Tag Archives: porcupines

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 348: Australopithecus and Gigantopithecus

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Thanks to Anbo for suggesting Australopithecus! We’ll also learn about Gigantopithecus and Bigfoot!

Further reading:

Ancient human relative, Australopithecus sediba, ‘walked like a human, but climbed like an ape’

Human shoulders and elbows first evolved as brakes for climbing apes

You Won’t Believe What Porcupines Eat

Past tropical forest changes drove megafauna and hominin extinctions

An Australopithecus skeleton [photo by Emőke Dénes – kindly granted by the author, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=78612761]:

Show transcript:

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

It’s officially monster month, also known as October, so let’s jump right in with a topic suggested by Anbo! Anbo wanted to learn about Australopithecus, and while we’re at it we’re going to talk about Gigantopithecus and Bigfoot. On our spookiness rating scale of one to five bats, where one bat means it’s not a very spooky episode and five bats means it’s really spooky, this one is going to fall at about two bats, and only because we talk a little bit about the Yeti and Bigfoot at the end.

In 1924 in South Africa, the partial skull of a young primate was discovered. Primates include monkeys and apes along with humans, our very own family tree. This particular fossil was over a million years old and had features that suggested it was an early human ancestor, or otherwise very closely related to humans.

The fossil was named Australopithecus, which means “southern ape.” Since 1924 we’ve discovered more remains, enough that currently, seven species of Australopithecus are recognized. The oldest dates to a bit over 4 million years old and was discovered in eastern Africa.

Australopithecus was probably pretty short compared to most modern humans, although they were probably about the size of modern chimpanzees. A big male might have stood about 4 ½ feet tall, or 1.5 meters. They were bipedal, meaning they would have stood and walked upright all the time. That’s the biggest hint that they were closely related to humans. Other great apes can walk upright if they want, but only humans and our closest ancestors are fully bipedal.

In 2008 a palaeoanthropologist named Lee Rogers Berger took his nine-year-old son Matthew to Malapa Cave in South Africa. Dr. Berger was leading an excavation of the cave and Matthew wanted to see it. While he was there, Matthew noticed something that even his father had overlooked. It turned out to be a collarbone belonging to an Australopithecus boy who lived almost 2 million years ago. Later, Dr Berger’s team uncovered more of the skeleton and determined that the remains belonged to a new species of Australopithecus, which they named Australopithecus sediba. More remains of this species were discovered later, including a beautifully preserved lower back. That discovery was important because it allowed scientists to determine that this species of Australopithecus had already evolved the inward curve in the lower back that humans still have, which helps us walk on two legs more easily. That was a surprise, since A. sediba also still shows features that indicate they could still climb trees like a great ape.

It’s possible that Australopithecus, along with other species of early humans, climbed trees at night to stay safe from predators. In the morning, they climbed down to spend the day mostly on the ground. One study published only a few weeks ago as this episode goes live suggests that the flexible shoulders and elbows that humans share with our great ape cousins originally evolved to help apes climb down from trees safely. Monkeys don’t share our flexible shoulder and elbow joints because they’re much lighter weight than a human or ape, and don’t need as much flexibility to keep from falling while climbing down. Apes and hominins like humans can raise our arms straight up over our heads, and we can straighten our arms out completely flat. Australopithecus could do the same. The study suggests that when another human ancestor, Homo erectus, figured out how to use fire, they stopped needing to climb trees so often. They evolved broader shoulders that allowed them to throw spears and other weapons much more accurately.

Australopithecus probably mostly ate fruit and other plant materials like vegetables and nuts, along with small animals that they could catch fairly easily. This is similar to the diet of many great apes today. The big controversy, though, is whether Australopithecus made and used tools. Their hands would have been more like the hands of a bonobo or chimpanzee, which have a lot of dexterity, but not the really high-level dexterity of modern humans and our closest ancestors. Stone tools have been found in the same areas where Australopithecus fossils have been found, but we don’t have any definitive proof that they made or used the tools. There were other early hominins living in the area who might have made the tools instead.

