Monthly Archives: December 2024

Episode 413: The Great American Interchange

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Thanks to Pranav for suggesting this week’s massive topic!

Further reading:

When did the Isthmus of Panama form between North and South America?

Florida fossil porcupine solves a prickly dilemma 10-million years in the making

Evidence for butchery of giant armadillo-like mammals in Argentina 21,000 years ago

Glyptodonts were big armored mammals:

The porcupine, our big pointy friend:

Show transcript:

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

This week, at long last, we’re going to learn about the great American interchange, also called the great American biotic interchange. Pranav suggested this topic ages ago, and I’ve been wanting to cover it ever since but never have gotten around to it until now. While this episode finishes off 2024 for us, it’s the start of a new series I have planned for 2025, where every so often we’ll learn about the animals of a particular place, either a modern country or a particular time in history for a whole continent.

These days, North and South America are linked by a narrow landmass generally referred to as Central America. At its narrowest point, Central America is only about 51 miles wide, or 82 km. That’s where the Panama Canal was built so that ships could get from the Atlantic Ocean to the Pacific and vice versa without having to go all around South America.

It wasn’t all that long ago, geologically speaking, that North and South America were completely separated, and they had been separated for millions of years. South America was part of the supercontinent Gondwana, while North America was part of the supercontinent Laurasia.

We’ve talked about continental drift before, which basically means that the land we know and love on the earth today moves very, very slowly over the years. The earth’s crust, whether it’s underwater or above water, is separated into what are called continental plates, or tectonic plates. You can think of them as gigantic pieces of a broken slab of rock, all of the pieces resting on a big pile of really dense jelly. The jelly in this case is molten rock that’s moving because of its own heat and the rotation of the earth and lots of other forces. Sometimes two pieces of the slab meet and crunch together, which forms mountains as the land is forced upward, while sometimes two pieces tear apart, which forms deep rift lakes and eventually oceans. All this movement happens incredibly slowly from a human’s point of view–like, your fingernails grow faster than most continental plates move. But even if a plate only moves 5 millimeters a year, after a million years it’s traveled 5 kilometers.

Anyway, the supercontinent Gondwana was made up of plates that are now South America, Africa, Australia, Antarctica, and a few others. You can see how the east coast of South America fits up against the west coast of Africa like two puzzle pieces. Gondwana actually formed around 800 million years ago, then became part of the even bigger supercontinent Pangaea, and when Pangaea broke apart around 200 million years ago, Gondwana and Laurasia were completely separate. North America was part of Laurasia. But Gondwana continued to break apart. Africa and Australia traveled far away from South America as molten lava filled the rift areas and helped push the plates apart, forming the South Atlantic Ocean. Antarctica settled onto the south pole and India traveled past Africa until it crashed into Eurasia. By about 30 million years ago, South America was a gigantic island.

It’s easy to think that all this happened just like taking puzzle pieces apart, but it was an incredibly long, complicated process that we don’t fully understand. To explain just how complicated it is, let’s talk for a moment about marsupials.

Marsupials are mammals that are born very early and finish developing outside of the mother’s womb, usually in a special pouch. Kangaroos, wallabies, koalas, wombats, and Tasmanian devils are all marsupials, and all from Australia. But marsupials didn’t originate in Australia and are still present in other parts of the world.

The oldest known marsupial appears in North America about 65 million years ago, which was part of the other supercontinent on Earth at the same time as Gondwana, called Laurasia. About the time marsupials were spreading out across Laurasia, from North America all the way to China, Laurasia and Gondwana were connected for a while along the northern edge of South America. Animals were able to cross from Laurasia to Gondwana before the two supercontinents split apart again. Marsupials spread from Laurasia and across Gondwana before the continent of Australia separated about 50 million years ago. Marsupials did so well in Australia that researchers think that before Australia was fully separated from Gondwana, marsupials actually started spreading back out of Australia and into Gondwana again.

While marsupials were doing extremely well in Australia, in South America, birds were the dominant vertebrate for a long time. We talked about terror birds in episode 202. Phorusrhacidae is the name for a family of flightless birds that lived from about 62 million years ago to a little under 2 million years ago. They were carnivores and various species ranged in size from about 3 feet tall to 10 feet tall, or 1 to 3 meters, and had long, strong legs that made them fast runners. The terror bird also had a long, strong neck, a sharp hooked beak, and sharp talons on its toes.

Other birds in North America were likewise huge, but could fly. Those were the teratorns, which are related to modern New World vultures. Since they had huge wingspans and could fly long distances easily, they could just fly between North and South America if they wanted to, so teratorns were found on both continents starting around 25 million years ago. They only went extinct around 10,000 years ago. The largest species known, Argentavis magnificens, lived in South America around six million years ago. It’s estimated to have a wingspan of at least 20 feet, or 6 meters, and possibly as much as 26 feet, or 8 meters. That’s the size of a small aircraft.

