Tag Archives: rodents

Episode 312: Little Bouncy Animals



Thanks to Zachary and Oran for this week’s topic, some little animals that bounce around like tiny kangaroos!

Further reading:

Evolution of Kangaroo-Like Jerboas Sheds Light on Limb Development

Supposedly extinct kangaroo rat resurfaces after 30 years

High-Speed Videos Show Kangaroo Rats Using Ninja-Style Kicks to Escape Snakes

Williams’s jerboa [picture by Mohammad Amin Ghaffari – https://www.inaturalist.org/photos/177950563, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=115769436]:

A drawing of a jerboa skeleton. LEGS FOR DAYS:

The San Quintin kangaroo rat lives! [photo from article linked above]

Show transcript:

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

This week we’re going to learn about two cute little animals suggested by Zachary and Oran! Both of these animals are rodents but although they look remarkably alike in some unusual ways, they’re not actually all that closely related.

First, Zachary suggested the jerboa. We talked about the pygmy jerboa in episode 136, but we haven’t talked about jerboas in general. It’s a small rodent that’s native to the deserts of Asia, north Africa, and the Middle East. It’s usually brown or tan with some darker shading on the back and tail. It looks sort of like a gerbil with long ears, long hind legs, and a tuft at the end of the tail. Its front legs are short and it has an adorable whiskery nose.

The reason the jerboa’s hind legs are so long while its front legs are really short is that it jumps around on its hind legs like a kangaroo. Not only can it jump really fast, up to 15 mph, or 24 km/h, it can change directions incredibly fast too. This helps it evade predators, because most animals are fastest when running in a straight line. The jerboa bounces in all sorts of directions, hopping or just running on its long hind legs, with its long tail held out for balance. It can also run on all fours with its short front legs helping it maneuver, but for the most part it’s a bipedal animal. It has tufts of stiff hairs under its toes that help it run through loose sand.

The jerboa eats plants, although sometimes if it finds a nice juicy insect it will eat it too. Mostly it just eats leaves, bulbs, roots, and some seeds. It gets all of the moisture it needs from its diet, which is good because it lives in the desert where there’s not much water available.

Some species of jerboa mainly eat insects and spiders, and some have short ears instead of long ears. This is the case for the thick-tailed pygmy jerboa that lives in parts of China, Mongolia, and Russia. Its head and body only measures about two inches long, or almost 5 cm, but its tail is twice that length. The reason it’s called a thick-tailed jerboa is because it stores fat at the base of its tail, which makes the tail look thick compared to many rodent tails.

The jerboa is mostly active at dawn and dusk, although some species are fully nocturnal. It spends the day in a burrow it digs in sand or dirt. A jerboa will usually have more than one burrow in its territory, with the entrances usually hidden under a bush or some other plant. Different burrows have different purposes. Some have numerous entrances and lots of side tunnels but are relatively shallow, which is useful if the jerboa lives in an area with a rainy season. A shallow burrow won’t flood if it rains a lot. Some burrows are temporary, which the jerboa may dig if it’s out and about during the day looking for food. A mother jerboa will dig a burrow with a roomy nesting chamber to raise her babies, and a jerboa’s winter burrow has a nesting chamber that’s deep underground to help it stay warm. Some species of jerboa construct unusual burrows, like the lesser Egyptian jerboa that has spiral-shaped burrows with storage chambers. Most jerboas are solitary animals, although sometimes a group will hibernate together in winter to help everyone stay warmer.

Scientists have been studying the jerboa to learn how different animals have evolved radically different leg lengths. The jerboa’s incredibly long hind legs are very different from its very short front legs, but it evolved from animals that had four short legs. But jerboas are born with four short legs, and as the babies grow up their hind legs grow longer and longer.

The jerboa is an incredibly efficient runner. Some species can jump as far as six feet in a single bound, or 1.8 meters, and up to three feet, or 90 cm, straight up.

The jerboa isn’t the only rodent that hops on its hind legs like a kangaroo. The kangaroo rat does too, and it’s Oran’s suggestion. Oran pointed out that a long time ago, I think in the humans episode, I said that humans are the only fully bipedal mammal, meaning we only ever walk on our hind legs. (Crawling when you’re a baby or trying to find something under the couch don’t count.) I was wrong about that for sure, because the kangaroo rat, the jerboa, and a few other mammals are also bipedal.

The kangaroo rat is native to parts of western North America. It looks a lot like a jerboa, with long hind legs and a long tail, although its ears are smaller. But the kangaroo rat and the jerboa aren’t closely related, although both are rodents. Their similarities are due to convergent evolution, since both animals live in very similar environments with the same selective pressures.

The largest species of kangaroo rat, the giant kangaroo rat, grows around 6 inches long, or 15 cm, with a tail about 8 inches long, or 20 cm. It can jump even longer than the jerboa although it doesn’t move as fast on average.

Like the jerboa, the kangaroo rat can change directions quickly, and it’s also mostly nocturnal and spends the day in a burrow. Some species spend almost all the time in burrows, only emerging for about an hour a night to gather seeds. Since owls like to eat kangaroo rats, you can’t blame them for wanting to stay underground as much as possible.