We also don’t really know what Australopithecus looked like. Some scientists think they had a lot of body hair that would have made them look more like apes than early humans, while some scientists think they had already started losing a lot of body hair and would have looked more human-like as a result.

There’s no question these days that Australopithecus was an early human ancestor. We don’t have very many remains, but we do have several skulls and some nearly complete skeletons, which tells us a lot about how our distant ancestor lived. But we know a lot less about a fossil ape that lived as recently as 350,000 years ago, and it’s become confused with modern stories of Bigfoot.

Gigantopithecus first appears in the fossil record about 2 million years ago. It lived in what is now southern China, although it was probably also present in other parts of Asia. It was first discovered in 1935 when an anthropologist identified two teeth as belonging to an unknown species of ape, and since then scientists have found over a thousand teeth and four jawbones, more properly called mandibles.

The problem is that we don’t have any other Gigantopithecus bones. We don’t have a skull or any parts of the body. All we have are a few mandibles and lots and lots of teeth. The reason we have so many teeth is because Gigantopithecus had massive molars, the biggest of any known species of ape, with a protective layer of enamel that was as much as 6 mm thick. Some of the teeth were almost an inch across, or 22 mm. A lot of the remaining bones were probably eaten by porcupines, and in fact the mandibles discovered show evidence of being gnawed on. This sounds bizarre, but porcupines are well-known to eat old bones along with the shed antlers of deer, which supplies them with important nutrients. The teeth were too hard for the porcupines to eat.

We know that Gigantopithecus was a big ape just from the size of its mandible, but without any other bones we can only guess at how big it really was. It was potentially much bigger and taller than even the biggest gorilla, but maybe it had a great big jaw but short legs and it just sat around and ate plants all the time. We just don’t know.

What we do know is that its massive jaw and teeth were adapted for eating fibrous plant material, not meat. The thick enamel would help protect the teeth from grit and dirt, which suggested it ate tubers and roots that would have had a lot of dirt on them, although its diet was probably more varied. Scientists have even discovered traces of seeds from fruits belonging to the fig family stuck in some of the fossilized teeth, and evidence of tooth cavities that would have resulted from eating a lot of fruit long before toothpaste was invented.

Many scientists thought at first that Gigantopithecus was a human ancestor, but one that grew to gigantic size. It was even thought to be a close relation to Australopithecus. Other scientists argued that Gigantopithecus was more closely related to modern great apes like the orangutan. The debate on where Gigantopithecus should be classified in the ape and human family tree happened to overlap with another debate about a giant ape-like creature, the Yeti of Asia and the Bigfoot of North America.

We talked about the Yeti way back in episode 35, our very first monster month episode in 2017. Expeditions by European explorers to summit Mount Everest, which is on the border between China and Nepal, started in 1921. That first expedition found tracks in the snow resembling a bare human foot at an elevation of 20,000 feet, or 6,100 meters. They realized the tracks were probably made by wolves, with the front and rear tracks overlapping, which only looked human-like after the snow melted enough to obscure the paw pads. Expedition leader Charles Howard-Bury wrote in a London Times article that the expedition’s Sherpa guides claimed the tracks were made by a wild hairy man, but he also made it clear that this was just a superstition. But journalists loved the idea of a mysterious wild man living on Mount Everest. One journalist in particular, Henry Newman, interviewed the guides and specifically asked them about the creature. He wrote a sensational account of the wild man, but he mistranslated their term for it as the abominable snowman.

The word Yeti comes from a Sherpa term yeh-teh, meaning “animal of rocky places,” although it may be related to the term meh-teh, which means man-bear. But the peoples who live in and around the Himalayas belong to different cultures and speak a lot of different languages. There are lots of stories about the hairy wild man of the mountains, and lots of different words to describe the creature of those stories. And the idea of the Yeti that has become popular in Europe and North America doesn’t match up with the local stories. Locals describe the Yeti as brown, black, or even reddish in color, not white, and it doesn’t always have human-like characteristics. Sometimes it’s described as bear-like, panther-like, or just a general monster.