In addition to giant predator birds, South America had crocodilians that could grow over 30 feet long, or 9 meters, and possibly as much as 40 feet long, or 12 meters. And, of course, it had ancestral forms of animals we’re familiar with today, like sloths, anteaters, armadillos, opossums, monkeys, capybaras, and lots more. Some of these were incredibly large too, like the giant ground sloth that was as big as an African elephant and the glyptodon that was related to modern armadillos. Glyptodon had a huge bony carapace and rings of bony plates on the end of its thick tail that made it into a club-like weapon, and it was the size of a car. Both the giant ground sloths and the glyptodonts were plant-eaters, as were the notoungulates.

The notoungulates are an extinct order of hoofed animals that lived throughout South America. They were probably most closely related to rhinoceroses, horses, and other odd-toed ungulates, but they’re completely extinct with no living descendants. Some were tiny and actually looked and probably acted more like rabbits than horses, while others were massive. We talked about trigodon in episode 387, and it and many of its close relations in the family Toxodontidae were the size and build of a modern rhinoceros. Trigodon even had a small horn on its forehead. A closely related group, Litopterna, is also a completely extinct order of ungulates, which were mostly smaller and more deer-like than the notoungulates.

The Pleistocene is also called the ice age, but it’s more accurate to say that it was a series of ice ages with long periods of warmer weather in between–tens of thousands of years of warmer climate, then a colder cycle that lasted tens of thousands more years. When the glaciers were at their maximum, with ice sheets covering some parts of the world over a mile thick, or a kilometer and a half, sea levels were considerably lower because so much of the world’s water was frozen solid. That exposed more land that would ordinarily be partially or completely underwater, and it also led to a dryer climate overall. At the same time, volcanic activity in the ocean separating what is now North and South America had been building up volcanic islands for millions of years. All these factors and more combined to form the Isthmus of Panama, also called Central America, that is basically a land bridge connecting the two continents.

This started around 5 million years ago and the isthmus was fully formed by about 3 million years ago, or at least that’s the most accepted theory right now. A 2016 study suggested that the land bridge started forming far earlier than that, possibly as early as 23 million years ago, possibly 6 to 15 million years. Studies are ongoing to learn more about the timeline.

What we do know is that once the land bridge opened up, animals started migrating into this new area. Animals from North America migrated south, and animals from South America migrated north. It didn’t happen all at once, of course. It was a slow process as various animal populations expanded into Central America over generations. Some animals had trouble with the climate or couldn’t find the right foods, while others did really well and expanded rapidly.

The ancestors of some animals that made it to North America and are still around include the Virginia opossum, the armadillo, and the porcupine. Meanwhile, the ancestors of llamas, horses, tapirs, deer, canids, felids, coatis, and bears traveled to South America and are still there, along with many smaller animals like rodents. Many other animals migrated, survived for a while, but later went extinct. This included a type of elephant called the gomphothere and saber-toothed cats that migrated south, while ground sloths, terror birds, glyptodonts, capybaras, and even a type of notoungulate migrated north.

You may notice that more animals that migrated south survived into modern times. South America was much warmer overall than North America, and most animals that traveled north had trouble adapting to a colder climate and competing with animals that were already well-adapted to the cold. Animals traveling south encountered warmer climates early, and if they were able to tolerate hot weather they didn’t have to worry about any climactic shocks on the rest of their journey south. As a result, North American animals were able to establish themselves in larger numbers, which helped them adapt even faster since more babies were being born and surviving.

One South America to North America success story is the porcupine. Porcupines are rodents, and there are two groups, referred to as old world and new world porcupines. Those are not great terms but that’s what we have right now. The old world porcupines are found in parts of Africa, Asia, and Italy, although they were once more widespread in Europe, while new world porcupines are found in parts of North and South America. Old world porcupines live exclusively on the ground and are larger overall than new world ones, which spend a lot of time in trees. Surprisingly, the two groups are only distantly related. They evolved spines separately. They’re also only very distantly related to hedgehogs.

The one thing everyone knows about the porcupine is that it has quills, long sharp spines that make hedgehog spines look positively modest. Porcupine quills are dangerous. They’re modified hairs, and actual hair grows in between the quills, but they’re covered in strong keratin plates and are extremely sharp. They also come out easily and regrow all the time. A porcupine can hold its spines down flat so it won’t hurt another porcupine, which is what they do when they mate.

