How Whales Dive, Feast, and Fast: The Ecophysiological Drivers and Limits of Foraging in the Evolution of Cetaceans

Whales are an extraordinary study group for questions about ecology and evolution because their combinations of extreme body sizes and unique foraging strategies are unparalleled among animals. From a terrestrial ancestry, whales evolved specialized oceanic foraging mechanisms that characterize the two main groups of living cetaceans: echolocation by toothed whales and bulk filter feeding by baleen whales. In toothed whales, lineage-specific increases in body size, enhanced diving capacity, and echolocation enable them to hunt the most abundant prey on the planet: deep-sea fish and cephalopods. Even greater body size increases, along with filter feeding and fasting capacity, permit large baleen whales to migrate long distances and exploit epipelagic patches of schooling prey, such as krill or fish, which are highly abundant but ephemeral. For both groups, prey abundance and distribution limit foraging performance, yielding divergent energetic niches that have shaped their convergent evolution to gigantism.