The abominable snowman, or Yeti, became popular in newspaper articles after the 1921 Mount Everest expedition, and it continued to be a topic of interest as expeditions kept attempting to summit the mountain. It wasn’t until May 26, 1953 that the first humans reached the tippy-top of Mount Everest, the New Zealand explorer Edmund Hillary and the Nepali Sherpa climber Tenzing Norgay. Many other successful expeditions followed, including some that were mounted specifically to search for the Yeti.

In the meantime, across the planet in North America, a Canadian schoolteacher and government agent named John W. Burns was collecting reports of hairy wild men and giants from the native peoples in British Columbia. He’s the one who coined the term Sasquatch in 1929. In the 1930s, a man in Washington state in the U.S, which is close to British Columbia, Canada, carved some giant feet out of wood and made tracks with them in a national forest to scare people, leading to a whole spate of big human-like tracks being faked in California and other places. But it wasn’t until 1982 that the hoaxes started to be revealed as the perpetrators got old and decided to clear up the mystery.

But in the 1920s and later, the popularity of the abominable snowman in popular media, giant gorillas like King Kong in the movies, the Yeti expeditions in the Himalayas, the mysterious giant footprints on the west coast of North America, and John Burns’s articles about the Sasquatch all combined to make Bigfoot, a catchall term for any giant human-like monster, a modern legend. People who believed that Bigfoot was a real creature started looking for evidence of its existence beyond footprints and reports of sightings. In 1960, a zoologist writing about a photograph of supposed Yeti tracks taken in 1951 suggested that the Yeti might be related to Gigantopithecus.

On the surface this actually makes sense. The Yeti, AKA the abominable snowman, is reported in the Himalayan Mountains of Asia. The mountain range started forming 40 to 50 million years ago when the Indian tectonic plate crashed into the Eurasian plate very slowly, pushing its way under the Eurasian plate and scrunching the land up into massively huge mountains. It’s still moving, by the way, and the Himalayas get about 5 mm taller every year. The eastern section of the Himalayas isn’t that far from where Gigantopithecus remains have been found in China, and we also know that at many times in the earth’s recent past, eastern Asia and western North America were connected by the land bridge Beringia. Humans and many animals crossed Beringia to reach North America, so why not Gigantopithecus or its descendants? That would explain why Bigfoot is so big, since in 1957 one scientist estimated that Gigantopithecus might have stood up to 12 feet tall, or 3.7 meters.

Some people still think Gigantopithecus was a cousin of Australopithecus, that it walked upright but was huge, and that its descendants are still around today, hiding in remote areas and only glimpsed occasionally. But people who believe such an idea are stuck in the past, because in the last 60 years we’ve learned a whole lot more about Gigantopithecus.

These days, more sophisticated study of Gigantopithecus fossils have allowed scientists to classify it as a great ape ancestor, not an early human. Gigantopithecus was probably most closely related to modern orangutans, in fact, and may have shared a lot of traits with orangutans. It probably could walk upright if it wanted to, but it wasn’t fully bipedal the way humans and human ancestors are. One theory prevalent in 2017 when we talked about the Yeti before was that Gigantopithecus mostly ate bamboo and might have gone extinct when the giant panda started competing with its food sources. This theory has already fallen out of favor, though, and we know that Gigantopithecus was eating a much more varied diet than just bamboo.

We also know that Gigantopithecus lived in tropical broadleaf forests common throughout southern Asia at the time. About a million years ago, though, many of these forests became grasslands. Gigantopithecus probably went extinct as a direct result of its forest home vanishing. It just couldn’t find enough food and shelter on open grasslands, and even though it held on for hundreds of thousands of years, by about 350,000 years ago it had gone extinct. Around 100,000 years ago the forests started reclaiming much of these grasslands, but by then it was too late for Gigantopithecus. Meanwhile, the oldest evidence we have of the land bridge Beringia joining Asia and North America was 70,000 years ago.

