Why some whales are giants and others are just big
Sophisticated sensors suction-cupped onto the backs of whales are helping biologists answer two long-standing questions: Why are whales so big? And why aren’t they bigger? Being big in general boosts whales’ ability to reach more food for less effort, helping them exploit the riches of the deep sea that are beyond the reach of many other creatures. By estimating the energy used — and gained — when foraging for 13 species of whales and porpoises, scientists have shown that how big the creatures get is influenced by feeding strategy and prey availability. The sizes of toothed whales like orcas, which use echolocation to hunt for individual prey, appear to be constrained by how much food they can grab during a dive, researchers report. That’s not the case, however, for blue whales and other filter feeders, which tend to be much larger than their toothed cousins. Filter feeders alive today aren’t constrained by...