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Episode 454: Bats!

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This week we’re going to learn about a bunch of bats! Thanks to John, Murilo, and Alexandra for their suggestions!

Further reading:

Why Bats Can’t Walk: The Evolutionary Lock That Keeps Them Flying

On a Wing and a Song—Bats Belt out High-Pitched Tunes to Woo Mates

Why some bats hunt during the day

Puzzling Proto-Bats

A pekapeka just walking around catching bugs on the ground [photo by Rod Morris, from link above]:

BLOOOOOOD! but a really cute smile too:

The western red bat looks ready for Halloween!

Show transcript:

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

This week as monster month continues, we’re going to learn about bats! We’ve talked about bats in lots of previous episodes, but we have a lot of really neat information in this one that we’ve never covered before. Thanks to John, Alexandra, and Murilo for their suggestions!

John suggested we learn about diurnal bats and also asked if there are any flightless bats, maybe ones that live on islands. There are lots of island-living bats, and many birds that live on islands evolve to be flightless. It makes sense that bats might do the same thing–but I couldn’t find any information about any known bat that has lost the ability to fly.

The reason seems to be how highly derived bats are. That means they’re specialized, the only mammal known that has ever evolved true flight. Unlike birds, which don’t need to use their legs when flying, bats’ legs are actually part of the wings. The wing membranes, called patagia, stretch not just between the elongated finger bones of the bat’s hands, they also stretch between the arms and legs, and connect the legs too.

A January 2025 study comparing bat skeletons to the skeletons of birds determined that unlike in birds, where the size of the legs doesn’t have anything to do with the size of the wings, in bats the leg size and the wing size are closely related. If a bat evolves smaller wings, its legs also evolve to become smaller. That’s why there are no bats that resemble ostriches, with tiny wings but really long legs.

Another possible reason is that bat legs have evolved to point backwards compared to other animals. It’s not just the feet, the knees are also rotated backwards. That’s why bats hang upside-down when they’re not flying. Many species of bat never land on the ground, because they literally can’t walk at all.

But there are a few species of bats that can walk quite well. One is the increasingly threatened New Zealand lesser short-tailed bat. It lives in a few places in both the North and South Islands, as well as some small islands off the coast, although it used to be much more widespread. It’s also called by its Maori name, the pekapeka.

The pekapeka mainly lives in forested areas and is quite small. It’s brown with a lighter belly, and it has big ears, as do most bats. Its eyes are small and its vision isn’t very good, but it has a good sense of smell. Its wings are small so its legs are correspondingly small too, but its legs are also strong despite their size. It has a clawed thumb toe on its feet and on its wings that helps it climb around in trees when it needs to, and it also spends about half of its time on the ground. It walks just fine, crawling with its wings folded so that the ends point up and back, out of the way. And yes, its legs are rotated backwards as you’d expect in a bat, and it roosts by hanging from its feet in trees.

The pekapeka flies normally and catches insects using echolocation, just like other microbats throughout the world. It especially likes moths. Unlike almost all other bats, it finds a lot of its food on the ground too, using its sense of smell to track down spiders, insects and larvae, and other small invertebrates. It will actually dig into the dirt and leaf litter to find food. It also eats nectar and flowers, and is an important pollinator of some plants.

One great thing about the pekapeka is that the males sing to attract a mate. The sound is so high-pitched that it’s not practical to share it here, because you probably wouldn’t be able to hear it, but I’ll link to an article that has a sample bat song so you can listen.

Another bat that can walk just fine is one suggested by Murilo, the vampire bat. In movies, vampire bats are usually depicted as being humongous, as big as a person! In reality, those big bats are actually megabats, and megabats mostly eat fruit. Megabats are the ones that are sometimes called sky puppies, because they don’t rely very much on echolocation so they don’t have the complicated ears and noses that microbats do. Until recently scientists thought megabats couldn’t echolocate at all, but now we know they can, they’re just not all that good at it. The vampire bat is tiny in comparison.

There are three species of vampire bat alive today. They share the same subfamily, Desmodontinae, but have been classified in different genera because they differ considerably from each other. Their other relations are ordinary bats that eat insects, fruit, and other things that you’d expect from bats. Vampire bats really do eat blood exclusively.

The hairy-legged vampire bat is the most basal of the three species, meaning it retains traits that haven’t changed as much from its ancestors. It feeds exclusively on bird blood. The white-winged vampire bat also mostly feeds on bird blood, but it will sometimes eat the blood of mammals. It’s the common vampire bat that eats the blood of mammals.

Vampire bats probably evolved from ancestors that ate insects. Scientists hypothesize that they might have originally specialized in eating ectoparasites of other animals, or possibly insects that were attracted to animal wounds. If that’s the case, the bat would have already been eating a lot of blood along with the insects, and at some point it started taking a shortcut to getting that yummy blood. We know this has happened at least one other time, in a bird.

I thought we had talked about the red-billed oxpecker in an old episode, but if we did, I couldn’t find it. It lives throughout the savannas of sub-Saharan Africa and is brown with a bright orange bill and eyes, with a yellow eye ring. It eats ticks that it picks off rhinoceroses, cattle, and other large mammals, but it actually mainly eats blood. It’s happy to eat the ticks, because they’re full of blood, and the animals it perches on are happy that it eats ticks, but the bird will also peck at wounds so it can drink blood directly from the animal.

So it’s likely that the vampire bat started out eating ticks or other ectoparasites, then began eating the blood that oozed from the wound after it removed a tick. From there it was a short step to biting the animal to cause blood to flow, and within four million years, it was fully adapted to drinking blood.