Snakes also like to eat kangaroo rats, especially the sidewinder rattlesnake. It’s a fast predator with venom that can easily kill a little kangaroo rat, but the kangaroo rat isn’t helpless. A study published in 2019 filmed interactions in the wild between the desert kangaroo rat and the sidewinder, using high-speed cameras. They had to use high-speed cameras because the snakes can go from completely unmoving to a strike in under 100 milliseconds. That’s less time than it takes you to blink. But the kangaroo rat can react in even less time, as little as 38 milliseconds after the snake starts to move. A lot of time the kangaroo rat will completely leap out of range of the snake, but if it can’t manage that, it will kick the snake with its long hind legs, which are strong enough to knock the snake away. Little fuzzy ninjas.

Unlike the jerboa, the kangaroo rat mostly eats seeds. The jerboa’s teeth aren’t very strong so it can’t bite through hard seeds, but the kangaroo rat’s teeth are just fine with seeds. The kangaroo rat also has cheek pouches, and it will carry lots of seeds home to its burrow. It keeps extra seeds in special burrow chambers called larders.

The kangaroo rat sometimes lives in colonies that can number in the hundreds, but it’s still a mostly solitary animal. It has its own burrow that’s separate from the burrows of other members of its colony, and it doesn’t share food or interact very much with its neighbors. It will communicate with other kangaroo rats by drumming its hind feet on the ground, including warning its neighbors to stay away and alerting them to predators in the area.

The kangaroo rat is vulnerable to habitat loss, since it mostly lives in desert grassland and humans tend to view that kind of land as useless and in need of development. An example of this is the San Quintin kangaroo rat, which is only found in western Baja California in Mexico. Only two large colonies were known when it was discovered by science in 1925, although it used to be much more widespread. But in the decades since 1925, the land was developed for agriculture until by 1986 the two colonies were completely wiped out. Scientists worried the species had gone extinct. Then, in 2017, a colony was discovered in a nature preserve and everyone breathed a sigh of relief. Other colonies have been discovered on farmland that has been abandoned due to drought. Still, the San Quintin kangaroo rat is critically endangered.

The kangaroo rat is actually helpful for the environment. Because it stores seeds underground, and sometimes forgets where it put them, it helps native plants spread. Its burrows help increase soil fertility and the spread of water through the soil. This is similar to the jerboa, which also eats enough insects to help reduce the number of agricultural pests in some areas.

There are also two species of kangaroo mouse, which are closely related to kangaroo rats. They mostly live in the state of Nevada in North America. There are also jumping mice that look like ordinary mice but with long hind legs. It also has cheek pouches. While some jumping mice live in western North America, some live in northeastern North America and Canada and are adapted to cold weather and long winters. One species of jumping mouse lives in the mountains in parts of China. There’s also a larger jumping rodent called the springhare that lives in parts of Africa, and which is about the size of a squirrel or a small rabbit. Like all these other rodents, it’s bipedal and hops on its hind legs like a little kangaroo, using its long tail for balance and to prop itself up when it’s standing. It mostly eats plants but will sometimes eat insects, and it spends most of the day in burrows. There’s also a hopping mouse native to Australia, which is a rodent with long hind legs and a long tail and long ears. It’s not closely related to the jerboa or the kangaroo rat, but it looks a lot like both because of convergent evolution. It mostly eats seeds.

All these animals are rodents, but Australia also has another animal called the kultarr that looks a lot like the kangaroo rat and the jerboa. It’s not a rodent, though. It’s actually a marsupial that’s completely unrelated to rodents although it looks like a rodent. That’s definitely what you call convergent evolution.

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

Thanks for listening!


Episode 301: Hairless Mammals



Thanks to Liesbet for this week’s suggestion, about two mammals that have evolved to be hairless!

Happy birthday this week to Declan and Shannon!

The hairless bat has a doglike face and a doglike tail but (and this is important) it is not a dog [photos from this site]:

The naked mole-rat’s mouth is behind its teeth instead of the usual “my teeth are in my mouth” kind of thing:

Show transcript:

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

This week we have a suggestion from Liesbet, who asked about furless animals. We’re going to learn about two mammals that don’t have fur, and they’re not ones you may be thinking of.

But first, we have two birthday shout-outs! Happy birthday to Declan and Shannon! I hope both your birthdays are so amazing that whatever town you live in finishes off the day by giving you the key to the city. What do you do with the key? I don’t know, but it sounds like something to brag about.

Mammals are famous for having hair, but not all mammals actually have hair. Cetaceans like whales and dolphins have lost all their hair during their evolution into marine animals, although before a baby whale is born it has a little bit of fuzzy hair on its head. Other mammals, like humans, pigs, walruses, and elephants, have evolved to only have a little hair. There are also domesticated mammals that have been bred to have no hair, like sphynx cats and Chinese crested dogs.

There are other domesticated hairless mammals, though, including two types of guinea pig. The skinny pig only has a little bit of fuzzy hair on its face and ears, while the baldwin pig only has a tuft of hair on its nose. But the animals we’re going to talk about today are hairless animals you may not have heard of.

For instance, the hairless bat, which lives in parts of Southeast Asia. Its dark gray body is almost completely hairless, although it does sometimes have little patches of fuzz on the head and tail, and longer bristles around the neck. It’s nocturnal and eats insects, but since it’s a fairly large bat, around 6 inches long, or 15 cm, it can eat fairly large insects. It especially likes grasshoppers, termites, and moths.

