirely transparent.

Johnsen and colleagues hope that further study of this phenomenon will shed light on human clotting disorders and inform research into anticoagulants.

"The human body is always at this sharp edge between clotting too little and too much, whether we're talking about the big clots in strokes, which cause terrible damage, or little micro-clots at the periphery, which cause so much misery," Johnsen said. "The clotting process for frogs is not so different from that of humans, so whatever we learn from the frogs could end up being relevant to human clotting."

But so much about this process, including how they survive with so little hemoglobin circulating while they sleep, remains unclear. So before glassfrogs can inform clinical research, Johnsen and colleagues will need to figure out just how the amphibians are manipulating their blood. 

"What these frogs are doing is the equivalent of a human taking all their blood and stuffing it into a lunch bag inside their body," Johnsen said. "How are glassfrogs doing that? The cool thing is that we just don't know."

Near-black frogs far outnumber their highlighter-yellow fellows in Chernobyl's radiation-blasted ecosystems, in a direct example of "evolution in action," a new study shows. The study, published Aug. 29 in the journal Evolutionary Applications, found that eastern tree frogs (Hyla orientalis) with more skin-darkening melanin pigment were more likely to survive the 1986 nuclear accident in Ukraine than frogs with lighter skin, leading to populations today that are dominated by darker frogs.

"Radiation can damage the genetic material of living organisms and generate undesirable mutations," researchers wrote in a post on The Conversation about their research. "However, one of the most interesting research topics in Chernobyl is trying to detect if some species are actually adapting to live with radiation. As with other pollutants, radiation could be a very strong selective factor, favoring organisms with mechanisms that increase their survival in areas contaminated with radioactive substances."

On April 26, 1986, a reactor at the Chernobyl nuclear power plant in Ukraine exploded, spewing radioactive materials across an 18-mile (30 kilometers) radius. 

"The Chernobyl accident released approximately 100 times the energy released by the nuclear bombs of Hiroshima and Nagasaki," Pablo Burraco, the study's lead author and a biologist with the Doñana Biological Station in Seville, Spain, told Live Science in an email.

Related: Frogs' skulls are more bizarre (and beautiful) than you ever imagined

Officials evacuated residents from the contaminated zone following the disaster and established a 1,040 square-mile (2,700 square kilometers) exclusion zone. In the decades since, the abandoned area has become a wildlife refuge. Burraco and his team wanted to understand how the nuclear meltdown drove evolution in the animals living there.

After studying more than 200 male frogs whose habitats were spread across 12 different breeding ponds throughout the radioactive contamination zone, researchers found that "on average, 44% were darker than those outside of Chernobyl," Burraco said. "We consider the most plausible explanation to [why] frogs within the Chernobyl Exclusion Zone [are changing color] is that the extremely high radiation levels at the moment of the accident selected for frogs with dark skin."

Why dark skin? It turns out that high melanin levels in frogs’ skin shielded them from radiation. 

"Melanin is known to protect against radiation because it can mechanically avoid the production of free radicals caused by the direct impact of the radioactive particles on cells," Burraco said. "Radiation can induce oxidative stress and damage essential structures for life such as the membrane of cells or even DNA."

Cells in the lighter frogs were bombarded with higher levels of damaging radiation, which killed them off at higher rates than their darker counterparts. After the blast, dark frogs had a higher likelihood of surviving, the study concluded. 

Researchers also looked for potential negative effects of excess melanin on the post-Chernobyl dark frogs. They found that like in other species, including certain types of fungi, having darker pigmented skin didn't harm the overall health of the amphibians and actually helped ionize radiation, which prevents ionized molecules from getting into cells and damaging them.

"The production of melanin can be metabolically costly, this has been described, for example, in several bird species," Burraco said. "However, in frogs, the main melanin pigment is called eumelanin and its production seems not to incur in physiological costs."

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

The axolotl (Ambystoma mexicanum) is an aquatic salamander renowned for its ability to regenerate its spinal cord, heart and limbs. These amphibians also readily make new neurons throughout their lives. In 1964, researchers observed that adult axolotls could regenerate parts of their brains, even if a large section was completely removed. But one study found that axolotl brain regeneration has a limited ability to rebuild original tissue structure.

So how perfectly can axolotl’s regenerate their brains after injury?

As a researcher studying regeneration at the cellular level, I and my colleagues in the Treutlein Lab at ETH Zurich and the Tanaka Lab at the Institute of Molecular Pathology in Vienna wondered whether axolotls are able to regenerate all the different cell types in their brain, including the connections linking one brain region to another. In our recently published study, we created an atlas of the cells that make up a part of the axolotl brain, shedding light on both the way it regenerates and brain evolution across species.

Why look at cells?

Different cell types have different functions. They are able to specialize in certain roles because they each express different genes. Understanding what types of cells are in the brain and what they do helps clarify the overall picture of how the brain works. It also allows researchers to make comparisons across evolution and try to find biological trends across species.

One way to understand which cells are expressing which genes is by using a technique called single-cell RNA sequencing (scRNA-seq). This tool allows researchers to count the number of active genes within each cell of a particular sample. This provides a “snapshot” of the activities each cell was doing when it was collected.

This tool has been instrumental in understanding the types of cells that exist in the brains of animals. Scientists have used scRNA-seq in fish, reptiles, mice and even humans. But one major piece of the brain evolution puzzle has been missing: amphibians.

Mapping the axolotl brain

Our team decided to focus on the telencephalon of the axolotl. In humans, the telencephalon is the largest division of the brain and contains a region called the neocortex, which plays a key role in animal behavior and cognition. Throughout recent evolution, the neocortex has massively grown in size compared with other brain regions. Similarly, the types of cells that make up the telencephalon overall have highly diversified and grown in complexity over time, making this region an intriguing area to study.

We used scRNA-seq to identify the different types of cells that make up the axolotl telencephalon, including different types of neurons and progenitor cells, or cells that can divide into more of themselves or turn into other cell types. We identified what genes are active when progenitor cells become neurons, and found that many pass through an intermediate cell type called neuroblasts – previously unknown to exist in axolotls – before becoming mature neurons.

We then put axolotl regeneration to the test by removing one section of their telencephalon. Using a specialized method of scRNA-seq, we were able to capture and sequence all the new cells at different stages of regeneration, from one to 12 weeks after injury. Ultimately, we found that all cell types that were removed had been completely restored.

We observed that brain regeneration happens in three main phases. The first phase starts with a rapid increase in the number of progenitor cells, and a small fraction of these cells activate a wound-healing process. In phase two, progenitor cells begin to differentiate into neuroblasts. Finally, in phase three, the neuroblasts differentiate into the same types of neurons that were originally lost.

Astonishingly, we also observed that the severed neuronal connections between the removed area and other areas of the brain had been reconnected. This rewiring indicates that the regenerated area had also regained its original function.

Amphibians and human brains

Adding amphibians to the evolutionary puzzle allows researchers to infer how the brain and its cell types has changed over time, as well as the mechanisms behind regeneration.

When we compared our axolotl data with other species, we found that cells in their telencephalon show strong similarity to the mammalian hippocampus, the region of the brain involved in memory formation, and the olfactory cortex, the region of the brain involved in the sense of smell. We even found some similarities in one axolotl cell type to the neocortex, the area of the brain known for perception, thought and spatial reasoning in humans. These similarities indicate that these areas of the brain may be evolutionarily conserved, or stayed comparable over the course of evolution, and that the neocortex of mammals may have an ancestor cell type in the telencephalon of amphibians.

While our study sheds light on the process of brain regeneration, including which genes are involved and how cells ultimately become neurons, we still don’t know what external signals initiate this process. Moreover, we don’t know if the processes we identified are still accessible to animals that evolved later in time, such as mice or humans.

But we’re not solving the brain evolution puzzle alone. The Tosches Lab at Columbia University explored the diversity of cell types in another species of salamander, Pleurodeles waltl, while the Fei lab at the Guangdong Academy of Medical Sciences in China and collaborators at life sciences company BGI explored how cell types are spatially arranged in the axolotl forebrain.

Identifying all the cell types in the axolotl brain also helps pave the way for innovative research in regenerative medicine. The brains of mice and humans have largely lost their capacity to repair or regenerate themselves. Medical interventions for severe brain injury currently focus on drug and stem cell therapies to boost or promote repair. Examining the genes and cell types that allow axolotls to accomplish nearly perfect regeneration may be the key to improve treatments for severe injuries and unlock regeneration potential in humans.

Originally published on The Conversation.

Frogs and toads make up the largest group of amphibians. Species in this order, called Anura, substantially outnumber those in the two other living orders of amphibians — Caudata (salamanders) and Gymnophiona (caecilians). As of August 2022, Anura had 7,486 of the 8,478 known amphibian species, according to Amphibian Species of the World, a reference website from the American Museum of Natural History in New York. 

Frogs and toads are among the most diverse animal groups. Though they might be most famous for their croaking and jumping, these animals have a wide variety of unique traits and behaviors. Like many other animals, frogs and toads are suffering greatly from human-related threats, and many species face imminent extinction. 

Frogs vs. toads

"Frog" and "toad" are common names that don't mean much from a scientific perspective. "Frog" can be thought of as the more encompassing word as it's the common name for the Anura order, and used in the common names of most of Anura's species. "Toad" is used more selectively in the common names of certain species or groups.

Amphibians with "toad" in their common names often have characteristics that are not typically thought of as frog-like. For example, "toads" usually live in drier habitats — and have drier, bumpier skin and shorter hindlimbs — than is typical for frogs, according to the Burke Museum in Seattle. However, all toads can be called frogs. 

Related: What's the difference between a frog and a toad?

Types of frog

Frogs come in a variety of shapes, colors and sizes. The largest frogs are Goliath frogs (Conraua goliath) from Cameroon and Equatorial Guinea; they can grow to be more than 1.1 feet (34 centimeters) long and weigh 7.3 pounds (3.3 kilograms), according to a 2019 study published in the Journal of Natural History. Goliath frogs appear to use their great size to shift rocks weighing more than 4 pounds (2 kg) to build "nursery ponds" that they clean and guard, Live Science previously reported. 

The world's smallest known frog is a tiny species called Paedophryne amauensis from Papua New Guinea. Described in a 2012 study published in the journal PLOS One, this frog grows to an average length of 0.3 inch (7.7 millimeters), making it the smallest known vertebrate on Earth, Live Science previously reported. 

Frogs are famed for their fantastic jumping skills, but not all frogs hop. Waxy monkey tree frogs (Phyllomedusa sauvagii) walk along branches, gripping them like monkeys do. These South American frogs secrete a natural opioid called dermorphin, which is many times stronger than morphine and has been used to create an illegal performance-enhancing drug for racing horses, according to the World Wildlife Fund. 

Many frogs utilize camouflage, whether it's to stay hidden from predators or blend into their environment so prey don't notice them. For example, Vietnamese mossy frogs (Theloderma corticale) from Vietnam resemble clumps of moss. Poison dart frogs are called the "jewels of the rainforest" because they come in various colors that warn predators they're toxic and shouldn't be eaten. However, even these bright colors can act as camouflage in a vibrant rainforest. 

Glass frogs have translucent green skin that makes their internal organs, and even beating hearts, visible to the human eye. They've evolved for predators to look straight through them. A 2020 study published in the journal Proceedings of the National Academy of Sciences (PNAS) found that these frogs aren't truly transparent, but their camouflage is flexible.

"The frogs are always green but appear to brighten and darken depending on the background," lead author James Barnett, a behavioral ecologist at McMaster University in Ontario, said in a statement at the time. "This change in brightness makes the frogs a closer match to their immediate surroundings, which are predominantly made up of green leaves."

While there are thousands of known frog species, there are likely many more that scientists haven't found yet. For example, researchers described six new species from Mexico in April 2022, and each can fit comfortably on a thumbnail. The researchers noted at the time that the frogs could represent the tip of a giant iceberg of unknown amphibians just in Mexico, Live Science previously reported.  

