Tory Blair, age 12, of Vancouver, British Columbia, Canada, for his question:
HOW CAN YOU TELL A PORPOISE FROM A DOLPHIN?
For many hundreds of years, sailors have called the dolphin their friend. They consider the big mammal to be a lucky creature. If they spot a group of dolphins leaping around a ship as it sails across the water, the sailors say their voyage will be smooth and happy. Even though dolphin meat is delicious, most sailors will refuse to kill or eat the friendly dolphin.
Both the dolphin and the porpoise are small whale like mammals. Although both live in the water, they must breathe air.
The easiest way to tell the two animals apart is to note their snouts. The dolphin's snout forms a beak. The porpoise's does not.
The porpoise usually grows to be about five feet long and weighs up to 100 pounds.
The dolphin grows to be about seven feet long and weighs up to 150 pounds.
You'll find the porpoise in the coastal waters of North America, South America, Europe, Asia and Africa. The dolphin, on the other hand, can be found in all the oceans of the world and even in some of the rivers.
One type of porpoise is a giant called the killer whale. This large porpoise can measure up to 20 or 30 feet long and weigh from three to 10 tons.
The smart members of the family are the dolphins. Scientists say that the bottle nosed dolphin is one of the most intelligent animals in the world.
Dolphins communicate with each other by making sounds that include clicks, whistles and barks. They can even imitate some human speech sounds. The sound is made as the dolphin blows air through the air passages it uses for breathing.
Experiments are currently being conducted by a group of scientists who believe that some day man will be able to communicate with the dolphin.
Dolphins have a natural sonar system that lets them locate underwater objects. He locates an object by making sounds and then listening for echoes the sounds make when reflected by the object. Scientists say these sounds originate in the animal's breathing system.
Scientists in the U.S. Navy are conducting research to learn more about the dolphin's use of echolocation, which is what the natural sonar system is called.
A baby dolphin is born in the water. The mother immediately pushes the infant to the surface for its first breath of air. The youngster immediately learns that he has to come to the surface in order to breathe.
A mother dolphin nurses her baby with milk for about a year.