Baiji: Lipotidae

Little is known about the baiji because so few of them are left in the world. In the wild they are extremely shy, easily frightened, and difficult to approach. The baiji are thought to live in groups of two to seven individuals, but groups as large as sixteen have been observed. They do not leap out of the water the way some other dolphins do, but only expose their head and beak when they come to surface after dives.

The baiji's dives are often short, only lasting ten to twenty seconds, but they can be as long as two minutes. While underwater, they emit a wide range of sounds. These includes a whistle sound used to communicate and a variation of clicks used in echolocation.

Echolocation involves making sounds that bounce off objects. Sense organs pick up the echo or reflected sound and use that information to locate objects. The forehead of a dolphin is a lump of fatty tissue called the melon. The dolphin makes sounds (scientists disagree about how this is done) that seem to be focused through the melon and skull and then sent out into the environment. When the sounds bounce back, the echo is passed through special tissue in the lower jaw to the inner ear. From the time it takes to collect the echoes, their strength, and their direction, dolphins construct a "sound picture" of their environment. This process is so sensitive that they can "see" an object less than one-half inch (1.25 centimeters) across at a distance of 50 feet (15 meters).

The baiji is a very fast and strong swimmer and has been seen swimming over 60 miles (100 kilometers) in three days going against the current. While resting, the baiji stays in areas of very slow current.

Little is known about how this animal reproduces, because there have been no studies conducted on baiji reproduction. It is thought that males become mature at four years of age, while females mature at the age of six. A single calf is born in the spring, after a pregnancy of ten to eleven months. These calves are about 3 feet (91 centimeters) long and weigh between 6 and 11 pounds (2.5 and 4.8 kilograms). The baiji can live up to twenty-five years in the wild.