Tag Archives: sheep

Episode 354: Sheep and Sivatherium

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Thanks to Hannah, who suggested sheep as this week’s topic! We’ll also learn about a few other hoofed animals, including the weird giraffe relative, sivatherium.

Further reading:

The American Jacob Sheep Breeders’ Association

What happened with that Sumerian ‘sivathere’ figurine after Colbert’s paper of 1936? Well, a lot.

A Jacob sheep ewe with four horns (pic from JSBA site linked above):

The male four-horned antelope [photo by K. Sharma at this site]:

A modern reconstruction of sivatherium that looks a lot like a giraffe [By Hiuppo – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=2872962]:

The rein ring in question (on the left) that might be a siveratherium but might just be a deer:

Show transcript:

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

This week we’re going to look at an animal suggested by Hannah a long time ago. Hannah suggested we talk about sheep, and I can’t even tell you how many times I almost did this episode but decided to push it back just a little longer. Finally, though, we have the sheep episode we’ve all been waiting for! We’re also going to learn about a strange animal called sivatherium and a mystery surrounding when it went extinct.

The sheep has cloven hooves and is a ruminant related to goats and cattle. It mostly eats grass, and it chews its cud to further break down the plants it eats. It’s one of the oldest domesticated animals in the world, with some experts estimating that it was first domesticated over 13,000 years ago. Mammoths still roamed the earth then. Sheep are especially useful to humans because not only can you eat them, they produce wool.

Wool has incredible insulating properties, as you’ll know if you’ve ever worn a wool sweater in the snow. Even if it gets wet, you stay nice and warm. Even better, you don’t have to kill the sheep to get the wool. The sheep just gets a haircut every year to cut its wool short. Wild sheep don’t grow a lot of wool, though. They mostly have hair like goats. Humans didn’t start selecting for domestic sheep that produced wool until around 8,000 years ago.

Like other animals that were domesticated a very long time ago, including dogs and horses, we’re not sure what the direct ancestor of the domestic sheep is. It seems to be most closely related to the mouflon, which is native to parts of the middle east. The mouflon is reddish-brown with darker and lighter markings and it looks a lot like a goat. Other species of wild sheep live in various parts of the world but aren’t as closely related to the domestic sheep. The bighorn and Dall sheep of western North America are closely related to the snow sheep of eastern Asia and Siberia. The ancestors of all three species spread from eastern Asia into North America during the Pleistocene when sea levels were low and Asia and North America were connected by the land bridge Beringia.

The male sheep is called a ram and grows horns that curl in a spiral pattern, while the female sheep is called a ewe. Some ewes have small horns, some don’t. This is the case for both wild and domestic sheep. Sheep use their horns as defensive weapons, butting potential predators who get too close, and they also butt each other. Rams in particular fight each other to establish dominance, although ewes do too.

But some breeds of domestic sheep are what is called polycerate, which means multi-horned. That means a sheep may have more than two horns, typically up to six. Many years ago I kept a few Jacob sheep, which are a polycerate breed, and in a Patreon episode from 2018 I went into really too much detail about this particular breed of sheep. I will cut that short here.

The Jacob is a hardy, small sheep with tough hooves, and it’s white with black spots. Ideally, a Jacob sheep will have four or six well-balanced horns. In a six-horned sheep, the upper pair branch upward, the middle pair curl like an ordinary ram’s horns, and the lower pair branch downwards. Sometimes a sheep will have three or five horns, or will start out with four horns but as they grow, two will merge so it looks like they have a single horn on one side. Sometimes a ram’s horns will grow so large that the blood supply is choked off for the lower pair, which will die and stop growing. Breeding a pair of six-horned Jacob sheep doesn’t guarantee that the babies will have more than two horns, though. It’s still a recessive trait.

Sheep, goats, cattle, and some antelopes are all bovids. Polyceratism appears to be a bovid trait. It’s caused by a mutation where the horn core divides during the animal’s development.

Occasionally, a sheep of non-polycerate breed, or a goat, or even a cow, is born with multiple horns. The blue wildebeest is also occasionally born with multiple horns. Sometimes an animal grows a lot of horns, like eight, but usually it’s three, four, five, or six.

