Whale and dolphin sonar evolution studied

BERKELEY, Calif., Sept. 10 (UPI) -- U.S. biologists have determined that, as bats developed sonar to chase flying insects, whales and dolphins developed sonar to chase squid at night.

And because squid migrate to deeper, darker waters during the day, toothed whales eventually perfected an exquisite echolocation system that allows them to follow the squid down to that "refrigerator in the deep, where food is available day or night, 24/7," said evolutionary biologist Professor David Lindberg of the University of California-Berkeley and coauthor of a new paper on the evolution of echolocation in toothed whales.

"When the early toothed whales began to cross the open ocean, they found this incredibly rich source of food surfacing around them every night, bumping into them," said Lindberg, a curator at University of California-Berkeley's Museum of Paleontology. "This set the stage for the evolution of the more sophisticated biosonar system that their descendents use today to hunt squids at depth."

Lindberg and graduate student Nick Pyenson reported their research in the July 23 online edition of the European journal Lethaia in advance of its print publication.