Samantha Price on how blue whales grew big eating tiny creatures

The 160-metric ton blue whale evolved a huge mouth – allowing it to eat millions of krill each day.

Samantha Price: The blue whale which is – we think – the largest ever living mammal… eats these tiny, almost microscopic krill and plankton. So this seems very strange, that you have a very large size but you’re eating something so small.

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Samantha Price is a researcher at the University of California, Davis. In a study published in May 2010 in the Proceedings of the Royal Society B, Price found that there’s a strong connection between what whales eat, and how they evolved to be so large.

Samantha Price: The diet of an animal is linked to a lot of other aspects of its biology; such as where it lives, and how it interacts with its environment, as well as its size.

For example, Price said, the 160-metric ton blue whale evolved a huge mouth – allowing it to eat millions of krill each day.

Samantha Price: If you specialize to catch vast quantities of these highly abundant and nutritious prey, it provides you the energy you need to grow so big.

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Price added that the whale family has the most diverse body sizes of any mammal family, from the giant blue whale down to porpoises and dolphins. She said that fish eaters – like dolphins – evolved smaller bodies over time, because a small size makes it easier to maneuver when catching fish close to the ocean’s surface. Her study sought to answer a long-standing question about how whales evolved to have such diverse body sizes.

Samantha Price: I think anytime you see such a diversity – really big and really small together – that always drives us scientists to try and understand how that evolved. We approached this question by looking whether the differences appeared slowly through time, or rapidly after the origination of modern whales.

She said ancient, or archaic whales disappeared about 35 million years ago, giving rise to modern whales.

Samantha Price: There’s a hypothesis that suggests that modern whales arrived soon after demise of archaic whales. The idea is that the environment was pretty empty when modern whales evolved. So the likelihood is they evolved rapidly to fill out the roles and empty niches that were there. By looking at how size evolved and its relationship to diet, we found that the largest differences in size indeed appeared a long time ago, in the early evolutionary history.

Price said that there are still many fascinating questions to answer about how whales evolved.

Samantha Price: One thing that got me interested in whale evolution, and still intrigues me – and we don’t have a good answer for – is how and why the whales became aquatic. So around 50 million years ago, ancestral whales lived on land. And we can identify them as whales, through the fossil record. They were the size of a dog. In the next 10 – 15 million years they became fully aquatic and if you look at the reconstructions we have of them, they look like modern whales, even though they were archaic whales. Ten to fifteen million years seems like a long time ago, but in evolutionary terms, this was a rapid change.

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