Episode 275: The Axolotl, the Hellbender, and Friends

This week it’s Zoe and Dillon’s episode! They wanted to learn about some really interesting salamanders, including the axolotl and the hellbender!

A big birthday shout-out to Heather R. too. The very happiest of birthdays to you!

Further reading:

Mexico City’s endangered axolotl has found fame—is that enough to save it?

How Do Salamanders Breathe?

Most wild axolotls are brown:

Most captive-bred axolotls are leucistic:

The hellbender doesn’t have external gills as an adult:

The red eft, the juvenile stage of the red-spotted newt:

Adult mudpuppies have external gills just like axolotls do:

Show transcript:

Welcome to Strange Animals Podcast. We’re your cohosts, Zoe and Dillon. And I’m your third cohost, Kate Shaw.

This week we have Zoe and Dillon’s episode, and they want to learn about the axolotl, the hellbender, and some other salamanders. It’ll be the greatest amphibian episode ever!

But first, we have a birthday shout-out! Happy birthday to Heather R.! I hope the weather is perfect for your birthday and you get to go out and appreciate it.

So, let’s start with the axolotl, because everyone loves it! “Axolotl” isn’t the way it’s pronounced in its native country of Mexico, since it comes from the name of an Aztec god of fire and lightning, but it’s the common pronunciation in English so I’m going to stick with that one. In addition to Zoe and Dillon, at least one other listener has suggested we cover the axolotl. That would be Rosy, and I apologize to anyone else who suggested it but whose name didn’t make it onto the suggestions list.

Way back in episode 104, about tiger salamanders, we learned that the tiger salamander is closely related to the axolotl. But the two species look very different most of the time because the axolotl exhibits a trait called neoteny. In most salamanders, the egg hatches into a larval salamander that lives in water, which means it has external gills so it can breathe underwater. It grows and ultimately metamorphoses into a juvenile salamander that spends most of its time on land, so it loses its external gills in the metamorphosis. Eventually it takes on its adult coloration and pattern. But the axolotl doesn’t metamorphose. Even when it matures, it still looks kind of like a big larva, complete with external gills, and it lives underwater its whole life.

Very rarely, an axolotl metamorphoses into an adult form, at which point it looks a whole lot like a tiger salamander. This generally happens if the individual is exposed to excess iodine in its diet, and metamorphosing like this may actually lead to the axolotl’s death. Axolotls exhibit neoteny because it gives them an advantage in their natural range, so even though it seems strange to us compared to all those other salamanders, it’s what the axolotl is supposed to do.

The axolotl’s natural range is very specific. Originally it lived in two large, cold lakes in the Valley of Mexico. This is where Mexico City is and it’s been a hub of civilization for thousands of years. A million people lived there in 1521 when the Spanish invaded and destroyed the Aztec Empire with introduced diseases and war. The axolotl was an important food of the Aztecs and the civilizations that preceded them, and if you’ve only ever seen pictures of axolotls you may wonder why. Salamanders are usually small, but a full-grown axolotl can grow up to 18 inches long, or 45 cm, although most are about half that length.

Also if you’ve only ever seen pictures of axolotls you may think they’re all white or pink. That’s actually rare in the wild. Most wild axolotls are brown, greenish-brown, or gray, often with lighter speckles. They can even change color somewhat to blend in with their surroundings better.

It’s captive axolotls that are so often white or pink, or sometimes other colors or patterns. That’s because they’re bred for the pet trade and for medical research, because not only are they cute and relatively easy to keep in captivity, they have some amazing abilities. Their ability to regenerate lost and injured body parts is remarkable even for amphibians, but, interestingly, axolotls that have been induced to metamorphose have much less regeneration ability. Researchers study axolotls to learn more about how regeneration works, how vertebrates evolved various aspects of anatomy, how genetics of coloration work, and much more. They’re so common in laboratory studies that you’d think there’s no way they could be endangered—but they are. Some conservationists think there may be as few as 50 individuals left in the wild.

