Sunday, March 16, 2014

Cetacean echolocation

"They can 'see' the fish and then they know to swim in that direction to catch it," says anatomist Jonathan Geisler of the New York Institute of Technology about the trait of echolocation in modern whales. Whales that use echolocation produce high-frequency vocalizations– clicks, squeaks, and squeals – through a soft-tissue nasal passage located between the blowhole and skull. These sounds echo off objects in the water, giving the animal a high-resolution audio image of its surroundings. Geisler led a research team that has determined that this trait existed in a species of whale 28 million years ago, suggesting that the sonar evolved shortly after whales split into 2 separate groups, toothed and baleen, and only 15 or 20 million years after the first whales evolved from wolf-sized land-dwellers and entered the ocean. The fossilized remains of Cotylocara macei (SKULL PICTURED ABOVE) were discovered near Summerville, South Carolina, U.S. The whale was 10' to 11' (3 to 3.4 m) in length and probably swam in a shallow ocean environment, feeding on fish and squid. Geisler postulates that this extinct whale already had a melon, the fat-filled organ in the head of modern whales that focuses the sound waves. Referring to a very deep pocket on top of the skull believed to be associated with an air sinus used in echolocation, the whale's genus name Cotylocara means "cavity head."

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