Another animal with more than two horns is the four-horned antelope that lives in India and Nepal. Its horns are quite small, just a pair of tiny points on the forehead with a pair of longer points behind them. The antelope itself is also small, not much more than two feet tall at the shoulder, or 60 cm. Its coat is reddish or yellowish-brown with white underparts, and a black stripe down the front of the legs. The longer horns grow up to about five inches long, or 12 cm, but the front horns are no longer than two inches, or five cm.

The four-horned antelope is shy and solitary, and lives in open forests near water. Since it’s so small, it frequently hides in tall grasses. Sometimes a four-horned antelope’s front two horns are just bumps covered with fur, which makes them look like ossicones although they’re still actually horns.

That brings us to the other group of animals with multiple horns, although they’re not actually horns. I mentioned ossicones in the tallest animals episode, about giraffes. They’re made of ossified cartilage instead of bone, and are covered in skin and fur instead of a keratin sheath. Antlers are actually very similar to ossicones in many ways. A deer’s antlers grow from a base that is similar to an ossicone, and as they grow, the antlers are covered with tissue called velvet that later dries and is scraped off by the deer to show off the bony antlers. Unlike horns, which are always unbranched, the ossicones of some extinct animals can look like antlers.

We talked about sivatherium in episode 256, about mammoths. It was an ancestor of modern giraffes that lived in Africa and India around a million years ago. It stood around 7 feet tall at the shoulder, or just over two meters, but had a relatively long neck that made it almost 10 feet tall in total, or about three meters. It had two pairs of ossicones, one pair over its eyes and another between its ears. Like the four-horned antelope, the front pair were smaller than the rear pair, but the rear pair was broad and had a single branch.

Sivatherium was once believed to be closely related to elephants, and reconstructions of it often made it look like a moose with a short trunk. But modern understanding of its anatomy suggests it looked like a heavily built giraffe with shorter legs and neck, sort of like the giraffe’s closest living relative, the okapi.

One interesting thing about Sivatherium is how recently it may have been alive. Some researchers think it may have been around only 8,000 years ago. There’s rock art in India and the Sahara that does seem to show a long-necked animal with horns that isn’t a giraffe. The art has been dated to around 15,000 years ago. But the big controversy is a figurine discovered in 1928.

That’s when a copper rein ring was found in Iraq and dated to about 2800 BCE. A rein ring was part of the harness to a four-wheeled chariot, with two holes to thread the reins through to keep them from tangling. Above the rings was a little decorative figure of an animal. This particular rein ring’s figure shows an animal with short horns above the eyes and branching horn-like structures farther back, between the ears. When it was originally discovered, scientists thought the figure represented a type of fallow deer found in the area, with the ends of the antlers broken off. But one researcher, Edwin Colbert, pointed out that no deer known has four antlers and the figure clearly has two little bumps over its eyes that are separate from the branched antler or horn-like structures farther back. In 1936 he published his conclusion that the animal wasn’t a deer at all but sivatherium, and a lot of scientists agreed.

That would mean sivatherium might have been alive less than 5,000 years ago. Part of the issue is that sivatherium’s branched ossicones weren’t very big in comparison to its head, while the fallow deer’s antlers are proportionally quite large. The figurine has structures that match sivatherium’s ossicones more than a deer’s antlers. But in 1977, two little pieces of copper were found in a storage box where they’d been since the original discovery of the rein ring. The pieces fit exactly onto the ends of the figure’s horns, showing that the horns are much bigger than originally thought.

That doesn’t explain everything, though. The figure still has those extra little horns over its eyes, and while the branched horns look like deer antlers, they still don’t look like fallow deer antlers. Some researchers point out that sivatherium had a lot of variation in the size and shape of its ossicones, too.

Ultimately there’s not enough evidence either way of whether the figurine depicts a deer or sivatherium. If sivatherium did live as recently as a few thousand years ago, hopefully remains of it will be found soon. Until we know for sure, you can still be glad that the giraffe is alive, because it’s just as amazing as its extinct relation.

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 278: Gender Diverse Animals

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This week is Connor’s episode, and we’re going to learn about some animals that don’t conform to “typical” gender roles, one way or another.

I’ll be at ConCarolinas this week, from June 3 through 5, including recording a live crossover episode with Arcane Carolinas!

