Notable Features

Dolphins are actually small, toothed whales belonging to the order cetacea. Like all mammals, dolphins have hair, have lungs to breathe air, give live birth, and provide milk for their young with mammary glands.

A dolphin's hair is in the form of whiskers on its chin when it is born, although the hair falls out shortly after birth. Dolphins nurse their young until they are old enough to eat solid foods. Because these animals have lungs, they must rise to the surface to breathe.

Dolphins breathe through the blowholes on top of their heads. Each time a dolphin surfaces, the flap over its blowhole opens. The dolphin then rapidly exhales and inhales, and the flap closes.

In one breath, dolphins may exchange up to 90 percent of the air in their lungs, compared with a human's air exchange, which is approximately 15 percent.

Animals living in the ocean have special adaptations that help them survive. Mammals are warm-blooded, meaning they maintain a constant body temperature. Dolphins have a layer of blubber under their skin that insulates their body against the cold water.

Dolphins can dive up to 984 feet (300 meters) below the ocean's surface, but they will rarely stay underwater for long periods of time. Dolphins use oxygen much more efficiently than humans because they store O2 in their blood and muscles, rather than in their lungs. During deep dives, their lungs and ribs partially collapse. They can stay underwater for approximately 20 minutes at a time.

Although dolphins lack vocal cords, they produce sound by pushing air back and forth between air sacs below their blowholes. In this way dolphins can produce a series of clicks and whistles, which they use to communicate with one another. Dolphins also produce clicks to orient themselves underwater.

Echolocation, a biological sonar, consists of a series of clicks that are sent from the air sacs through a structure called the melon. The melon is the fatty bulge that looks like the dolphin's forehead; it helps direct sound traveling through the water. When the sound hits an object, it will bounce back as "echoes." The returning echoes travel through fat in the dolphin's lower jaw and vibrate against its inner ear. By analyzing these, dolphins can learn the size, density, speed, and direction of movement of objects around them.

Echolocation allows dolphins to find food and other objects in dark, murky water, where sight is nearly useless.

Dolphins separate themselves into social groups based on gender. Females and calves associate in groups, or "pods," while males may roam individually or in "bachelor" groups. Female calves stay with their mothers' pod for life, but male calves leave the pod between 2 and 4 years of age.

Dolphins reach sexual maturity in six to 10 years and reproduce in the spring. Gestation lasts approximately 11 months, and females give birth to one calf every two years.

Mothers nurse the calves for about a year. During this time, "baby-sitters" from the pod may watch the calf while the mothers are feeding. If a mother becomes annoyed with the calf, or wants to gain its attention, she slaps the water surface with her tail.

Since the days of ancient Greece and Rome, dolphins have delighted and intrigued people with their inquisitive nature. They have even been rumored to make friends with boaters and bathers. Their curious behavior has convinced many people that dolphins are very intelligent animals.

When in aquariums and zoos, they quickly learn behaviors; they appear to be healthier when they are presented with games and tasks to perform. Although trainers rate their intelligence as equal to that of smart dogs, scientists disagree as to exactly how "smart" dolphins are. Until scientists devise a way to measure intelligence, this shall remain a mystery.