There is no evidence that any Gigantopithecus descendant survived to populate the Himalayas or migrated into North America. For that matter, there’s no evidence that Bigfoot actually exists. If a live or dead Bigfoot is discovered and studied by scientists, that would definitely change a lot of things, and would be really, really exciting. But even if that happened, I’m pretty sure we’d find that Bigfoot wasn’t related to Gigantopithecus. Whether it would be related to Australopithecus and us humans is another thing, and that would be pretty awesome. But first, we have to find evidence that isn’t just some footprints in the mud or snow.

Some Bigfoot enthusiasts suggest that the reason we haven’t found any Bigfoot remains is the same reason why we don’t have Gigantopithecus bones, because porcupines eat them. But while porcupines do eat old dry bones they find, they don’t eat fresh bones and they don’t eat all the bones they find. For any bone to fossilize is rare, so the more bones that are around, the more likely that one or more of them will end up preserved as fossils. Bones of modern animals are much easier to find, porcupines or no, but we don’t have any Bigfoot bones. We don’t even have any Bigfoot teeth, which porcupines don’t eat.

Porcupines can be blamed for a lot of things, like chewing on people’s cars and houses, but you can’t blame them for eating up all the evidence for Bigfoot.

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 198: Pop Goes the Mustelid

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Let’s learn about a whole lot of mustelids, including some otters, weasels, and their relations and ancestors! Thanks to Jacob for the suggestion!

Further reading:

Weasels in Stone: Mustelid Evolution

With voices joined in chorus, giant otter families create a distinct sound signature

Further watching/listening:

Video of giant river otters making noise

Giant river otters:

The least weasel is possibly the most cute:

This mink would like to keep its fur for itself please and thank you:

The Patagonian weasel:

The greater grison looks like a badger and a honey badger:

The fisher:

The Chinese ferret badger has a long nose compared to most mustelids:

Show transcript:

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

This week we’ll learn about some mustelids, better known as weasels and their close relations! Thanks to Jacob for this week’s suggestion.

The weasel is a member of the family Mustelidae. Members of the family are called mustelids, which includes wolverines and badgers, which we talked about in episode 62, otters, which we talked about in episode 37, and ferrets, which we talked about in episode 150. Most mustelids have short legs and long, slender, flexible bodies, although badgers are an exception since they’re broad-bodied. This body shape allows a mustelid to enter the burrows of other animals and kill them, because mustelids are carnivores.

But not all animals that look like weasels and ferrets are actually mustelids. The mongoose, for instance, is not a mustelid.

The study of how mustelids evolved and spread throughout much of the world is a pretty hot topic these days, which makes it confusing to summarize since so much new knowledge keeps shaking up what we know. But I’ll do my best.

The first mustelids evolved around 30 million years ago in what is now Eurasia, and spread to North America much later and eventually into South America. The oldest mustelid fossils found in North America are a group of animals called oligobunines. I read that word as oligobunnies every single time, but they didn’t look like bunnies. They probably looked like wolverines, which are related to badgers but look more like miniature bears with longer tails, but they probably spent more time underground than wolverines do.

At least one oligobunid might have grown as big as a black bear, at least a small bear. Megalictis was probably an ambush predator and lived around 21 million years ago in what is now the upper Midwest of North America. It had teeth meant for crushing bones. Another oligobunid, Zodiolestes, is one we talked about briefly in episode 103, about trace fossils. The first fossil Zodiolestes was found in a corkscrew-shaped Palaeocastor burrow, presumably because it got stuck in the burrow while it was hunting, but Zodiolestes was also adapted to dig. The oligobunids went extinct around 10 million years ago, possibly outcompeted by a new wave of modern mustelids that evolved in Asia and spread into North America.