The vampire bat has extremely sharp front teeth that stick out so that it can use them to make little cuts in an animal’s skin, after first using its teeth to shave the fur down so it can reach the skin more easily. Its fangs lack enamel, so they stay razor sharp. The vampire bat’s saliva contains anticoagulants, so the blood won’t clot right away and the bat can lick it up until it’s full, which takes about 20 minutes. It digests blood extremely quickly, so that it absorbs the nutrients from the blood and starts urinating the extra liquid within a few minutes of starting to feed. That way it can eat more and it can also stay light enough to take flight if it’s disturbed. If you were wondering, its poop is the same as other bat poop. It does echolocate, although not as expertly as bats that eat insects, but the common vampire bat also has specialized thermoreceptors on its nose that sense heat. It’s the only mammal known that can detect infrared radiation, and the only other vertebrates known that can do the same thing are some snakes.

Because vampire bats have to be able to walk around on animals to find a good spot to bite them, the bats have evolved to be able to walk, run, and even jump just fine. Like the pekapeka, it folds the ends of its wings back out of the way and basically walks on the wrists of its wings and its backwards-pointing feet.

Even though the pekapeka and the vampire bat are comfortable running around on the ground, neither has lost the ability to fly. Being able to fly seems to be baked into being a bat. So while it’s not impossible that a bat might eventually become truly flightless, it’s unlikely.

As for bats that are diurnal, or daytime bats, there are a few. A study published in 2018 determined that of the four known species of bat that routinely go out hunting during the daytime, all four live on islands where there are no predatory birds. That doesn’t mean that all bats that live in places where there aren’t any hawks or eagles or crows are active during the day, because most species are still nocturnal, but that seems to be the one requirement for a daytime bat.

John was also interested in learning about the biggest fossil bat ever found. Bats are delicate creatures and don’t fossilize very well, so the bat fossil record is really fragmentary. For example, until 2015 the oldest pekapeka fossil discovered was only 17,500 years old. In 2015, a new fossilized pekapeka ancestor was discovered on the South Island that’s been dated to 16 to 19 million years ago. The fossil shows that the bat was adapted to walk just as the modern pekapeka is, and its teeth are similar so it probably had a similar diet—but it’s estimated to be three times the size of the pekapeka! That sounds like it must have been a huge bat, but the pekapeka only weighs 15 grams at most. That’s barely more than half an ounce, or about the same weight as a CD or DVD, not counting the case. Its ancestor is estimated to have weighed as much as 40 grams, which is almost as heavy as a golf ball. It’s also what a typical vampire bat weighs, if you were wondering.

An even bigger fossil bat has been discovered in a fossil site in France, a country in Europe, and another in Tunisia, a country in North Africa. It’s called Necromantis and is estimated to have weighed as much as 47 grams, which is the same weight as two mice. Two nervous mice, because Mecromantis had strong jaws and big teeth, which suggests it ate small vertebrates–like mice. It lived between 44 and 36 million years ago in areas that were most likely tropical.

An ancestor of the vampire bat was even bigger, possibly as much as 60 grams. That’s just over 2 ounces! That’s a bit heavier than a tennis ball. It lived in South America during the Pleistocene, so recently that in addition to fossils, we also have subfossil remains. That means they’re mineralized but not yet fully fossilized. It’s called Desmodus draculae, and it was most likely still around when humans migrated to South America around 25,000 years ago. Big as it was, it still wasn’t as big as a typical megabat.

Because bat fossils are so rare, it’s led to a scientific mystery. We don’t have any fossils of bat ancestors that weren’t yet bats, but were evolving into bats. In other words, we don’t know what bats looked like before they evolved to be flying animals. The best guess is that the earliest bat ancestors were shrew-like animals that lived in trees and ate insects.

So far we haven’t mentioned any bats that live in Arizona, suggested by Alexandra, so let’s learn about the western red bat. Most bats are black, gray, or brown in color, but the western red bat is a cheerful orange with white shoulder patches and black wing membranes. It’s ready for Halloween all the time! Males are usually more brightly colored than females.

The western red bat lives throughout western North America in summer. It migrates to the southern parts of its range in winter, as far south as Central America. It’s also called the desert red bat but it actually spends most of its life in forests, where its red coat blends in with dead leaves. It eats insects and while it doesn’t spend much time on the ground, every so often it will drop to the ground to catch an insect before hopping back into the air. Not only that, but when the western red bat migrates, it will sometimes fly along with flocks of migrating birds in the daytime.

Unlike many bats, the western red bat is solitary most of the year. Also unlike most bats, instead of having just one baby at a time, it can have up to four babies in a litter. The mother has four nipples instead of just two as in most bats, and for the first three or four weeks of the babies’ lives, the mother has to carry them around while she hunts, until they learn to fly.

As a last note about bats, Murilo specifically mentioned that vampire bats carry diseases that humans can catch. (If diseases bother you, you can stop listening now because we’re almost done.) The common vampire bat does occasionally bite humans, usually the bare big toe of someone sleeping outside, or sometimes the earlobe or even the nose. Vampire bats do show a lot of resistance to blood-borne diseases, but they still spread diseases. The best way to avoid catching a disease from a vampire bat is to not sleep outside without shelter if you can avoid it, if you’re in an area of South America where vampire bats live. That means that if you’re out camping, bring a tent even if it’s hot. Also, avoid eating the meat of wild boar from South America. Not only can boars catch diseases from vampire bats that they pass on to humans, but wild boars also eat fruit partially eaten by fruit bats that also carry diseases. The fruit bats drop partially eaten fruit, the wild boar eats the fruit along with the saliva left on it by the bat, and then the boar can get sick from the saliva.

Most mammals can catch rabies. If you see a bat out in the daytime crawling on the ground, don’t assume that you’re seeing a very rare daytime bat that can also walk around like a pekapeka. Leave the bat alone and contact animal control, because most likely the poor bat has contracted rabies. If you touch the bat, even if it doesn’t bite you, you will have to get a series of rabies vaccines to make sure you don’t come down with rabies, which is an incurable disease and always fatal. That is way scarier than anything else we’ve ever talked about on monster month episodes!

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 373: The Tasmanian Devil and the Thylacine

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Thanks to Carson, Mia, Eli, and Pranav for their suggestions this week!