Related: Adorable 'chocolate frog' discovered in crocodile-infested swamp

Where do frogs live?

Frogs are found on every continent except Antarctica. They need to be around water sources to reproduce, but their habitats are extremely varied otherwise. Poison dart frogs hop through the tropical rainforests of Central and South America, while northern leopard frogs (Lithobates pipiens) inhabit much of North America's marshlands, brushlands and other habitats, including farmland and golf courses, according to the University of Michigan's BioKids website. 

Some species live in highly specialized environments. For example, Vietnamese mossy frogs live in mossy, flooded caves and the banks of rocky mountain streams around 2,300 to 3,300 feet (700 to 1,000 meters) above sea level, according to the Smithsonian's National Zoo & Conservation Biology Institute in Washington, D.C. Meanwhile, desert rain frogs (Breviceps macrops) appear to live exclusively in the white sand dunes of Namibia and South Africa, burrowing into the sand during the day and feeding at night, according to the International Union for Conservation of Nature (IUCN). 

Frogs have lungs, but they can also breathe through their skin by absorbing oxygen from water. They can still drown if their lungs fill with water or there's not enough oxygen in the water they're swimming in, according to the Burke Museum. 

What do frogs eat?

Frogs have a wide diet that includes insects, spiders, worms, slugs, larvae and small fish. These amphibians play a vital role in the world's ecosystems by helping to keep insect populations under control, according to the San Diego Zoo. They catch prey using their quick, sticky tongues. A 2017 study published in the Journal of the Royal Society Interface found that frog tongues can catch insects in 0.07 second — five times faster than the blink of a human eye. 

Related: Watch this frog light up after it swallows a firefly

Some frogs seek out much larger prey than flies and slugs. For example, cane toads (Rhinella marina), which typically grow to 9 inches (23 cm) in length, scarf down small birds, mammals and snakes with ease, as well as other amphibians and even table scraps and pet food, according to the Florida Fish and Wildlife Conservation Commission. Their native range stretches from the Amazon basin in South America up to southern Texas. But humans have introduced cane toads elsewhere, and their insatiable appetites can be a big problem for wildlife. They are an invasive species in areas such as Florida and Australia, where they compete with native amphibians and poison animals that try to feed on them, including pets and, in Australia's case, endangered species such as Tasmanian devils (​​Sarcophilus harrisii), according to the San Diego Zoo.

How do frogs reproduce?

Frogs have many mating strategies, and scientists are still learning about these animals' sex lives. For most species, mature males initiate the breeding process by calling loudly to tell females they are ready to mate, according to the Australian Museum in Sydney. Females filled with eggs approach calling males and choose one to mate with, usually in water. Fertilized eggs, or frog spawn, can incubate for anywhere between 48 hours and 23 days before hatching, depending on the species, according to the San Diego Zoo. Small, legless, fish-like tadpoles emerge from the eggs and begin life feeding on algae.  

Tadpoles' transformation into mature frogs starts with the release of hormones from their thyroid glands, according to the book "Developmental Biology" (Sinauer Associates, 2000). Over time, tadpoles grow legs, lose their tails and emerge from the water capable of living on land. The word "amphibian" comes from the Greek words "amphi" and "bios," which translate to "both life," because they live in water and on land, according to the Oxford Learner's Dictionaries.  

Related: 'Ancient death trap' preserved hundreds of fossilized frogs that drowned during sex

Do frogs hibernate?

Frogs are ectothermic, or "cold-blooded," like other amphibians, reptiles and snakes. This means they can't regulate their own body temperature internally like mammals do, and they rely on the external environment to stay warm, according to Froglife, a conservation charity based in the U.K. To survive winter in colder environments, frogs may go into a state of dormancy, called brumation, underwater or under log piles. Brumation is similar to hibernation, except frogs may occasionally emerge from their dormant state to eat. 

Wood frogs (Lithobates sylvaticus) have an even more extreme winter survival strategy to survive in the northern forests of Alaska and Canada: They allow ice to fill their abdominal cavities and encase their internal organs. In this state, wood frogs' hearts stop beating and they appear to be frozen solid, but they're still alive in a state of suspended animation. The frogs survive because their livers produce glucose that prevents their cells from freezing. They begin to thaw out in spring, and at some point — though scientists aren't sure how — their hearts start beating again and they go on their way, according to the National Park Service. 

Are frogs poisonous?

The bumps on amphibians' skin aren't warts, and people can't contract warts from handling these animals. The myth that people can get warts from frogs likely stems from the wart-like appearance of the bumps, according to the Burke Museum. However, many frogs produce poisonous secretions that can irritate human skin or cause serious harm if ingested. For example, the most toxic poison dart frogs in the genus Phyllobates produce batrachotoxin, which disrupts the human body's nervous system and can cause paralysis, extreme pain and heart failure. As well as potential toxins, frogs can carry bacteria and parasites, according to the Burke Museum. 

The secretions of frogs have played an important role in the development of human medicine; they're used, for example, to make painkillers and antibiotics. Furthermore, around 10% of physiology and medicine Nobel Prize winners used frogs as part of their research, according to Save the Frogs, an amphibian conservation charity based in California.

A few frogs are venomous as well as poisonous. Poison is harmful if ingested, but animals are venomous if they inject their toxins. A 2015 study published in the journal Current Biology found that two Brazilian frog species possessed bony spines on their skulls that they could use like venomous fangs. These frogs, called Bruno's casque-headed frogs (Aparasphenodon brunoi) and Greening's frogs (Corythomantis greeningi), headbutt potential predators to stab them with the spines and transfer toxins, according to the Natural History Museum in London.

Related: Frogs' skulls are more bizarre (and beautiful) than you ever imagined

Are frogs endangered?

Amphibians are the most threatened group of vertebrates on Earth; 40% of the amphibian species assessed by the IUCN are at risk of extinction. This means that many frog species are declining and need help from humans if they are to survive. According to the IUCN SSC Amphibian Specialist Group, some of the main threats facing amphibians are habitat loss and degradation, pollution, disease, invasive species, trade and climate change. 

Frog extinction has disturbing implications for humans. The amphibians are highly susceptible to environmental disturbances, making frog populations a good indicator of the health of an environment, according to Save the Frogs. Therefore, the sheer number of amphibians at risk of extinction can be viewed as a wake-up call for the environmental damage that humans are causing to the planet. 

Additional resources

For more information about how venomous frogs headbutt potential predators, watch this short YouTube video from the Natural History Museum in London. For tips on how to help your local frogs, check out the National Wildlife Federation website. To learn more about different frog species, check out "Frogs and Toads of the World" (Princeton University Press, 2011). 

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

A bizarre, newly discovered species of ancient salamander recently received a digital makeover. Researchers used X-ray images to create a 3D model of the animal's oddly shaped skull, which had been trapped inside a Jurassic rock first uncovered around 50 years ago.  

The newly identified species, which scientists named Mamorerpeton wakei, dates to around 166 million years ago, during the Jurassic period (201.3 million to 145 million years ago). Researchers estimated that these ancient salamanders grew to be around 6.3 inches (16 centimeters) long, and the shape and structure of their bones suggested they were an aquatic species that likely swam around ancient ponds or lakes, slurping up smaller creatures with powerful suction. 

Part of the ancient amphibian was collected unintentionally in the early 1970s, by another group of researchers on Scotland's Isle of Skye. This team had unearthed a lump of limestone with a single bone protruding from the surface, suggesting that there might be something of interest inside. However, the limestone block was deemed less important than other fossils that were collected at the time, and the limestone — along with its undetermined contents — went into storage. However, another research team uncovered additional fragments of the specimen between 2016 and 2019, suggesting that the long-ignored rock in storage might contain part of the unknown creature's skull.

For the new study, the authors used X-rays to scan the skull block without damaging any of the fragile bones inside. The team generated around 800 individual projections, or images, of the bones inside the block and then used a computer program to reassemble the skull, which had been crushed and mangled inside the rocky matrix, back into its original 3D shape.

Related: 10 coolest non-dinosaur fossils unearthed in 2021 

"Initially, we thought the material would represent Mamorerpeton kermacki," an ancient salamander species known from rocks of the same time period in England, lead study author Marc Jones, an evolutionary biologist at University College London, told Live Science in an email. However, the skull reconstruction revealed that it was actually a new species from the same genus, Jones added.  

The researchers were surprised to discover just how dramatically the skull differed from those of salamanders alive today.

"There is a lot of variation in skull structure among modern salamanders," Jones said. "But the new fossil salamander is different from all of them." Some of the bones resembled those seen in frogs, and a couple of standout features were crocodile-like structures on the roof of the skull and bony projections behind the eye, both of which are unlike anything seen in modern salamanders. Attachment of the jaw muscles also differed from the jaws of most modern salamanders.

The unusual characteristics of the skull, combined with its salamander-like structures, suggest that M. wakei may have been an evolutionary cousin of many modern salamanders, of which there are around 750 species, according to the study. Previously, other researchers had identified ancient salamanders from the genus Karaurus as the most likely common ancestors of modern salamanders, Jones said. M. wakei and Karaurus show lots of similarities, which hinted that the new species may also be a common ancestor of modern salamanders. But comparisons to a broad sample of amphibians show that neither are the common ancestor of modern salamanders. Instead, these species represent an evolutionary side branch, Jones said. The new discovery shows that salamander evolution is "more complicated than previously assumed," he added. 

The researchers said the discovery highlights the importance of assessing all fossil discoveries — even those that initially seem unremarkable. It is "common" for fossils like this to slip under the radar because it can be expensive and time-consuming to analyze them, Jones said. But as technology continues to advance, long-ignored fossils like this one can provide new insight into the evolution of modern creatures, which is "important for understanding why they are the way they are," he added.

The study was published online July 11 in the journal Proceedings of the National Academy of Sciences.

Originally published on Live Science.

It was a cold case with hundreds of victims. For decades, scientists puzzled over a gruesome mystery: What killed hundreds of fossilized frogs found at an ancient "death trap" in Germany dating to millions of years ago? These frogs seemed to be completely healthy when they died, but researchers recently determined that the amphibians may have drowned during aggressive underwater sex. 

For the new study, scientists analyzed the remains of 168 frogs found at an old mining site in the Geiseltal valley, in central Germany's Saxony-Anhalt region. The specimens were originally collected between the 1930s and 1950s, along with around 50,000 other fossils. Around half of those were vertebrates, and included horse ancestors, large crocodiles, giant snakes and ground-dwelling birds, researchers said in a statement.

The fossilized frog bones date back to around 45 million years ago during the Eocene epoch; at the time, the site was a coastal swamp bordering the Palaeo-North Sea, which covered most of northern Germany. Chemical conditions within the swamp delayed the decay of dead organisms until they could be fossilized by minerals in the water, which preserved the paleontological "treasure trove" of specimens, according to the statement. 

Analysis of the bones revealed that the frogs weren't killed by predators or disease. Through the process of elimination, the scientists concluded that the most likely cause of death was mating, as male frogs in species alive today are known to sometimes hold females under the water as they mount them, causing the females to drown. "By studying the bones of the fossil frogs we were able to narrow down the options of death," lead study author Daniel Falk, a paleontologist at University College Cork in Ireland, told Live Science in an email. "The only explanation that makes sense is that they died during mating."

Related: Lost fossil 'treasure trove' rediscovered after 70 years 

Other paleontologists had previously proposed that the frogs died due to extreme environmental changes such as flooding or drought. Another hypothesis suggested that the culprit was sudden oxygen depletion in the water, which would have affected the amphibians' ability to absorb oxygen through their skin, known as cutaneous respiration, and led to mass drownings. 

