Dolphins

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Most dolphin species are about 6 ft in length, the males averaging 4 to 8 in longer than females. The largest is the bottle-nose dolphin which can reach over 9ft in length and weigh 440 lbs! The smallest species is the buffeo, found in the Amazon River. The buffeo rarely grows over 3.9 ft in length and 66 lbs in weight, really smalled compared to the bottle_nose.

Dolphins feed on live food and are predators, except when trained otherwise in captivity. The primary food is fish, mostly things like herring, mackerel, and sardines. Some species seem to prefer squid, occasionally, shrimp and other crustacean are consumed, and even mollusk shells have been found in their stomach contents. Food consumption is estimated at about 66 lb a day for an individual about 8.2 ft in length and 220 lb in weight.

The body is sleek and smooth and the hairless skin is rubbery to the touch. Most species have jaws that protrude into a beak like snout. Above the upper jaw is a large mass of fat and oil-containing tissue forming the so-called "melon" that looks much like a bulging forehead.
The anterior appendages contain the skeletal remnants of five digits that form the flippers, which the animal uses primarily as stabilizers, although occasionally in an oar like fashion. The hind appendages are virtually absent and consist of a pair of small pelvic bones, deeply embedded in the connective tissue at the base of the tail.

The dorsal fin is formed from subcutaneous dermal tissue and is not movable by muscle action. The caudal, or tail, fin is also primarily dermal in origin, rather than skeletal, and consists of a pair of horizontally extending flukes. The locomotion of dolphins is typical of the whale. The main thrust comes from vertical oscillations of the tail and flukes, and most species tested are capable of sustained swimming speeds of up to 18.6 mph and they jump at this high speeds travelling 30 ft or more. Their normal "cruising speed" is about 23 to 25 mph, and if they are bow riding, they have been known to get up to 30mph. Bow riding is when the dolphin rides teh bow of a wave produced by a ship. « mai multe referate din Engleza