The main problem is habitat loss. One lake where the axolotl was once found is completely gone, drained to control flooding and provide more land for people to use. The other lake isn’t so much a lake anymore as a series of canals in Mexico City, and they’re polluted and home to introduced species of fish that eat axolotl eggs. Even though part of their range was designated as a nature reserve in 1993, that hasn’t done much to stop the pollutants or invasive fish.

Not only that, the captive-bred axolotls are so different from their wild cousins that some people think they should be considered a different species. You couldn’t take a pet axolotl and dump it into a lake and expect it to live. Conservation efforts in Mexico are focusing on a captive breeding program of axolotls caught in the wild. Since the salamander’s native range isn’t healthy right now, the group is trying to establish temporary homes in university ponds prepared just for that purpose. So far the project is a success.

At the same time, conservationists and just regular people who like axolotls are working hard to get its native habitat cleaned up. This includes educating people about the axolotl, and helping people set up small farms that use traditional methods that don’t require fertilizer or insecticides that run off into the water. These farms are called chinampas and are made up of artificial islands with canals around them. The islands actually help filter pollutants from the surrounding water, and the canals are ideal for axolotls to live in. The farmers also install screens with filters to keep invasive fish out and clean up the water even more, and some of the captive-bred wild axolotls have been introduced to these canals successfully.

Even though the axolotl has external gills to collect oxygen from the water, it has lungs too. It will sometimes gulp air from the surface, but most of the time it gets all the oxygen it needs from its gills. It eats small animals like worms, insects, and even small fish, but while it does have tiny teeth, they’re actually vestigial. The axolotl doesn’t chew its food but instead sucks its prey whole right down into its stomach.

We talked about the hellbender briefly in episode 14, but that was five years ago. In fact, it was exactly five years ago. Episode 14 was released on May 8, 2017, and this episode is being released on May 9, 2022. I swear I did not plan it that way but it’s pretty neat.

The hellbender has a restricted range too, although it’s not as restricted as the axolotl’s. It lives in parts of the eastern United States, especially in the Appalachian Mountains and the Ozarks. It can grow nearly 30 inches long, or 74 cm, and is heavy for its size, up to 5.5 lbs, or 2.5 kg. This is the fifth heaviest amphibian alive today in the whole world! It needs clean, shallow, fast-moving streams with lots of rocks, because it spends almost all its life in the water hiding among rocks. But the rocks are important for another reason too. As water rushes over and around rocks, it splashes around and absorbs more oxygen. Well-oxygenated water helps the hellbender breathe, which is even more complicated than it sounds.

Like other salamanders, the hellbender hatches from eggs laid in the water and at first are just big tadpoles with external gills. They metamorphose in stages until they’re full grown at almost two years old, at which point they lose their gills, although they may retain a nonfunctioning gill slit. The adult hellbender has large lungs, but it doesn’t use them for breathing. They’re just for buoyancy. The hellbender absorbs oxygen from the water through its skin, which is why it needs well-oxygenated water flowing quickly across it all the time. To increase its surface area and help it absorb that much more oxygen, its skin is loose and has folds along the sides.

The hellbender is flattened in shape, which helps it hide under rocks and helps keep it from being swept away by currents when it’s moving around in the water. It’s brown with black speckles on its back. It mostly eats crawdads, also called crayfish, but it will eat small fish and amphibians, tadpoles, the eggs of frogs and fish, and in fact it will also eat the eggs of other hellbenders. Occasionally a hellbender will eat a smaller hellbender too. It’s a solitary animal except during breeding season, and even then, once the female has laid her eggs in a nest the male makes and the male fertilizes them, the pair don’t spend any time together. The male actually chases the female away. Then he spends the next few months guarding the eggs and making sure they get enough oxygen by waving his tail and skin folds over them.

The hellbender doesn’t have very good eyesight, although it has a good sense of smell. It’s very territorial and seldom leaves the small stretch of water where it lives and hunts. Very occasionally it will leave the water and walk around on land. Most of the time it walks around underwater, though, instead of swimming. Its toes have rough pads that help it walk even on slippery rocks. During the day, though, it usually hides under its home rock. Its skin contains light-sensitive cells, which are mostly concentrated in its tail. This means that it can actually sense how much light is shining on its body even if its head is hidden under a rock. The reason its tail has more light-sensing cells is because its tail is more likely to be sticking out from under its rock. Since a lot of animals eat the hellbender, it needs to be fully hidden by its rock during the day.