The hairless bat roosts in colonies of up to a thousand individuals, and it lives in caves, hollow trees, or rock crevices. Although it uses echolocation, it doesn’t have a nose leaf like many microbats have, but instead has a little doglike snout. Its tail is skinny like a little dog’s tail instead of being connected to the hind legs or body by patagia. It has a little throat pouch that secretes strong-smelling oil.

It also has a sort of pocket on either side of the body. Originally people thought that mother bats used these pouches to carry their babies, since hairless bats usually have two babies at a time. Instead, it turns out that mother bats leave their babies at home when they go out to hunt, and the pockets are used for something else. The pockets are formed by a fold of skin and the end of the wing fingers and membranes fit into them. The bat uses its hind feet to push the wings into the pockets, sort of like stuffing an umbrella into the little cover that it comes in when you first buy it. This allows the bat to run around on all fours without its wings getting in the way. Since most bats can’t walk on all fours at all, this is pretty amazing.

Our other hairless animal today is the naked mole-rat, which is not a mole or a rat. It is a type of rodent but it’s more closely related to porcupines than to rats. It lives in tropical grasslands in parts of East Africa and spends almost its entire life underground. It lives in colonies of up to 300 individuals, and the colony’s tunnels and nesting burrows are extensive, often covering up to 3 miles, or 5 km. It eats roots of plants and the colony carefully only eats part of each root so that they don’t kill the plant. The roots continue to grow, providing the colony with lots of food.

The naked mole-rat grows about 4 inches long, or 10 cm, although dominant females are larger. It has tiny eyes and doesn’t see very well, since most of the time it doesn’t need to see, and it has a chonky body but short, spindly legs. It pretty much has no hair except for whiskers and some tiny hairs between the toes, and its skin is so pale it’s almost translucent. It digs with its protruding front teeth, and these teeth are not in its mouth. They grow out through the skin and the animal’s mouth is actually behind the teeth. This way the mole-rat can dig without getting dirt in its mouth, but it sure looks weird to us.

But that’s not even close to the weirdest thing about the naked mole-rat. We haven’t even scratched the surface of weirdness!

The naked mole-rat lives underground in a part of the world where it’s always warm, and its tunnel system has no exits to the surface except for temporary exits when new tunnels are being excavated, because the dirt has to go somewhere. Its environment is so consistent in temperature that it doesn’t need to regulate its body temperature like every other mammal known. It’s ectothermic, which is sometimes called cold-blooded. Reptiles and amphibians are ectothermic but all other mammals known are endothermic. It’s kind of our thing. But the naked mole-rat is different. Its metabolism is extremely low, and as a result it can live for more than 30 years when most rodents the same size are lucky to live 2 or 3 years.

The naked mole-rat’s skin isn’t just hairless, it also lacks neurotransmitters. This means its skin doesn’t feel pain. The animal also lives in an environment that’s remarkably low in oxygen, and scientists think this contributes to the fact that the mole-rat never shows evidence of cancer except in captivity where its environment is higher in oxygen.

The naked mole-rat’s colony is led by a dominant female, called a queen, and she’s the only female in the colony that has babies. When a female achieves dominance, either by founding a new colony, taking over after the current queen dies, or defeating the current queen in a fight, she then grows larger and becomes able to reproduce. Only a few males in the colony mate with her. All the other members of the colony are unable to reproduce. They’re considered workers and help take care of the queen’s babies, maintain tunnels, forage for food, or act as soldiers to keep snakes and other predators out. If this sounds like the way some insect colonies are structured, especially bees and ants, you’re right. It’s called eusociality and the mole-rat is the only type of mammal known with this sort of social structure. There’s another type of mole-rat from southern Africa that’s also eusocial, but it has fur.

All that is so weird that I almost forgot the mole-rat is hairless. That now seems like the most normal thing about it.

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

Thanks for listening!


Episode 268: Rediscovered Animals!



My little cat Gracie got lost but she’s home! Let’s learn about some other rediscovered animals this week!

A very happy birthday to Seamus! I hope you have the best birthday ever!

Further listening:

The Casual Birder Podcast (where you can hear me talk about birding in Belize!)

Further reading:

Bornean Rajah Scops Owl Rediscovered After 125 Years

Shock find brings extinct mouse back from the dead

Rediscovery of the ‘extinct’ Pinatubo volcano mouse

Gracie, home at last! She’s so SKINNY after a whole week being lost but she’s eating lots now:

The Bornean Rajah scops owl (photo from article linked above):

The djoongari is the same as the supposedly extinct Gould’s mouse (photo from article linked above):

The Pinatubo volcano mouse:

Show transcript:

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

While I was researching animals discovered in 2021, I came across some rediscoveries. I thought that would make a fun episode, so here are three animals that were thought to be extinct but were found again!

A couple of quick things before we get started, though.

First, happy birthday to Seamus! I hope you have a brilliant birthday and that it involves family, friends, or at least your favorite kind of cake, but hopefully all three.

Next, a few weeks ago I appeared on the Casual Birder Podcast talking in depth about my trip to Belize and some of the birds I saw there. I’ll put a link in the show notes. It’s a great podcast that I really recommend if you’re interested in birding at all, and the host has such a lovely calming voice I also recommend it if you just like to have a pleasant voice in the background while you do other stuff.

