Science Says: Diet plays big role in how huge whales can get

A new study finds diet plays a big role in how large whales can get


The study included 90 blue whales, the biggest animal ever to live. Size estimates vary, but the American Cetacean Society says blue whales can grow about 100 feet (30 meters) long and weigh more than 100 tons (91,000 kilograms). The study also included the biggest whale with teeth, the sperm whale, which can stretch about 60 feet (18 meters) long, the group says.

When toothed whales hunt, they capture one prey at a time, seeking them out in the murky depths with a sonar-like detection. The study found that as body size increases in such whales, they become progressively less efficient as they hunt — they recover fewer calories from their meals per calorie burned in each dive. That results from limits on availability of prey.

“It looks like you cannot be much bigger than a sperm whale" when hunting the way it does, said Nicholas Pyenson of the Smithsonian's National Museum of Natural History, who was part of the research.


That “allows them to exploit a very large prey resource that's very rich in a small amount of time," said Jeremy Goldbogen of Stanford University, another researcher. "They get a huge bang for the buck."

So why aren't they even bigger than they are? Maybe blue whales are limited by the seasonal nature of the most nutritious krill patches, which grow gigantic and dense in the summer, Goldbogen said. And calculations indicate that to sustain a blue whale that's 115 feet (35 meters) long, “you'd need a density of prey that is just not seen anywhere in the world,” Pyenson said.

But maybe there's also some kind of limiting factor in how their bodies function, Goldbogen said. He noted a recent study that found a blue whale's heart beats up to 37 times a second after deep dives, and that appears to be about as fast as the organ can pump.


The study provided a comprehensive look across big whale species, and the success in collecting the data “boggles the mind,” she said.

“You try to go out and put a tiny tag on the back of the biggest animal in the world,” she said.