However, the frog's bones showed evidence that the corpses floated after the animals died, which ruled out swamp desiccation, Falk said. "Frogs and toads will also migrate if water conditions in their pond are not suitable," which probably rules out oxygen depletion, he added. "There’s also no evidence that they were washed in during floods."

Other causes of death, such as predation, disease, malnourishment or old age, would have left distinct signatures in the frog's remains, Falk said. This left mating as the most plausible cause of death for these fossilized frogs.

During mating, frog males mount females from behind and then climb on top of the female's backs. On land, this is not an issue for the females. But some species of frogs mate in water, which can force the females under the surface and drown them if the males take too long. This mating behavior is seen in some modern species of frogs — among certain species, it can be "very common," Falk said.

Drowning is more likely to happen when groups of males try to mate with a single female, forming what is known as a breeding ball, Falk said. "This often happens in species that engage in mating congregations during a short explosive breeding season," he explained. It's possible that this is what took place tens of millions of years ago with the Geiseltal frogs, who may have migrated to the swamps once a year for mass breeding, he added.

However, researchers were unable to determine the gender of the frogs from just their bones, so there is no way to determine if the fossilized frogs are all female, Falk said. This makes it impossible to definitively prove their hypothesis. 

Several other sites around the world that date to different time periods also preserve fossils from seemingly healthy frogs in which the causes of death are uncertain. The team suspect that frogs at these sites may also have drowned during sex, which hints the phenomenon is far more prevalent in ancient frog populations than once thought. "This suggests that the mating behaviors of modern frogs are really quite ancient and have been in place for at least 45 million years," Falk said.

This poses another potential mystery: After millions of years of frog evolution have elapsed, why are females still drowning during sex? For species who still procreate this way, the benefits of mating in water must outweigh the costs — but it's unclear how. 

The researchers suspect that further study of how these fossilized frogs died could reveal clues about amphibian evolution and how amphibians have adjusted as their ecosystems changed over time. "If we understand how and why these frogs died so long ago, we can learn to protect not only modern frogs, but also learn how ecosystems evolve and how animals adapt in a variable environment," Falk said.

The study was published online July 5 in the journal Papers in Palaeontology.

Originally published on Live Science.

When the Aztecs settled the Valley of Mexico around what is now Mexico City in the 13th century, they found a large salamander living in the lake surrounding the island where they built their capital, Tenochtitlán. They called the salamander "axolotl" after Xolotl, their god of fire and lightning. Xolotl was said to have transformed into a salamander, among other forms, to avoid being sacrificed so the sun and moon could move in the sky; he was eventually captured and killed, according to Aztec mythology. 

In the same vein, axolotls were commonly killed for food by the Aztecs and are still eaten in Mexico today. But beyond Aztec mythology and the dinner plate, axolotls have become one of the world's most famous salamanders, whether as pets thanks to their charisma and easy care, or more recently as highly sought-after characters in the popular online games Minecraft and Fortnite. The creatures' extraordinary ability to regenerate body parts has even made them an interesting study subject for scientists. But in their native home in Mexico, the salamanders are rapidly disappearing and are considered critically endangered. 

Axolotls (Ambystoma mexicanum) are amphibians belonging to the single living genus of the family Ambystomatidae. There are more than 30 salamander species in the Ambystoma genus, known as the mole salamanders, according to the University of California, Berkeley’s, AmphibiaWeb. 

Axolotls can grow on average to a length of 9 inches (20 centimeters), but some have grown to more than 12 inches (30 cm) long. In captivity, the salamanders live an average of 5 to 6 years, but some have lived for up to 17 years, according to the University of Liverpool's The Animal Ageing and Longevity Database.

Where do axolotls live?

Wild axolotls live exclusively in the swampy remnants of Lake Xochimilco and the canals leading to it on the southern edge of Mexico City. Axolotls also once lived in Lake Chalco, another of Mexico City's five "great lakes" where the ancient Aztecs settled. But all of those lakes, except for Xochimilco, were drained by the 1970s to prevent flooding and to allow urban expansion, NBC News reported.

Axolotls' carnivorous diet historically put them at the top of the food chain. They eat anything they can snatch: Mollusks, fish and arthropods like insects and spiders. They even eat each other. In the 1970s and 1980s, though, the United Nations Food and Agricultural Organization introduced tilapia and carp fish to the salamanders' habitat to provide local people with more protein, according to JSTOR Daily. Those fish chow down on young axolotls and are an invasive threat to the salamanders.

How do axolotl reproduce?

Axolotl reproduction starts with dancing — literally. After a male and female nudge and stroke one another's urogenital opening called the cloaca, the salamanders step in a circle in a sort of waltz, according to the University of Michigan's Animal Diversity Web. The male then struts away while seductively shimmying his tail, luring the female to follow. As the two dance partners step together, the male drops a small white capsule full of sperm called a spermatophore. With the female in tow, the male moves forward until the female just skirts over the spermatophore and picks it up with her cloaca.

Axolotls go through this courtship once a year, typically between March and June. When the courtship dancing is done, the female axolotl will individually attach her 100 to 300 jelly-coated eggs to aquatic plants or rocks. Around 10 to 14 days later, the eggs hatch, and the young fend for themselves. It takes about a year for axolotls to become sexually mature.

Axolotls are one of several salamander species, however, that never metamorphose into terrestrial adults that are primarily lung-breathing. American evolutionary biologist Stephen Jay Gould described the adult salamanders as "sexually mature tadpoles" because they forever retain their juvenile characteristics: a fully aquatic lifestyle, a finned tail, and frilly gills. This evolutionary phenomenon of "everlasting youth" is called paedomorphosis, or neoteny. Scientists can force axolotls in the lab to metamorphose by introducing iodine to their environment or injecting them with thyroid hormones, but axolotl metamorphosis rarely occurs in the wild, researchers reported in 2015 in the journal BioScience.

Biologists considered this obligate trait of axolotls a major force of evolution – a characteristic that could genetically isolate a population from other nearby salamander species and, consequently, could drive the rapid development of new species. But a 2021 study in the journal Proceedings of the National Academy of Sciences (PNAS) found that select sets of genes from axolotls and their relatives are almost indistinguishable. Throughout their history, the various salamander species (some with obligate paedomorphosis, others not) have interbred, providing new and potentially important context for researchers trying to conserve axolotls and their relative, and implying that scientists could look to related but less-endangered salamander species to answer research questions for which axolotls have been used.

Why are axolotls endangered?

The International Union for Conservation of Nature and Natural Resources considers axolotls critically endangered and their population declining. Surveys in 1998 and 2008 found that the population density had dropped from about 6,000 individuals per square kilometer (0.4 square miles) to 100 individuals per square kilometer. A more recent survey in 2015 found about 35 individuals per square kilometer.

Pollution has been particularly detrimental to the species. Poor waste regulations and increasing tourism in Mexico City mean that trash, plastics, heavy metals and high levels of ammonia spilled from waste-treatment plants clog the canals where the salamanders live.

In coordination with the Mexican government, scientists, farmers and nonprofit organizations are working to restore the axolotl’s habitat, using floating islands of water plants, logs and mud called chinampas to filter the polluted water, National Geographic reported. Organizations are also providing opportunities for interested tourists to see the salamanders in their natural habitats, with proceeds going toward conservation efforts. 

While a substantial captive axolotl population exists in research labs around the world, accounting for several thousand individuals, these salamanders stem from 34 individuals shipped to Paris from Xochimilco, Mexico in 1863. Consequently, the population suffers from high rates of inbreeding – a major problem for forming a healthy and sustainable population.

Axolotls in research

Among the axolotl's trademark talents is its ability to regrow almost any body part: feet, legs, tails and even bits of the heart and brain. The amphibians can even mobilize stem cells — cells that can pretty much form into any cell necessary — to repair an injured spinal cord, scientists reported in 2021 in the journal eLife. And axolotls don't stop with the regeneration of their own body parts. All sorts of organs, including eyes, can be transplanted between axolotls without rejection by the recipient body's immune system. In 1968, researchers showed that they could even transplant the head of one axolotl to another axolotl, and it functioned normally. The combination of these abilities makes axolotls attractive model organisms for scientists.

This ability to regenerate limbs and organs has contributed to a huge swath of research in regenerative biology, especially for medical applications. Researchers in 2013 discovered that white blood cells called macrophages are essential for axolotls’ regenerative abilities. Without these cells, the salamanders just form a scar at the injury site, implying that macrophages in some way pump the brakes of scar formation. In 2021, researchers reported in the journal Frontiers in Cell and Developmental Biology that the salamander’s macrophages come from its liver, not from bone marrow as they do in humans. While tissue and organ regeneration in humans is likely far more complicated than in a salamander, the finding provides researchers with a new and somewhat unexpected place to look in humans for potential regenerative therapies.

In 2018, researchers discovered another oddity about axolotls: Their genome is enormous. At about 32 billion pairs of DNA nucleotides, the axolotl genome dwarfs the human genome (which is about 10 times smaller) and ranks as the largest animal genome sequenced from beginning to end so far. Researchers in 2021 finally put those 32 billion base pairs in the order they’re found on the salamander’s chromosomes and uncovered how they’re packaged. They reported in PNAS that the massive scale of the axolotl genome comes with some interesting consequences: The cell cycle that produces new cells takes 3 to 4 times longer than the typical 24 hours in most vertebrates. And the genes responsible for making a protein in the body sometimes spanned hundreds of thousands of base pairs long — 100 to 1,000 times longer than in humans. Researchers are still wading through data from the genome to uncover the molecular secrets behind the axolotl's regenerative abilities, and to learn if such genetic machinery could ever be activated in humans to do the same.

Additional resources

• Check out some more key facts about axolotls, especially if you’re interested in finding out more about the axolotl's incredible regenerative abilities.
• What could happen if wild axolotls disappear for good?
• Discover how scientists and farmers in Mexico City are working to restore the axolotl’s habitat for the species to survive.

This article was updated on May 24, 2022, by Live Science Contributor Jeremy Rehm.

A pair of newfound species of glass frog — amphibians with transparent underbellies that put all their internal organs on display — have been discovered in Ecuador. But the naming of one of the species has triggered controversy. 

One of the new species has been, Hyalinobatrachium nouns, is lime-green on top and clear as window glass underneath; it's named after the Nouns decentralized autonomous organization (DAO), a group that buys and sells non-fungible tokens (NFTs) with cryptocurrency. The Nouns DAO won the right to name the frog species after donating (in traditional cash) to the environmental nonprofit Rainforest Trust. But because cryptocurrency is carbon-intensive, some conservationists are unhappy with the association.

"When charities get involved in crypto projects, they legitimize them — they legitimize a whole ecosystem that has a very high environmental impact," Peter Howson, a researcher from Northumbria University in the United Kingdom who studies environmental technologies, told Popular Science.

The little frogs at the center of the controversy were discovered in 2019. They're boggle-eyed and almost cartoonishly cute, with an eye-catching pattern on their backs of lime green with light yellow spots. The two new species look nearly identical and are very similar in appearance to other Hyalinobatrachium glass frogs. In fact, researchers led by Juan Manuel Guayasamin, a biologist at Universidad San Francisco de Quito in Ecuador, had to use genetic sequencing to discover that the frogs were unique species. 

H. nouns and the other newly described frog, now known as H. mashpi, live in the Ecuadorian Andes. They were quite genetically distinct despite being found only 11.7 miles (18.9 kilometers) apart, the researchers reported March 18 in the journal PeerJ. The species were separated by the Intag-Guayllabamba river valley. Numerous river valleys cut through the Ecuadorian Andes, the researchers wrote, which have led to a great deal of amphibian diversity in the region as populations get cut off from one another and diverge into different evolutionary paths. Of the 1,120 amphibian species reported in the Andes, about 70% are endemic, or found nowhere else on Earth, the researchers wrote. 