Further reading:

Species of algae with three sexes that all mate in pairs identified in Japanese river

How a microbe chooses among seven sexes

Facultative Parthenogenesis in California Condors

The sparrow with four sexes

Chinstrap penguins make good dads:

Laysan albatrosses make good moms:

Black swans make good dads:

Some rams really like other rams (photo by Henry Holdsworth):

New Mexico whiptail lizards are all females:

California condor females don’t always need a male to produce fertilized eggs:

Clownfish change sex under some circumstances:

The white-throated sparrow essentially has four sexes:

You are awesome (photo by By Eric Rolph)!

Show transcript:

“Hey y’all, this is Connor. Welcome to a very special Pride Month edition of the Strange Animals Podcast.”

This week we have Connor’s episode! We decided to make it the very last episode in our Kickstarter month so that it’s as close to the month of June as possible, because June is Pride Month and our episode is about gender-diverse animals! Don’t worry, parents of very young children, we won’t be discussing mating practices except in very general terms.

Pride month celebrates people’s differences when it comes to gender expression and sexuality. That’s why its symbol is the rainbow, because a rainbow is made up of all different colors the same way there are different kinds of people. Sometimes people get angry when they hear about Pride month because they think there are only two genders, and that those two genders should only behave in certain ways. Pffft. That’s not even true when it comes to animals, and humans are a lot more socially complicated.

For instance, let’s start by talking about a humble creature called algae. If you remember episode 129, about the blurry line between animals and plants, you may remember that algae isn’t actually a plant or an animal. Some species resemble plants more than animals, like kelp, but they’re not actually plants. In July of 2021, scientists in Japan announced that a species of freshwater algae has three sexes: male, female, and bisexual. All three sexes can pair up with any of the others to reproduce and their offspring may be male, female, or bisexual at random.

Even though the algae has been known to science for a long time, no one realized it has three sexes because most of the time, algae reproduces by cloning itself. The research team thinks that a lot of algae species may have three sexes but researchers just haven’t been looking for it.

Yes, I realize that was a weird place to start, but it’s also fascinating! It’s also not even nearly as complicated as a protozoan called Tetrahymena thermophila, which has seven sexes.

Let’s look at a bird next, the penguin. You’ve probably heard of the book And Tango Makes Three, about two male penguins who adopt an egg and raise the baby chick together. For some reason some people get so angry at those penguins! Never trust someone who doesn’t like baby penguins, and never trust someone who thinks animals should act like humans. The events in the book are based on a true story, where two male chinstrap penguins in New York’s Central Park Zoo formed a pair bond and tried to hatch a rock, although they also tried to steal eggs from the other penguins. A zookeeper gave the pair an extra penguin egg to hatch instead.

The most interesting thing about the story is that same-sex couples are common among penguins, in both captivity and in the wild, among both males and females. Since penguins sometimes lay two eggs but most species can only take care of one chick properly, zookeepers often give the extra eggs to same-sex penguin pairs. The adoptive parents are happy to raise a baby together and the baby is more likely to survive and be healthy. Occasionally a same-sex penguin couple will adopt an egg abandoned by its parents.

If you remember episode 263 a few months ago, where we talked about animals that mate for life, you may remember the Laysan albatross. In that episode we learned about a specific Laysan albatross named Wisdom, the oldest wild bird in the world as far as we know. While I was researching Wisdom, I learned something marvelous. As many as 30% of all Laysan albatross pairs are both females. Sometimes one of the females will mate with a male and lay a fertilized egg, and then both females raise the baby as a couple. Sometimes one of the females lays an unfertilized egg that doesn’t hatch. There are many more Laysan albatross females than males, which may be the reason why females form pairs, but it’s perfectly normal behavior. It’s also been a real help to conservationists. Sometimes an albatross pair will nest in an area that’s not safe, like on an airfield. Instead of leaving the egg to be smashed by an airplane, conservationists take the fertilized egg from the unsafe nest and use it to replace the unfertilized egg of a female pair. The egg is safe and the chick has adoptive parents who raise it as their own.

Many other birds develop same-sex pairs too. This is especially common in the black swan, where up to a quarter of pairs are both male. One or both of the males will mate with a female, but after she lays her eggs the males take care of them and the cygnets after they hatch. Cygnets raised by two dads are much more likely to survive than cygnets raised by one mom and one dad. The males are stronger and more aggressive, so they can defend the nest and babies more effectively.

