『Strange Animals Podcast』のカバーアート

Strange Animals Podcast

Strange Animals Podcast

著者： Katherine Shaw
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 A podcast about living, extinct, and imaginary animals! 博物学 生物科学 科学 自然・生態学
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  • Episode 436: Red-Eyed Tree Frog

    Episode 436: Red-Eyed Tree Frog
    2025/06/09
    Thanks to Trech for suggesting this week's topic, the red-eyed tree frog! Further reading: Tadpoles hatch in seconds to escape predator The colorful red-eyed tree frog [photo by Geoff Gallice]: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to have a short little episode about a little frog, suggested by Trech. The frog in question is the red-eyed tree frog, which is native to Central America, including parts of Mexico, and northwestern South America. It lives in forests, always around water. You might be thinking, “of course, frogs live in water,” but remember that this is a tree frog. It lives in trees. But it still needs water for its babies, just not quite in the way most frogs do. Before we learn about that, let’s learn about the frog itself. A big female can grow about 3 inches long, or 7.5 cm, while males are smaller. It’s a cute frog, of course, because frogs are always cute, but it’s also brightly colored. It’s bright green with red eyes, blue and yellow stripes on its sides, and orange feet. Ordinarily, a frog with such bright colors would warn potential predators that it’s toxic, but the red-eyed tree frog isn’t toxic at all. Its bright colors have a different purpose. When it’s sitting on a leaf, the bright colors are hidden and only the frog’s smooth green back is showing, which makes it look like just another leaf. Only its eyes are bright, but it closes its eyes when it’s resting. But if a predator approaches, the frog opens its eyes suddenly and jumps up, revealing all those bright colors. The predator is startled, and maybe even hesitates because it thinks the frog might be toxic, and by the time the predator decides it should try eating the frog after all, the frog is long gone. Oh, and if you’re wondering, the red-eyed tree frog can see through its eyelids. They’re actually not eyelids like we have, but a membrane that it can move over its eyes. The frog is nocturnal and eats insects like mosquitoes, crickets, and moths. It has a good sense of smell, which helps it find insects in the dark. The tree frog also has suction cups on its toes that help it stay put on smooth leaves. During the day it sticks itself to the underside of a leaf to sleep where it’s more hidden. The female also lays her eggs on the underside of a leaf. This protects them from heavy rain, since the frogs breed during the rainy season, and it also helps hide them from predators. The female chooses a leaf that’s growing above water, and if the leaf isn’t very big she’ll lay eggs on both sides of it and fold the leaf to help hide all the eggs. The eggs stick to the leaf with a type of jelly that also helps keep them from drying out. The eggs hatch in about a week, but they can hatch a few days early if a predator approaches. The embryonic tadpoles in their eggs can sense vibrations, and if a predator like a snake shakes the leaf as it approaches the eggs, the tadpoles can hatch within seconds. They drop straight down into the water below the leaf. Hatching early when in danger is called phenotypic plasticity, and it’s really rare. It’s especially unusual because the embryonic tadpoles can actually tell the difference between a typical predator of frog eggs and vibrations caused by other animals or the wind. They can hatch so quickly because the stress reaction causes the pre-tadpoles to secrete an enzyme from their little noses, which weakens the egg wall and allows them to push and wiggle their way out. Tadpoles stay in the water for several weeks, or sometimes several months depending on conditions, during which time they eat algae and other tiny food in the water. As they grow bigger, the tadpoles can eat bigger food, including other tadpoles. They switch to tiny insects after they metamorphose into froglets. At some point during its development, a red-eyed tree frog needs to eat enough food containing carotenoids in order to develop...
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    6 分
  • Episode 435: The Narwhal and the Unicorn