Only one species of porcupine lives in North America, called the North American porcupine. It lives throughout much of the northern and western part of the continent, from way up in the far north of Canada down to central Mexico, although it doesn’t live in most of the southeast. We don’t know if the North American porcupine developed after South American porcupines migrated north, or if it developed much earlier, around 10 million years ago. Porcupine experts have been arguing about this for years, because there aren’t very many porcupine fossils to study.

Then a nearly complete fossil porcupine was discovered in Florida. It was such a big deal that the scientific team that discovered it decided to create an entire college course for paleontology students to help study the specimen. The resulting study was published in May of 2024, and the results suggest that the North American porcupine evolved a lot longer ago than the Isthmus of Panama formed.

The North American porcupine had to change a lot to withstand the intense cold when its ancestors were tropical animals. The North American porcupine is very different from its South American cousins. It spends less time in trees and doesn’t have a prehensile tail, it eats a lot of bark instead of mostly leaves, and it has thick insulating fur between its quills. The fossilized specimen discovered in Florida still had a prehensile tail and didn’t have the strong jaw it needed to gnaw bark off trees, but it already showed a lot of adaptations that are seen in the North American porcupine but not in South American species.

Ultimately, of course, a lot of large animals went extinct around 12,000 to 10,000 years ago, the end of the Pleistocene. Animals like mammoths that were well-adapted to cold died out as the climate warmed, and so did their predators, like dire wolves and the American lion. The notoungulates and other megaherbivores in South America went extinct too.

One animal that I haven’t mentioned yet that migrated south successfully was Homo sapiens. Maybe you’ve heard of them. Until very recently, the accepted time frame for humans migrating into South America was about 16,000 years ago, although not everyone agreed. But in July of 2024, a new study pushed that date back to 21,000 years ago.

The study examined glyptodont fossils found in what is now Argentina. The fossils were found on the banks of a river and were determined to show butchering marks from stone tools. The bones were dated to almost 21,000 years ago, which means that humans probably moved into South America a lot earlier than that. It takes time to travel from Central America down to Argentina.

One detail most people don’t know about when it comes to the Great American Interchange is how marine animals were affected. It was exactly opposite for them. Instead of a new land to explore, which caused very different animals to encounter each other for the first time, the Isthmus of Panama cut populations of marine animals from each other. They’ve been evolving separately ever since. So I guess whether a land bridge is bad or good depends on your point of view.

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. 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 412: Whales and Dolphins

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Thanks to Elizabeth, Alexandra, Kimberly, Ezra, Eilee, Leon, and Simon for their suggestions this week!

Further reading:

New population of blue whales discovered in the western Indian Ocean

An Endangered Dolphin Finds an Unlikely Savior–Fisherfolk

The humpback whale:

The gigantic blue whale:

The tiny vaquita:

The Indus river dolphin:

The false killer whale:

Show transcript:

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

This week we’re going to have a big episode about various dolphins and whales! We’ve had lots of requests for these animals lately, so let’s talk about a bunch of them. Thanks to Elizabeth, Alexandra, Kimberly, Ezra, Eilee, Leon, and Simon for their suggestions.

We’ll start with a quick overview about dolphins, porpoises, and whales, which are called cetaceans. All cetaceans alive today are carnivorous, meaning they eat other animals instead of plants. This includes the big baleen whales that filter feed, even though the animals they eat are tiny. Cetaceans are mammals that are fully aquatic, meaning they spend their entire lives in the water, and they have adaptations to life in the water that are simply astounding.

All cetaceans alive today belong to either the baleen whale group, which filter feed, or the toothed whale group, which includes dolphins and porpoises. The two groups started evolving separately about 34 million years ago and are actually very different. Toothed whales are the ones that echolocate, while baleen whales are the ones that have extremely loud, often beautiful songs that they use to communicate with each other over long distances. It’s possible that baleen whales also use a limited type of echolocation to navigate, but we don’t know for sure. There’s still a lot we don’t know about cetaceans.

Now let’s talk about some specific whales. Ezra wanted to learn more about humpback and blue whales, so we’ll start with those. Both are baleen whales, specifically rorquals. Rorquals are long, slender whales with throat pleats that allow them to expand their mouths when they gulp water in. After the whale fills its mouth with water, it closes its jaws, pushing its enormous tongue up, and forces all that water out through the baleen. Any tiny animals like krill, copepods, small squid, small fish, and so on, get trapped in the baleen. It can then swallow all that food and open its mouth to do it again. The humpback mostly eats tiny crustaceans called krill, and little fish.

