There are about 32 species of dolphins.  Dolphins live in almost all of the oceans and they usually stay close to land.  Dolphins can be 4 to 30 feet long and can weigh 100 to 20,000 pounds.  Dolphins have 200 to 250 sharp teeth.  A dolphin does not chew food, it eats it whole usually head first.  In one day a dolphin can eat an amount of fish and squid equal to nearly one-third of its weight.  Dolphins are swift enough to go farther than their prey.  They follow schools of fish in groups of different sizes.   Dolphins communicate by making whistling or clicking sounds.  Dolphins must go to the surface for air because they do not have gills to help breathe in water, they do this about every 30 seconds to 1 minute.  When a baby dolphin is born it immediately swims to the surface for air.