One mustelid, Ekorus ekakeran, lived about six million years ago in what is now Africa, with fossils found in Kenya. But it didn’t look like any other mustelid. It had long legs, for one thing. It stood almost two feet tall at the shoulder, or 60 cm, and was built more like a leopard than a mustelid. It would have been a much faster runner than other mustelids as a result, although it was probably an ambush predator. Researchers think it was eventually outcompeted by big cats when they evolved as the forests changed into grasslands.

The biggest mustelid that ever lived, as far as we know, is Enhydriodon, a type of gigantic otter. It lived in Africa around 4 million years ago and may have been the size of a small bear, even bigger and heavier than Megalictis. We only have a single fossil of Enhydriodon, though, a skull, so scientists can only estimate the animal’s size compared to what we know about extinct and living otters. It probably lived on land, although that’s about as far as our knowledge of it goes.

Another giant mustelid was Plesiogulo, which evolved in Asia and crossed into North America 6 1/2 or 7 million years ago when the continents were connected by the Bering land bridge. Researchers weren’t sure for a long time if Plesiogulo was directly ancestral to living wolverines, but recent studies indicate that it probably was. It was larger than modern wolverines.

But what about living mustelids? The biggest known mustelid that’s still alive is the giant otter, which lives in much of northern and central South America, especially around the Amazon River, although it’s increasingly rare due to habitat loss, hunting for its fur, and pollution. It can grow up to 5 1/2 feet long, or 1.7 meters. It mostly eats fish but will eat other animals too, including crabs, snakes, turtles, and even small caimans. It’s a social animal that lives in family groups of up to twenty members that hunt and play together. It has short dense fur that’s usually brown or sometimes reddish, but it has white markings on its throat and upper chest. When it pops its head and neck out of the water, called periscoping, other otters can see its unique white markings and recognize who they’re looking at. It’s also really noisy as it communicates with other otters with barks, whines, growls, and softer sounds like humming. Each family group has a unique vocalization that identifies the group to other otters, and if a strange otter approaches the territory the whole family will scream at it to get out or else.

The sea otter is a little shorter than the giant otter, just under 5 feet long, or 1.5 meters, but it’s heavier than the giant otter. A big male can weight up to 119 pounds, or 54 kg. It lives along the coast of the North Pacific and while it can walk, it spends almost all its time in the water. Instead of blubber to keep it warm, the sea otter has incredibly dense fur, the densest coat ever measured. For almost two centuries people hunted it so aggressively for its fur that by 1911, there were fewer than 2,000 of them left. Fortunately, conservationists worked to get an international ban on sea otter hunting, and its numbers have rebounded although it’s still endangered.

The sea otter eats fish and anything else it can catch, especially shellfish, and it uses its front paws while hunting. It catches fish with its paws instead of with its mouth, it turns over rocks to look underneath them, and it pulls mollusks off of rocks and twists them open with its paws. This is all really unusual. No other otter uses its paws in this way. Not only that, the sea otter is a tool-user. It uses rocks to break open shellfish that it can’t twist open or bite through, and will in fact use two rocks at once for this purpose. One of the rocks it holds, but the other it keeps in a little pouch of skin under its arms to act as a hard surface to set the mollusk on. The sea otter also uses this built-in pocket to hold food. It has two pockets, one under each front leg, and it usually keeps its rock in the right pocket while it keeps its food in the left pocket. It floats on its back to eat, then rolls over and over in the water to clean its fur of any bits of food. It has to keep its fur incredibly clean for it to insulate the otter properly, so it grooms itself throughout the day. Pascal in Animal Crossing is a sea otter, by the way, and adorable.

The smallest living mustelid is the least weasel, which is native to northern North America and much of Eurasia but has been introduced in New Zealand and several islands throughout the world, where it’s an invasive species. The smallest subspecies of least weasel grow less than 10 inches long, or 26 cm, with a short tail. It’s brown with a white belly during the summer but its winter coat is completely white. It eats mice, voles, and other small rodents and will even kill rabbits although rabbits are much bigger than it is. Generally it only attacks young rabbits, though.