The humpback grows up to 56 feet long, or 17 meters, with females being a little larger than males on average. It’s mostly black in color, with mottled white or gray markings underneath and on its flippers. Its flippers are long and narrow, which allows it to make sharp turns.

The humpback is closely related to the blue whale, which is the largest animal ever known to have lived. It can grow up to 98 feet long, or 30 meters, and it’s probable that individuals can grow even longer. It can weigh around 200 tons, and by comparison a really big male African elephant can weigh as much as 7 tons. Estimates of the weight of various of the largest sauropod dinosaurs, the largest land animal ever known to have lived, is only about 80 tons. So the blue whale is extremely large.

The blue whale only eats krill and lots of it. To give you an example of how much water it can engulf in its enormous mouth in order to get enough krill to keep its massive body going, this is how the blue whale feeds. When it finds an area with a lot of krill floating around, it swims fast toward the krill and opens its giant mouth extremely wide. When its mouth is completely full, its weight—body and water together—has more than doubled. Its mouth can hold up to 220 tons of water. Since the whale is in the water, it doesn’t feel the weight of the water in its mouth.

Blue whales live throughout the world’s oceans, but a few years ago scientists analyzing recordings of whale song from the western Indian Ocean noticed a song they didn’t recognize. It was definitely a blue whale song, but one that had never been documented before. Not long after, one of the same scientists was helping analyze humpback whale recordings off the coast of Oman and recognized the same unusual blue whale song.

After the finding was announced, other scientists checked their recordings from the Indian Ocean and a few realized they had the mystery blue whale song too. The recordings come from a population of blue whales that hadn’t been documented before, and which may belong to a new subspecies of blue whale.

Elizabeth, Alexandra, and Leon all wanted to learn about dolphins. Kimberly also specifically wanted to learn about the Indus River dolphin and Leon about the vaquita porpoise. Dolphins and porpoises are considered toothed whales, but they’re also relatively small and can swim very fast. Orcas are actually dolphins even though they’re often called killer whales.

Even a small cetacean is really big, but the exception is the vaquita. It’s the smallest cetacean alive today, not even five feet long, or 1.5 meters. It lives only in the upper Gulf of California and is gray above and white underneath, with black patches on its face.

The vaquita spends very little time at the surface of the water, so it’s hard to spot and not a lot is known about it. It mostly lives in shallow water and it especially likes lagoons with murky water, since that’s where it can find lots of the small animals it eats, including small fish, squid, and crustaceans.

The vaquita is critically endangered, mostly because it often gets trapped in illegal gillnets and drowns.  There may be as few as ten individuals left alive. Attempts at keeping the vaquita in captivity have failed, but it’s strictly protected by both the United States and Mexico. Some scientists worry that even though vaquita females are still having healthy calves, there are so few of the animals left that they might not recover and are functionally extinct. But only time will tell, so the best thing everyone can do is what we’re already doing, keeping the vaquita and its habitat as safe as possible.

Another small cetacean is the Indus River dolphin, which grows up to 8 and a half feet long, or 2.6 meters. As you can probably guess from its name, it actually lives in fresh water instead of the ocean, specifically in rivers in Pakistan and India. It’s pinkish-brown in color and has a long rostrum, or beak-like nose, which turns up slightly at the end and is filled with sharp teeth that it uses to catch fish and other small animals. Because the rivers where it lives are murky, the dolphin doesn’t have very good eyesight. It probably can’t see anything except light and dark with its tiny eyes, but it can sense its surroundings just fine with echolocation.

Like most cetaceans, the Indus River dolphin is endangered, but it’s doing a lot better these days than it was just a few decades ago. In the 1970s only about 150 of the little dolphins were left alive, and by 2001 there were a little over 600. Today there are around 2,000. Habitat loss, pollution, and accidental drowning in fishing nets are still ongoing problems, but these days the fishing families that live along the river are helping it whenever they can. The fishers rescue dolphins who get stranded in shallow water and irrigation canals, and the government encourages this by paying the fishers a small amount for their help. Since this part of the country is very poor, a little bit of extra money can mean a big difference for the families, and of course their help means a lot to the dolphins too.

One interesting thing is that the Indus River dolphin often swims on its side. That is, it just tips over sideways and swims around as though that’s the most normal thing in the world. Scientists think this helps it navigate shallow water. And the Indus River dolphin isn’t very closely related to other dolphins and whales.

Quite a while ago now, Simon brought the false killer whale to my attention. In 1846 a British paleontologist published a book about British fossils, and one of the entries was a description of a dolphin. The description was based on a partially fossilized skull discovered three years before and dated to 126,000 years ago. It was referred to as the false killer whale because its skull resembled that of a modern orca. Scientists thought it was the ancestor of the orca and that it was extinct.