Further reading:

RNA for the first time recovered from an extinct species

Study finds ongoing evolution in Tasmanian Devils’ response to transmissible cancer

Tasmanian devil research offers new insights for tackling cancer in humans

The Tasmanian devil looks really cute but fights all the time [picture by JJ Harrison (https://www.jjharrison.com.au/) – Own work, CC BY-SA 3.0]:

The Thylacine could opens its jaws verrrrrrry wide:

Show transcript:

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

This week we’re going to cover two animals that a lot of people have suggested. Carson and Mia both want to learn about the Tasmanian tiger, and Eli and Pranav both want to hear about the Tasmanian devil. We talked about the Tasmanian tiger, AKA the thylacine, in episode 1, and I thought we’d had a Tasmanian devil episode too but it turns out I was thinking of a March 2019 Patreon bonus episode. So it’s definitely time to learn about both!

The thylacine was a nocturnal marsupial native to New Guinea, mainland Australia, and the Australian island of Tasmania, and the last known individual died in captivity in 1936. But thylacine sightings have continued ever since it was declared extinct. It was a shy, nervous animal that didn’t do well in captivity, so if the animal survives in remote areas of Tasmania, it’s obviously keeping a low profile.

The thylacine was yellowish-brown with black stripes on the back half of its body and down its tail. It was the size of a big dog, some two feet high at the shoulder, or 61 cm, and over six feet long if you included the long tail, or 1.8 meters. It had a doglike head with rounded ears and could open its long jaws extremely wide. Some accounts say that it would sometimes hop instead of run when it needed to move faster, but this seems to be a myth. It was also a quiet animal, rarely making noise except while hunting, when it would give frequent double yips.

A 2017 study discovered that the thylacine population split into two around 25,000 years ago, with the two groups living in eastern and western Australia. Around 4,000 years ago, climate change caused more and longer droughts in eastern Australia and the thylacine population there went extinct. By 3,000 years ago, all the mainland thylacines had gone extinct, leaving just the Tasmanian population. The Tasmanian thylacines underwent a population crash around the same time that the mainland Australia populations went extinct—but the Tasmanian population had recovered and was actually increasing when Europeans showed up and started shooting them.

Because the thylacine went extinct so recently and scientists have access to preserved specimens less than a hundred years old, and since the thylacine’s former habitat is still in place, it’s a good candidate for de-extinction. As a result, it’s been the subject of many genetic studies recently, to learn as much about it as possible. It’ll probably be quite a while before we have the technology to successfully clone a thylacine, but in the meantime people in Australia keep claiming to see thylacines in the wild. Maybe they really aren’t extinct.

The Tasmanian devil is related to the thylacine. It’s about the size of a small to average dog, maybe a bulldog, which it resembles in some ways. It’s compact and muscular with a broad head, relatively short snout, and a big mouth with prominent lower fangs. It’s not related to canids at all, of course, and if you just glanced at a Tasmanian devil, your first thought wouldn’t be “dog” or “thylacine,” it would probably be “giant mouse.”

The Tasmanian devil is black or grayish-brown, usually with patches of white on the chest and rump. It also has rounded pinkish ears, long whiskers, paws with relatively long toes, and a long tail. Since the devil stores fat in its tail, a fat-tailed devil is a happy, healthy devil.

It’s mainly a scavenger and will eat roadkill and other dead animals, although it will also kill and eat small or even large animals, and will also eat plant material and insects. It often eats every trace of a carcass, including bones and fur. This is good for other animals and for ranchers, since it reduces the presence of insects attracted to dead animals and reduces the spread of disease. Its digestion is extremely fast and efficient, and its jaws are extremely strong.

The Tasmanian devil is usually solitary, but it does get together with other devils to socialize and fight while eating. When a devil finds a carcass, it will make extremely loud calls to alert other devils to come share its meal. Then, because they’re called devils and not angels for a reason, the animals will fight over the food.

Tasmanian devils fight a lot. Researchers think the white markings help direct other devils to attack parts of the body that are less vulnerable to injury. The white fur is more visible in the dark, giving other devils a target. The white markings are usually on the devil’s chest, sides, and rump, with none on the face or legs. Males fight each other during breeding season, and the females pick the winners to mate with. If a female doesn’t like a male, she’ll fight him.

Devils are marsupials, which means babies are born very early and finish developing in their mother’s pouch. The Tasmanian devil’s pouch is rear-facing and contains four teats. The problem is, the mother has 20 or even 30 babies at a time. They’re born about the size of a jellybean and the only part that’s developed at that point is the forelegs so it can crawl into the mother’s pouch. The legs have claws and—you guessed it—the little squidge babies fight for a teat. Once one gets to a teat, it clamps on and doesn’t let go for the next three months. Babies that don’t get a teat die.

Like the thylacine, the Tasmanian devil once lived on mainland Australia but is now restricted to the island of Tasmania. Also like the thylacine, it shows low genetic diversity and was once killed for bounty by early settlers. It’s affected by habitat loss like many other animals, and it’s especially vulnerable to being run over by cars because it eats so much roadkill.

But the devil’s biggest issue today is a disease called devil facial tumor disease, or DFTD. DFTD is spread when an infected animal bites another one, which causes cancerous growths in and around the mouth. After a few months the tumors get so big that the devil can no longer eat and starves to death. Since devils bite each other all the time, the disease spreads quickly throughout a population.

In 2019 some researchers predicted the Tasmanian devil would be extinct by 2024. But here it is 2024 and not only is the devil not extinct, it’s actually doing a lot better now than it was just a few years ago.

Part of that is due to conservation efforts, where healthy devils are quarantined from infected ones in captive breeding programs. But part of it is natural. In 2018 a small population of devils was discovered that appeared to have developed a natural resistance to DFTD. Genetic studies done since then revealed some surprises. Not only are younger devils showing a genetic resistance to DFTD, there’s evidence that resistance to other transmissible cancers has developed in the past. Researchers think the Tasmanian devil might be especially prone to transmissible cancers but is also able to develop resistance relatively quickly. The devils with this resistance start growing tumors, but then the tumors stop growing and soon just disappear. Naturally, scientists are looking at the genetics of this trait to see if it can be applied to humans with certain types of cancer.