So that gives us some background about mustelids. Let’s talk about some interesting kinds of mustelid next, starting with the mink. You may have heard something about the mink in the news lately, because mink are kept in large numbers in fur farms and they’ve started to contract a mutated version of the Covid-19 virus. The virus is so widespread among mink in the country of Denmark that as of last week as this episode goes live, Denmark has decided to kill every single mink in captivity. That’s as many as 19 million animals. Keep in mind that these animals were eventually going to be killed anyway for their fur. That doesn’t make it any less sad, though. The same mutated virus has spread through fur farms in other countries, including Spain and the United States, leading to thousands of animals being killed to stop the spread. So far studies do not indicate that the minks are spreading the mutated version of the virus to humans. The Netherlands had already been planning to ban mink farming in a few years, but after an outbreak of the coronavirus earlier in 2020 the country decided to ban it by the end of this year. Good for them.

In the wild, where it belongs, the mink lives near rivers, lakes, or other sources of fresh water, and sometimes even along the coast. It eats fish, rabbits and other small mammals, eggs, small crustaceans like crayfish, and anything else it can catch. A big male can grow up to two feet long, or 62 cm, and it’s brown in color with a dense undercoat that helps keep it warm in cold weather. There’s a species that lives in North America and a species that lives in Europe, but while they look almost identical, they’re actually not very closely related.

If you think of weasels, you probably think of an animal that looks a lot like the mink or the ferret, with sleek fur. But the Patagonian weasel is quite different in many ways. It lives in Patagonia, which is the southern part of South America, and is the only member of its own genus. Its coat is shaggy with a bushy tail. It’s mostly white or off-white with brown patches and grows up to 14 inches long not counting its short tail, or 35 cm. We know almost nothing about the Patagonian weasel. We’re not even sure what it eats, except that it does probably eat small burrowing rodents, and it’s sometimes been kept by ranchers to kill rats the way ferrets were once used in England.

The greater grison is another unusual-looking mustelid native to Central America and northern South America. It’s shaped sort of like an otter but instead of brown fur it’s gray on top and black underneath. A white stripe separates the gray and black fur on its head and the sides of its neck. Most of its face is black, then the white stripe usually just above the eyes, then gray on top of its head. It can grow up to two feet long, or 60 cm, not counting its bushy tail, which can grow up to 14 inches long, or 20 cm. Like all mustelids, its ears are small and round and its body is long with short legs. Although it looks like an otter, including having webbed toes, it’s probably more closely related to the Patagonian weasel, and like the Patagonian weasel, we don’t know a whole lot about it.

The fisher is a mustelid that lives in North America, mostly in parts of Canada and in mountainous areas of northern and western United States. It used to be more widespread, but, you guessed it, it was trapped and killed for its fur until the 1930s and even as late as the 1980s in some areas.

Despite its name, the fisher doesn’t actually eat fish very often. The name fisher comes from a Dutch word, visse, which refers to a different mustelid, the European polecat. The fisher is also sometimes called the fisher cat even though it and the polecat are not cats. It’s a big animal, too. A big male fisher can grow nearly four feet long, or 1.22 m, although females are much smaller, and part of that length is the tail that can be as much as 16 inches long, or 41 cm.

The fisher has big feet that helps it walk on snow, retractable claws, and it can even rotate its hind feet nearly completely backwards, which means it can climb down trees headfirst. It lives in forests and spends a lot of time in trees, hunting birds and other small animals, but it mostly eats showshoe hares and porcupines. Yes, porcupines! Almost nothing will bother a porcupine, but the fisher will attack it from the front, biting its less protected face repeatedly until it dies. In areas where fishers were hunted to extinction, porcupines became so numerous that they started killing trees, since in winter porcupines eat tree bark and will also eat sapling trees. Fortunately, the population of fishers has grown and conservationists have reintroduced it into parts of its former range. It’s no longer considered endangered, hurrah! This is good because they’re hard to keep in captivity and they’re also susceptible to accidental poisoning when they eat rodents that have died from eating poison.