Finally, thanks for the well wishes from last week, when I let our emergency episode run. I’m actually fine, but my little cat Gracie got frightened while I was bringing her into the house from a vet visit, and she ran away. That was on Friday, March 11 and I spent all night looking for her, but then we had a late-season snowstorm come through and dump six inches of snow on my town, which made me even more frantic. At dawn on Saturday I put on my boots and heavy coat and spent all day searching for Gracie, and on Sunday I was still searching for her. I didn’t have time to work on a new episode. In fact, I searched every day as much as possible all week long, until I was certain she was gone forever. I couldn’t bring myself to work on this episode because rediscovered animals just seemed like a cruel joke when my little cat was gone. I was almost done with a different episode when on Saturday night, March 19, 2022, eight full days after Gracie had disappeared, I got a phone call. Someone had seen a little gray cat under their shed, over half a mile from my house! I rushed over and THERE WAS GRACIE! I found her! She is home!

So I’ve been researching rediscovered animals with Gracie purring in my lap, in between her going to her bowl to eat. She’s lost a lot of weight but other than that she seems healthy, and she’s very happy to be home.

The person who found Gracie first noticed her around their birdfeeder, so we’ll start with a rediscovered bird.

There are two subspecies of Rajah scops owl that are only found on two islands in southeast Asia, Borneo and Sumatra. The subspecies that lives in Sumatra is fairly common throughout the mountains on that island, where it lives in the lower branches of trees in higher elevations. It’s a tiny owl that only weighs about 4 ounces, or 100 grams. As the article I link to in the show notes points out, that’s about the weight of four AA batteries.

The subspecies that lives on Borneo, though, was always much rarer and had a much smaller range. In fact, no one had seen one since 1892 and researchers thought it was probably extinct. There’s another owl that lives in the mountains of Borneo, the mountain scops owl, that’s fairly common.

In May of 2016, a team of scientists started a 10-year study of birds that lived on Mount Kinabalu in the country of Malaysia in northern Borneo. One team member, Keegan Tranquillo, was checking bird nests that very same month and noticed an owl that didn’t look like the mountain scops owl. It was larger and its plumage was different.

Tranquillo contacted ecologist and bird expert Andy Boyce, who came out to take a look. When he saw the owl, Boyce was excited at first but then filled with anxiety. He knew the owl must be incredibly rare and would be in great danger of going extinct if conservation efforts weren’t put into place. Many areas of Borneo are under pressure from logging, mining, and palm oil plantations, which is leading to habitat loss all over the island.

Not only that, the more Boyce looked at the owl, the more he noticed differences from the Sumatran subspecies of Rajah scops owl. He suspected it might not be a subspecies but a completely separate species. That made it even more important to protect the owl and study it.

The owl’s rediscovery was announced in May 2021. Studies of the owl are ongoing but hopefully will soon result in more information about it and its habitat.

Next, let’s talk about a rodent, since Gracie likes to play with toy mice. This rediscovery came from Australia, where a study of extinct Australian rodents and their living relations found something surprising. It’s the opposite of the owl we just talked about, that might end up being a separate species of its own.

The mouse in question was once called Gould’s mouse. It used to be common throughout Australia, where it’s a native mammal, but it was declared extinct in 1990 after no one had seen it since the 1840s. Researchers suspected it had gone extinct after colonizers brought cats to Australia, although diseases and competition from introduced species of mice and rats also had a big impact.

Meanwhile, another native mouse, called the djoongari or Shark Bay mouse, was driven nearly to extinction. Fortunately, the djoongari survived on a few islands off western Australia. Conservation efforts in 2003 introduced it to more islands, where it spread and did well. It’s a social mouse that lives in family groups in a burrow it digs under bushes. It lines the burrow with dry grass to make it warmer and more comfortable.

The djoongari is a large mouse, up to 4.5 inches long not counting the tail, or 11.5 centimeters. The tail is a little longer than the head and body combined. It has long, shaggy fur that’s a mixture of dark and light brown with a paler belly and feet, and it has a tuft of dark fur at the end of its tail like a tiny lion.

In early 2021, the researchers studying native rodent DNA realized that the living djoongari and the extinct Gould’s mouse had the exact same genetic profile! They were the same animal! That means Gould’s mouse didn’t go extinct, although technically it didn’t exist in the first place.

That doesn’t mean the djoongari is perfectly safe, of course. Its range is still extremely restricted and it’s vulnerable to the same factors that nearly drove it to extinction in the first place. But at least it’s still around and can be protected.

We’ll finish with another mouse. In 1991, a volcano in the Philippines erupted. The volcano was called Mount Pinatubo on the island of Luzon, and the eruption was enormous. It was ten times stronger than the eruption of Mount St. Helens in 1980. Lava and ash filled valleys up to 600 feet deep, or 183 meters. More than 800 people died from the eruption itself and the devastation afterwards, during landslides caused by all the ash every time it rained.

In addition to the awful situation for people, animals were affected too. Most of the forests near the volcano were completely destroyed. Scientists thought the Pinatubo volcano mouse had probably gone extinct since it only lived on that one volcanic mountain, which had just blown up. Surveys of the area a few years after the eruption didn’t turn up signs of any of the mice.