Glass frogs are known for their doting parenting style, which is unusual for amphibians. Females will stay on their eggs as the males fertilize them, protecting the brood. In some species, the fathers then take over, staying with the eggs as they develop, according to a 2017 study published in the Journal of Evolutionary Biology.

The Noun DAO is a group of people who pool together their crypto assets, voting on what to spend them on. Noun NFTs are mostly bought with the cryptocurrency Ethereum. One of the members of the Noun DAO is also on the board of the Rainforest Trust, Popular Science reported.

The controversy arises from the fact that cryptocurrencies get their value through a process called "proof of work," in which computers compete against one another to solve mathematical puzzles. This is extremely carbon-intensive, as it involves large amounts of computing power. James Deutsch, the CEO of Rainforest Trust, said the organization's leadership did not want to be seen as promoting cryptocurrencies and is worried about cryptocurrencies' impacts. 

"I am impressed that this group of very energetic, creative and wealthy people have taken the NFT art concept and used it specifically for charitable purposes," Deutsch told Popular Science. "But having said all that, it still wouldn't justify buying into something that was inherently destructive."

Originally published on Live Science

The main difference between frogs and toads can be seen in their hind legs and skin. Both frogs and toads are amphibians that belong to the scientific order Anura within the animal kingdom. 

In general, toads have warty, drier skin with heavyset bodies and stumpy legs, whereas frogs have silky skin and longer legs. 

The "true frogs" include about 400 species that belong to the family Ranidae, whereas more than 300 species of "true toads" are members of the family Bufonidae, according to Wildlife Preservation Canada. 

If you happen to look down while taking a stroll in the woods or a marsh, here are some distinguishing characteristics to help you know the difference between a true frog and a true toad. 

Most true frogs have long legs for hopping, while toads sport stumpy bodies and shorter legs for walking, Wildlife Preservation Canada noted. Their skin also looks different, with toads generally having dry skin covered in "warts" and parotoid glands that secrete a poison to help toads defend against predators, according to the National Wildlife Federation. 

True frogs have smooth, moist skin and pads on their toes to help with climbing, according to the San Diego Zoo. 

And while toads generally lay their eggs in long strands, true frogs lay their eggs in a cluster that resembles a bunch of grapes, Wildlife Preservation Canada said.

Not all frogs and toads are easy to distinguish, however, leading biologists to squabble over the definition.

There are some frogs that have skin covered in warts, and toads that have smooth, slimy skin, according to the Exploratorium, a San Francisco science museum, in their online exhibit about frogs and toads. And many species will fit equally well into either category.

Frog and toad appearance can also signal their defenses. For instance, those with brightly colored bodies are advertising to enemies (including you) that they have toxic skin, the San Diego Zoo said. Frogs and toads with "mottled green or brown colors" use camouflage to hide from predators, the zoo said. One clever species, the Oriental fire-bellied toad, uses both strategies: The top of its body is a dull green, but when disturbed this amphibian arch upward to reveal a red belly and warn predators that they have toxic skin.

When threatened, toads can also puff up its body to appear bigger and unswallowable to a hungry predator, the zoo said.

Originally published on Live Science.

More than one-fifth of reptile species across the globe are threatened with extinction, with those living in forests found to be in far greater danger than those inhabiting arid areas, a new study reports.

In the most comprehensive extinction-risk assessment ever carried out on reptiles, researchers discovered that as many as 21.1% of all known species were at risk.

"It's just overwhelming the number of species that we see as being threatened," said study co-author Neil Cox. The researchers published their findings on April 27 in the journal Nature.

Prior to this new research, there had been no formal attempt to determine how many reptiles were at risk of extinction. Instead, conservationists relied on the International Union for Conservation of Nature's (IUCN) Red List of Threatened Species, which provides the risk status of birds, mammals and amphibians.

By using the Red List's criteria, the study researchers discovered 1,829 out of 10,196 reptile species were vulnerable, endangered or critically endangered — a total of 21.1% of the known species.

They also found that 57.9% of turtles and 50% of crocodiles are threatened; overall, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are considered threatened by the IUCN, according to the Red List.

The global study was carried out over 15 years with the help of 961 researchers representing 24 countries across six continents.

For the study, researchers assessed preexisting surveys and datasets of turtles, crocodiles, lizards, snakes and tuatara in Africa, the Americas, Asia, Australia, the Caribbean, Europe and Oceania. Tuatara are endemic to New Zealand and are considered to be the last survivors of an order of reptiles that can be "traced back to the Triassic period, according to the New Zealand Department of Conservation.

The authors said reptiles were being threatened globally by agriculture, logging, urban development and invasive species. This would explain why the researchers found that 30% of reptiles living in forests were at risk of extinction compared to 14% of reptiles living in arid habitats, the authors said.

The researchers also found that threatened reptiles were concentrated in Southeast Asia, West Africa, northern Madagascar, the Northern Andes and the Caribbean — a finding that will enable conservationists to concentrate their efforts in places with the greatest need.

The study authors also narrowed down the primary threats for different groups of reptiles. For instance, lizards that live on islands are threatened by predators that have been introduced there by people. By comparison hunting and poaching are the main threats to turtles and crocodiles, the IUCN said.

How climate change is threatening reptiles is not known for certain due to a lack of long-term studies, the authors said. However, they wrote in the paper that climate change is a "looming threat" because it reduces the window when temperatures are right for the cold-blooded animals to forage, and it can also alter the sex ratios of offspring in species where that is determined by temperature.

"Reptiles are not often used to inspire conservation action, but they are fascinating creatures and serve indispensable roles in ecosystems across the planet," Sean T. O’Brien, President and CEO of NatureServe, which led the study in collaboration with the IUCN and Conservation International, said in a statement. We all benefit from their role in controlling pest species and serving as prey to birds and other animals."

Six newly-described species of miniature frogs from Mexico and Guatemala are so tiny that each can fit comfortably on a human thumbnail. Two of the species are smaller than 0.7 inches (18 millimeters) long, and the tiniest of them — Craugastor candelariensis — is Mexico's smallest frog, measuring no more than 0.5 inches (13 mm) long.

The wee frogs live in moist leaf litter on forest floors and are known as direct-developing frogs, which means that they don't undergo a tadpole stage as part of their life cycle, the researchers who described the species wrote in a new study. Rather, the frogs hatch from eggs as miniature versions of their adult forms. 

Hatchlings are thought to measure less than than 0.4 inches (10 mm) long, but scientists aren't certain about that because no one has ever seen these frogs hatch, said lead study author Tom Jameson, a researcher in the Department of Zoology at the University of Cambridge in the United Kingdom, and a doctoral candidate in the Cambridge Climate, Life and Earth (C-CLEAR) program. 

"We know very little about their reproduction, life history, and behaviour," Jameson told Live Science in an email.

Related: Cannibal toads eat so many of their young, they're speeding up evolution

Other scientists had collected the frogs years ago and placed them in museum collections, cataloging the minuscule amphibians as undefined species in the Craugastor genus or as possibly belonging to the miniature frog species C. pygmaeus or C. hobartsmithii, the study authors reported April 4 in the journal Herpetological Monographs.

However, the diminutive frogs all looked so similar that scientists couldn't be sure exactly where the frogs fit on the Craugastor family tree. 

"We revisited this classification because one of my co-authors, Jeff Streicher [a senior curator of amphibians and reptiles at the Natural History Museum in London], did some genetic analysis back in 2012 and found a pattern that suggested multiple undescribed species," Jameson explained.

The researchers then followed up on Streicher's findings by conducting DNA analysis of the Craugastor specimens in question, and using computed X-ray tomography (CT) scans to create 3D digital models that highlighted differences in the shapes of frog bones and body parts. When their analysis was done, the scientists grouped the specimens into six new species: C. bitonium, C. candelariensis, C. cueyatl, C. polaclavus, C. portilloensis and C. rubinus.

"We found that each species was genetically distinct," Jameson said. "We also found differences in skull shape, level of ossification of the skeleton, and in external features like the number of tubercles [hardened bumps] on the hands and feet." 

Because the frogs are so small, they're on the menu for just about every predator in their woodland ecosystem, including birds, lizards, small mammals, and even large insects and other frogs, Jameson said. But the frogs face much greater risks from human activities, he added.

"The real threat to these frogs comes from habitat loss, climate change (further modifying habitats), and disease," such as the highly infectious fungal disease chytridiomycosis, or chytrid disease, Jameson wrote in the email. Chytrid disease is caused by the fungus Batrachochytrium dendrobatidis, which infects amphibians through their skin and is easily spread to new habitats by humans, according to the Cornell Wildlife Health Lab at Cornell University in Ithaca, New York.

Despite their small size, these frogs could represent the tip of a very big iceberg of unknown amphibian biodiversity in the region, the study authors reported. 

"We suspect that additional species await discovery, particularly in western Mexico and east of the Isthmus of Tehuantepec where our sampling efforts were limited," the authors wrote.

Originally published on Live Science.

Scientists have regrown frogs' amputated legs after giving them a "cocktail" of drugs encased in a silicon stump. 

African clawed frogs (Xenopus laevis) are like humans in that they can't naturally regrow lost limbs. In the new study, researchers successfully coaxed the frogs to grow replacement limbs in 18 months following a treatment that lasted just 24 hours. While there's a massive difference between frogs and humans, the finding raises the possibility that in the future, humans could also regrow limbs.

"It's exciting to see that the drugs we selected were helping to create an almost complete limb," first author Nirosha Murugan, a research affiliate at Tufts University in Massachusetts, said in a statement. "The fact that it required only a brief exposure to the drugs to set in motion a months-long regeneration process suggests that frogs and perhaps other animals may have dormant regenerative capabilities that can be triggered into action."

Related: 13 extremely strange animal feet

Animals have natural abilities to regenerate themselves. For example, human bodies close open wounds and can even use stem cells to regrow parts of the liver. Some animals, such as salamanders, can regrow whole limbs and other missing parts. The mechanisms behind limb regeneration are not fully understood, but neither humans nor adult frogs are capable of regrowing legs and arms, perhaps because those limbs are so complex. 

Both humans and frogs cover an open amputation wound in scar tissue to stop further blood loss and infection. Humans have developed prosthetic replacement limbs but scientists have been unable to recover or reverse the loss of a major limb like an arm or leg. 

The latest research used multiple drugs to regenerate lost limb tissue. The team surgically amputated frogs' legs and then applied a silicone cap they called a "BioDome" to each frog's wound. The cap released a cocktail of five drugs, including growth hormones, that perfomed different roles, such as encouraging nerves and muscles to grow. One of the drugs also prevented the frogs' bodies from producing collagen, which normally causes wounds to scar over.

"Using the BioDome cap in the first 24 hours helps mimic an amniotic-like environment, which, along with the right drugs, allows the rebuilding process to proceed without the interference of scar tissue," co-author David Kaplan, a professor of engineering at Tufts University, said in the statement. 

Embryos and fetuses develop in an amniotic sac during pregnancy. The team was able to trigger some of the same molecular pathways in the frogs that are used when an embryo is growing and taking shape. 

The new legs looked similar to normal legs with similar bone structure, except for the toes, which lacked underlying bones. The frogs were able to use their new leg to swim like a regular leg. 

The findings were published Jan. 26 in the journal Science Advances. 

Originally published on Live Science.

Conservationists in Taiwan are racing to contain an invasion of non-native and highly toxic toads before the warty amphibians cause widespread damage to their new ecosystem. 

The cane toad (Rhinella marina) is a highly toxic species of toad native to the Americas, from the Central Amazon in Peru to the Rio Grande Valley in Texas. However, the species was also introduced across the globe in the early 20th century to various places, including the Caribbean, Australia and large parts of the Pacific, according to Amphibia Web. Adult cane toads range from 3.5 to 5.9 inches (9 to 15 centimeters) in length and have yellow and brown skin covered with irregular warts. When threatened, cane toads release a milky-white toxin from their skin known as bufotoxin, which oozes from glands behind their eyes and is lethal to most animals. 