Birds aren’t the only animals that form same-sex pair bonds. Many mammals do too. It’s been documented in the wild in lions, elephants, gorillas, bonobos, dolphins, and many more. In species that don’t typically form pair bonds, homosexual behavior is still pretty common. It’s so common among domestic sheep that shepherds have to take into account the fact that up to 10% of rams prefer to mate with other rams instead of with ewes. Some rams show attraction to both males and females. This happens in wild sheep too, where rams may court other rams the same way they court ewes. Some ewes also show homosexual behavior.

The New Mexico whiptail is a lizard that lives in parts of the southwestern United States and northern Mexico. It can grow over nine inches long, or 23 cm, and is black or brown with yellow racing stripes. It eats insects and is an active, slender lizard that’s common throughout its range. And every single New Mexico whiptail lizard is a female.

The lizards reproduce by a process called parthenogenesis. That basically means an animal reproduces asexually without needing to have its eggs fertilized. The lizards do mate, though, but not with males. Females practice mating behaviors with each other, which researchers think causes a hormone change that allows eggs to develop. Females who don’t mate don’t develop eggs.

Female birds can sometimes reproduce asexually too. It’s been documented in turkeys, chickens, pigeons, finches, and even condors. A study published in late 2021 detailed two instances of parthenogenesis in California condors in a captive breeding program. In both cases the females were housed with their male mates, and in both cases the pairs had produced offspring together before. But in both cases, for some reason the females laid eggs that hatched into chicks that were genetically identical to the mothers. It’s possible parthenogenesis is even more common in birds than researchers thought.

In many species of reptile, whether a baby is a male or female depends completely on how warm its egg gets during incubation. For example, the American alligator. The mother gator builds a nest of plant material and lays her eggs in it. As the plant material decays, it releases heat that keeps the eggs warm. How much heat is generated depends on where the mother alligator builds her nest and what plants she uses, which in turns affects the eggs. If the temperature in the nest is under 86 degrees Fahrenheit, or 30 Celsius, during the first few weeks of incubation, most or all of the eggs will hatch into females. If the temperature is 93 F or 34 C, most or all of the eggs will hatch into males. If the temperature is between the two extremes, there will be a mix of males and females, although usually more females.

Because climate change has caused an overall increase in temperatures across the world, some already vulnerable reptile populations, especially sea turtles, are hatching almost all males. Conservationists have to dig up the eggs and incubate them at a cooler temperature in captivity, then release the babies into the ocean when they hatch.

Other animals change from male to female or vice versa, depending on circumstances. The clownfish, for example. Clownfish start out life as males but as they grow up, most become females, although only the dominant pair in a colony actually reproduces. Clownfish live in colonies led by the largest, most aggressive female, with the largest, most aggressive male in the group as her mate. If something happens to her, her former mate takes her place, becoming a female in the process. The largest juvenile male then becomes her mate and remains male even though he puts on a growth spurt to mature quickly. If Finding Nemo was scientifically accurate, it would have been a much different movie.

Another group of fish that live around reefs are wrasses, which includes the famous cleaner fish that cleans parasites and dead tissue off of larger fish. Wrasses hatch into both males and females, but the males aren’t the same type of males that can breed. Those develop later. When the dominant breeding male of the group dies, the largest female or the largest non-breeding male then develops into a breeding male. But sometimes a non-breeding male will develop into a female instead.

The term for an animal that changes sex as part of its natural growth process is sequential hermaphroditism. It’s common in fish and crustaceans in particular. Other animals have the reproductive organs of both a male and a female, especially many species of snail, slug, earthworm, sea slug, and some fish. We talked about the mangrove killifish in episode 133, and in that episode I said it was the only known vertebrate hermaphrodite. That’s actually not accurate, although I was close. It’s the only known vertebrate hermaphrodite that can self-fertilize. Almost all mangrove killifish are females, although they also produce sperm to fertilize their own eggs. The eggs hatch into little clones of the mother.

We’ve talked about seahorses before too, especially in episode 130. Seahorse pairs form bonds that last throughout the breeding season. The pair participate in courtship dances and spend most of their time together. When the eggs are ready, the female deposits them in a special brood pouch in the male’s belly, where he fertilizes them. They then embed themselves in the spongy wall of the brood pouch and are nourished not only by the yolk sacs in the eggs, but by the male, who secretes nutrients in the brood pouch. So basically the male is pregnant. The female visits him every day to check on him, usually in the mornings. When the eggs hatch after a few weeks, the male expels the babies from his pouch and they swim away, because when they hatch they are perfectly formed teeny-tiny miniature seahorses.