The Pinatubo volcano mouse was only described in 1962 from a single specimen collected in 1956. It was a large mouse, almost the size of a rat, with long hind legs for jumping and climbing and a tail much longer than the length of its head and body together. It mostly ate earthworms and other small animals, but not a lot was known about it.

More than 20 years after the eruption, a team of scientists surveyed the animals living on the mountain. The conditions were difficult for the team to navigate, since there was still a lot of ash and erosion in the area that made the steep slopes unstable. The lush forests were gone, replaced by grass and bamboo, shrubs, a few trees, and other plants. They didn’t expect to find a lot of animals, although they thought they’d find introduced species of rats and mice that had moved into the disturbed areas from other parts of the island.

But to their surprise, they found 17 species of mammal on the mountain. Eight were bats, there were wild pigs and deer, and the rest were rodents. And the rodents were mostly native species, not introduced ones—including the Pinatubo volcano mouse!

Researchers theorize that a mouse that lives on an active volcano as its only habitat must have evolved to weather occasional eruptions. The mice were actually most numerous in the places that had been the most destroyed. The term for a species that thrives in environments that have seen widespread natural destruction is “disturbance specialist,” and that’s just what these mice are.

It just goes to show that no matter how bad things may be, there is life. And where there’s life, there’s hope. And probably mice.

Now, if you will excuse me, I have to go make a chocolate cake to take to the person who found Gracie.

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

Thanks for listening!


Episode 157: Rodents of Unusual Size



Uh, yeah, not the legless lizard episode. But just as interesting! This week let’s learn about the largest rodents in the world! Hint: way bigger than a rat.

Further reading:

Rodents of Uncertain Systematics

The mellow and photogenic capybara:

Oh to be a capybara in an open bath with an orange on its head:

Hey, pacarana:

Oh to be a paca with half an orange:

Oh to be a chevrotain with a piece of orange. (The chevrotain is not a rodent. It has hooves. Episode 116 explains this creature):

Show transcript:

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

Yes, I know, last week I said we might have an episode this week about legless lizards and other snakey things that aren’t snakes, but I got this episode ready first so instead, this week we’re going to learn about some rodents of unusual size!

Rodents are mammals in the order Rodentia, and there are thousands of them throughout the world. Mice and rats are rodents, of course, but so are chipmunks and squirrels, hamsters and gerbils, prairie dogs and guinea pigs, and many others. But you may notice that all the animals I just mentioned are pretty small. That’s because most rodents are on the small side. But not all of them.

The biggest rodent alive today may be one you’ve heard of, the capybara. It’s native to much of South America and lives in forests, rainforests, and other areas, but always near water. It really likes water and eats a lot of aquatic plants, although it also eats grass, fruit, tree bark, and other plants. Like other rodents, its teeth grow throughout its life but constantly wear down as it eats tough plants.

So how big is the capybara? It grows to about two feet tall, or 62 cm, and four feet long, or 1.3 meters. Females are usually a little larger than males. Basically they’re the size of a big dog, but a big dog with webbed toes, small ears, big blunt muzzle, basically no tail, and a calm outlook on life. Because unlike many rodents who tend to be nervous and quick-moving, the capybara is pretty chill.

The capybara is semiaquatic and likes to hang out in the water, often in social groups. It can hold its breath underwater for up to five minutes, and can even sleep while submerged with just its nose above water. That’s why its nose, eyes, and ears are close to the top of its head, so it can be alert to predators while remaining safely underwater.

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. If the female is a member of a group of capybaras, all the babies stay together in the middle of the group and all the females care for them. In most mammals, the female will only let her own babies drink her milk, but a female capybara will suckle any babies in the group who are hungry. Like I said, they’re pretty chill.

There are actually two species of capybara, but some people consider the lesser capybara to be a subspecies of capybara and anyway, we don’t know much about it. Other than that, though, the capybara is most closely related to the guinea pig. Like the guinea pig and like humans, the capybara can’t synthesize vitamin C in its body and has to get it through its diet. That means if a capybara in captivity doesn’t receive fruit and other plant material containing vitamin C, eventually it will show symptoms of scurvy.

The capybara is killed for its meat and hide, but it’s also sometimes kept as a pet. It’s not a domesticated animal and it’s as heavy as a full-grown human, so while the capybara isn’t specifically dangerous it’s not really a good pet. Also, it will eat your garden and wallow in mud and if you don’t have a pool it’s going to wander around until it finds one. It’s probably better to get a dog.

While the capybara is a strong swimmer, it can move fast on land when it wants to. It can run up to 22 miles per hour, or 35 km/hour. This is what a capybara sounds like.

[capybara sounds]

Big as the capybara is, even bigger rodents used to live in South America. Around 8 million years ago a rodent called Phoberomys pattersoni [foe-barommis] lived in what is now Venezuela and nearby areas, especially around the Orinoco River. It was discovered in 2000 when an almost complete skeleton was found, and it was really big. We’re talking nine feet long, or 2.75 meters, and that doesn’t even include its tail. It stood over four feet tall, or 1.3 meters. It was described in 2003 and is a relative of guinea pig and the capybara.