Researchers in Taiwan learned of a possible cane toad invasion at a farm in a small town in Taiwan's central mountain range, after a local resident shared photos of a cane toad online. After seeing the photo, researchers from the Taiwan Amphibian Conservation Society immediately came to the farm to investigate.

Related: Mug shots: 10 lost amphibians

"A speedy and massive search operation is crucial when cane toads are first discovered," Lin Chun-fu, an amphibian scientist at Taiwan's Endemic Species Research Institute, told French news agency AFP. They reproduce rapidly, and "they have no natural enemies here in Taiwan," he added.

When the researchers arrived at the farm, they found 27 toads in the immediate vicinity. Since then, they have captured more than 200 cane toads in the area surrounding the town, according to AFP.

"I was shocked and worried when they found more than 20 [right away]," Yang Yi-ju, a toad expert at National Dong Hwa University who organized the search, told AFP. Cane toads are an extremely successful invasive species. They are only native to 14 countries but are now found in more than 40 countries, which has landed them a spot on the list of the 100 Worst Invasive Species overseen by the Invasive Species Specialist Group, an international advisory body of scientists and policy experts. 

Female cane toads can lay up to 30,000 eggs at a time and can mate year-round, Live Science previously reported. Unlike other toads, which are exclusively predators, cane toads can also act as scavengers, so they always have plenty of food to eat. Without natural predators, their numbers quickly explode, and they can seriously damage ecosystems where they're introduced.

In the past, people deliberately released these toads in countries that were suffering from pest problems. For instance, in 1935, Australia introduced the toads to eat cane beetles (Dermolepida albohirtum) that were ravaging sugarcane fields. But while the toads successfully squelched the beetle infestations, the toad population quickly grew out of control. 

Researchers believe that a black market pet trade could have caused the recent Taiwan cane toad invasion. Cane toads have long been a popular pet in Taiwan and are also used in traditional medicines, according to AFP. But in 2016, the Taiwanese government banned the import of cane toads, which led people to breed and sell them illegally. The leading theory is that the invasive cane toads either escaped or were abandoned by one of these black market traders. 

The researchers also think the invasion may have started months ago and gone unnoticed until now. "Taiwanese farmers generally ignore toads and even look favorably at toads when they find them, because they help rid the land of pests and are also a good luck symbol," Yang told AFP. "It never occurred to them that this is an invasive species from a foreign land."

The researchers are now hopeful that they have contained the invasion, but it is too early to tell for certain. "Next spring during mating season is when we [will] truly know for sure if we have contained it," Yang told AFP.

Originally published on Live Science.

Poison dart frogs are small, brightly colored amphibians that live on tropical rainforest floors across Central and South America. They are members of the family Dendrobatidae, and there are more than 175 known species, according to San Francisco Zoo. Poison dart frogs are tiny, measuring  just 1 to 2 inches (2.5 to 5 centimeters) long, and unlike many other amphibians they are diurnal, meaning they are active in the daytime, according to the Rainforest Alliance.

Poison dart frogs are named for the toxins they secrete from their skin, which have traditionally been used to tips of hunters' weapons. For example, the Emberá and Noanamá Indigenous people in western Colombia have used the skin of golden poison frogs (Phyllobates terribilis) to tip blowgun darts for hundreds of years, according to the American Museum of Natural History. 

Poison dart frogs come in a range of vivid colors, and so they are sometimes known as the "jewels of the rainforest." Their vibrant coloring warns predators that the frogs are poisonous and should be avoided. This survival mechanism is called aposematism. Some species of poison dart frogs also use their colors and patterns as camouflage. For example, dyeing dart frogs (Dendrobates tinctorius) use their bright-yellow and black patterns to blend in with their natural habitat when viewed from a distance, according to research published in 2018 the journal Proceedings of the National Academy of Sciences (PNAS).

Related: Adorable 'chocolate frog' discovered in crocodile-infested swamp

The huge variety of colors among poison dart frog species may be a result of the frogs’ ancestors becoming separated around 10,000 years ago, when what is now Panama flooded, isolating the frogs in different locations. The various frog populations then evolved their own colorization, according to the Smithsonian Institute.

How poisonous are poison dart frogs?

Poison dart frogs’ toxicity differs between species. The most toxic species of poison dart frogs belong to the genus Phyllobates. These frogs secrete a potent toxin called batrachotoxin, according to the Encyclopedia of Toxicology. Golden dart frogs are considered one of the most toxic animals on Earth, according to National Geographic.

Batrachotoxin is a powerful steroidal alkaloid that interferes with the  body’s nervous system. The brain sends instructive electrical messages to different parts of the body that pass through sodium channels. Batrachotoxins keep these channels open and disrupt the brain's messaging system, causing several debilitating and potentially fatal conditions, such as paralysis, extreme pain and even cardiac failure. 

There is, however, one animal that can withstand the poisonous powers of golden dart frogs: fire-bellied snakes (Liophis epinephelus). These snakes are the only known natural predators of dart frogs because they are immune to the frogs’ toxins, according to the Animal Diversity Web. 

Poison dart frogs have also developed techniques to avoid poisoning themselves. A study published in the Journal of General Physiology proposed that poison dart frogs have "toxin sponge" molecules that prevent the batrachotoxin from binding with sites on the frogs’ own cells, providing them with immunity to their own poison. 

Related: Why don't poisonous animals die from their own toxins?

What do poison dart frogs eat?

As tadpoles (the stage before the animals reach adulthood), their diet consists of whatever is available to them, such as algae, dead insects and in some cases other tadpoles. Adult poison dart frogs are omnivores, but they predominantly feast on insects such as ants, termites and beetles, according to the San Diego Zoo Wildlife Alliance. 

Poison dart frogs obtain their toxicity through their diet. Although it remains largely unknown which insects are responsible for giving these frogs their poisonous powers, a study published in the journal PNAS proposed that melyrid beetles (genus Choresine) might be the culprits. 

Related: Photos: The poisonous creatures of the North American deserts

These beetles contain high levels of batrachotoxin and have been found in the bellies of pitohui birds — which produce the same secreted poison as poison dart frogs. "The family Melyridae is cosmopolitan, and relatives in Colombian rainforests of South America could be the source of the batrachotoxins found in the highly toxic Phyllobates frogs of that region," the study researchers wrote. 

Wild poison dart frogs that are put into captivity lose the majority of their toxicity, whereas frogs born and raised in captivity don't develop the toxins at all. This is due to the difference between a wild and captive diet, according to the San Diego Zoo Wildlife Alliance. 

What is the life cycle of a poison dart frog?

Mating occurs throughout the year but particularly during the rainy seasons, at a site on the forest floor chosen by the male. To mate, the female deposits the unfertilized eggs on leaf-litter in a dark and moist environment, and the male releases his sperm onto the eggs to fertilize them. A frog's clutch can vary in size, but some species produce as many as 40 eggs at a time, according to the Smithsonian's National Zoo & Conservation Biology Institute. 

The parent frogs guard their unborn offspring for between 10 and 18 days, occasionally watering them with their urine. The eggs hatch into tadpoles, which latch onto their mother's back, and she then carries them to a pool of water. The pool becomes a nursery for the tadpoles for the next few months, until they undergo metamorphosis and become adult frogs, according to the Smithsonian. 

A study published in the journal Symbiosis suggests that bromeliad plants also benefit from having tadpoles between their leaves. Researchers proposed that the plants benefit from absorbing the nitrogen that is produced from the tadpoles feces and which acts as a fertilizer. 

Adult poison dart frogs vary in size between species and can range between 0.75 and 1.5 inches (20 to 40 millimeters) in length, according to the Smithsonian. Females tend to be larger than males, and males can also be distinguished from females by their larger front toe pads in some species — such as blue poison dart frogs (Dendrobates azureus) according to Peoria Zoo in Illinois. 

The age these amphibians reach sexual maturity also differs between species. For example, strawberry poison dart frogs (Oophaga pumilio) reach maturity after ten months of adulthood, according to the Animal Diversity Web, whereas blue poison dart frogs take two years before they’re ready to mate, according to Toronto Zoo. The average lifespan of a poison dart frog is between three and 15 years, according to National Geographic. 

Additional resources

• Poison Dart Frogs (Pilot Books: Nature's Deadliest)
• Magnificent Book of Reptiles and Amphibians
• Aposematic Poison Frogs (Dendrobatidae) of the Andean Countries

The hatchlings of the invasive cane toad in Australia don't stand a chance against their deadliest predator: cannibal tadpoles who guzzle the hatchlings like they're at an all-you-can-eat buffet. But now, the hatchlings are fighting back.

They're developing faster, reducing the time that hungry tadpoles have to gobble them up, a new study finds. 

"If cannibals are looking for you, the less time you can spend as an egg or hatchling, the better," said study lead researcher Jayna DeVore, who did the research as a postdoctoral research associate at the University of Sydney and is now a biologist for the Tetiaroa Society, a nonprofit conservation organization in French Polynesia. 

Developing quickly, however, has its pitfalls. Compared with typically growing hatchlings, those that grew faster fared worse when they reached the tadpole stage of life, the researchers found. So it isn't "worth it to try to defend yourself in this way unless cannibals are definitely coming for you," DeVore told Live Science.

Related: Image gallery: Invasive species 

The cane toad (Rhinella marina) is a poster child for invasive species. The warty toxic toad, notorious for gulping down anything that fits into its wide mouth, is native to South America. In the 1930s, farmers in Queensland, Australia, thought the toad would be the perfect predator to gobble up beetles that were destroying sugarcane fields. But with no natural predators Down Under, the toad population ballooned from only 102 individuals to more than 200 million, according to WWF Australia. 

Another reason for their population spike is that female toads can lay more than 10,000 eggs at a time in small ponds. "When these eggs first hatch, the young can't swim or eat yet, so they can pretty much only lie there on the bottom of the pond until they develop into tadpoles," DeVore said.

The hungry tadpoles strike during this vulnerable hatchling period. "Once the hatchlings develop into tadpoles, they are too large and mobile for other tadpoles to eat them, so the cannibals have to work quickly if they want to consume them all," DeVore said.

Tadpoles that cannibalize the younger generation are doing themselves a huge favor; they're getting nutrients and eliminating later competition for resources. "When I first saw this behavior in the wild, I was amazed at how voraciously cane toad tadpoles sought out cane toad hatchlings and ate them," DeVore said. To determine whether this behavior was "normal" or whether it was an adaptation to extreme competition among invasive cane toads, DeVore and her colleagues compared Australia's invasive cane toads with the native-range ones, or cane toads from their indigenous regions.

Warty toad arms race

Several experiments revealed that the invasive toads — both the hatchlings and the cannibalistic tadpoles — are evolving at breakneck speed. 

In one experiment done more than 500 times with different individuals, DeVore and her colleagues placed one tadpole in a container with 10 hatchlings. Although the native-range tadpoles did engage in some cannibalism, "we found a hatchling was 2.6 times as likely to be cannibalized if that tadpole was from Australia than if it was from the native range," she said.

Moreover, the invasive tadpoles were much more attracted to the hatchlings than the native tadpoles were. In another experiment, the team placed tadpoles in a pool with two traps; one trap held hatchlings, and the other was empty. "In Australia, the cannibalistic tadpoles were attracted to the hatchlings; the odds that an Australian tadpole would enter the trap containing hatchlings were about 30 times those of it entering the empty trap," DeVore said. 

Related: Survival of the grossest: 8 disgusting animal behaviors 

In contrast, the native-range "tadpoles were not attracted to the hatchlings; they were just as likely to enter the empty trap as the hatchling trap," she said. "This demonstrated that this strong attraction to the vulnerable hatchling stage, which is what helps the cannibalistic tadpoles to detect and locate their victims in Australia, is not present in the native range."

