Chimpanzees

The height of chimpanzees varies from about 39 in (1 m) in males to about 36 in (90 cm) in females. An adult wild male weighs about 132 lb (60 kg), but in captivity can grow up to 220 lb (100 kg). The weight of females range from about 66 lb (30 kg) in the wild to as much as 190 lb (87 kg) in captivity.

Chimpanzee pelage is primarily black, turning gray on the back after about 20 years of age. Both sexes have a short white beard, and baldness frequently develops in later years. The skin on the hands and feet is black, and that of the face ranges from pink to brown or black. The ears are large and the nostrils are small. Chimpanzees have heavy eyebrows, a flattened fore-head, large protruding ears, and a short neck. The jaw is heavy and protruding, and the canine teeth are large. Male chimpanzees have larger canines than females, and these are used in battle with other males and during predation. Although chimpanzees have long powerful fingers, they have small weak thumbs. Their big toes function like thumbs, and their feet as well as their hands are used for grasping.

The genitalia of both sexes are prominent. Areas of the female's genital skin become pink during estrus, a period that lasts two to three weeks and occurs every four to six weeks. The characteristic gait on the ground is the "knuckle-walk," which involves the use of the knuckles for support. Chimps spend much of their time climbing in trees, and they sleep alone every night in nests that they make with branches and leaves. A mother sleeps with her baby until her next infant is born. Chimpanzees live up to 40-45 years.