Some people think the hellbender is poisonous or venomous, but it’s actually completely harmless unless you are a very small aquatic animal.

Because salamanders, like other amphibians, have to keep their skin moist, they’re vulnerable to water pollution. Any pollutants in the water are liable to be absorbed into the salamander’s body, which can make it sick. Habitat loss, disease, and invasive species are also major causes of declines in salamander species.

Salamanders have been around for at least 180 million years. Amphibians in general probably developed from lobe-finned fish around 360 million years ago. A study published in 2020 examined 3D scans of skulls from 148 species of salamander to compare minute differences and learn more about how they evolved. Animals that undergo metamorphosis, including salamanders, have very different skulls from animals that don’t, since different parts of the skull develop in stages independently of other parts. The study found that while salamanders have always been metamorphic, different life cycles have evolved separately at least eleven times.

One of the things Zoe asked in particular was whether salamanders actually breathe through their nostrils. It depends on the species. Salamanders are definitely complicated when it comes to breathing. Like many amphibians, the salamander doesn’t have special muscles to move air in and out of its lungs the way mammals do. Instead, it moves air in and out by gular pumping, also called buccal pumping.

A salamander lowers the floor of its mouth, expanding the throat, which pulls air into the throat by way of the nostrils. Then the salamander closes its nostrils and raises the floor of its throat. This causes the air to enter the lungs. It does the same process in reverse to breathe out. That’s why salamanders and other amphibians appear to be gulping all the time. That’s how they breathe.

Complicated as this sounds, the salamander doesn’t have to concentrate to do it any more than we have to concentrate to breathe. Also, even if it mostly gets oxygen through its lungs, all salamanders appear to be able to absorb a certain amount of oxygen through the skin too.

Zoe and Dillon were especially interested in salamanders that live in their part of the world, which is the state of Pennsylvania in the eastern United States. In addition to the hellbender, there are several dozen salamander species known from Pennsylvania, and probably quite a few that haven’t been discovered yet. This includes the red-spotted newt, which lives in forests in muddy or wet areas. It grows up to about 5 inches long, or 13 cm, and eats insects, worms, frog eggs and tadpoles, and other small animals.

As an adult, the red-spotted newt is greenish-brown, often with a row of red spots outlined with black along its sides and tiny black dots all over, and a yellow or orange belly. The adult mostly lives in the water, but during the juvenile stage it mostly lives on land and can travel widely, especially after rain. It also looks very different during the juvenile stage, with a bright orangey-red body and spots outlined with black, which is why it’s often called a red eft. An eft is a juvenile salamander. The bright red coloring may tell you not to eat the red eft, because it’s poisonous! Its skin contains toxins that make it taste bad and can make a potential predator sick.

Another salamander common throughout Pennsylvania is the spotted salamander, which can grow almost 10 inches long, or 24 cm. It’s a big, strong salamander that’s black or gray with big yellow or orangey spots all over. As a juvenile it looks very similar, although smaller, but with tiny spots or no spots.

Finally, to wrap around to where we started, another large species of salamander that lives in parts of western Pennsylvania, and other nearby areas, is the mudpuppy. It looks a lot like a juvenile hellbender but isn’t as big, with the largest measured adult growing just over 17 inches long, or almost 44 cm. Like the axolotl, the mudpuppy exhibits neoteny. It lives in lakes, ponds, and streams and retains its gills throughout its life. Its gills are large and reddish in color. If a mudpuppy lives in your pond or backyard stream, you can be sure the water is clean because its gills are very sensitive to pollutants.

The mudpuppy spends most of its time under rocks and walking along the bottom of the lakebed or streambed, looking for food. It’s gray, black, or reddish-brown, sometimes with speckles or spots. It has a lot of tiny teeth where you’d expect to find teeth, and more teeth on the roof of its mouth where you would not typically expect to find teeth. It needs all these teeth because it eats slippery food like small fish, worms, and frogs, along with insects and other small animals.