Fighting back

To fight back, invasive hatchlings have evolved an escape strategy. When the researchers compared the time eggs and hatchlings spent developing, they found that the invasive toads developed faster than the native-range ones.

In both groups, "we found that cane toad clutches from Australia developed more quickly; they reached the invulnerable tadpole stage in about four days, whereas native range clutches took about five days," DeVore said.

In addition, the invasive hatchlings had a more "plastic," or flexible response than the natural-range hatchlings when a cannibal tadpole was present; the hatchlings from Australia were "more likely to be able to smell when cannibals are around and actually accelerate their development in response," DeVore noted.

While these strategies helped the hatchlings survive, they paid for it later. The researchers tested 1,190 tadpoles for survival, development, growth and plasticity, and found that those that developed faster as eggs and hatchlings to escape cannibalism fared worse and developed more slowly at the tadpole stage than the native-range tadpoles, the team found. 

Could cannibalism lead to extinction?

Could the cane toads eat themselves into extinction? Probably not, DeVore said.

"Australian cane toads may well be their own worst enemy, but I wouldn't expect them to go extinct anytime soon," she said. That's because the cannibals benefit too much from eating their own kind. After gaining nutrients and limiting competition, the cannibalistic tadpoles "transform into toads more quickly and at a larger size," she said. It's even possible that these "successful" toads will more rapidly invade new places in Australia.

"The good news is that cannibalism can control population growth," DeVore said. "So, although cane toads are unlikely to drive themselves extinct, these cannibalistic behaviors may help to regulate their abundance post-invasion."

The study was published in the Aug. 31 issue of the journal Proceedings of the National Academy of Sciences.

Originally published on Live Science.

With big, cartoonish eyes, a coy cheek-to-cheek grin and skin like milk chocolate, this frog is so adorable you could just eat him up. The scientists who discovered it in the swamps of New Guinea were apparently thinking the same thing; they've nicknamed it the "chocolate frog."

This candy-colored amphibian, described for the first time in a study published May 20 in the Australian Journal of Zoology, is closely related to the iconic green tree frog (Litoria caerulea) that's common throughout northern and eastern Australia. From there, New Guinea is just a short hop away; the two islands were even connected by a land bridge until about 10,000 years ago. Over their long history as neighbors, Australia and New Guinea have hosted many of the same types of animals.

In their new study, researchers based at Australia's Queensland Museum wanted to paint a clearer family portrait of the green tree frog's lineage on both islands. So, they traveled to New Guinea and collected frog specimens in the island's southern, savannah-like ecosystems, as well as the swampy forests to the north. It was there — in a hot swamp full of crocodiles — that the team found the chocolate frog.

Related: Eye-swallowing and mouth birth: Freaky facts about frogs

"We named the new frog Litoria mira because the word 'mira' means 'surprised' or 'strange' in Latin," lead study author Paul Oliver, a biologist at Queensland Museum and Griffith University in Australia, said in a statement.

A DNA analysis showed that L. mira's closest living relative is Litoria caerulea, and both frogs have an identical mating call, which the researchers described as a "deep, rasping bark repeated in long series, 'crawk, crawk, crawk.'"

Still, the two cousins have some clear differences. Besides L. mira's cocoa-colored skin, the frog is also smaller (and dare we say cuter) than its common green cousin, with males measuring just under 3 inches (76 millimeters) from head to bum, and females measuring just over that — which in either case is about the width of a standard credit card.

While this barking brown frog is arguably the strangest discovery from the team's research, they also catalogued 29 additional relatives of the green tree frog hopping through New Guinea, further demonstrating how life on the island and on the Australian mainland has been intimately tied for thousands of years. Crawk, crawk!

Originally published on Live Science.

For knife-toothed kukri snakes, the tastiest parts of a frog are its organs, preferably sliced out of the body cavity and eaten while the frog is still alive. After observing this grisly habit for the first time in Thailand, scientists have spotted two more kukri snake species that feast on the organs of living frogs and toads.

The new (and gory) observations suggested that this behavior is more widespread in this snake group than expected. Two snakes also eventually swallowed their prey whole, raising new questions about why they would extract the living animals' organs first.

The scientists documented a Taiwanese kukri snake (Oligodon formosanus) and an ocellated kukri snake (Oligodon ocellatus) pursuing amphibian organ meals, tearing open frogs' and toads' abdomens and burying their heads inside, according to the studies. O. formosanus would even perform "death rolls" while clutching its prey, perhaps to shake the organs loose. As the snakes swallowed the organs one by one, the amphibians were still alive. Sometimes, the process would take hours, the researchers reported.

Related: Beastly feasts: Amazing photos of animals and their prey

There are 83 species of kukri snakes in the Oligodon genus in Asia. The snakes typically measure no more than 3 feet (100 centimeters) long, and the group's name comes from the kukri, a curved machete from Nepal, as its shape is reminiscent of the snakes' large, highly modified rear teeth. Kukri snakes use these teeth for slicing into eggs, but they can also be formidable slashing weapons (as some very unfortunate frogs have discovered).

In one study, published Feb. 15 in the journal Herpetozoa, scientists described three snake attacks on rotund banded bullfrogs (Kaloula pulchra), which are so round that they are also known as bubble frogs or chubby frogs. They have brown backs with lighter stripes down their sides and cream-colored stomachs, and they measure up to 3 inches (8 cm) long, according to Thai National Parks. 

Two of the attacks were by Taiwanese kukri snakes, and took place in Hong Kong in October 2020. One snake, filmed on Oct. 2 in a residential neighborhood garden, emerged from a hole in the ground to bite a passing bubble frog, slicing open the frog and stuffing its head inside. Snake and frog tussled for about 40 minutes; the snake performed about 15 body rotations, or "death rolls," during the battle, according to the study. 

"We believe that the purpose of these death rolls was to tear out organs to be subsequently swallowed," Henrik Bringsøe, lead author of both studies and an amateur herpetologist and naturalist, said in a statement.

A second Taiwanese kukri snake was discovered on Oct. 8 in an urban park while "energetically" dining on a frog's organs that were "exposed and visible," the study authors wrote.

The third attack on a bubble frog was by a small-banded kukri snake — the species that was first documented exhibiting this behavior — on Sept. 15, at a factory site outside a small village in northeastern Thailand. During the struggle, the snake performed 11 death rolls, its teeth buried firmly in the frog's belly.

"The snake’s efforts resulted in its teeth penetrating the abdomen to such an extent that blood and possibly some organ tissue appeared," the scientists reported. "Eventually, the frog was swallowed whole while still alive."

Another study, published on the same day in Herpetozoa, presented an observation of an ocellated kukri snake feasting on an Asian common toad (Duttaphrynus melanostictus) inside a lodge in a national park in southern Vietnam. These toads are stout, thick-skinned and variably colored, and they measure about 3 inches (8.5 cm) long, according to Animal Diversity Web, a biodiversity database maintained by the University of Michigan's Museum of Zoology. 

Observers recorded this attack on May 31, 2020. The toad was already dead at the time, "and the snake was moving its head and neck side to side as if trying to work its way inside," the study authors wrote. Minutes later, the snake gulped down the toad whole.

In the 2020 study about small-banded kukri snakes eviscerating Asian common toads, the scientists hypothesized that the snakes selectively ate the organs to avoid the toads' deadly toxins. However, the ocellated kukri snake swallowed the toad after its organ appetizer, hinting that the snakes might have some natural resistance to the toads' poison. 

Chubby frogs also have a built-in deterrent that may encourage predators to go straight for their organs. While the frogs aren't toxic, they defensively secrete a sticky mucous that has an unpleasant taste, according to the University of California, Berkeley's AmphibiaWeb.

"We hope that future observations may uncover additional aspects of the fascinating feeding habits of kukri snakes — though we may indeed call them gruesome!" Bringsøe said in the statement.

Originally published on Live Science.

The Southern Appalachian mountains are a global biodiversity hot spot for salamanders. Dr. Deb Miller and Dr. Matt Gray lead the Amphibian Disease Laboratory at the University of Tennessee and are looking at various strategies to prevent a fungus that is deadly to salamanders from entering the U.S. via the international pet trade. They are also conducting research to learn more about the disease, and looking at potential strategies to reduce the spread of the fungus in case it does enter the country.

Why do the Appalachian mountains have so many salamanders?

The intersection of North Carolina, Tennessee and Georgia is a global biodiversity hot spot for salamanders. Tennessee, for example, has around 60 species, more than the entire continent of Europe.

The southern Appalachian Mountain Range is one of the oldest mountain ranges in the world, so there has been a lot of opportunity for many species to evolve over a long period of time. The temperate conditions and high elevations create a forest system with lots of moisture and accumulated leaf litter. Over time, that creates the perfect habitat for salamanders.

What is the fungus that threatens the salamanders?

Batrachochytrium salamandrivorans, or Bsal, is the second chytrid fungus that has been discovered. The first chytrid fungus that many people have heard about is called Batrachochytrium dendrobatidis, or Bd, and that’s been associated with the decline of over 500 amphibian species globally and over 100 species extinctions.

Bsal fungus specifically attacks the outer covering of a salamander's skin, but we are finding that it can attack frog skin as well. The skin is one of the most important organs in an amphibian’s body. It is so important because some salamanders don’t have lungs, and so the skin is a major source for respiration for them. It also maintains the right amount of hydration so that their body systems, including their heart, can function properly.

The name salamandrivorans literally means that it eats the salamander. In actuality, it destroys the skin with a coating of fungus. The skin stops functioning, and the animal shuts down and dies.

The fungus hasn't yet entered North America, but what was its effect on amphibians in Europe?

The discovery of a new chytrid fungus in Northern Europe was very alarming. It was discovered in 2010, and since then, salamander populations all over Europe have seen precipitous declines. There’s now research that indicates that it may have actually been introduced around Germany and spread out from there.

It has been found in Southeast Asia infecting salamanders but having no effects on them. It seems to live with the salamanders there. But it is believed to have been introduced to Europe through the international pet trade. We have not detected Bsal yet here in North America, or any place in the Western Hemisphere, but we are concerned that the pet trade is the most likely route for introduction here.

What are the steps being taken to prevent it from entering the US?

The United States has been fairly proactive in its response to Bsal. The US Fish and Wildlife Service passed a moratorium in 2016 on the importation of around 200 species of salamanders that could serve as possible hosts to Bsal. That effectively stopped most of the salamander trade coming into our country. However, since then, we’ve learned that frogs can become infected with Bsal too, which constitute 95% of trade, so the threat of introduction to the U.S. remains.

There has been very limited surveillance for Bsal out in the pet industry, and we’re working on partnerships that would expand sampling for Bsal. It’s also in the industry’s interest because it threatens the captive populations and their profits.

What is your research focusing on?

With regard to pathology, we’re looking at a few different things. One, what does it do to the body other than taking away the skin? What is the critical point at which we might be able to do something? And are there bacteria or other opportunistic pathogens playing a role in the sickness?

In terms of research on transmission and disease intervention strategies, we’ve been looking at what happens if it gets into a pond system here. Could we go into that pond system and reduce the density of the salamanders, just as humans are doing with social distancing during the pandemic?

Bsal spreads through water, but also direct contact, and so we reduce that ability for either the pathogen to swim or for salamanders to bump into each other by increasing the number of plants around their habitat, and hence the habitat complexity.

We also are looking at plant-derived fungicides. Salamander skin has lots of natural microbes on it, and we’re trying to supplement their natural microbiome on their skin to help in the defense of this pathogen. So we collaborate with colleagues from several universities to investigate all of those questions.

What role do salamanders play in this ecosystem?

It’s been estimated that in a typical pond system, amphibians can consume over a million insects in a year, including mosquitoes. They consume adults as well as larvae before they can bite you or transmit a zoonotic disease. Both tadpoles and salamander larvae love to eat the little mosquito larvae, which are very nutritious. They play a similar role to that of bats in the air.

