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Why Are Whales So Big?


How do whales spray water? Why are humpback whales so fat and blue whales so long, and why are blue whales blue? Do whales have belly buttons? How do you weigh a whale? And how do whales drink water in the salty ocean? We have a whale of a time answering questions about these ocean-dwelling mammals with paleontologist Nick Pyenson, author of Spying on Whales: The Past, Present and Future of Earth's Most Awesome Creatures.

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Do whales have belly buttons? - Olive, 5, Cleveland, Ohio

"Yes! Whales do have belly buttons because they're mammals, just like you or me," Nick Pyenson says. "And the belly buttons that we all have are a sign that we were once connected to our mothers in our mother's womb. They're hard to see, kind of folded in and under the whale, but yes, whales have belly buttons."

It may be hard to believe it, but whales are closely related to even-toed hoofed mammals-cows, pigs, deer, camels, sheep.

"But whales look really different [from those animals] and that has to do with their evolutionary history--how they evolved, how they came to be. So we can look at whale fossils to see how that happened. Fossils can tell you a lot that you wouldn't otherwise know. And that's so true about whales," Pyenson says.

Besides fossils, there are other tools scientists can use to figure out that whales are related to land mammals.

"We can look at their DNA. DNA shows us that they fit in with all these other hoofed mammals. And whales are mammals: they breath air; they have babies that suckle from their moms; they have hair, little tiny whiskers when they're born. Fossils tell us the earliest whales lived on land with four legs, tails without flukes, nostrils that were long and at the end of their snouts. Scientists dissecting whales know that whales have multi-chambered stomachs. So that's how we figured out how whales were related to those kind of mammals."

But just to be clear, whales have lived in the ocean for a very long time! Whales have been around for 50 million years, and they've been aquatic animals for about 40 million of those years.

And as for why whales are so big, it turns out that's still being investigated! Whales only started to get really big very recently. Well, recently in the way paleontologists think of time. Fossil records show that about 4.5 million years ago, whales' size began to increase significantly. Nick and some other paleontologists believe that whales got so big because their large size and lots of blubber allows them to migrate long distances to get to food sources.

In this episode we'll also learn how to weigh a whale! Hint: it doesn't involve a really big bathroom scale.

Melody is the Contributing Editor for But Why: A Podcast For Curious Kids and the co-author of two But Why books with Jane Lindholm.
Jane Lindholm is the host, executive producer and creator of But Why: A Podcast For Curious Kids. In addition to her work on our international kids show, she produces special projects for Vermont Public. Until March 2021, she was host and editor of the award-winning Vermont Public program Vermont Edition.
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