While Tasmanian devils fight each other, they don’t actually fight humans. Scientists report that it’s actually quite easy to work with. This makes it a lot easier to check the health of a captured animal. Hopefully it won’t be long before the entire population of Tasmanian devils is healthy and its numbers start to increase again.

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 250: Mystery of the Golden Toad

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This week let’s look at a scientific mystery: what caused the golden toad to go extinct, and is it still alive after all?

Further reading:

A deadly fungus is killing frogs, but the bacteria on their skin could protect them

The male golden toad:

The female golden toad (photo by Mary Crump):

Monteverde Cloud Forest Reserve is gorgeous and hopefully still hides some golden toads:

Show transcript:

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

This is our 250th episode, not counting the various bonus episodes, and I should have prepared a special show as a result but I didn’t notice until just now. But let’s pretend this is a special episode 250 show. It’s all about the golden toad.

The golden toad is from a tiny area of Costa Rica in Central America. I really do mean a tiny area. North of the city of Monteverde is the Monteverde Cloud Forest Reserve, and the toad was only known from one small part of the reserve that was less than two square miles in size, or about four square kilometers. Specifically, it’s from a single ridge in the nature reserve.

A cloud forest is a type of high altitude rainforest. Because temperatures tend to be much cooler than in an ordinary rainforest, a cloud forest can look very different and sometimes wonderfully strange. Cloud forests are foggy a lot of the time and the trees are often covered in thick mosses. In some cloud forests the trees are quite small while ferns and other plants can grow extremely large.

The Monteverde Cloud Forest Reserve is home to thousands of plant and animal species, many of them found nowhere else in the world. That includes the golden toad.

The golden toad gets its name from the male’s coloring. The males are a beautiful golden orange while the females are mostly gray or black with yellow, red, or green markings. As in many frogs and toads, females are larger than males, with a big female growing over two inches long from nose to butt, or about 5.5 centimeters.

The golden toad was only discovered by scientists in 1964 and described in 1966. The last golden toad was a male observed in May of 1989 during what should have been the mating season, but he was all alone. The golden toad was declared extinct in 2004 after repeated searches turned up no toads at all.

It’s easy to think that because the golden toad was restricted to such a small area, it was inevitable that it would go extinct, but the toads were actually common throughout their range until suddenly they weren’t. We’re not sure what happened. Here’s the story.

When the toad was first discovered, researchers estimated that there were around 1,500 adult toads living on the ridge. Most of the time the toads were hard to find, since during the dry season, or when they weren’t actively hunting the insects they ate, they’d stay in underground burrows where it was always nice and damp. But when the spring rains started, the males would hop out and gather around shallow puddles at the base of trees. Females would join the males, and because there were always more males than females, they’d all try to be the one to fertilize her eggs. During this time researchers were able to observe and count the toads, which they described as looking like living jewels.

The female golden toad laid her eggs in the pools of rainwater. The eggs hatched quickly but the tadpoles needed to live in their pool for at least four more weeks until they metamorphosed into toadlets that lived on land. If there was too much rain, the pools would overflow and the tadpoles were in danger of being washed out to die. If there wasn’t enough rain, the pools would dry out and the tadpoles would also die. But most years conditions were pretty good and lots of tadpoles lived to grow up. Until 1987.

A behavioral ecologist who specializes in amphibians, Martha Crump, was studying the golden toads in 1987. In April things seemed normal. The females laid their eggs in the shallow pools as usual, but then the rains stopped. The pools dried out and the eggs and tadpoles all died. When it rained again in May, the females laid more eggs and Dr. Crump counted them, because scientists do a lot of counting. She counted about 43,500 toad eggs. But the pools dried up again, and it was sadly easy for Dr. Crump to count how many tadpoles survived. It was only 29.

The next year, in 1988, there were only ten adult golden toads found. In 1989, one golden toad. In 1990 and beyond, zero golden toads.

The unusually dry spring of 1987 was a devastating blow to the golden toad population, but the adults weren’t affected. They had their nice damp burrows to live in and lots of insects to eat. Dry conditions happen every so often but not every year. Obviously something else happened between 1987 and 1988 to kill off almost all the adult toads too.

Researchers couldn’t figure out what might have happened. One hypothesis was that drought caused by the El Niño weather pattern was unusually severe in 1987 and killed off the adults as well as that year’s eggs and tadpoles. Another was that pesticides had found their way into the environment and killed the toads. Many researchers hoped that the toads were actually still alive, just hiding in their burrows until conditions improved, and every spring for many years toad experts waited to see if the living jewels would emerge during the spring rains. But they never did.

At the same time, though, toads, frogs, and other amphibians around the world were declining in numbers and going extinct. A veterinarian named Lee Berger, who was working toward her doctorate degree, discovered why in 1998. It’s a disease called chytridiomycosis, which is caused by a fungus. The disease infects the animal’s skin, and since amphibians absorb water, oxygen, and some essential minerals through their skin, the disease kills them rapidly.

Chytridiomycosis doesn’t kill every frog. Some species are more or less immune to the disease’s effects, but when infected frogs are taken to other places by people, as pets or food or whatever reasons people have for moving frogs around, the disease spreads rapidly. By the time Dr. Berger identified the cause, dozens of species of amphibian had already gone extinct as a direct result of the disease, and it’s continued ever since. The fungus spreads through water, so if a healthy frog moves into an infected pond, it’s likely to contract the disease.

There’s no cure for chytridiomycosis and treatment isn’t always effective. It doesn’t mean all amphibians are doomed, though. Studies of species that show natural immunity reveal that some amphibians have beneficial bacteria on their skin that stops the fungus from infecting it. Frogs from parts of Costa Rica show various levels of resistance to the fungus even though Costa Rica is particularly hard-hit when it comes to the disease.

