How whales got so big

Sci­ence be­lieves it now has the an­swer

Cape Breton Post - - Science - BY SETH BORENSTEIN

Scientists think they have an­swered a whale of a mys­tery: How the ocean crea­tures got so huge so quickly.

A few mil­lion years ago, the largest whales, av­er­aged maybe 15 feet long. That’s big, but you could still hold a fos­sil skull in two hands.

Then seem­ingly overnight, one type of whale — the tooth­less baleens — be­came huge. Mod­ern blue whales get as big as 100 feet, the largest crea­tures ever on Earth. Its skull is now big­ger than a mini­van and could prob­a­bly fit more than five peo­ple in­side, re­searchers said.

“We re­ally are liv­ing in the time of giants,” said study coau­thor Ni­cholas Pyen­son of the Smith­so­nian Nat­u­ral His­tory Mu­seum. “Why is that?”

And it hap­pened “in the blink of an evo­lu­tion­ary eye,” which makes it harder to fig­ure out what hap­pened, said Gra­ham Slater at the Uni­ver­sity of Chicago, lead au­thor of the study in Tues­day’s Pro­ceed­ings of the Royal So­ci­ety B.

Their study has pro­posed an an­swer: Ice ages in the last 3 to 5 mil­lion years started it, chang­ing the oceans and food sup­ply for whales.

The re­searchers used fos­sil records of the smaller whales to cre­ate a fam­ily tree for baleen whales — which in­clude blue whales, hump­backs and right whales. Us­ing com­puter sim­u­la­tions and knowl­edge about how evo­lu­tion works, they started fill­ing in the gaps be­tween the small whales and the mod­ern su­per-sized ver­sion.

They keyed in on a time pe­riod when the whales got huge and smaller whale species went ex­tinct, some­where be­tween a few hun­dred thou­sand years ago and 4.5 mil­lion years ago.

They con­cluded that when the size changes started, the poles got colder, ice ex­panded and the wa­ter cir­cu­la­tion in the oceans changed and winds shifted. Slater and Pyen­son said cold wa­ter went deep and moved closer to the equa­tor and then even­tu­ally bub­bled

back up in patches rich with the small fish and other small crit­ters that whales eat.

Be­fore that, whale food was spread out, rel­a­tively easy to get at. Now, they are gi­ant buf­fets amid hun­dreds of miles of whale food deserts. That’s why you can see lots of whales in the sum­mer in Cal­i­for­nia’s Mon­terey Bay, Slater said.

Baleen whales, which have no teeth, feed by gulp­ing tremen­dous amount of ocean, fil­ter­ing out the wa­ter and eat­ing the crit­ters they cap­ture. Toothed

whales, like sperm whales, hunt in­di­vid­ual fish or squid, so the ocean changes that made food less evenly spread out didn’t af­fect them as much. But baleen whales hunt schools of fish or swarms of krill, Pyen­son said.

“If you are a whale, the eas­i­est way to take ad­van­tage of dense but sparsely avail­able re­sources is to get big,” Slater said. “If you are big, you ba­si­cally can get more miles to the gal­lon.”

Baleen whales went from 15 to 100 feet in about the same

time as hu­mans evolved, he said.

Olivier Lam­bert at the Royal Bel­gian In­sti­tute of Nat­u­ral Sciences, who wasn’t part of the study, calls it “a re­ally con­vinc­ing sce­nario.” But he said the lack of fos­sils in cer­tain time pe­ri­ods is an is­sue.

As oceans warm from man­made cli­mate change, the seas will be more like it was when the whales were smaller and they will have a more dif­fi­cult time sur­viv­ing, Slater and oth­ers said.

AP PHOTO/J. SCOTT APPLEWHITE

A new study ex­plains how the baleen whale fam­ily, which in­cludes hump­back whales, grew seem­ingly sud­denly only a few mil­lion years ago from smaller crea­tures to the ocean giants they are now.

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