Getting Bigger

An adult blue whale can reach a length of a hundred feet and weigh up to 200 tons. That makes it the biggest animal on Earth -- not only today, but, as far as anyone knows, in the planet’s entire history.

It’s not the only giant roaming the world’s oceans, though. Several other species of whale are also enormous. But that hasn’t always been the case. In fact, a recent study found that these whales began growing so large only a few million years ago.

Blue whales and their kin are filter feeders -- they filter small organisms from the water as they swim along. They can consume tons of them every day. And the recent study says the supply of these creatures may be the key to the increased size of the whales.

Until a few million years ago, no filter feeders grew larger than about 30 feet. But that began changing about three million years ago. Researchers say that may be the result of a change in climate patterns around the globe. 

Winds over the oceans began getting stronger. That stirred up the water, dredging more nutrients from the deep ocean up to the surface. More nutrients created an explosion in the population of the small organisms on which the whales feed.

A greater food supply made it possible for the whales to grow much bigger than in earlier eras. And the larger size made it possible for them to withstand seasonal dips in the supply, and to travel greater distances to find better feeding grounds. So filter feeders quickly grew to giant proportions -- the biggest animals ever.