    Episode 435: The Narwhal and the Unicorn
    2025/06/02
    Thanks to Owen and Aksel, and Dylan and Emily for their suggestions this week! Further reading: Where did the unicorn myth come from? The narwhal is my favorite whale: 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 Owen and Aksel, and a related suggestion by Dylan and Emily. Owen and Aksel suggested we talk about the narwhal, which we haven’t really discussed since episode 5 even though it’s one of my favorite animals. Dylan and Emily suggested we learn about animals that might have inspired legends of the unicorn. These two topics are definitely linked! The narwhal is a toothed whale, but it doesn’t have very many teeth—in fact, most narwhals don’t have any teeth at all. It swallows its food whole and doesn’t need to chew, mostly small fish but also squid and other small animals. Male narwhals do have one tooth, a tusk that can be almost 10 feet long, or over 3 meters. The tusk is a spiral shape, developed from what would have been the left canine tooth, but instead of growing downward like a regular tooth, it grows forward, directly through the front of the lip. A lot of times people get confused and think the tusk is a horn that grows from the narwhal’s forehead, and that’s mainly because the narwhal is closely related to the unicorn legend. That sounds weird at first, since the narwhal is a whale that can grow up to 18 feet long, or 5.5 meters, and lives in cold waters of the Arctic Circle. The unicorn is supposed to be a horse-like animal with a spiral horn growing from its forehead, although it’s also sometimes depicted as more goatlike in appearance, with cloven hooves and a little beard. It also usually has a long tail with a tuft at the end like a donkey or zebra. In the olden days in Europe, the unicorn’s single spiral horn was supposed to have curative properties. If you ground up a little bit of the horn, known as alicorn, people thought it acted as a medicine to cure you of poisoning or other ailments. The alicorn was actually the tusk of the narwhal, but traders claimed it was a unicorn horn because they could charge more for it. The legend of the unicorn having a long spiral horn doesn’t come from ancient stories, it comes from the appearance of the narwhal’s tusk. The narwhal is as mysterious as the unicorn in its own way. In fact, the narwhal seems a lot less plausibly real than a unicorn and a lot of people actually don’t realize it’s a real animal. The biggest question about the narwhal is what its tusk is used for. Most males have one, and occasionally a male will grow two tusks. Most females don’t have one, although about 15% of females will grow a tusk, usually smaller than the male’s. Females live longer than males on average, so obviously the tusk isn’t helping males survive. Most scientists assume that it’s just a way for males to attract mates. But the narwhal’s tusk seems to be useful for more than just decoration. It contains high concentrations of nerve endings, and scientists think it might help the whale sense a lot of information about the water around it. Narwhals have been observed smacking fish with their tusks to stun them, so that the whale can slurp them up more easily. And even though it’s technically a tooth, the narwhal’s tusk can bend up to a foot, or about 30 cm, in any direction without breaking. The narwhal is pale gray in color with darker gray or brown dapples, but like gray horses, many narwhals get paler as they age. Old individuals can appear pure white. This can make them easy to confuse with another small whale that’s closely related, the beluga, which shares other characteristics with the narwhal. The beluga is white, has a small rounded head and doesn’t have a dorsal fin, and has a neck so that it can bend it head around. Most whales have lost the ability to move their heads. The beluga also lives in the same areas as the narwhal and both ...
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    9 分
  • Episode 434: The Real Life Dragon

    Episode 434: The Real Life Dragon
    2025/05/26
    Thanks to Jaxon for suggesting this week's topic, Coelurosauravus! Further reading: Coelurosauravus New Research Reveals Secrets of First-Ever Gliding Reptile The modern Draco lizard glides on "wings" made from extended rib bones: Coelurosauravus glided on wings that were completely different from any other wings known [art from the first link above]: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to learn about an extinct animal suggested by Jaxon. It’s called Coelurosauravus and it lived around 255 million years ago in what is now Madagascar. Coelurosauravus was a member of the Weigeltisauridae family, reptiles whose fossils have been found not just in Madagascar but in parts of Europe, and maybe even North America (although we’re not sure yet). They were gliding reptiles that probably lived in trees and ate insects and other small animals, sort of like modern gliding lizards. But while most gliding lizards are very small, Coelurosauravus grew over a foot long, or around 40 cm, and that’s nowhere near the weirdest thing about it. To explain why Coelurosauravus was so very peculiar, we have to learn a little about other gliding reptiles. Back in episode 255 we learned about kuehneosaurids, and that’s a good place to start. Kuehneosaurids lived around 225 million years ago in what is now England. This wasn’t all that long after Coelurosauravus lived and not that far away from where some of its relations lived, but the two weren’t related. Kuehneosaurus looked like a big lizard although this was before modern lizards evolved, but it was a reptile and it was even larger than Coelurosauravus. Kuehneosaurus grew about two feet long, or 70 cm, including a long tail, and probably lived in trees and ate insects. Kuehneosaurus glided on sail-like structures on its sides that were made from extended ribs with skin stretched over them. Its wings weren’t all that big, although they were big enough that they could act as a parachute if the animal fell or jumped from a branch. Another gliding reptile, Kuehneosuchus, had wings that were much longer. In a study published in 2008, a team of scientists built models of kuehneosuchus and tested them in a wind tunnel used for aerospace engineering. It turned out to be quite stable in the air and could probably glide very well. We don’t know a whole lot about the kuehneosaurids because we haven’t found very many fossils. We’re not even sure if the two species are closely related or not. We’re not even sure they’re not the same species. Individuals of both were uncovered in caves near Bristol in the 1950s, and some researchers speculate they were males and females of the same species. Despite the difference in wings, otherwise they’re extremely similar in a lot of ways. Generally, researchers compare the kuehneosaurids to modern draco lizards, which we talked about in episode 237, even though they’re not related. Draco lizards are much smaller, only about 8 inches long including the tail, or 20 cm, and live throughout much of southeastern Asia. Many gliding animals, like the flying squirrel, have gliding membranes called patagia that stretch from the front legs to the back legs, but the draco lizard is different. It has greatly elongated ribs that it can extend like wings, and the skin between the ribs acts as a patagium. This skin is usually yellow or brown so that the lizard looks like a falling leaf when it’s gliding. Draco lizards can fold their wings down and extend them, which isn’t something the kuehneosaurids appear to have been able to do. But now let’s return to Coelurosauravus. It too had wing-like structures on its sides that consisted of skin stretched over bony struts. But in this case, the bones weren’t elongated ribs. Coelurosauravus had about 30 pairs of long, flexible bones that extended from the sides of its belly, and it could open and close its wings like draco lizar...
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    6 分

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