The fungus especially thrives in cooler areas in high elevations—exactly the kind of place where the golden toad lived. Even so, the golden toad might have survived and developed a resistance to the disease, except for the bad luck of a drought year that killed off all the eggs and tadpoles at the worst possible time.

But while researchers have searched for the golden toad for years without luck, it might still be around. In 1991 one farmer reported seeing a pool full of healthy golden toads in a remote part of the cloud forest, including young toads. Other people have reported sightings too.

The important thing is that the Monteverde Cloud Forest Reserve is still protecting the golden toad’s habitat, along with all the other animals and plants in the reserve. If the golden toad is still hanging on, hopefully with individuals that have developed a resistance to chytridiomycosis, it has a safe place to increase in numbers.

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 184: The Mosquito!

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Thanks to Kaiden who suggested we learn about mosquitoes this week! You know what eats a lot of mosquitoes? Bats! If you don’t already listen to the excellent podcast Varmints!, jump on over to it to listen to last week’s episode about bats! I cohosted with Paul and had a great time, and I know you’ll like the episode and the podcast in general. It’s family friendly and lots of fun!

Further reading:

The Paleobiologist Who Inspired the Science in ‘Jurassic Park’

SMACK SMACK SMACK SMACK:

Mosquito larvae:

An elephant mosquito in amber:

Show transcript:

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

This week we have a great listener suggestion from Kaiden, who wants to learn about mosquitoes! This is especially great because last week I was a guest co-host on the awesome podcast Varmints!, and we talked about bats! As you may know, bats eat a LOT of mosquitoes. I’ll put a link to the Varmints! page in the show notes in case you don’t already subscribe. I think you’d like it.

The mosquito is a common insect that lives all over the world, except for Antarctica and Iceland. There are something like 3,500 species of mosquito known. In areas where it gets cold in winter some species of mosquito may hibernate, but most enter a state called diapause. This basically means that any eggs and larvae delay their development until it warms up, then develop into adults normally.

The mosquito is a type of fly, and like other flies it only has one pair of wings. Most mosquito species are only 3-6 millimeters long, gray or black in color, with long, extremely thin legs and narrow wings. The largest known species of mosquito is called the elephant mosquito, which can grow up to 18mm long. That’s almost three-quarters of an inch. Its wingspan is even larger, 24 mm, which is just shy of a full inch across.

The mosquito eats nectar. Oh, sorry, that’s the male mosquito. The female mosquito is the one who drinks blood, and she needs the blood to develop her eggs. But in fact, the female mosquito also eats nectar too, and mosquitoes even help pollinate some flowers. Some species of mosquito can develop eggs without blood, but most need the extra protein and nutrients that blood provides. In some species, the female can produce one clutch of eggs without blood, but she has to have blood to develop more eggs.

The female mosquito has a long, thin proboscis that she uses to pierce the skin of an animal and suck its blood, although the process is a lot more complicated than it sounds. The proboscis is made up of a sheath that protects the other mouthparts, including a pair of mandibles and a pair of maxillae. The mandibles and maxillae are actually the parts that cause the bite. If you look at a mosquito that has landed on your arm and is biting you, it looks like the proboscis must be stuck in your skin like a teensy hypodermic needle, but what you’re seeing is the proboscis sheath. The mosquito touches the sheath to your skin and bends it back slightly, which exposes the mouthparts and acts as a guide as the mouthparts bite you. The mandibles are the pointy ones and the maxillae have flattened ends. The mosquito moves her head slightly back and forth to lever them all into your skin, and the only reason this doesn’t hurt like crazy is because they’re so incredibly tiny, plus it happens very quickly.

Once the mouthparts have pierced the skin, the mosquito injects saliva, which contains proteins that act as an anticoagulant so the blood continues to flow without clotting. The itching and swelling associated with a mosquito bite are due to this saliva, which your body reacts to as a foreign substance, which of course it is.

This biting and saliva injecting process actually takes place very quickly, and then the mosquito sucks the blood up. She can hold up to three times her weight in blood. Not only that, but if she’s not disturbed, she will start digesting the blood quickly and will eject as much of the liquid as possible to make room for more blood, since she doesn’t need the liquid part of the blood.

Vampire bats do this too, if you’ve listened to our vampire bats episode or the new Varmints! episode about bats. They digest the blood they drink quickly, then pee out the excess liquid so they’re light enough to fly. But in the case of the mosquito, she just needs as many nutrients from the blood as possible to develop her eggs. That’s why a single mosquito may bite you numerous times. She needs to fill her stomach with the nutritious solids in the blood while excreting as much extra liquid as she can.

Once she has all the blood she needs, the mosquito will hide somewhere for a few days while her eggs develop. Then she’ll fly out to find a good place to lay them.

Mosquitoes lay their eggs in water, usually stagnant water like small ponds. The larvae stay in the water after they hatch. You may have seen mosquito larvae, since they’re distinctive. They’re only a few millimeters long and skinny, with a bristly-looking head. The larvae come to the surface to breathe through a siphon in the abdomen, so they will hang head downward just under the water’s surface. If something startles them, the larvae will curl up and sort of jerk their way through the water. Mosquito larvae eat algae and other tiny food.

Even after a larva pupates, it can still move around in the water. It doesn’t eat, but it needs to breathe, so it will hang just under the water with the breathing siphon in its abdomen at the surface, just as it did as a larva. After a few days, the pupa splits open and the adult mosquito emerges. Females fly off but the males stay in a group, and female mosquitoes join the group to find a mate.

The mosquito’s feet are adapted to allow it to stand wherever it likes. Its feet have microscopic hairy pads like those found on gecko toes that allow it to stick to smooth surfaces, and it also has microscopic hooks that help it stay in place on skin. And it also has feathery scales on its feet that are only a few microns across that allow it to stand on water. Since some species of female mosquitoes lay their eggs directly into water, being able to stand on the water’s surface is useful.

Mosquitoes spread a lot of diseases, which get injected along with the anticoagulant saliva. These include malaria, West Nile virus, zika, yellow fever, dengue fever, and many others. An estimated two million people die of mosquito-spread diseases every year, which makes the mosquito the deadliest animal in the world.