Even though the mudpuppy has all those teeth, it’s harmless to humans and just wants to be left alone, but that’s pretty much the case for all salamanders. And some people.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 014: Giant Salamanders

In episode 14, we discuss the big three of giant salamanders–and some possible mystery relatives.

The Chinese giant salamander. An orange one. Enormous. Mostly harmless. Just wants to eat a snail.

The Japanese giant salamander:

The HELLBENDER reverb reverb reverb

The Pacific giant salamander. Not as giant but has an angry:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re looking at giant salamanders. Yup.

Salamanders are amphibians. Think “wet lizards” or “skinny frogs with tails.” A lot of people think snakes are slimy, but they’re not. Snakes are reptiles and their scales are satiny smooth and dry. Amphibians don’t have scales and they do have slimy skin, which they need to keep moist.

Some salamanders are completely aquatic but most live at least part of their lives on land, usually in wet areas. When I was a kid, I used to like turning over rocks in the creek behind our house, because frequently I’d find a salamander underneath. I wouldn’t catch it, just look at it, which is what you should do if you find a salamander—partly because it’s not good to disturb a wild animal that’s just trying to live its life, and partly because salamanders secrete toxins through their skins. The toxins won’t kill you, but if you get any in your eyes or mouth you could be in for some unpleasant symptoms.

There are two species of salamander known to be venomous, in a way, but they don’t inject venom with special fangs. When the sharp-ribbed salamander is attacked, it pushes its pointed ribs through tubercules along its sides. The tubercules secrete toxins that coat the rib points, which then pierce right through the salamander’s skin and into its attacker.

There are hundreds of salamander species throughout the world, some of them tiny, most of them a few inches long [about 5 or 6 cm], but there are three that are much bigger than that. The biggest is the Chinese giant salamander. The biggest ever found was just shy of six feet long [two meters]. Six feet long! The closely related Japanese giant salamander is almost as big, some five feet long [1.5 meters].

There’s a third giant salamander right here in the southeastern United States where I live, and while at two and a half feet long [76 cm] it’s not nearly as long as its cousins, it has a much better name. The Chinese giant salamander’s local name is infant fish, because some of the sounds it makes remind people of babies crying, which is creepy as heck. The Japanese giant salamander is called the giant pepper fish, because when it’s disturbed it secretes a whitish mucus that smells like pepper. But the North American giant salamander? We call that thing the H E L L B E N D E R.

I did try to find audio of the Chinese giant salamander crying. I had no luck, which is probably a good thing actually, because it’s a distress call. I did find this awesome audio of a Pacific giant salamander. Despite the name giant in its name, it’s not very big compared to the other giants, only about a foot long at most [30 cm], but it does have a cute vocalization.

[Pacific giant salamander call]

(He’s so mad.)

The Chinese and Japanese giant salamanders are so closely related that they readily interbreed. We know that because some fool decided to introduce some Chinese salamanders into streams in Japan. Hellbenders are not as closely related to the Asian salamanders.

All three of the giant salamanders are endangered, mostly due to habitat loss and pollution. They like clean, swift-moving mountain streams with rocks of just the right size—not too big, not too small. But the Chinese salamanders are also considered a delicacy, so they’ve been overhunted as well. Poaching is a major issue, ironically to stock salamander farms. The adults breed readily in captivity, but farmers haven’t had much success getting captive-born individuals to breed, so they continue to capture adults from the wild.

Giant salamanders are fully aquatic, although they can and do get out of the water occasionally for short periods. All three have thick folds of skin along their sides, which increases their surface area, and that’s important because they breathe through their skins. Larval giant salamanders have gills, but when they mature they lose those gills. The hellbender may retain a gill slit but it no longer functions.

While giant salamanders do have a single lung, they don’t use it to breathe. They use it for buoyancy. They like fast-moving water because it’s well oxygenated. A salamander will also rock gently to increase the amount of water moving over its skin, and male salamanders will wave fresh water over their eggs. Males dig and defend the nests. In Japan, they’re called den-masters.

