The Bottle-Nosed Porpoise

摘要: The order Cetacea comprises more than 40 species of marine mammals that live their long lives in the waters great oceans or, much less frequently, rivers (the Amazon) or estuaries. All adult are large, and one, blue whale, is largest animal ever lived—larger dinosaur. whale almost as a football field weighs up to 150 tons (136 metric tons). It presumed developed from primitive land carnivores, but origin return sea lack fossil definition. In Eocene Age, were already abundant. They have large torpedolike bodies with forelimbs serving flippers, no hindlimbs, dorsal fin, notched, flattened tails called “flukes” powerful aids swimming diving. Over time, nostrils moved top head single double blowholes. When whales exhale, cloud water drops vapor blown out. These blow clouds form unique pattern differs species. Ordinarily, breathe every 2–3 min, they can dive depths for food stay under min without breathing. porpoises about half teeth carnivorous, eating only flesh, mostly fish squid. other rows baleen (whalebone) strain krill, plankton larval mixture constitutes principal food. gestation period year. young then nursed another Their life expectancy long, 25–40 years, so each female may produce 10–15 offspring lifetime.