Or maybe not, because in 1861, a dead but very recently alive one washed up on the coast of Denmark.

The false killer whale is dark gray and grows up to 20 feet long, or 6 meters. It mostly eats squid and fish, including sharks. It’s not that closely related to the orca and actually looks more like a pilot whale. It will sometimes hang out with dolphins, including occasionally hybridizing with bottlenose dolphins, but then again sometimes it will eat dolphins. Watch out, dolphins.

Finally, Eilee wanted to learn about little-known whales, and that definitely means beaked whales. There are 24 known species of beaked whale, but there may still be species unknown to science. We know very little about most of the known species, because they live in remote parts of the ocean. They prefer deep water and are extremely deep divers, with the Cuvier’s beaked whale recorded as diving as deep as 1.8 miles, or almost 3 km, and staying underwater without a breath for 222 minutes. That’s approximately 220 minutes longer than a human can hold their breath.

Let’s finish with Sato’s beaked whale, which was only described in 2019. It’s black with a chunky body and small flippers and dorsal fin. It also has a short beak. It lives in the north Pacific Ocean and was thought to be a darker population of Baird’s beaked whale, which is gray, but genetic studies and a careful examination of dead beached individuals proved that it was a completely different species. It grows up to 23 feet long, or 7 meters, but since no female specimens have ever been found, we don’t know if the female is larger or smaller than the male.

We basically know nothing about this whale except that it exists, and the fact that it is alive and swimming around in the ocean right now, along with other whales, is an amazing, wonderful thing.

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. 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 411: Lionfish and Sea Squirrel

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Thanks to David and Jayson for their suggestions this week!

Further reading:

Unveiling the lionfish invasion in the Mediterranean Sea

DeepCCZ: The Weird and Wonderful Megafauna of the Abyssal CCZ

The red lionfish is beautiful but does not look like a lion [photo by Alexander Vasenin – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=25523559]:

The sea squirrel is yellow above and red underneath (pictures from article linked above):

Under side of a gummy squirrel photographed on shipboard showing its bright red feeding palps (flower-like structure) and underbelly.

Gummy squirrel (“Psychropotes longicauda”) at 5100 m depth on abyssal sediments in the western CCZ. This animal is ~60 cm long (including tail), with red feeding palps (or “lips”) visibly extended from its anterior end (right).

Show transcript:

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

This week we’re going to learn about two interesting marine animals suggested by Jayson and David.

Let’s start with David’s suggestion, the lionfish. The lionfish doesn’t actually look like a lion although it is a fish. It lives in shallow tropical water in the Indian Ocean and western Pacific, especially around coral reefs.

There are twelve species of lionfish known, but they’re mostly fairly similar. The lionfish is brown or dark red in color with white stripes, fan-like fins, and lots of long spines, all of which are striped black and white or red and white to make them more visible. When a fish or other animal has markings that make it stand out against the background, you can be pretty sure that it’s dangerous, and that’s the case for the lionfish.

The lionfish’s spines are venomous, especially the spines on the dorsal fin. If it feels threatened, it will point the dorsal fin at the predator and keep it pointed at it no matter which direction the predator moves. If the predator swims below the lionfish, the lionfish will turn upside-down in the water to keep the dorsal fin pointed at it. Most predators back off at that point, and I don’t blame them because that sounds really scary.

People have died from lionfish venom, but it’s rare. Mostly it’s just extremely painful and makes the person feel really sick for a day or two. Divers have to be careful when they’re around lionfish, because lionfish can be aggressive and will point that dorsal fin at the diver as a warning. You don’t want a lionfish to point at you.

The lionfish eats smaller fish, including smaller lionfish, invertebrates, and other small animals. It confuses other fish by blowing water at them. The little fish turns to face into what it thinks is a weird water current, and suddenly, there’s a lionfish that just gulps it down.

As David points out, even though the lionfish is dangerous, it’s definitely beautiful. Some people keep lionfish in saltwater aquariums, although they’re hard to care for in captivity, and unfortunately sometimes the fish escape into the wild or are released. The red lionfish is especially invasive in the Caribbean Sea, the Gulf Coast, and off the southeastern coast of the United States. Lionfish have also been introduced to parts of the Mediterranean Sea, where they’re becoming more and more invasive.

Because invasive lionfish eat so many native fish, and because it’s spreading rapidly and becoming extremely common, people have been trying to find ways to reduce the invasive population. It turns out that lionfish are good to eat if you’re careful when handling the spines during cleaning, so people in areas where it’s invasive are encouraged to catch lionfish to eat. Invasive lionfish are even served in fancy restaurants. Since the red lionfish can grow around 18 inches long, or 47 cm, there’s lot a of meat on one.