Let’s finish with a little songbird that’s common throughout eastern North America, the white-throated sparrow. It has a white patch on its throat and a bright yellow spot between the eye and the bill. There are two color morphs, one with black and white stripes on its head, one with brown and tan stripes on its head. Both males and females have these head stripes. The male sings a pretty song that sounds like this:

[white-throated sparrow call]

A 30-year study into white-throated sparrow genetics has revealed some amazing things. The color morphs are due to a genetic difference that affects a lot more than just feather colors. Black morph males are better singers, but they don’t guard their territory as well or take care of their babies as well as brown morphs do. They also aren’t as faithful to their mates as the brown morph males, which are fully monogamous and are diligent about helping take care of their babies. Despite their differences in raising offspring, both morphs are equally successful and equally common.

All this seems to be no big deal on the surface, maybe just pointing to the possibility that the species is in the process of splitting into two species or subspecies. But that’s not the case.

Black morphs always mate with brown morphs. A black morph male will always have a brown morph mate, and vice versa. Genetically, the two morphs are incredibly different—so different, in fact, that they seem to be developing a fully different set of sex chromosomes. In other words, there are male and female black morph birds and male and female brown morph birds that are totally different genetically, but still members of the same species that only ever breed with each other. In essence, the white-throated sparrow has four sexes.

Usually I try to end episodes with something funny, but today I’m going to speak directly to you. Yes, you! If you’re listening to this or reading the transcript, my words are meant just for you. You are an amazing person and I love you. You deserve to be happy. If anyone has ever told you there’s something wrong with the way you are, or the way you wish you were or want to be, they’re wrong. They probably also don’t like penguins, so you don’t have to believe anything they say. If you’ve ever read books by Terry Pratchett, you may recognize this quote: “Be yourself, as hard as you can.”

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 171: The Animals of St. Kilda

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Thanks to Emma for the suggestion! Let’s learn about some animals that live on the St. Kilda islands off the coast of Scotland!

St. Kilda:

Soay rams (kept on farms, not the feral sheep):

A small flock of Soay sheep (these are from a farm too):

A Boreray ram (on a farm):

A Boreray ewe with her babies (also on a farm, or at least I think so):

The St. Kilda wren (not a sheep):

The St. Kilda field mouse (also not a sheep) is the size of a hamster:

Show transcript:

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

This week’s episode is a suggestion from Emma, who long ago told me about the interesting history and unique animals of the island of St. Kilda in Scotland. I’ve been meaning to cover it ever since, so finally I’m getting around to it after only two years or so.

Emma says, “It’s an amazing little island and sort of a reverse of the usual ‘humans cause extinction’ story. The humans on the island went ‘extinct’, being evacuated from the island partly because increased mainland human contact was bringing illnesses they couldn’t fight without hospitals. Two lots of rad ancient sheep and some unique wrens and mice are happily living there to this day.”

St. Kilda is not one but a group of islands off the coast of Scotland, but the largest island and the only one where people once lived is called Hirta. In 1930, everyone who still lived there moved to the mainland, but by that time hardly anyone remained on St. Kilda anyway. The island probably never had more than a few hundred people in residence at any given time. In 1957 St Kilda was designated as a nature reserve and in 1986 as a World Heritage Site.

Since then, as Emma says, the animals of the islands have mostly been left alone. This includes two breeds of sheep that were left behind on two of the smaller islands when the last residents moved away.

One of these sheep breeds is the Soay, which originally lived on a tiny island called Soay, which actually means “sheep island.” The island of Soay is only about 250 acres in size, or 100 hectares, but that’s not the only place they used to be found. The breed has lived in northern Europe for probably 4,000 years, and was a popular sheep in Britain for centuries. When all the people moved away, 107 sheep living on Soay were moved to Hirta. The sheep on Hirta are feral and receive no care from humans, but they also have basically no predators on the island. They have been studied since 1955 by a small team of scientists and conservationists.

The Soay is a primitive breed of sheep that closely resembles its wild ancestor, the Asiatic mouflon. It’s brown, usually with lighter markings on the face and rump, and the rams often grow a short mane of hair in addition to wool. Rams have dark brown horns and ewes often grow smaller horns too. It also has a short tail. In late spring, Soay sheep shed their fleece naturally instead of needing to be shorn. This is the case with many primitive sheep breeds. Its wool is considered high quality and sought after by handcrafters.