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

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Pity the toads that encounter Asian kukri snakes in Thailand. These snakes use enlarged, knifelike teeth in their upper jaws to slash and disembowel toad prey, plunging their heads into the abdominal cavities and feasting on the organs one at a time while the toads are still alive, leaving the rest of the corpse untouched.

While you're recovering from the horror of that sentence, "perhaps you'd be pleased to know that kukri snakes are, thankfully, harmless to humans," amateur herpetologist and naturalist Henrik Bringsøe, lead author in a new study describing the gruesome technique, said in a statement.

This grisly dining habit was previously unknown in snakes; while some rip chunks from their prey, most snakes gulp down their meals whole. Scientists had never before seen a snake Bury its head inside an animal's body to slurp up organs — sometimes taking hours to do so, Bringsøe and his colleagues reported. 

Related: Beastly feasts: Amazing photos of animals and their prey

The victims of this horrific organ-slurping were poisonous toads called Duttaphrynus melanostictus, also known as Asian common toads or Asian black-spotted toads; they are stout and thick-skinned, measuring about 2 to 3 inches (57 to 85 millimeters) in length, according to Animal Diversity Web (ADW), a wildlife database maintained by the University of Michigan's Museum of Zoology. During the deadly battle, the toads fought "vigorously" for their lives, with some defensively secreting a toxic white substance, according to the study. The snakes' grisly evisceration strategy could be a way to avoid the toad's poisonous secretions while still enjoying a tasty meal, the researchers wrote.

Kukri snakes in the Oligodon genus are so named because their slashing teeth resemble the kukri, a forward-curving machete from Nepal. While kukri snakes aren't a threat to people, their teeth can cause painful lacerations that bleed heavily, because the snakes secrete an anticoagulant from specialized oral glands, according to the study.

"This secretion, produced by two glands, called Duvernoy's glands and located behind the eyes of the snakes, are likely beneficial while the snakes spend hours extracting toad organs," Bringsøe explained.

Macabre mealtime

The researchers described three observations in Thailand of kukri snakes (Oligodon fasciolatus), which can measure up to 45 inches (115 centimeters) long, consuming Asian common toads. In the first incident, which took place in 2016, the toad was already dead when the witnesses discovered the scene, "but the soil around the two animals was bloody, indicating there had been a fight which eventually killed the toad," the scientists wrote. The snake sawed through the toad's body by swinging its head from side to side; it then slowly inserted its head into the wound "and subsequently it pulled out organs like liver, heart, lung and part of the gastrointestinal tract."

In a second event, an epic battle between a kukri snake and a toad on April 22, 2020 lasted nearly three hours; the snake attacked, withdrew, and attacked again, deterred only temporarily by the toad's poison defense. After finally subduing the toad, the snake extracted and swallowed organs while the toad was still breathing, according to the study. 

On June 5, 2020, a kukri snake took a different approach and didn't disembowel the toad at all, instead devouring it whole. But in a fourth observation this year on June 19, the snake eviscerated its toad prey, slicing into the abdomen to reach its organ meal.

Young toads potentially produce less poison than adults do, which may have enabled the snake in the June 5 observation to safely gulp it down in one piece; another possibility is that kukri snakes are immune to the toad species' toxins, but they disembowel adults anyway because the toads are simply too big for them to swallow, the researchers reported. 

However, there's not yet enough data to answer these questions, Bringsøe said in the statement. 

"We will continue to observe and report on these fascinating snakes in the hope that we will uncover further interesting aspects of their biology," he said.

The findings were published online Sept. 11 in the journal Herpetozoa.

Originally published on Live Science.

Being swallowed alive by a frog is a death sentence for most insects, but one beetle species shrugs off being digested and instead finds freedom by sneaking out through its captor's anus. 

When the pond frog Pelophylax nigromaculatus was presented with the aquatic beetle Regimbartia attenuata, it quickly snapped up the beetle, swallowing it whole and alive. But the meals ended with a strange twist, researchers recently discovered.

In most of the experiments, the beetles reappeared within six hours, slipping out of a frog's anus, or vent. Though muscles typically hold the vent tightly shut, those muscles loosen up when the frog poops; the beetles could be stimulating the frogs' defecation reflex in order to temporarily open this unusual emergency exit, according to the new study.

Related: Eye-swallowing and mouth birth: Freaky facts about frogs

Shinji Sugiura, an associate professor in the Graduate School of Agricultural Science at Kobe University in Japan, studies anti-predator defenses in wetland insects, and he suspected that the beetle R. attenuata had evolved some type of defense against frogs in their marshy habitat. However, that defense turned out to be very different from what he expected, Sugiura told Live Science in an email.

In September 2019, he provided a juvenile P. nigromaculatus frog with an adult beetle under laboratory conditions. Sugiura guessed that the frog might spit the beetle out, but 105 minutes later, he was astonished to see the live beetle emerging from the opposite end of the frog. 

"I used a video camera to record the behavior," he said. "I was very surprised to watch the footage of the beetle escaping from the frog vent."

He conducted the experiment more than a dozen times, and 93% of the swallowed beetles were excreted — always headfirst, Sugiura reported today (Aug. 3) in the journal Current Biology. The beetles were "frequently entangled in fecal pellets," but they "recovered immediately," resuming their beetle business and surviving for at least two weeks following excretion.

Other aquatic beetles in the experiments weren't so lucky. When Sugiura tempted the frogs with the beetle Enochrus japonicus, all of the beetles died inside the frogs and were partly excreted more than 24 hours after being swallowed.

The dark and perilous path from a frog's mouth to its anus travels through the esophagus, stomach, small intestine and large intestine. For a swallowed beetle, passing through this dank and airless internal tunnel from end to end required a minimum of six minutes, though most emerged between one hour and six hours after they were eaten, according to the study. 

Frogs typically don't defecate so soon after a meal; this hinted that the beetles were actively provoking the frogs to poop, rather than passively waiting to pass. To test whether the beetles might be using their legs to do this, Sugiura offered the frogs beetles whose legs were fixed together with sticky wax.

None of those beetles survived, Sugiura reported.

"This study is the first to document active prey escape from the vent of a predator and to show that prey may promote predator defecation to hasten escape from inside the predator's body," Sugiura wrote. Further experiments are required to piece together how the beetles encourage the frogs to relax their sphincter muscles; "however, I speculate that R. attenuata use the legs and body to stimulate the frog's hind gut," he told Live Science.

While R. attenuata's escape technique is new to scientists, these insects aren't the only beetles that can evade digestion after they've been eaten. In 2018, Sugiura found that bombardier beetles (Pheropsophus jessoensis), when swallowed by a frog or toad, release a spray of chemicals so toxic that the amphibian inverts its own stomach to vomit out the beetle. The beetle then scuttles away — dripping with mucus and digestive fluids, but otherwise unharmed, Live Science previously reported.

Originally published on Live Science.

UPDATE: The tadpole titan affectionately known as "Goliath" died in 2019, according to a tweet written on May 26, 2020 by herpetologist Earyn McGee; she introduced Twitter to Goliath in 2018, when this article was originally published. Scientists with the Southwestern Research Station in Arizona preserved the tadpole and are studying it to better understand its unusual size and morphology, according to the tweet.

An enormous tadpole found in the wild is bigger than a can of Coke — and it's still growing.

Biologists discovered the sizable swimmer in a shallow pond in southeastern Arizona; they were removing invasive American bullfrogs (Lithobates catesbeianus) with the Southwestern Research Station (SWRS), a year-round field station run by the Science Department at the American Museum of Natural History in New York City.

As a volunteer probed a mostly drained pond, she stumbled upon an oversize bullfrog tadpole — the wriggly amphibian was so big that the volunteer initially thought it was a fish, herpetologist Earyn McGee, a doctoral candidate at the University of Arizona and a scientist at SWRS, wrote in a blog post on July 23. 

Related: Pictures: Cute and Colorful Frog Images

What’s the story behind this massive weirdo, which biologists have nicknamed "Goliath?"

McGee tweeted photos of Goliath on June 13, generating more than 13,000 likes and drawing dozens of curious commenters. She explained that Goliath was definitely much larger than the average American bullfrog tadpole, suggesting that his unusual size was likely due to "some sort of hormone imbalance." Researchers at SWRS suspect that this imbalance will likely prevent poor Goliath from ever metamorphosing into a frog, and they are currently investigating what may have caused his unusual condition, McGee wrote.

McGee told Live Science in an email that prior studies describe tadpoles that are similarly massive, but Goliath was the biggest tadpole that she had ever seen in person. And for a growing tadpole, bigger isn't necessarily better, McGee added.

"The drawbacks of Goliath's size is that his respiratory and circulatory system may not continue to support his body size as he continues to grow," she said. On the other hand, a really big bullfrog tadpole would be able to grab more food than smaller tadpoles, which could work out in a giant's favor if food supplies in a small pond are low, McGee explained.

American bullfrogs are the biggest of the North American frogs. They grow to lengths of 8 inches (20 centimeters) or longer, and weigh as much as 1 pound (0.5 kilograms), while tadpoles typically grow to be about 6 inches (15 cm) long, according to the U.S. Fish and Wildlife Service (FWS). The frogs are native to central and eastern states, but were introduced in the southwest in the 1900s because of the widespread popularity of frog legs as food, and can now be found in all lower 48 states, according to the FWS.

Researchers at SWRS brought Goliath back to the station and placed him in a tank for closer examination. To provide a sense of the tadpole's substantial size, one of McGee's photos positioned Goliath next to a banana, and another photo compared him to a can of Coke. His exact measurements — along with data about his growth rate, feeding habits and behavior — are being collected by scientists for a peer-reviewed study, McGee wrote in a tweet.

Original article on Live Science.

Frogs' heads may look smooth and rounded on their surfaces, but peek under the skin of some species and you'll find skulls that resemble the heads of mythical dragons, studded with spikes, spines and other bony structures.

Scientists recently highlighted the diversity of frog skulls in a series of incredible images, part of a new study investigating skull evolution and function in armored frogs.

In these frogs, skulls can be shield-shaped or exceptionally wide; they may be pocked by grooves or adorned with pointy bits that may provide extra protection against being eaten, the researchers reported.

Related: In photos: Cute and colorful frogs

Artificial color in the images indicates variations in bone density in different skull parts, said lead study author Daniel Paluh, a doctoral candidate in the Department of Biology at the University of Florida. In the image of the horned frog Hemiphractus scutatus, "blue parts of the skull, such as the braincase, are lower density than the green regions, including the jaws," Paluh told Live Science in an email.

There are approximately 7,000 known frog species. For the study, the scientists collected data from 158 species representing all of the major frog families. They found that not only was there a lot of variety in skull shapes; some of those variations appeared across different lineages, separated by millions of years of evolution.

"For example, large, fortified skulls with intricate patterns of pits and grooves have independently evolved in the African bullfrog, South American horned frog and the Solomon Island leaf frog," Paluh said. "And all of these species are ambush predators that will eat other vertebrates."

Shovel-headed tree frogs, whose flattened skulls resemble gardening tools, use their heads to block entry to the cracks and holes where they live. Their skulls also have spines, ridges and grooves, "in addition to very wide skull roof bones that provide protection from predators," Paluh explained. 

"Because all frogs look so similar, there has been limited interest in studying the evolution of their anatomy," Paluh said. "Our study demonstrates there is still much to learn about the evolution, ecology and anatomy of these amazing animals."

The findings were published online today (March 27) in the journal Proceedings of the National Academy of Sciences.

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Originally published on Live Science.

The world's largest frogs may also have the best pollywog daycare on the market. To protect its wee tadpoles, these enormous amphibians build their own "nursery ponds," sometimes moving rocks more than half their weight to do so, and then guarding the pond to ensure the next generation's survival, a new study details.