Because mosquitoes are such disease spreaders, people keep trying to figure out better ways to kill them off or at least stop them from spreading disease. One way to stop mosquitoes from spreading is to make sure there is no stagnant water around your house to breed new mosquitoes. A female mosquito will lay her eggs in even small amounts of water, such as an empty drink can that has collected rainwater, so getting rid of trash helps. In the past, people tried poisoning water or spraying insecticides, but this isn’t always very effective against mosquitoes and also kills other insects that may be beneficial.

But as genetic engineering becomes more sophisticated, scientists have discovered new ways to help stop mosquitoes from spreading disease.

For example, let’s talk briefly about dengue fever. I won’t go into symptoms or anything like that, don’t worry. It’s mostly a tropical disease found primarily in parts of Asia, Africa, and Central and South America, and it’s spread by the yellow fever mosquito, which also spreads many other diseases. People do die from dengue fever but most recover and are fine, but of course no one wants to get sick. There’s a vaccine as of 2016, but it’s not fully effective and has some side effects.

To help stop the spread of dengue fever, people have tried releasing animals into standing water that eat mosquito larvae, such as guppies native to the area. This has actually helped. In northern Vietnam, copepods that eat mosquito larvae were introduced into water storage tanks and did such a good job that the yellow fever mosquito was actually eliminated in the area for years. Some species of elephant mosquitoes, which you may remember from a few minutes ago are the largest mosquitoes in the world, don’t drink blood at all. Its larvae eat the eggs and larvae of other mosquito species, which gives it enough nutrients as an adult to lay plenty of eggs. One species of elephant mosquito specializes in eating the larvae of the yellow fever mosquito and has been introduced into some areas to help control its population.

Genetically modified male yellow fever mosquitoes have been introduced into the wild to mate with ordinary female mosquitoes in many places. The males contain a gene that causes larvae to die before reaching adulthood, and it has helped quite a bit. The yellow fever mosquito population has been reduced by over 90% in the places where the males were released, but it doesn’t affect other mosquito species that don’t carry the diseases. The problem is that genetically modified males have to be continuously bred and released in order for the program to keep working.

Very recently, as of January of 2020, scientists have engineered an antibody for the yellow fever mosquito. It basically stops the dengue virus from replicating in the mosquito, which means it can’t be passed to a human. There have been attempts to do this before, but it was only effective for one or another strain of the dengue virus. This new antibody is effective against all strains of the virus. This will help people while not killing the mosquitoes. The team is also working to engineer an antibody for other mosquito-borne viruses.

So, is it true that some people get targeted by mosquitoes more than others? As someone who seems to be a mosquito magnet when I go outside in the evening when mosquitoes are most active, I would say yes–and science agrees with me. Mosquitoes are attracted to some people more than others. The mosquito has a good sense of smell and can track animals by smelling their sweat and the carbon dioxide they exhale. They also tend to prefer people with type O blood and high body heat, but how attractive a person is to a mosquito depends on genetic traits too.

Some species of mosquito prefer some types of animals over others too. Some feed almost exclusively on birds, for instance. But in a pinch, a female mosquito will bite just about any animal, and it doesn’t even need to be warm-blooded. Mosquitoes will bite reptiles, amphibians, and even fish if they’re partly out of water. Some mosquitoes will even bite caterpillars. Caterpillars don’t have blood, but they do have hemolymph, which is just as nutritious to the mosquito.

Occasionally mosquitoes are found in amber, which as you may recall from episode 108 is fossilized tree resin. The oldest known was found in 79-million-year-old amber, so that means that yes, it could have bitten a dinosaur. But even if it still contained genetic material from dinosaur blood, and even if scientists were able to extract the dinosaur genetic material, it would be damaged DNA. Without a full genome of that particular dinosaur to compare against, we wouldn’t be able to repair the DNA sufficiently to actually clone a dinosaur. But we might be able to clone the actual mosquito and compare it to modern mosquitoes to learn more about them! It’s not as exciting as a dinosaur, but on the other hand there’s not a lot of danger of being stomped on or eaten by a mosquito.

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. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

 

Episode 162: Some Seals and the END OF THE WORRRRLLLDDDD

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Thanks to Kim and Pranav for their unsettling suggestions for this episode! I swear the reason I decided to do this episode this week was to celebrate getting over my cold, but then I realized I needed to address the virus everyone is talking about right now. I hope you all stay well and safe out there!

The Hawaiian monk seal OMG LOOK YOU CAN SEE ITS BELLY BUTTON, SO CUTE:

Show transcript:

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

I’m finally over my cold, so to celebrate let’s do a little bit of an unusual episode. Last year Kim suggested we do an episode about zoonotic diseases and diseases found in polar ice, and Pranav suggested an episode about what happens after humans go extinct. Those two topics seemed to go together, muahahaha.

Zoonotic diseases are diseases that humans can catch from other animals. Rabies is a good example, since it affects all mammals and is passed from one animal to another. In fact, let’s learn a little bit about rabies since naturally people are afraid of catching it but most people don’t know much about it.

Rabies is caused by a virus, specifically the lyssavirus. It acts on the body’s central nervous system, eventually infecting the brain. After that, it infects the salivary glands in order to be transmitted to other animals through a bite wound.

When an animal is infected with rabies, it may not show symptoms for a long time—sometimes years, although it’s more usually a few days to a few months. It starts as a fever and a headache, which are also symptoms of many other diseases. But within a few days of the first symptoms, the animal becomes aggressive, attempting to bite any other animal that it encounters. It has difficulty swallowing, which is why in cartoons animals with rabies are shown foaming at the mouth. This actually happens, but it doesn’t look like shaving cream and you’re not fooling anyone. The foam is just saliva that the animal can’t swallow. In the old days, rabies was called hydrophobia, which means fear of water, because in addition to not being able to swallow, the infected animal actually shows a fear of water. This all happens because the virus wants to be transmitted to other animals, and it does so through contact with infected saliva. If an infected animal could swallow its saliva and drink water, it would be much less likely to transmit rabies. So the virus hijacks the central nervous system to make the animal afraid of water and unable to swallow.

