Strange Animals Podcast

This week we're going to learn about some animals that seem to have individual names! Further reading: Bottlenose dolphins can use learned vocal labels to address each other How Do Dolphins Choose Their Name? Vertical transmission of learned signatures in a wild parrot Baby Parrots Learn Their Names from Their Parents Study: African Elephants Address Each Other With Name-Like Calls Marmoset Monkeys Use Names to Communicate with Each Other The green-rumped parrotlet (photo by Rick Robinson, taken from this site): Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to learn about some animals that seem to be using names to refer to other individuals or themselves. Let’s start with bottlenose dolphins, because they’re well-studied and scientists have known about this particular aspect of their society for over a decade. Every bottlenose dolphin has a signature whistle that identifies it to other dolphins. The signature whistles can be complex and the dolphin may add or change details to indicate its mood or other information. It’s not precisely a name in the way humans would think of it, but it is an identifier. The dolphin creates its own signature whistle when it’s young. Some dolphins pattern their whistles on their mother’s signature whistle, while others mimic their siblings or friends. Some seem to pattern theirs on a distant acquaintance, which sounds to me like they just like something about an unusual whistle and decide to incorporate it into their own whistle. As dolphins grow up, females typically don’t change their whistles, but males often do. Male dolphins often pair up together and remain bonded, and a pair may change their signature whistles to be similar. When a dolphin is trying to find a friend it can’t see, it will mimic that friend’s signature whistle. If a mother can’t see her calf and is worried, she’ll do the same, and her calf will answer by repeating its signature whistle. A lost calf will imitate its mother’s whistle. But it’s even more complicated than it sounds, because a group of dolphins who get together to forage may choose a shared whistle that the whole group uses. This helps them coordinate their behaviors to work together. Each member of the group uses a slightly different version of the group whistle, which means that each member can identify who’s speaking. Other cetaceans seem to use a similar kind of name. Sperm whales, for instance, have a unique click sequence that they use to announce themselves when approaching other whales. The signature clicks always appear at the beginning of a sequence and don’t vary. Bottlenose dolphins and many other cetaceans are extremely social animals. So are parrots. Studies of parrot calls indicate that parrots appear to have signature calls that they use the same way as dolphins do, to identify themselves to other parrots and as a way for other parrots to call for them. A study of wild green-rumped parrotlets in Venezuela discovered that the birds give a unique signature call to each baby while it’s still in the nest, and the baby continues to use its call its whole life, often with small changes. The study set up video cameras to monitor 16 nests of a large wild population of the parrots. The population has been well studied and is used to using nesting tubes that scientists have set up for them. This makes it easier for the scientists to monitor nesting behaviors. In this case, to test whether the names had something to do with genetics or not, the scientists sneakily moved half of the eggs from one nest to another, so that half the parents unknowingly raised some chicks that weren’t actually related to them. Despite the egg switcharoo, all the chicks were given names that were similar to the parents’ signature calls. The parents started using a specific signature call soon after the eggs hatched, and the babies started imitating it.