Giant salamanders are flattish in shape with broad bodies and wide heads. Their feet have stubby little toes. They eat fish, snails, crawdads, worms, insects, small mammals, snakes, frogs—basically anything they can catch. They snap up prey fast, sucking it in my creating a vacuum when they open their huge mouths. They range in color from slate gray to black to brownish with dapples. Occasionally an orangish or pink individual is discovered.

All the giant salamanders have poor eyesight, but they have a good sense of smell. In addition, the Chinese and Japanese giant salamanders have sensory cells along the sides of their bodies that detect vibrations in the water. The hellbender doesn’t have that kind of sensory cells as far as I’ve been able to find out, but it does have light sensitive cells on its body, especially the tail. This lets it know when its tail is safely hidden, rather than sticking out from under a rock.

Larval hellbenders look a lot like another large salamander in the area, called the mudpuppy or water dog. The mudpuppy can grow a bit over a foot in length [31 cm], but it retains its gills throughout its life. Don’t be fooled by fake hellbenders.

So those are the three giant salamanders in the world, but there are rumors of other giants in the streams and rivers of California. In the 1920s, an attorney named Frank L. Griffith, who was hunting in the area, spotted five salamanders in a lake in the Trinity Alps in northern California. The salamanders ranged in size between five and nine feet long [1.5 and 2.7 m]. He hooked one with a line, but he wasn’t strong enough to land it and it escaped. In the 1940s, animal handler Vern Harden claimed he’d seen eight-foot [2.4 m] salamanders in Hubbard Lake.

Thomas L. Rodgers, a biologist at Chico State College, conducted four expeditions to the Trinity Alps in 1948 in search of the giant. The expeditions didn’t find anything bigger than foot-long [30 cm] Pacific giant salamanders, but Rodgers suggested that the Trinity Alps giant might be a subspecies of the Pacific giant that grows to an enormous size, or might be a cryptobranchid like the eastern hellbender or the Asian giant salamanders.

In 1951, herpetologist George S. Myers published a paper about his own sighting. He said that in 1939 he was contacted by a commercial fisherman who had dredged up a two and a half foot [76 m] salamander in a catfish net from the Sacramento River. Myers described the salamander as dark brown with dull yellow spots, and said that it resembled the Chinese and Japanese giant salamanders but appeared to be a different species.

In 1960, Bigfoot hunter Tom Slick convinced an expedition looking for Bigfoot to hunt for the salamander too, with no luck. Also in 1960, Tom Rogers mounted another expedition, this time with some zoology professors and ten interested laymen. Again, they only found the foot-long Pacific giant salamander.

Rodgers decided he was wrong about the existence of a new giant salamander, and in 1962 denounced the previous sightings as misidentifications and hoaxes. More recently, a 1997 expedition led by Japanese-American writer Kyle Mizokami likewise came up with no sightings.

It’s not out of the realm of possibility that a giant salamander lives in the Trinity Alps and just hasn’t been found. It’s the right climate with the right conditions. And new salamanders are occasionally discovered in the United States. In 2009, a new species of lungless salamander was discovered in the Appalachian foothills. Yeah, that’s near where I live!

But that one is barely an inch long [2.5 cm]. It should be a little easier to spot a salamander longer than a grown man is tall, not to mention that two of the Trinity Alps giant salamander sightings report salamanders in lakes. If they’re cryptobranchids, they need running water to survive—streams or shallow rivers.

And as for the third sightings, the one where George Myers actually got a first-hand look at a giant salamander caught in the Sacramento River, there’s more to the story. Tom Rogers, the biologist who led five different expeditions to search for the salamander, also saw the Sacramento specimen. The fisherman had managed to keep it alive in his bathtub. Rogers identified it as a Chinese giant salamander, and in fact it turned out to be a lost pet named Benny that had escaped while being taken to Stockton Harbor by steamer.