But since then, paleontologists have found fossils of rodents that are estimated to be even bigger. Around 3 million years ago an animal called the giant pacarana grew to an estimated five feet tall, or 1.5 meters, with a body ten feet long, or 3 m. But we don’t know for sure if it was bigger or smaller than that estimate, since so far all we have is a fossilized skull discovered in 1987 and described in 2008. Another closely related rodent is only known from some teeth. Some researchers think it used its massive teeth like elephants use their tusks, to fend off predators and fight each other.

So if there was once a giant pacarana, what’s a regular pacarana? It’s another South American rodent, and while it’s not exactly capybara size it’s much larger than a mouse. It grows more than 3 ½ feet long, or 100 cm, and is shaped sort of like a capybara with a tail, although its head is more rodent-like. It’s dark brown-gray with rows of white spots down its sides and a thick tail covered with fur. It’s the only living member of the family Dinomyidae and it has many unusual features compared to other rodents. I’d tell you what they are but they’re all things like “it has a flatter sternum,” which wouldn’t mean a whole lot to most of us. Shout-out to any rodent experts listening, though.

The pacarana was discovered by scientists in 1873 when a Polish nobleman traveling in Peru shot one and sent its skin and skeleton home, where it was studied by the director of the Berlin Zoo. But after that one specimen was killed, the pacarana seemed to vanish. Then in 1904 someone sent two pacaranas to a museum in Brazil. The museum’s director gave them to the local zoo where they could be taken care of, although the female died after giving birth shortly afterwards.

It turns out that the pacarana isn’t all that rare, but it’s shy and hard to spot in its habitat, forested mountains in South America. But because it’s seldom seen, not very many zoos have them, but zookeepers all report that pacaranas are docile and friendly. I can confirm that they are very, very cute although I haven’t seen one in person.

The pacarana is named after another rodent called the paca, which looks similar but has a shorter tail and is smaller than the pacarana, although still a pretty big rodent. The paca grows up to about two and a half feet long, or 77 cm, not counting its 9-inch tail, or 23 cm, and is dark brown with rows of white spots on each side. It looks kind of like a chevrotain, which as you may remember from episode 116 is also called the mouse deer even though it’s not a mouse or a deer. The paca lives in a burrow that can be ten feet long, or 3 meters, usually with two entrances that it covers with leaves to hide it. It likes fruit, leaves, flowers, fungi, and other plant material, but it will also eat insects.

The paca likes to swim and can stay underwater even longer than the capybara, as much as 15 minutes. It usually mates in the water too. It’s mostly nocturnal, although some populations may be crepuscular, and it lives in much of Central and South America, although it’s also present in southern Mexico.

After her babies are born, the mother paca tucks her babies in a hole she digs that’s too small for predators to enter. But the hole is also too small for her to enter. To let the babies know it’s safe to come out, she calls to them in a low trill. The paca, in fact, makes a lot of sounds, and its voice is way louder than you’d think. It has resonating chambers in its cheeks to make its voice even louder.

Here are some sounds that a paca makes:

[paca calls]

Ages ago, Llewelly sent me a link to an article about some interesting rodents of South America. I’ve included a link to it in the show notes in case you want to learn more about South American rodents that aren’t quite as big as the ones we’ve covered today, but which are just as interesting.

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon if you’d like to support us that way.

Thanks for listening! Oh, and this is what a baby capybara sounds like.


Episode 143: Rats, Giant Rats, and Rat Kings



It’s almost Halloween!! We’ve got a great episode this week about rats–ordinary rats, giant rats, and the strange phenomenon called the rat king.

Speaking of bonus episodes, I’ve unlocked a few for anyone to listen to. Just click through and listen in your browser, no login required:

Spooky Animals Stories

Irrawaddy dolphins and Dracula ants

The Soay Island Sea Monster

Further viewing:

A squirrel king video (the squirrels were captured and freed by a veterinarian later)

A typical brown rat, a la Ratatouille:

A typical black rat:

A typical fancy (aka domesticated) rat:

A giant pouched rat heading to work to sniff out landmines:

Two rat kings (preserved):

An X-ray of a rat king’s tails (the arrows show places where the tails are fractured):

Show transcript:

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

It’s finally the Halloween episode! I hope you all have your costumes ready to go! This week we’re going to learn about an animal sometimes associated with Halloween, the rat, including some mystery rats.

But first, my yearly housekeeping and promo-ing! You can still pick up a copy of my fantasy adventure book Skytown, available from Fox Spirit Books. I’ll put a link in the show notes. It has some adult language but is otherwise suitable for younger teens through adults. I’m also working on a nonfiction book associated with Strange Animals Podcast, but we’ll see how that goes.

If you want to support the show financially, I am always happy to take your money. We’ve got a Ko-fi account where you can tip me the cost of a coffee, or more, and we’ve also got a Patreon account if you want to set up recurring donations and get bonus episodes in exchange, as well as other perks. There are links to both in the show notes and on the website, strangeanimalspodcast.blubrry.net. Also on the website we’ve got two pages now that list what animals we’ve covered so far. One page is for everything, the other is just for cryptids for those of you who are just here for the mystery animals.

Speaking of Patreon bonus episodes, I’ve unlocked a few episodes so that anyone can listen to them. They won’t show up in your feed, but there are links in the show notes and you can just click on the link and listen in your browser. You don’t need a Patreon login or anything. This time I’ve unlocked some fun ones, including an episode about animal ghosts from last Halloween.

Now, on to the rats.