Thanks to Eilee and Alexis for their suggestions this week, two amazing frogs! Further reading: Paradoxical frog: The giant tadpole that turns into a little frog Fungus is wiping out frogs. These tiny saunas could save them. How to build a frog sauna The paradoxical frog [photo by Mauricio Rivera Correa - http://calphotos.berkeley.edu, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=6703905]: The Vietnamese mossy frog [photo by H. Zell - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=81804225]: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. Let’s start 2025 off right with an episode about frogs! Thanks to Alexis and Eilee for their suggestions. Let’s start with Eilee’s suggestion, the paradoxical frog. The paradoxical frog is a type of tree frog that lives in South America. Like other frogs, it likes ponds and shallow lakes. Some individuals are green and some are brown, and a frog may have darker stripes or splotches, or might just be plain. The tadpoles eat algae and other tiny food, while the adults eat insects. As with most frogs, the paradoxical frog hatches into a larval stage called a tadpole or pollywog, which is fully aquatic. It later metamorphoses into its adult form as a frog. Most tadpoles start out very small and grow larger, then metamorphose into a juvenile frog which then grows to fully adult size. But while the paradoxical frog’s tadpole starts out small, it can grow to as much as 11 inches long, or 28 centimeters! It’s the largest tadpole in the world as far as we know. So how big is the adult frog if the tadpole is so enormous? About 3 inches long, or 7.5 cm, from snout to vent. That’s why it’s called the paradoxical frog, because a paradox is something that seems contradictory to expectations. Instead of the ordinary way of things, where a small tadpole grows into a bigger frog, in this case a big tadpole grows into a smaller frog. It’s sometimes called the shrinking frog. One interesting detail is that not all of the tadpoles are that big. If a female lays her eggs in a small body of water that’s likely to dry up, or that doesn’t have a lot of food available, or if there are a lot of predators in the water, the tadpole metamorphoses quickly and doesn’t grow very big. But if the tadpole is in a better location it matures much more slowly, which allows it to reach much larger size before metamorphosing. I should also mention that the 11-inch-long tadpole that is the largest ever measured was actually raised in captivity. In the wild, the largest paradoxical frog tadpole ever measured was 6 ½ inches long, or almost 17 cm. That’s still really big, but not that ridiculously big. But the confusing thing is that the tadpole is big and bulky, up to four times the size of the adult frog. Where does all that mass go after it transforms? Early scientists who learned about the paradoxical frog wondered the same thing. They were so confused that they suggested that the frog actually came first and later metamorphosed into the tadpole, which then metamorphosed into a fish. But the main reason the tadpole is so long is its tail. When it metamorphoses into a frog, it absorbs the tail and therefore appears to shrink. The bulkiness of the tadpole’s body matches the bulkiness of the frog’s body. And unlike most frogs, which metamorphose into juvenile frogs that still have some growing to do, the paradoxical frog metamorphoses into a completely adult frog. It’s as big as it will ever get and fully mature, ready to mate and lay eggs. Next, Alexis wanted to learn about the Vietnamese mossy frog. It lives in parts of Vietnam, Laos, and other nearby areas. It prefers mountainous rainforests and the female often chooses to lay her eggs in a tree hollow or even a rock cavity where water has collected. Instead of laying her eggs in the actual water, though, she lays them on rocks or branches above the water.

Thanks to Pranav for suggesting this week's massive topic! Further reading: When did the Isthmus of Panama form between North and South America? Florida fossil porcupine solves a prickly dilemma 10-million years in the making Evidence for butchery of giant armadillo-like mammals in Argentina 21,000 years ago Glyptodonts were big armored mammals: The porcupine, our big pointy friend: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week, at long last, we’re going to learn about the great American interchange, also called the great American biotic interchange. Pranav suggested this topic ages ago, and I’ve been wanting to cover it ever since but never have gotten around to it until now. While this episode finishes off 2024 for us, it’s the start of a new series I have planned for 2025, where every so often we’ll learn about the animals of a particular place, either a modern country or a particular time in history for a whole continent. These days, North and South America are linked by a narrow landmass generally referred to as Central America. At its narrowest point, Central America is only about 51 miles wide, or 82 km. That’s where the Panama Canal was built so that ships could get from the Atlantic Ocean to the Pacific and vice versa without having to go all around South America. It wasn’t all that long ago, geologically speaking, that North and South America were completely separated, and they had been separated for millions of years. South America was part of the supercontinent Gondwana, while North America was part of the supercontinent Laurasia. We’ve talked about continental drift before, which basically means that the land we know and love on the earth today moves very, very slowly over the years. The earth’s crust, whether it’s underwater or above water, is separated into what are called continental plates, or tectonic plates. You can think of them as gigantic pieces of a broken slab of rock, all of the pieces resting on a big pile of really dense jelly. The jelly in this case is molten rock that’s moving because of its own heat and the rotation of the earth and lots of other forces. Sometimes two pieces of the slab meet and crunch together, which forms mountains as the land is forced upward, while sometimes two pieces tear apart, which forms deep rift lakes and eventually oceans. All this movement happens incredibly slowly from a human’s point of view--like, your fingernails grow faster than most continental plates move. But even if a plate only moves 5 millimeters a year, after a million years it’s traveled 5 kilometers. Anyway, the supercontinent Gondwana was made up of plates that are now South America, Africa, Australia, Antarctica, and a few others. You can see how the east coast of South America fits up against the west coast of Africa like two puzzle pieces. Gondwana actually formed around 800 million years ago, then became part of the even bigger supercontinent Pangaea, and when Pangaea broke apart around 200 million years ago, Gondwana and Laurasia were completely separate. North America was part of Laurasia. But Gondwana continued to break apart. Africa and Australia traveled far away from South America as molten lava filled the rift areas and helped push the plates apart, forming the South Atlantic Ocean. Antarctica settled onto the south pole and India traveled past Africa until it crashed into Eurasia. By about 30 million years ago, South America was a gigantic island. It’s easy to think that all this happened just like taking puzzle pieces apart, but it was an incredibly long, complicated process that we don’t fully understand. To explain just how complicated it is, let’s talk for a moment about marsupials. Marsupials are mammals that are born very early and finish developing outside of the mother’s womb, usually in a special pouch. Kangaroos, wallabies, koalas, wombats, and Tasmanian devils are all marsupials, and all from Australia.

