Dolphin is the name of a group of sea animals closely realated to whales an porpoises. Like whales and porpoises, dolphins are mammals, not fish. Mammals, unlike fish, feed their young with milk that is produced in the mother's body. Also unlike the fish, dolphins have lungs and are warm blooded, that is, their body temperature always stays about the same, regardless of the temperature of their surroundings. Many scientists believe that the dolphins rank among the most intelligent animals, along with chimpanzees and dogs.
Dolphins, whales, and porpoises are members of a group of mammals called cetaceans. Dolphins and porpoises are very similar in appearance. Their chief difference occur in the snout and teeth. Dolphins have a beak like snout and cone shaped teeth. Porpoises have a rounded snout and a flat or spade shaped teeth.
Scientists apply the term dolphin to two families of cetaceans, marine dolphins and river dolphins.
There are thirty-two species of marine dolphins. They are found in nearly all oceans, and most of them live only in salt water. Many species of marine dolphins remain near land for most of their lives, but some live in open sea. River dolphins live in fresh or slightly salty water.
The attraction between dolphins and people goes back thousands of years. Ancient Greek artists decorated coins, pottery, and walls with pictures of dolphins, and the animals appear in Greek and Roman mythology. The ancient Greeks considered the common dolphin sacred to the god Apollo. For centuries, sailors have regarded the presence of dolphins near ships as a sign of a smooth voyage.
On the other hand, hunters of several nations, including Sri Lanka and Japan, kill thousands of dolphins annually. The dolphins provide meat eaten by people and animals, and the oil from their bodies...