HOW DOLPHINS LIVE AT SEA: SPECIAL TALENTS

leapingdolphin.jpg (9955 bytes) Dolphins not only communicate with sound, they also "see" with it. They can make an incredible variety of clicks, beeps, whistles, snaps, groans and calls. A dolphin emits sound through nasal passages inside its melon (forehead). The sound travels out in waves, hits an object and bounces back. The reflected sound waves are first received by the skull and jaw, then transmitted to the ear. The dolphin assembles the waves into a mental image of what is in the water. This sending and receiving of sound waves is called "echolocation," and people hear it as lots of quick clicking noises. By echolocating, dolphins can tell how big something is, which direction it is going, how fast, and what is inside it. To communicate, dolphins whistle a "tune." Each dolphin has its own special whistle. Dolphins make so many different sounds that it is possible that they have their own language. People have tried for many years to figure out whether the communications are really a language and whether humans can interpret it.
A dolphin can eat 15 to 20 pounds of food a day—mostly fish, but also squid and other seafood. A group of dolphins sometimes surrounds a school of fish and herds them together. Then the dolphins catch the fish in their mouth and swallow them whole. Sometimes dolphins herd fish into shallow water where it’s easier to catch them; the dolphins will even slide up onto the beach to get the fish, then wriggle back into water deep enough to swim. Dolphins also dive, as deep as 1,700 feet, for food. They can hold their breath for as long as 7 minutes, then they must come up for air.
Like people, dolphins must breathe air. What about when they are asleep? They sleep just barely below the surface of the water and are always partly awake. Every few minutes, they rise to the surface to breathe through their blowhole. When a baby dolphin is born, the mother or a helping "auntie" dolphin gently pushes the baby to the surface for its first breath. Babies nurse and stay close to their mothers for one to two years. Dolphins live in families of a big male, a few females with babies, and a few "teenagers." The families form groups called "pods" and the pods join together in "herds" that can number in the hundreds. Dolphins live to be 25 or 30 years old. diverswithdolphin.jpg (10439 bytes)

 

DOLPHIN FACTS

Proper name: Dolphins, porpoises and whales share the same order: Cetacea. There are roughly 35 species of dolphins and porpoises. Generally, people call both dolphins and porpoises "dolphins." Fishermen often call them all "porpoises." Scientists divide theme into four families: Delphinidae (dolphins), Phocoenidae ("true" porpoises), Monodontidae (belugas and narwhals) and Platanistidae (river dolphins).
Size The largest dolphin is the orca, or killer whale; it can weigh nine tons and grows to 20-30 feet long. The smallest is the vaquita, which is a delicate four feet long.
Life span Dolphins live to be 25-30 years old, in general, but some are thought to live into their 50s.
Habitat Although most dolphins live in the ocean, some live in rivers or even in lakes that are formed when part of a river is cut off.
Food Dolphins eat fish, squid and crustaceans like shrimp.
Bonus fact Dolphins are mammals, like people. Although they live in the water, they breathe air. They have babies (instead of laying eggs) and feed their babies, called "calves," milk.