Wednesday, December 5, 2018

Speaking of Science: What we can learn from whales, the eating champions of the world

Speaking of Science
Talk nerdy to us

A humpback whale leaps in water near Hawaii. (Reed Saxon/AP)

No creature on Earth is as successful an eater as the baleen whale. By swimming through clouds of krill with their mouths open wide, then sorting food from water by filtering it through a curtain of bony bristles, these cetaceans have grown bigger than any animal in the history of the planet. The largest dinosaur would have been dwarfed by the average 300,000-pound blue whale. Massive woolly mammoths would have swooned to see rorquals swallow half a million calories in a single mouthful.

In this season of gluttony, it seems fitting to celebrate these eating champions of the world. So I called Nick Pyenson, the curator of fossil marine mammals at the Smithsonian's National Museum of Natural History and the author of the book "Spying on Whales," for insights on how their tremendous capacity for consumption came to be.

The first whales had jaws full of teeth, like their four-legged ancestors that abandoned the land for the ocean about 50 million years ago. But chewing, at least the way we do it, is not an effective strategy for dining at sea.

"The rules of engagement are totally different underwater," Pyenson told me. Whales "can't use claws to subdue prey. . . . They don't have opposable thumbs." Imagine trying to munch on a meal you couldn't even hold.

For that reason, most of today's whales that have teeth, such as dolphins and beluga, are suction feeders. They use their pearly whites to grab onto prey, then take advantage of the temporary pressure differential created when they open their mouths to slurp the food down their gullets.

But this strategy entails spending a lot of time chasing single large prey, Pyenson said. So sometime around 30 million years ago, when a changing ocean environment probably led to a surge in planktonic organisms, whales picked up a new technique — swimming through a mass of many millions of small critters.

This "lunge feeding" technique is the "largest biomechanical event on the planet," Pyenson said. And it's a genius way to eat. "It's got a huge return on investment."

Baleen is essential to this strategy. But the origins of this structure — which is made from keratin, like hair and nails, rather than dentin and enamel, like teeth — have long been a mystery. Did early whales have both baleen and teeth? How long were they munchers before they became gulpers?

In a new study in the journal Current Biology, Pyenson and his colleague, Carlos Mauricio Peredo, offer a clue: The newly discovered prehistoric whale Maiabalaena nesbittae, which lived about 33 million years ago, didn't have teeth or baleen. To Pyenson, this suggests that the ancestors of today's baleen whales totally gave up on teeth in favor of suction feeding, setting the stage for the rise of baleen a few million years later.

Whether you spend the next few weeks gorging yourself on latkes or black-eyed peas or roast beast or stale cookies from the nondenominational office holiday party, I hope this gives you a little something extra to chew on.

— Sarah

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