The presence of rats is usually considered bad luck, undoubtedly because rats evolved to take advantage of humans’ habit of storing grain for later. If rats ate the grain, humans and their livestock could starve. But rats are also considered bad omens or evil when they’re just going about their lives, being rats.

The rat is a rodent that resembles a big mouse, not surprising since they’re closely related. There are lots of rat species and subspecies, but the most well known are the black rat and brown rat. These are the ones most likely to live in cities and houses, especially the brown rat. The brown rat is also sometimes called the Norway rat even though it’s originally from Asia.

The brown rat is a relatively large rodent, up to about a foot long, or 30 cm, with a tail that’s nearly as long. The black rat is a little smaller and less bulky, with larger eyes and ears, and has a tail that’s longer than its body. Male rats are usually larger and heavier than females. A rat’s tail is bare of fur and has thin skin, and if a predator grabs it by the tail it can shed the skin of the tail, called degloving. The skin will grow back, but until it does the tail is prone to infection. That’s one of the reasons why you should never pick up a pet rat by the tail. Also, picking a rat up by the tail can injure it.

The domesticated rat, also called the fancy rat, is descended from the brown rat. Rat catchers, especially a man named Jack Black, whose title was Royal Rat Catcher and who lived in the mid-19th century, kept interestingly patterned or colored rats he caught in his job. At the turn of the 20th century, fancy mice were a popular pet in Europe, and in 1901 a woman named Mary Douglas suggested the UK group called the National Mouse Club also accept rats. I don’t know about you, but I would totally join the National Mouse Club just for the name. It’s actually still around today, in fact, and I just looked and it costs money to join, so never mind. It’s not like I have any pet mice anyway. Domesticated rats are intelligent, clean pets, and friendly if they’re properly socialized. Rats do leave scent trails for other rats by releasing small amounts of urine as they move around, though, so be aware of this before you let your pet rat run around the house.

The rat has good hearing, smell, and sense of touch, with lots of sensitive whiskers to help it find its way even in the dark. Many of the sounds it makes are in the ultrasonic range so aren’t audible to human ears, including laughter. That’s right, rats laugh. It’s more of an ultrasonic chirping sound, but it occurs when rats are playing, and when a pet rat is tickled by its owner. Young rats laugh more than old rats.

This is what a rat laugh sounds like, slowed down so it’s audible to human ears.

[rat laughing/chirping]

The rat can also swim well, dig well, and shows signs of being surprisingly intelligent. It’s an omnivore that will eat anything it can find or catch. It will kill and eat small animals or sometimes even larger animals like ducks. Some rat populations have learned to dive for mollusks and catch fish.

Rats are social animals and live in large groups, usually in burrows with extensive tunnel systems. In cities, instead of digging burrows rats will live in sewers, alleys, and buildings. Rats go where people go, and they live where people live. While the rat is mostly nocturnal, it’s not unusual to see a rat during the day too.

Rats do carry diseases which they can spread to humans and other animals through their urine and feces, through bites, or through fleas or mites. You’ve probably heard that rats carry a type of flea that spreads the black death, which killed millions of people throughout the 14th century and later. Researchers think that the black death was an especially dangerous version of the bubonic plague. The bubonic plague is actually still around, but these days it’s rare, usually not as dangerous as the version of the disease spread in the middle ages, and can be cured with modern medicine. Humans aren’t the only animals that can catch the plague, by the way. So can cats, dogs, and the rats themselves.

So a rat can grow to about a foot long not counting the tail, or 30 cm. Even a big rat doesn’t weigh more than about two pounds, or a little under a kilogram. But what about giant rats? Or, you might say, rodents of unusual size.

Occasionally someone reports seeing or killing a rat twice the normal size or more, but while you can find pictures of giant dead rats online, it’s really easy to fake that kind of picture. Some are obviously examples of forced perspective, where the rat looks big because it’s actually quite close to the camera, some are plain old photoshopped, and some aren’t actually rats at all.

There are some rodents that look a lot like regular old rats but are much larger. Most are rare or not well known outside of its native habitat, like the Sumatran giant rat that grows up to two feet long, or about 61 cm, not counting its tail. It’s brown with longer fur than the actual brown rat, and it lives in parts of southeastern Asia, but it’s only distantly related to the rat.

The African giant pouched rat is also only distantly related to the actual rat although it looks quite similar. Unlike rats, but like some other rodents, it has cheek pouches that it uses to carry food. It’s bigger than the brown rat, up to about a foot and a half long not counting the tail. or 45 cm, and until 2003 it was a popular exotic pet in the United States. But in 2003, some giant pouched rats imported to the midwest from Africa spread a disease called monkey pox to other animals that were then all sold as pets, especially prairie dogs. In the next five weeks 71 people were infected with the disease. Fortunately no one died, but monkey pox is related to smallpox and can be deadly to humans. As a result of the outbreak, the United States no longer allows any rodent to be imported from Africa.

Also in 2003, the remake of a horror movie about a man named Willard and his rats was released. The rat named Ben was played by a giant pouched rat. I have not seen the movie because I’m a wimp about horror movies, but if you like them and are, you know, a grown-up type person, apparently that was a pretty good one. The original movie was released in 1971 with a sequel in 1972, and all I know about it is that Michael Jackson sang the theme song, which is probably the only song I know that’s about a rat. It’s a pretty song.