The fisher is supposed to be a loud animal with a terrifying scream at night, but people who study fishers don’t report hearing them scream or make loud sounds at all. The calls are all probably made by the red fox, which sounds like this:

[fox sound]

There are so many mustelids that I don’t even know what other ones to feature. It’s surprising how little we know about so many of them. The Vietnam ferret-badger was only described in 2011, for instance, and only known from two specimens. It’s related to other ferret-badgers found in Asia, including the Chinese ferret-badger. As you might guess from the name, it looks sort of like a badger but also like a ferret, which is a neat trick because those two animals do not actually look very much alike. It grows around 17 inches long, or 43 cm, plus another 9 inches, or 23 cm, for its tail. It’s dark brown above and lighter brown underneath, with a white stripe on its head and neck and a black mask on its face. Its muzzle is longer than most mustelids’, who usually have quite short noses. It’s an omnivore that eats fruit as well as insects, worms, frogs, and other small animals.

In general, as I’ve mentioned over and over, mustelids have historically been killed for their fur. Sable and ermine are both names of furs that come from mustelids. At least one species was driven to extinction by fur hunters, the sea mink. It lived along the northeastern coast of North America and was related to the American mink. We don’t even know exactly how big it was, because it was driven to extinction before it could be examined by scientists, except that it was probably bigger than the American mink. We don’t even have a complete specimen, just some skull fragments and teeth. It wasn’t as aquatic as otters are, but it occupied a similar ecological niche and spent much more time in the water than its close relations. It probably went extinct in the late 19th century. Other species of mustelid may have been driven to extinction without ever being known to science too. Certainly many species came close to extinction and are still threatened by habitat loss and other factors.

That’s depressing to think about, so let’s finish with a mystery that’s a little different from our usual mystery animals. This one’s a mystery song called “Pop Goes the Weasel.” You’re probably familiar with the tune even if you’re not sure about the words. There are lots of different lyrics to the song with various versions in different places. I learned it this way:

Round and round the mulberry bush / The monkey chased the weasel / The monkey stopped to pull up his socks / Pop! Goes the weasel.

A penny for a spool of thread / A penny for a needle / That’s the way the money goes / Pop! Goes the weasel.

What on earth do those lyrics mean? Do they mean anything? Why is there a weasel in the song?

The earliest lyrics known date back to at least the early 19th century in England, because the oldest versions of the song reference a famous pub in London from the time. The melody was probably much older and the words were fitted to the song at some point. By 1850 it was a popular dance, but even then no one knew what the lyrics meant.

There are lots of suggestions, some of which make more sense than others. The oldest lyrics seem to be these:

Half a pound of tuppenny rice / Half a pound of treacle / That’s the way the money goes / Pop! Goes the weasel.

Up and down the City road / In and out the Eagle / That’s the way the money goes / Pop! Goes the weasel.

The line “that’s the way the money goes” basically tells the story. It’s a song about how everything is a penny here, a penny there, and suddenly you’re broke. And if you’re going in the Eagle Tavern on London’s City Road too often, you’re drinking up whatever money you have left. But that still doesn’t explain the weasel.

One explanation is that to pop something was slang for pawning it, and that the term weasel is Cockney rhyming slang for a coat. You know, “weasel and stoat” rhyme with coat, therefore you can just say weasel and everyone who knows the rhyme knows that you’re talking about a coat. So if you pop a weasel, you’re pawning your coat to get a little extra money.

This sounds plausible, and there’s some evidence that the line “pop goes the weasel” was the only line of the song originally, with the other lyrics added later, which would explain why that one line is slang while the other lines aren’t. Anyway, it’s a fun song that you will not be able to get out of your head now.

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Thanks for listening!