No one’s sure why it’s called a lionfish. It doesn’t look remotely like a lion. It’s also called the zebrafish because of its stripes.

Next, Jayson wants to learn about the sea squirrel. Despite its name, it is not a squirrel, although it does live in the sea. It’s a type of sea cucumber that lives mostly in the Atlantic and the northeastern Pacific, but it’s also a deep-sea animal so you’re not likely to see it on your next trip to the beach. It’s yellow on top and red underneath, with 18 red feeding palps. These palps look like little flower petals surrounding its mouth, which is underneath the body. Its body is flattened on the bottom like a slug’s, but it has tiny tube feet that it uses to move around slowly.

None of this sounds like a squirrel, but that’s because I forgot to mention the rear appendage, which sticks up and back and is shaped sort of like a squirrel tail. Since the sea squirrel’s body is long and slender, it does resemble a squirrel in shape very slightly.

The sea squirrel is actually quite large. If you count the “tail,” it can measure almost 3 feet long, or 80 cm. It lives on the sea floor, where it eats whatever tiny food it can find that has sunk down from above.

The deep ocean floor mostly doesn’t have strong currents, and scientists think that’s why the sea squirrel has a tail. It’s not actually a tail, it’s a sail—or at least, that’s what we think it is. Larval sea squirrels have an appendage that almost definitely acts as a sail, allowing it to travel to new parts of the ocean without needing to swim. In adults, the tail may catch any small currents in the water, which may move the animal a short distance away. Since the sea squirrel doesn’t walk very quickly and can’t swim at all, and it finds all its food underfoot, getting moved to a new part of the sea floor where it hasn’t already eaten everything is beneficial.

Sometimes people call the sea squirrel the gummy squirrel because it kind of looks like a big piece of gummy candy, but it’s probably not a good idea to eat it. For one thing, scientists think its body may contain toxins, since its bright yellowy-green color may act as a warning to potential predators. Since nothing has been found that eats the sea squirrel, the warning must be working.

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. 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 410: Electric Catfish

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Thanks to Cosmo for suggesting this week’s animal, the electric catfish!

Further reading:

The shocking truth about electric fish

Efficient high-voltage protection in the electric catfish

Gimme kiss [electric catfish photo from this site]:

Show transcript:

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

This week we’re finally going to talk about a fish Cosmo wanted us to learn about, the electric catfish!

Catfish are really common fish that live throughout the world, except for Antarctica. We’ve talked about various types of catfish in lots of different episodes, since there are well over 3,000 known species and they’re incredibly diverse. The electric catfish lives in freshwater in tropical areas in western and central Africa, as far north as the Nile River.

All animals generate electric fields in their nerves and the contracting of muscles. Animals that can sense these fields are called electroreceptive. An electroreceptive animal can find hidden prey without using its other senses.

Many electroreceptive animals can also generate weak electrical fields, usually less than a single volt—small electrical pulses or a sort of wave, depending on the species, that can give them information about their environment. Like a dolphin using echolocation, a fish using electro-location can sense where potential prey is, where predators, plants, and rocks are, and can even communicate with other fish of its same species. Of course, those same electric pulses can also attract electroreceptive predators.

Some fish can generate an electric shock so strong it can stun or kill other animals. The most famous is the electric eel, which we talked about way back in episode 10, but the electric catfish falls in this category too.

The electric catfish isn’t a single species but several in the family Malapteruridae. Some are very small, but one grows as much as four feet long, or 1.2 meters, and can weigh over 50 lbs, or 23 kg. That’s Malapterurus electricus, THE electric catfish.

The electric catfish is grayish-brown mottled with black spots. Like a lot of catfish, it’s a cylinder-shaped chonk, and has three pairs of barbels around its broad mouth. Barbels are the feelers that give the catfish its name, because they look sort of like a cat’s whiskers. Sort of. Not actually very much like a cat’s whiskers. The electric catfish also has what look like surprisingly kissy lips, which are often pale in color so they stand out, especially when the mouth is open, which is frankly hilarious. It doesn’t have a dorsal fin and it’s not a fast swimmer. It spends most of its time lurking in rocky areas in muddy, slow-moving water. It’s also nocturnal.

The electric catfish eats other fish, although it will also eat pretty much anything it can swallow. It likes muddy water because it doesn’t want potential prey to see it, and of course it doesn’t want any potential predators to see it either. That includes humans, who consider it a delicacy. Humans also sometimes keep electric catfish as aquarium fish, which is sort of the opposite of being killed and eaten.