Of course, mammals can only live a few days without water, so once an animal reaches this stage it dies within a few days. Occasionally a human who contracts rabies and starts showing symptoms is rushed to the hospital and treated, but once they’ve reached the final stages of hydrophobia, it’s extremely rare that they survive even with the best medical care available.

So that’s horrifying. Some species of mammal are resistant to rabies and while they may get sick, they don’t usually die from it, including the vampire bat and the Virginia opossum. Birds can catch rabies but usually don’t show symptoms and recover without spreading it. Rabbits and hares, and many small rodents like guinea pigs and rats, almost never catch rabies and as far as researchers know, don’t pass the disease to humans.

And, of course, a vaccine was developed as long ago as 1885, with a more effective vaccine developed in 1967. The vaccine is mostly given to dogs, cats, and other pets, but humans who work with certain wild animals, like bats, are also given the vaccine. In some areas with widespread rabies among wild animals, vaccine-laced baits left for animals to find and eat have helped limit the spread of the disease.

If you are bitten by an animal, even if the animal doesn’t show symptoms of rabies, you should get the rabies vaccine and treatment as soon as possible. Rabies is most commonly spread to humans by dogs, especially stray dogs.

Feeling nervous yet?

What about diseases that spread from animals to humans that aren’t as well-known as rabies, or which appear to be new diseases? This is what has happened with the COVID-19 virus, also called the coronavirus, that has people worried at the moment. If you’re listening to this long after it came out and have no idea what COVID-19 is, at the time of release it’s March of 2020. Also, what’s the future like? Do we have flying cars yet?

The COVID-19 virus was first reported in China and researchers think it may have originated in bats, since it’s very similar to another coronavirus found in bats. There’s also some discussion that it may have originated in pangolins, or that there may be two strains of the disease. It’s still so early in the disease’s study that we don’t know for sure, but it does appear to be a zoonotic disease.

But how would a bat virus get into a human? It’s not like rabies where infected animals are trying to bite and infect others. I mean, when’s the last time a bat sneezed on you? Well, in parts of China people still catch and eat wild animals, including bats. Most of the initial cases of COVID-19 were in people who had gone to a market where bats and other animals were for sale as meat.

Wildlife trafficking is a source of many zoonotic diseases, and it doesn’t matter whether the animal is caught to be shipped live or killed and sold as meat or body parts. Not only is it really bad for endangered species, and of course for the individual animal killed, it also puts people at risk. China has put some stricter guidelines in place to limit the practice, and hopefully other countries will do the same.

COVID-19 is a virus with flu-like symptoms, spread the same way colds and flu are spread. While most people who catch it recover after a few weeks, it can be especially dangerous for people who already have other health issues. I know you’ve been told this constantly the last few weeks, but wash your hands with soap and hot water before you eat or rub your eyes or chew on that fingernail or pick your nose. Your mouth, nose, and eyes are lined with mucus membranes, which are easy for viruses to penetrate. Regular skin is too tough for the virus to get through. That’s also why you should cover your nose and mouth when you sneeze, so no one breathes in the germy droplets you just sneezed out. Hopefully it won’t be long before a vaccine is developed, but until then, if you feel sick the best thing is to stay home and take care of yourself, and not go out and potentially get other people sick.

Right, that’s enough about your run-of-the-mill zoonotic diseases because we’re all feeling icky and nervous now. Let’s move on to diseases found in polar ice!

As you probably also know, right now the earth’s overall global temperature is rising. This is causing more ice to melt at the poles, including some of what’s called the permafrost. The permafrost is a layer of soil that remains frozen and never thaws out, or at least it doesn’t thaw completely for years—sometimes thousands and thousands of years. That kind of permafrost is mostly found near the north and south poles. But now that the earth is warming, more permafrost is starting to melt. That means everything in the permafrost is thawing out too. That includes bacteria and viruses that were frozen thousands of years ago.

Some bacteria and viruses can remain dormant in ice, then thaw out and be just fine. Researchers have found active viruses in dead bodies that are thawing after sometimes hundreds of years. The only known outbreak so far has been a case of anthrax in Siberia that spread to living reindeer from a thawed corpse of a reindeer that died some 75 years ago. The infected reindeer herd then spread the disease to some people living nearby, and one twelve-year-old boy died.

But anthrax is a well-known disease that’s still around today. What makes us all uneasy about this is that there might be unknown diseases or especially dangerous strains of known diseases that could spread to animals and people. So could that happen? Are we all DOOMED?

No, we’re not all doomed, no matter what you keep hearing on the news. Even if a virus or bacterium is fine after being thawed out, it still needs to find a host quickly or it will degrade and die anyway. The reason the anthrax virus was able to infect reindeer was because they were grazing in the area where the dead reindeer thawed out. That virus got lucky, but most don’t. The areas of the world with permafrost are ones that are difficult to live in, so there aren’t as many animals around in the first place. There are even fewer people. Instead of being worried about catching a disease from permafrost, we should probably worry about other issues stemming from climate change. If you’re like me, of course, you can manage to worry about EVERYTHING at once, but you can put polar ice diseases near the bottom of the list.

Of course, there is another aspect of melting ice and disease. In 2004 some sea otters in Alaska were diagnosed with a version of distemper that was only known from eastern North America and Europe. This population of sea otters had never been anywhere but in Alaska, so how did they catch the virus? It wasn’t until researchers noticed that outbreaks of distemper corresponded with the melting of Arctic sea ice that they realized that infected animals from other parts of the country were moving west into newly ice-free territories, spreading the virus to otters that wouldn’t have been exposed otherwise. This particular strain of distemper affects otters, seals, and other marine mammals. It’s dangerous enough that conservationists are now vaccinating Hawaiian monk seals against distemper just in case it spreads to them, since only about 1,400 Hawaiian monk seals are alive to start with.