Thanks to Elizabeth, Alexandra, Kimberly, Ezra, Eilee, Leon, and Simon for their suggestions this week! Further reading: New population of blue whales discovered in the western Indian Ocean An Endangered Dolphin Finds an Unlikely Savior--Fisherfolk The humpback whale: The gigantic blue whale: The tiny vaquita: The Indus river dolphin: The false killer whale: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to have a big episode about various dolphins and whales! We’ve had lots of requests for these animals lately, so let’s talk about a bunch of them. Thanks to Elizabeth, Alexandra, Kimberly, Ezra, Eilee, Leon, and Simon for their suggestions. We’ll start with a quick overview about dolphins, porpoises, and whales, which are called cetaceans. All cetaceans alive today are carnivorous, meaning they eat other animals instead of plants. This includes the big baleen whales that filter feed, even though the animals they eat are tiny. Cetaceans are mammals that are fully aquatic, meaning they spend their entire lives in the water, and they have adaptations to life in the water that are simply astounding. All cetaceans alive today belong to either the baleen whale group, which filter feed, or the toothed whale group, which includes dolphins and porpoises. The two groups started evolving separately about 34 million years ago and are actually very different. Toothed whales are the ones that echolocate, while baleen whales are the ones that have extremely loud, often beautiful songs that they use to communicate with each other over long distances. It’s possible that baleen whales also use a limited type of echolocation to navigate, but we don’t know for sure. There’s still a lot we don’t know about cetaceans. Now let’s talk about some specific whales. Ezra wanted to learn more about humpback and blue whales, so we’ll start with those. Both are baleen whales, specifically rorquals. Rorquals are long, slender whales with throat pleats that allow them to expand their mouths when they gulp water in. After the whale fills its mouth with water, it closes its jaws, pushing its enormous tongue up, and forces all that water out through the baleen. Any tiny animals like krill, copepods, small squid, small fish, and so on, get trapped in the baleen. It can then swallow all that food and open its mouth to do it again. The humpback mostly eats tiny crustaceans called krill, and little fish. The humpback grows up to 56 feet long, or 17 meters, with females being a little larger than males on average. It’s mostly black in color, with mottled white or gray markings underneath and on its flippers. Its flippers are long and narrow, which allows it to make sharp turns. The humpback is closely related to the blue whale, which is the largest animal ever known to have lived. It can grow up to 98 feet long, or 30 meters, and it’s probable that individuals can grow even longer. It can weigh around 200 tons, and by comparison a really big male African elephant can weigh as much as 7 tons. Estimates of the weight of various of the largest sauropod dinosaurs, the largest land animal ever known to have lived, is only about 80 tons. So the blue whale is extremely large. The blue whale only eats krill and lots of it. To give you an example of how much water it can engulf in its enormous mouth in order to get enough krill to keep its massive body going, this is how the blue whale feeds. When it finds an area with a lot of krill floating around, it swims fast toward the krill and opens its giant mouth extremely wide. When its mouth is completely full, its weight—body and water together—has more than doubled. Its mouth can hold up to 220 tons of water. Since the whale is in the water, it doesn’t feel the weight of the water in its mouth. Blue whales live throughout the world’s oceans, but a few years ago scientists analyzing recordings of whale song from the we...