Contracting a muscle causes a tiny, tiny electrical impulse, as I mentioned earlier, but in electric fish certain muscles have developed the ability to generate much stronger electrical impulses. Instead of muscles, they’re called electric organs. The interesting thing is that this is only found in fish, but that the ability evolved separately at least six times in different lineages of fish.

The electric catfish uses its ability to generate electric shocks as a defense when it needs to, but mainly it uses it to stun or outright kill other fish, which it then gulps down. It can discharge up to 300 volts of electricity in pulses that last only a few milliseconds, but since it can generate up to 500 pulses in waves, that’s a lot of electricity. That’s not enough to kill a person, but you’d definitely feel it and try to get away.

But, you may ask, how does the electric catfish not shock itself? Water is a really good conductor of electricity, which is one reason why this ability is only found in fish. A study published in 2022 asked that question too. The scientists used a high speed digital camera to observe captive electric catfish, and got them to discharge electricity by tickling them with a paintbrush. This allowed the scientists to see if the catfish was actually affected by its electricity at all, because the main outward sign of electrocution is involuntary muscle contractions. They determined that no, the catfish didn’t show any sign of being shocked. They also weren’t shocked when the scientists were the ones generating electricity in the tank. The conclusion is that the electric catfish is shielded by a layer of fat and other tissues that resist electric shocks, which are especially dense around the animal’s heart and nervous system.

Arthritis in humans is sometimes alleviated by the application of mild electric shocks, carefully administered by doctors, but in ancient times before electricity, people figured out that handling some fish helped arthritis. Since electric fish are pretty common in different parts of the world, different cultures figured this out at different times. The ancient Greeks would put an electric ray on the arthritic body part, for instance, while the ancient Egyptians used the electric catfish. The ancient Egyptians depicted the electric catfish in carvings and paintings that are over 5,000 years old. I have arthritis in my thumbs but I don’t think I want to touch an electric catfish with my thumbs.

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. 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 409: Guinea Pigs and Capybaras

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Thanks to Mary, Mila, and Riley for their suggestions this week!

Further reading:

Comfortable and dermatological effects of hot spring bathing provide demonstrative insight into improvement in the rough skin of Capybaras

Comfort of capybaras determined by SCIENCE:

An especially attractive guinea pig:

Guinea pigs come in lots of colors, patterns, and fur types [picture taken from this excellent site]:

Show transcript:

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

This week we’re going to learn about two rodents, one small and one big. Thanks to Mary and Mila who both suggested the guinea pig, and thanks to Riley who suggested the capybara.

This episode is a bit unusual because part of it comes from a Patreon episode from 2023. Like, literally a big chunk of this episode is the original audio from that one, and you’ll be able to tell the difference in audio and know just how lazy I was this week. The episode actually came together in an unusual way too. Riley’s parent emailed me last week with some new suggestions, including capybaras, but wasn’t sure if we had already covered the topic. I thought we had, but of course there’s always more to learn about an animal. Well, since this is the beginning of a new month I was on the Patreon page to upload the December episode, and while I was there I did a quick search for capybaras and discovered the episode I was thinking of. I decided to add some more information about guinea pigs to it since I already mention guinea pigs a lot in that episode, and here is the result!

The capybara is a rodent, and a very big one. It is, in fact, the biggest rodent alive today. To figure out just how big the capybara is, picture a guinea pig. The guinea pig is also a rodent, native to the Andes Mountains in South America. No one’s sure why the guinea pig is called that in English, since it doesn’t come from Guinea and doesn’t have anything to do with anything else called guinea, but as someone who had two pet guinea pigs when I was a kid, I know exactly why they’re called guinea pigs. This is what an actual pig sounds like:

[pig squealing]

And this is what a guinea pig sounds like:

[guinea pig squealing]

Also, it’s sort of shaped like a pig. The guinea pig is a chonky little animal with short legs, only a little stub of a tail, and little round ears. Its face is sort of blocky in shape and it has a big rounded rump, similar to that of a capybara. The guinea pig is actually closely related to the capybara, and is a pretty good-sized rodent in its own right. It grows about 10 inches long, or 25 cm, on average, and roughly half that size tall.

The guinea pig has been domesticated for at least 7000 years, but it wasn’t domesticated for people to keep it as a pet. In South America and many other places now, it’s a very small farm animal raised for its meat. Guinea pig has been an important source of protein for all that time, so important that it was considered sacred in many cultures.

In the early 16th century when Europeans started arriving in South America, sailors took guinea pigs with them on ships so they’d have fresh meat on the voyage. But when the cute little animals arrived in Europe, people started buying them as pets.