We haven’t talked about any particular kind of animal yet this episode, so let’s learn about those seals. The Hawaiian monk seal lives around the Hawaiian islands in the Pacific Ocean, but its closest relatives, the Mediterranean monk seal and the extinct Caribbean monk seal, are both native to the Atlantic Ocean.

Hawaii, of course, is an archipelago of 137 volcanic islands, most of them quite small, that span 1,500 miles, or 2,400 km. Seven of the eight biggest islands are the ones where humans live, and many of the islands are part of a protected marine wildlife reserve. The oldest island in the archipelago is probably 28 million years old, while the youngest, which is actually called Hawai’i or just the Big Island, is only about 400,000 years old and is still volcanically active. There’s another volcanic island southeast of Hawai’i that’s still growing underwater, too.

All the islands are so far away from any continent that there are only two mammals native to the area, the Hawaiian monk seal and a species of bat. The bat probably colonized the islands after being blown there by storms, but how did seals whose ancestors were native to the Atlantic reach these islands in the middle of the Pacific? The Atlantic and Pacific Oceans are separated by two big continents on either side. Even humans didn’t settle on Hawaii until 1700 years ago at most.

Before around 3 or 4 million years ago, though, North America and South America were separate continents with a seaway between. It wasn’t until around 3 million years ago that the Isthmus of Panama formed as two tectonic plates collided, forming volcanic islands and pushing the land up. When the oceans were finally separated by this new land, it stopped marine animals from being able to pass back and forth, but of course it also allowed land animals to pass between North and South America, the Great American Interchange which we’ve talked about in previous episodes from time to time. The Hawaiian monk seal’s ancestors probably lived in the shallow seaway between North and South America, and around three million years ago one population was cut off from the rest. That population eventually migrated to the Hawaiian islands and evolved into the seals that live there today.

The Hawaiian monk seal mostly lives around the smaller islands, although sometimes it comes to the larger ones. It’s gray with a pale belly, and a big female can grow up to 8 feet long, or 2.4 meters, while males are a little smaller. Babies are born with black hair. Most of the time the seal is in the water, hunting fish, cephalopods, and crustaceans, but for about ten days out of the year it spends most of its time on land because that’s when it molts. It doesn’t just shed its hair, it also sheds the outer layer of its skin. This is probably itchy and uncomfortable until the new hair and skin grow back. The seal can hold its breath for up to 20 minutes and can dive deeply, but it usually hangs out in shallow water around the islands. It usually sleeps on the beach but sometimes in underwater caves where there’s trapped air to breathe. It also gives birth on the beach. I have to say, it sounds like it has a pretty sweet life, except the part where sharks eat it.

In the 19th century many species of seal, including the Hawaiian monk seal, were either driven extinct or nearly driven extinct by hunters. The hunters wanted the oily fat that seals produce to keep them warm in cold water, which burns really well. Fortunately, once electricity was invented and became widespread, no one wanted to burn stinky whale and seal oil for light. But many species of seal, just like many species of whale, are still having trouble recovering. The Hawaiian monk seal is so endangered that conservationists provide veterinary care when appropriate, especially to young seals that are injured by aggressive older males and by fishing equipment. And, of course, they also provide vaccines to protect the seals from diseases like distemper.

Let’s finish up with Pranav’s question. What will happen after humans go extinct?

That won’t happen for a very, very long time—hopefully millions of years, if we’re careful with our resources and wash our hands. But everything ends eventually. One day we’ll all be gone but the earth will continue without us until the sun burns out and becomes a red giant, destroying the inner planets of our solar system. That won’t be for another 5 billion years or so, so you don’t need to lie awake and worry about it happening any time soon. The earth is only about 4 ½ billion years old now so it’s probably not even halfway through its lifespan.

In the meantime, continental drift will continue to happen just as it always has. Australia will eventually crunch into eastern Asia. Africa will merge into Europe. The Americas might end up squished up with Europe and Africa again, or they might end up merging with Asia on the other side of the landmass. Either way, there will probably be another supercontinent for a while, until the tectonic plates start separating again in their constant, slow dance. Oceans will expand and contract, mountains will build up and wear down, and through it all, for thousands of millions of years, animals of all kinds will continue to evolve.

When I was a kid, I had a book called After Man by Dougal Dixon, which speculated about what animals would look like in the future. I remember being kind of disappointed that they mostly didn’t look too different from the animals we have today. Rabbits were going to do well, I remember that. But of course that’s just speculation, and we can’t possibly know what will evolve in the future. It is fun to wonder, though. Mammals have been going strong for a long time now, but that doesn’t mean they always will. Various extinction events will occur as they always have, wiping out the dominant species and opening up ecological niches for new species to evolve. It might be birds next instead of mammals. It might be reptiles again. It might be something else that hasn’t even evolved yet.

I know we all secretly want to go back in time to see what dinosaurs and other extinct animals really looked like. But we’re very lucky to be alive right now. Travel is reasonably safe, quick, and inexpensive compared to how it used to be in the olden days, so we can go to different parts of the world and see animals where they live. If we can’t travel far, we can go to zoos where animals are usually kept in habitats that mimic their natural habitats as much as possible. We can watch high-quality videos of animals in the wild. We can listen to podcasts that talk about how we’re all going to die one day, sorry about that. We even happen to live at the same time as the largest animal ever known to live, the blue whale, which always just blows my mind. We are so lucky that the blue whale is still around and wasn’t killed off for whale oil along with all those seals!

And, best of all, we know a lot more about how the world works these days. We know the mistakes we’ve made in the past, like killing whales and seals for oil, and we know how to make things better in the future for everyone, people and animals alike. So instead of worrying too much about what horrible things might happen, do your best to make the world a better place every day and wash your hands with soap and warm water. Whenever you do start to worry, just think about a blue whale swimming around in the ocean happily eating krill, or a Hawaiian monk seal lounging on a sunny Hawaiian beach. I think I need a vacation.

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!