The giant pouched rat is sometimes trained to detect landmines, since it has a good sense of smell and isn’t heavy enough to set off the landmines. The problem is that the giant pouched rat doesn’t actually breed well in captivity, so breeding pouched rats that are especially tame and good at detecting explosives is proving to be difficult. Researchers aren’t even sure what causes the females to come into season so that they can have babies. In other rodents, the release of certain hormones controls this cycle, but that doesn’t seem to be the case in giant pouched rats.

As if the bomb-sniffing and acting skills weren’t enough, the giant pouched rat has also been trained to detect tuberculosis in children. The rat does this by sniffing samples of spit taken from children, and a trained rat is so good at detecting the infection that it’s actually 68% more accurate than the standard medical test.

Not to be outdone, researchers in North America are working on ways to train brown rats as search and rescue animals for areas where search and rescue dogs can’t enter.

We got a little off-topic there but you have to admit, the giant pouched rat is a pretty neat rodent, even if it’s not actually part of the rat family.

Another rodent once thought to be a type of rat was a mystery for centuries. In 1503 the Florentine explorer Amerigo Vespucci reached Brazil, and while he was there he visited the volcanic island Fernando de Noronha and wrote about it later. One of the things he mentioned was that the island was home to very large rats.

Since Vespucci was the first European ever to visit the island, and no one from anywhere in the world was living on it at the time, the rats he saw can’t have been the rats he was used to. That would have been the black rat, since the brown rat hadn’t spread throughout Europe yet. It did so later, outcompeting the black rat in most environments. But in 1503, the black rat was the one Vespucci would have known, and the rats he saw on the island were bigger.

Other explorers and sailors visited the island in the years after 1503, and by 1888 when biologists came looking for the very big rat, all they found were the descendants of black rats brought there by ships.

Then, in 1973 paleontologists from Brazil and the United States visited the island to see what had once lived there. And they found remains of the very large rat. It turns out that the rat wasn’t actually a rat, although it was a rodent. And while it was larger and heavier than the black rat, it wasn’t enormous. It was about the size of a typical brown rat, in fact. Ironically, it was probably driven to extinction by the ship rats that colonized the island soon after Vespucci visited.

Vespucci’s rat has been named Noronhomys vespuccii and was given its own genus. Reseachers think that its ancestor might have been semiaquatic like some rodents that still live in South America and that are related to Vespucci’s rat. Rodents that were already in the water would have been occasionally swept out to sea and floated or swam to the island. But once a population of the rodents was established on the island, they evolved to be exclusively terrestrial.

But let’s get back to actual rats. A lot of people are afraid of rats, and it’s true that a cornered rat will bite to defend itself. Rats still carry diseases too. As a result, there are lots of superstitions about rats. For instance, according to folklore than goes back almost two thousand years, the best way to get rid of rats is to write the rats a polite letter requesting that they leave. Fold it up carefully and slide it into the rat’s hole. I am pretty sure that one doesn’t work.

Rats are supposed to be able to foretell misfortune and death. If a rat chews up someone’s clothes or belongings, that person is supposedly going to die soon. If you see rats leaving a ship, it’s an omen that the ship is going to sink. I’ve been reading about superstitions, and it’s amazing how many animals are supposed to foretell death and bad luck. It’s almost like people are trying to blame an animal for random events.

Finally, it wouldn’t be Halloween without something spooky, weird, or gross, or better yet, all three. So let’s learn about something called the rat king.

A rat king isn’t one animal but a group of rats joined together by their tails. This sounds like something out of folklore but it’s actually a real occurrence, although it’s rare. The oldest report known dates to 1564, but specimens are occasionally uncovered even today. All reliable reports of rat kings are of black rats. The black rat has a long, thin, flexible tail that it uses to help it climb.

Not much is known about how rat kings form, but the most widely accepted suggestion is that a group of rats huddling together for warmth get their tails tangled together without realizing it. When each rat tries to separate itself from the group by pulling, the knot tightens. Eventually the rats are permanently stuck together.

It seems reasonable to think that a bunch of rats stuck together by their tails wouldn’t survive long. They’d starve to death or kill each other trying to get free. But a rat king made up of seven rats found in the Netherlands in 1963 was examined and even X-rayed to learn more about it, and where the tails were intertwined there was some evidence of calluses forming. This suggests the rats may have survived for some time.

Most rat kings are made up of young rats, possibly siblings sharing a nest. It’s possible the mother of the 1963 rat king fed them and kept them alive until they were discovered by a farmer, who killed them.

Rats aren’t the only animals found with their tails knotted together. It happens to squirrels occasionally too. If you check the show notes, I’ve included a link to a video of a squirrel king. In the case of squirrels, pine sap and nesting material can glue or tangle the tails of young squirrels together, and we have not just video evidence from 2013 and 2018, but the evidence of veterinarians who managed to separate the squirrels in both cases so they wouldn’t die.

So the rat king sounds horrifying and kind of is, but it’s also sad and not really spooky at all. It’s funny how often understanding something that sounds scary makes you realize it’s not actually all that scary after all. People and rats may not always get along, since rats are very interested in eating food people want to keep for ourselves. But rats laugh, so they can’t be all bad.

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon if you’d like to support us that way.

Thanks for listening, and happy Halloween!