Also like many primitive breeds, the Soay doesn’t have much of a flocking instinct. Soay sheep have been exported from the islands and are kept on farms in many areas for their wool, but if a sheep dog tries to herd a flock of Soay, the poor dog is going to be so frustrated. Soay scatter instead of flocking together. It can also be an aggressive sheep, especially the rams, but it’s also a small breed, with even a big ram rarely heavier than 70 lbs, or 32 kg. And these days, the feral Soay sheep are actually getting smaller overall and have been for the last twenty years. The research team that studies the sheep thinks it’s because climate change has led to shorter, warmer winters, which allows more of the sheep to survive, including smaller sheep that would ordinarily have trouble in cold weather. The smaller sheep breed and their offspring are more likely to be small too, and after twenty years of this the breed overall is smaller than it used to be.

While the Soay used to be a popular breed throughout much of Europe, it’s an at-risk rare breed these days. There are fewer than 1500 breeding ewes registered on farms, in addition to the feral flock on Hirta.

The other breed of St. Kilda sheep is called the Boreray, and it’s also a feral sheep on one of the St. Kilda islands. In this case it lives on the island of Boreray. It’s even rarer than the Soay sheep, the rarest sheep breed in the UK. In 1999 there were only 84 individuals known, but a conservation effort by the Rare Breeds Survival Trust has increased the number to nearly 900 breeding ewes as of 2018.

The Boreray is a little smaller than the Soay and shares characteristics with that breed, including a short tail and its fleece shedding naturally in late spring. It’s usually gray or white, although sometimes brown, often with a speckled black face. Its wool is much coarser than the Soay’s and was traditionally used to make tweed fabric or carpets.

But sheep are domesticated animals, feral or not. What about some of the other animals of St. Kilda?

The St. Kilda wren is a subspecies of Eurasian wren that’s found nowhere else in the world. Like other wrens it’s a tiny songbird, brown and gray with a short tail. It was only recognized as a separate subspecies in 1884, and as happened a lot in those days, museum collectors killed so many of them to stuff and mount that the bird nearly went extinct. Fortunately, early conservationists realized the danger in time, and a special Act of Parliament in 1904 protected the bird. After all the people were evacuated from Hirta, a small team of scientists studied the wren. In 1931 68 nesting pairs were counted, and in 2002 230 breeding pairs were counted. That’s still a low population, but since the wren has almost no predators on St. Kilda, that’s a decent number for such a small habitat.

The St. Kilda wren eats insects, spiders, and other small invertebrates. The male builds the nest out of dead grass and other plants, moss, and seabird feathers.

This is what the St. Kilda wren sounds like:

[St Kilda wren singing]

Another animal found nowhere else in the world is the St. Kilda field mouse, a subspecies of wood mouse. There used to be another mouse subspecies found only on St. Kilda, the St. Kilda house mouse. Both mice were described in 1899, and both are larger than mainland mice. But because the house mouse is dependent on humans, once everyone evacuated the islands the St. Kilda house mouse went extinct within two years.

But the field mouse was fine, and is common throughout the island of Hirta and at least one other island. It actually moved into the abandoned buildings after the house mice went extinct, since houses are full of little nooks and crannies that mice can use as homes. Researchers think the mouse may have been on the islands for something like a thousand years, arriving with Viking settlers.

The St. Kilda field mouse is twice as large and heavy as mainland mice, probably because it basically has no predators. It’s an omnivore like most other mice, and eats seeds, moss, insects and other small animals, and even scavenges meat from dead sheep and birds.

Many sea birds nest on St. Kilda, including Atlantic puffins and northern gannets. The grey seal started breeding on Hirta after everyone left. But except for the sheep, the mice, and the gray seals coming ashore during breeding season, there are no other mammals living on St. Kilda. There are also no trees, no bees, and a limited number of plants and animals, all due to how remote the islands are. They’re 41 miles, or 66 km, away from the Outer Hebrides, a series of much larger islands off the Scottish coast.

Humans have probably lived on Hirta for two thousand years, maybe longer, and have visited the St. Kilda islands as long as 5,000 years ago. But now that the people are gone, the mice and sheep and birds are free to live their quiet lives. As long as they don’t mind a few curious scientists keeping an eye on them.

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

Thanks for listening!