Guinea pigs eat plants, mostly grass, and are social animals. If you want a pet guinea pig, make sure to get at least two. Like rabbits and some other animals, including the capybara, the guinea pig excretes special pellets that aren’t poop, but are semi-digested pellets of food. The guinea pig eats the pellets so they can pass through the digestive system again and the body can extract as many nutrients as possible from it. What’s left is then excreted as a regular poop pellet.

Even in places where the guinea pig is routinely kept as livestock and eaten, people breed guinea pigs as pets too. The pet variety is smaller than the meat variety and has different markings and different colors. Guinea pigs naturally have short, smooth hair and are usually reddish-brown in color, but different colors, fur length and texture, and white markings have been bred into different varieties. There are even mostly hairless varieties.

Most people these days are familiar with what a guinea pig looks like, but most people are not familiar with what a capybara looks like.

So, picture a guinea pig. Now, imagine it growing and growing and growing until it’s the size of a large dog. Instead of orange and white, or black and white, or any of the other colors and patterns of a pet guinea pig, imagine its fur as being a solid rusty-brown color. The capybara can grow almost 4.5 feet long, or 134 cm, and can stand up to two feet tall, or 62 cm. That is a big rodent!

The capybara lives throughout most of South America, although it doesn’t live in the Andes or in Patagonia. It’s semi-aquatic and spends a lot of time in the water, sometimes even sleeping in the water with just its nose poking up so it can breathe. It can hold its breath for up to five minutes, and of course it swims extremely well. It even has webbed toes. It eats a lot of water plants and also eats grass, fruit, and other plants and plant parts.

The capybara has some features that are typical of rodents, like its teeth. Rodent teeth grow continuously since they’re easily worn down by chewing, especially chewing tough plants like grass. It also has some features that are uncommon in rodents. For instance, it can’t synthesize vitamin C, a trait it shares with the guinea pig and with humans. If a capybara kept in captivity isn’t given fruit and other foods that contain vitamin C, eventually it will develop scurvy.

But the capybara doesn’t otherwise have any resemblance to a pirate. It’s a sociable animal and famously chill. In the wild it lives in groups that can number up to 100 individuals, although up to 20 is more common.

The capybara has a scent gland on its nose called a morillo. The female has a morillo but the male’s is bigger since he scent marks more often by rubbing the gland on plants, trees, rocks, other capybaras, and so on. During mating season, the female capybara attracts a male by whistling through her nose, because who doesn’t like a lady who can whistle through her nose? The capybara will only mate in water, so if a female decides she doesn’t like a male, she just gets out of the water and walks away from him.

The female usually gives birth to four or five babies in one litter. Females with babies, called pups, help care for the babies of their friends. Most often, the pups who are too young to wander around without someone to watch them carefully, stay in a group. One or two females remain close to the pups to watch them while the other mothers find food, and the babysitters trade out every so often. When a capybara pup gets hungry, if its mother isn’t nearby, another lactating female will allow the pup to drink some of her milk. This is rare in most animals, since producing milk takes a lot of energy and a mother animal naturally wants to expend her energy on her own babies. But it’s beneficial for the whole group for capybara pups to be cared for by all the mothers.

Capybaras are big enough that adults have a certain amount of protection from predators, but they do have to worry about animals like jaguars, caimans, and anacondas. Smaller predators like eagles will eat capybara pups if they can catch them. Fortunately the capybara can swim fast and run fast, and with everyone in its group watching out for danger, it’s a lot safer than it is by itself.

The capybara does well in captivity and is a popular animal in zoos, and in some zoos you might even be able to pet one. You’ve probably seen pictures of capybaras relaxing in what looks like a big outdoor tub with tangerines floating in it, or if you’re from Japan or just familiar with Japanese customs, relaxing in a yuzu bath. Hot springs baths, called onsen, are popular in Japan, and in winter when the days are short and chilly, adding a citrus fruit called yuzu to the bath is supposed to help prevent colds and help moisturize the skin. Some zoos in Japan now extend this custom to capybaras, because it’s adorable.

As an added bonus, it turns out that the yuzu bath is really good for the capybara. The capybara is a warm-weather animal, and winters in Japan can be very cold and dry. As a result, the capybara’s skin becomes dry too. Soaking in natural hot springs, with or without yuzu, restores the capybara’s skin to its normal condition, which is a lot more comfortable for the capybara and helps it stay healthy. We know this is the case because of a study published in December 2021 in the journal Nature.

Before we go, here’s one last interesting fact about the guinea pig, to bring us back to the beginning of this episode. The guinea pig is a fully domesticated animal and its wild ancestor appears to have gone extinct. There are related species that resemble a guinea pig, but there are no wild guinea pigs in the world today.

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. 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!