If these were the only sightings of giant salamanders in North America that aren’t hellbenders, it wouldn’t be looking good for them. But we’re definitely not done. In his blog, zoologist Karl Shuker reports hearing from a woman who sighted a huge salamander in Redwood Park in Arcata, California in 2005. She described it as several feet long [1 meter] with a rounded head instead of flat like known giant salamanders, no skin folds along its sides, and reddish markings. She spotted it walking on land after a rain. Shuker suggests she might have seen an unusually large coastal giant salamander, which can reach almost a foot and a half in length [45 cm] and which she said her salamander resembled in many respects. Remember that Pacific giant salamander sound I played earlier? The coastal giant salamander is a type of Pacific giant salamander.

California isn’t the only state with a mystery giant salamander, though. Three other states have interesting reports, and all of them are pink.

Pink salamanders actually aren’t all that uncommon. Alibinism in salamanders is well known and not rare, and they frequently look pink due to blood vessels visible through their unpigmented skin.

In the early 1960s, biology student Mary Lou Richardson was bowhunting along Florida’s St. Johns River with her father and a friend. All three saw an animal the size of a donkey with a big flat head and a small neck. Other tourists saw the animal that same day, and local fishermen were familiar with it going back to 1955. It’s not clear from the description if the animal was a salamander or something else.

Then, on May 10, 1975, five people on a fishing trip on the St. Johns River saw a weird pink animal’s head and neck on the water. It was only 20 feet [6 m] from their boat and watched them for about eight seconds before diving again. One witness, Dorothy Abram, described it as having a head the size of a human’s with small horns like a snail’s. Another witness, Brenda Langley, also noted it had “this little jagged thing going down its back.” Presumably she meant serrations of some kind. The party also said the animal had large dark eyes and gills or gill-like flaps on either side of its head.

In Ohio, the first white settlers near Scippo Creek, called Catlick Creek Valley at the time, discovered what they called giant pink lizards living in the area. They were three to seven feet long [1 to 2.1 m] and lived in and around water. They also had moose-like horns, pretty big ones apparently. But after a drought followed by a devastating wildfire, by 1820 the pink lizards seemed to have died out.

And in South Carolina around 1928, nature writer Herbert Sass and his wife were boating on Goose Creek near Charleston when Sass saw something big under the water. He lifted it with an oar and although it almost immediately slipped back into the water, they were able to get a good look. Their description sounds a lot like a hellbender or other giant salamander, in this case as thick around as a man’s thigh and five or six feet long [1.5 to 2 m]. It was salmon pink and orange.

The St. Johns River monster might have been a manatee. The area where it was spotted is a manatee refuge and manatees have been responsible for other mystery animal sightings in the past. Then again, manatees don’t have snail horns, serrated backs, or gills, and known giant salamanders don’t either. It’s important to note too that in the 1975 sighting of the monster, dubbed Pinky because of course it was, witnesses described it as being dinosaur-like and said the skin appeared to be stretched so tightly over its head that the shape of the bones were visible. That doesn’t sound like either a manatee or a salamander, more like a reptile of some kind.

The Ohio and South Carolina sightings are much more interesting in regards to giant salamander sightings. Ohio is historically part of the hellbender’s range, and a population of hellbenders have recently been reintroduced there. Shuker suggests the horns described on the so-called pink lizards might actually have been branching external gills seen underwater. Most species of salamander lose their gills after they grow out of their larval stage, but not all, including mudpuppies. Mudpuppies aren’t as big as hellbenders, but that doesn’t mean there wasn’t once a variety that grew much larger.

South Carolina is also part of the hellbender’s range, and Sass’s pink and orange animal might very well have been an exceptional large specimen. Sass himself called it a hellbender.

Even if none of these mystery salamanders are ever discovered, or if they turn out to be known animals, we still have hellbenders around, and the Chinese and Japanese giant salamanders too. The best thing we can do is keep their habitats as pristine as possible, since salamanders need clean streams to thrive. Next time you go hiking, pick up any trash you find and pack it out with you. The salamanders will thank you.

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us and get twice-monthly bonus episodes for as little as one dollar a month.

Thanks for listening!