Dolphin, a toothed whale that is related to the porpoise. The dolphin has a long, streamlined body; some species have a prominent beaklike snout. The dolphin travels in schools and can swim at a speed of up to 25 mph (40 km/h). After a gestation period of one year, the female gives birth to one young. The young suckles for up to two years.Dolphins are intelligent, playful animals.
Dolphins are intelligent, playful animals. They emit a variety of sounds to communicate with other dolphins. Like other toothed whales, they use echolocation (which is similar in principle to sonar) to avoid obstacles and to locate prey.
There are 37 species of dolphins. The common dolphin is found chiefly in the Mediterranean and the North Atlantic. It is about eight feet (2.4 m) long including a six-inch (15-cm) snout. The common dolphin is brownish-black above with dark flippers and snout, and a white belly; there are bands or stripes of tan or yellow on the sides. The common dolphin travels in schools of up to a thousand or more individuals. It feeds mainly on fish.
A sleeping dolphin usually rests at or near the surface of the water. That way, the dolphin is not too far from the air it needs to breathe.
A sleeping dolphin usually has one eye closed. The dolphin’s breathing rate slows down. Still, it seems to be aware of the fact that it is breathing. When you sleep, you are not aware of your breathing. You don’t need to be conscious in order to breathe. But many scientists think that dolphins do need to be conscious.
Scientists also think that dolphins (and all other whales) sleep with one side of the brain resting at a time. The side that is awake controls the dolphin’s breathing. It also controls the animal’s movement. Resting one side of the brain at a time makes it possible to sleep underwater.
The bottle-nosed dolphin, or bottlenose, is found in warm and temperate North American coastal waters. It is dark gray above with lighter underparts. It is up to 12 feet (3.7 m) long and has a three-inch (8-cm) snout. The bottle-nosed dolphin feeds on fish, squid, and crabs. It can be trained to perform at zoos and aquariums, and is used in research on animal communication and learning.
Bottle-nosed dolphins belong to the same family as killer whales and pilot whales. They, too, live and travel in social groups. Some people call this group a pod, but others call it a school. A school usually has about 12 dolphins. Some schools may combine to form a herd of up to 1,000 dolphins.
A bottle-nosed dolphin school is not just a place to live. It’s also a place to learn. Young calves learn by imitating their mothers or other adult dolphins. Calves turn, dive, and surface—right along with the adults.
Play is also important to bottle-nosed dolphins. They enjoy leaping and tail splashing. Sometimes, they even walk backward on their tails! Young dolphins like to play by chasing each other around. But if play gets out of hand, a mother may warn a youngster by butting it with her head.
Bottle-nosed dolphins hunt in several different ways. How they hunt seems to depend on where they are at the time.
In the open ocean, bottle-nosed dolphins often form hunting herds. The dolphins circle a school of fish. Then they splash frantically to move the fish closer and closer together. Once the fish are tightly packed, the dolphins can take turns feeding.
Closer to shore, dolphins may drive a school of fish toward a rocky reef. Dolphins have even been known to beach themselves and grab their prey.
Bottle-nosed dolphins also hunt alone. A lone hunter may hit a fish with its flukes. Then it grabs the stunned fish and enjoys a quick meal.
Spinner dolphins were named for the midair spins they do. Spinner dolphins can whirl and twirl—just like acrobats. How do they do this? First, the dolphin makes a dive. Then it leaps straight up into the air. It may leap 10 feet (3 meters) high. Then it spins—sometimes seven times in one leap.
Most other kinds of dolphins can somersault, or flip head over tail. But a spinner dolphin is the only one that can spin with its nose pointed to the sky and its tail to the water.
Spinner dolphins may perform such stunts to communicate with the schoolmates. They may be letting the others know where to find fish. Or, they may be jumping just for the fun of it.
Spinner dolphins are unusual in another way. They have more teeth than any other whale. A spinner dolphin may have up to 252 teeth.
Amazon river dolphins swim upside down. Scientists aren’t sure why Amazon river dolphins do this. The humps on their backs may help them feel around the river bottom to find food.
Swimming upside down may also help the dolphins see. Even though their eyes are small, these dolphins do have good eyesight. But their puffy cheeks may be a problem. It’s hard to look down over those cheeks! The dolphins may be able to see prey better while swimming on their backs.
River dolphins usually live in fresh water or in water that is only slightly salty. Amazon river dolphins may be bright pink, bluish-gray, or off-white in color. They have humps instead of dorsal fins. And they have long, narrow beaks that they use for feeding.