Quote:Migrating Squid Drove Evolution Of Sonar In Whales And Dolphins, Researchers Argue



Science Daily — Behind the sailor's lore of fearsome battles between sperm whale and giant squid lies a deep question of evolution: How did these leviathans develop the underwater sonar needed to chase and catch squid in the inky depths?



Now, two evolutionary biologists at the University of California, Berkeley, claim that, just as bats developed sonar to chase flying insects through the darkness, dolphins and other toothed whales also developed sonar to chase schools of squid swimming at night at the surface.



Because squid migrate to deeper, darker waters during the day, however, 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 David Lindberg, UC Berkeley professor of integrative biology and coauthor of a new paper on the evolution of echolocation in toothed whales published online July 23 in advance of its publication in the European journal Lethaia.



"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, former director and now a curator in UC 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."