The finding marks the first time scientists have described the Goliath frog's (Conraua goliath) unique nest-building and parenting tactics. However, local frog hunters in Cameroon have known about it for years, and they were the first to tell the researchers about the frogs' parental dedication.

In fact, the researchers were studying something completely different (they were studying the diet of Goliath tadpoles) when "we heard about the breeding behavior of the Goliaths and decided to investigate if it [were] true or not," said study senior researcher Mark-Oliver Rödel, curator of herpetology at the Natural History Museum in Berlin. [15 of the Largest Animals of Their Kind on Earth]

The 7.3-lb. (3.3 kilograms) Goliath frog is native to Cameroon and Equatorial Guinea. To learn more about its nesting quirks, the scientists spent part of spring 2018 searching a 1,300-foot (400 meters) section of the Mpoula River in western Cameroon. They also interviewed four frog hunters and two villagers who lived near the river to learn more about C. goliath's habits.

In all, the scientists found 22 breeding sites, 14 of which had almost 3,000 eggs apiece. The team even set up a time-lapse video at one nest, which showed a Goliath guarding the nest at night. 

These frogs are creative builders, constructing three different types of nests, the researchers found. One type, the rock-pool nest, was built on larger rocks within the river, meaning that "frogs were using pre-existing structures for breeding," the researchers wrote in the study. 

For the second type, frogs used naturally existing shallow pools near the river as nests. It appeared that the frogs had enlarged these pools, the researchers noticed, in essence turning a cottage into a McMansion. For the third type, the frogs dug small ponds, surrounding them with large stones, some weighing up to 4.4 lbs. (2 kg). 

Impressively, none of these nests had debris in them, suggesting that the frogs also acted as housekeepers, keeping the ponds clean for their tadpoles. "We have never observed them directly, but from indirect evidence, it is apparent that they push out material (e.g. leaves, pebbles) from natural ponds or push away larger and smaller stones to create their 'own' ponds," Rödel told Live Science in an email. 

It's likely that the male frogs, which are more than 1.1 feet (34 centimeters) long, use "their huge and very muscular hind legs" to move the stones, he added. 

While the researchers never directly witnessed a Goliath frog digging a nest, "the most detailed description we got (from one frog hunter) was that the male would construct the nest while the female waits in proximity," the scientists wrote in the study. "Once the nest is finished, the male whistles to attract the female, which then is grasped by the male and eggs are deposited. Afterwards, the female would guard the nest and subsequently open the nest towards the river."

Is daycare worth the cost?

The frogs invest a substantial amount of energy into nest-building, cleaning and guarding. But is it worth it? If their tadpoles survive, it absolutely is, but it appears each nest has benefits and challenges, the researchers found. Nests within a riverbed can flood from heavy rains, allowing predators such as shrimp and fish to get inside and devour the tadpoles, said Rödel, who is also the president of Frogs & Friends, the nongovernmental organization that co-funded the research. [So Tiny! Miniature Frog Species Are Among World's Smallest (Photos)]

Digging a pond alongside the river would sidestep these predators, but if it doesn't rain for a spell, the pond could dry up, killing the tadpoles. "Thus, each of the three nest types has advantages and disadvantages, and the frogs need to choose what is best at a certain time," Rödel said. 

Goliath frogs aren't the only amphibian superparents out there. The gladiator frog (Hypsiboas rosenbergi) in South America builds nests for its young, while the male African bullfrog (Pyxicephalus adspersus) guards tadpoles and digs channels up to 40 feet (12 m) long to allow tadpoles to escape from drying pools, the researchers noted. However, Goliath is the only known African frog to build nesting ponds, the researchers said.

Unfortunately, the Goliath frog is endangered, according to the International Union for Conservation of Nature, largely because of habitat loss and fragmentation, pollution, disease and hunting. (The frogs are considered a luxury food and are often served at weddings, Rödel said.)

It would be a shame to lose these creatures without fully understanding them, he said. "The reason why we wanted (and actually did) study the tadpoles, was that we needed to know more about the biology of the species, just to make sure we know what to do in case a captive breeding program might be the last chance for the Goliaths' survival in the future."

The study was published online Friday (Aug. 9) in the Journal of Natural History.

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Originally published on Live Science.

In eastern Brazil's Atlantic Forest, poisonous "pumpkin toadlets" use their vivid colors to warn off predators. But these tiny frogs also broadcast a secret visual signal: They glow bright blue under ultraviolet light.

Scientists unexpectedly discovered the glowing patterns in two species of pumpkin toadlets (Brachycephalus ephippium and B. pitanga) while investigating the tiny frogs' mating calls. To the human eye, the frogs appear orange, red or yellow in natural light.

But when researchers shone a UV lamp on the frogs, blue patterns emerged on the toadlets' heads, backs and legs. [In Photos: Cute and Colorful Frogs]

Fluorescence is extremely rare in land animals with backbones, and while scientists don't know how the pumpkin toadlets use their glow, it may help them to recognize prospective mates or protect them from predators, the researchers reported in a new study.

Unlike bioluminescence, in which chemical reactions in an animal's body generate light, fluorescence won't work in complete darkness. In fluorescence, special molecules absorb light and then emit it at longer wavelengths, creating a glow that usually shows up in shades of red or green.

Corals, scorpions and a rare type of sea turtle fluoresce; in 2018, scientists discovered that chameleons fluoresce, too. Another team of researchers found in 2017 that two species of South American tree frog had fluorescent skin, according to the authors of the new study. However, the pumpkin toadlets' glow is more like that of chameleons, originating in the animals' bones.

In fact, bony plates on the toadlets' head and back were "exceptionally fluorescent," though chemical analysis would be required to identify the compounds that lend the frogs their intense shine, the scientists reported.

How does glowing benefit the toadlets? There's no evidence yet to suggest how the frogs use their glow, but it may serve as an extra warning to predators about the frogs' toxic coating, as some birds and spiders can see fluorescence in natural light, lead study author Sandra Goutte told Live Science. Goutte is a postdoctoral associate at New York University Abu Dhabi in the United Arab Emirates.

Another possibility is that the tiny frogs use their glow to communicate with each other. Pumpkin toadlets lack a middle ear, so they can't hear themselves calling; it's possible that a glowing signal helps them with mating success or allows the frogs to recognize their own species.

"But that's only true if the frogs can see it," Goutte said. "And we don't know if they do."

The findings were published online today (March 29) in the journal Scientific Reports.

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Originally published on Live Science.

Jan Freedman, curator of natural history at The Box — a museum in Plymouth — was walking with his family at the Venford Reservoir in Dartmoor when his 8-year-old son spotted the gory corpse, he told Live Science in an email.

In a photo of the remains, which Freedman shared in a tweet on March 24, the toad's glasslike intestines spill onto the ground, and the peeled skin of its underside — still attached below the jaw — stretches over its back. [Beastly Feasts: Amazing Photos of Animals and Their Prey]

"The head was the only part that wasn't turned inside out, so we could see it was a common toad (Bufo bufo)," Freedman said. "We have seen plenty of toads in our garden and at other spots on Dartmoor, but nothing like this." Freedman wrote in the tweet that he suspected this was the work of a predator — but what kind of predator was it?

Freedman hoped that biologists on Twitter could explain the toad's intriguing (and gory) state, and they did not disappoint. One of the responders, Jack Ashby, a museum manager at the University Museum of Zoology in Cambridge, initially thought that the frog had been pulled apart by a crow, "as this is something that Australian crows do to invasive toxic cane toads."

In Australia, crows have learned to sidestep toxic glands in the toads' heads and backs by flipping the toads over and slicing into the skin of their bellies to devour their insides, a behavior that was documented in 2018 by photographer Steve Wilson.

"European toads also have toxin glands in their skin, so it's not surprising that a predator would remove it," Ashby told Live Science in an email. In the photo of the inside-out toad, its flesh appeared to have been delicately removed, "which one might expect to be more easily done with a nimble beak," he added.

The jaws that bite, the claws that catch

However, there's another predator known for adroitly stripping toxic toads of their skin — the European otter (Lutra lutra). Though these otters are primarily fish eaters, they are also known for eating mammals, birds and amphibians, Amy Schwartz, a researcher and doctoral candidate with the School of Biosciences at Cardiff University in the U.K., told Live Science in an email.

Toads are often on the menu for otters in spring, when large numbers of the amphibians gather in ponds to breed, Schwartz explained. She suspected that an otter had skinned the toad in the photo because she had previously seen similar evidence: at a pond in Pembrokeshire — "in an area full of otters" — where multiple toad skins floated on the surface of the water.

After closely examining the image, Ashby also concluded that the predator was probably an otter. Many of the muscles and bones of the leg and spine were missing, which hinted that the toad had been attacked by a mammal — "something large enough to chew up whole toad legs," he said.

The detail that cinched it for Ashby was the empty skin that once held the toad's foot, which must have been yanked from the skin by a predator strong enough to remove the entire leg — "muscle, bone, tendons and ligaments" — in one piece.

"This requires a serious amount of force, presumably by an animal holding the carcass in its paws and pulling the leg out of its skin by its teeth," Ashby said. "It’s a lot easier to imagine an otter doing this" than a bird.

And as it happens, toad skin is surprisingly easy to remove, as it is only very loosely attached to the animal's body, Ashby said.

"The only places it is attached firmly is around the hands and feet, and the skull," he said. "If you're not worried about keeping the skin in one piece, it can be pulled off like a pair of leggings and a skin-tight shirt after snipping around the 'waist.'"

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Originally published on Live Science.

On a lonely plateau in India's Western Ghat mountains, an ancient family of frogs has quietly hidden among the fallen leaves for millions of years, evading human detection. Measuring about the width of a human adult's thumbnail, these tiny frogs sleep by day, hunt by night and wear a galaxy of light-blue speckles on their brown backs to blend in with their dark, little world.

Now, for the first time, a team of researchers, has described the quiet little amphibian. The team has dubbed this newfound amphibian the "starry dwarf frog" (Astrobatrachus kurichiyana) and, according to the team's new paper, which was published today (March 12) in the journal PeerJ, it is the only known species in a never-before-described family that may have lurked alone on its branch of the frog family tree for eons. [40 Freaky Frog Photos]

"This is an oddball frog — it has no close sister species for maybe tens of millions of years," study co-author David Blackburn, the associate curator of herpetology at the Florida Museum of Natural History, said in a statement.

Part of that oddball nature is the starry dwarf's unusually small size. As its nickname suggests, this frog is teeny-tiny, measuring a maximum of 1.14 inches (29 millimeters) from snout to butt — a little longer than the diameter of a U.S. quarter.

Equally striking are its stars. The frog's constellation-speckled back blends in perfectly with the crumpled leaves that carpet its forest habitat, giving the nocturnal amphibians a fine place to hide during the daylight hours. While the team saw some starry dwarf emerge at night, the frogs quickly scampered back beneath the leaves as soon as they were confronted with a flashlight's glare, the researchers wrote. That penchant for stealth may be a key to the frog's longevity, which is impressive considering the starry dwarf is the only known species belonging to an ostensibly ancient family.

"These frogs are relics… This lineage could have been knocked off [the evolutionary tree] at any point in time," lead study author Seenapuram Palaniswamy Vijayakumar, a postdoctoral fellow at George Washington University, said in the statement. "We should be celebrating the very fact that these things exist."

There may well be other "oddball" frogs hopping around India's Western Ghats — a 1,000-mile-long (1,600 kilometer) mountain range made up of isolated plateaus along the country's southwest coast. Like the Galapagos Islands, these plateaus have served as factories of biodiversity for tens of millions of years, each one housing novel species of amphibians and reptiles found nowhere else, the researchers wrote. Finding more of those species may be as simple as turning over a new leaf.

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Originally published on Live Science.