Adult chimpanzees have a head and body length ranging between 635 and 925 mm. When standing erect, they are 1 to 1.7 m tall. In the wild, males weigh between 34 and 70 kg, whereas females are slightly smaller, weighing between 26 and 50 kg. In captivity individuals typically attain greater weights, with the top weight reaching 80 kg for males and 68 kg for females. Although data from individual subspecies are not available, it appears that P. t. schweinfurthi is smaller than P. t. verus, which is smaller than P. t. troglodytes. Some of the differences seen between captive chimps and wild chimps may be due to subspecific differences in size.
The arms are long, such that the spread of the arms is 1.5 times the height of an individual. Legs are shorter than are the arms, which allows these animals to walk on all fours with the anterior portion of the body higher than the posterior. Chimpanzees have very long hands and fingers, with short thumbs. This hand morphology allows chimpanzees to use their hands as “hooks” while climbing, without interference from the thumb. In trees, chimpanzees may move by swinging from their arms, in a form of brachiation. Although useful in locomotion, the shortness of the thumb relative to the fingers prevents precision grip between the index finger and thumb. Instead, fine manipulations require using the middle finger in opposition to the thumb.
The long hands of chimpanzees also function in quadrupedal locomotion. Fingertips are typically curled upward into the palm during locomotion, and the weight is borne along backs of the fingers. Much of the length of the hand thus contributes to the length of the forelimbs while walking. In combination with the short legs, this gives the back a downward slope from neck to rump, and orients the head into a forward facing position.
Chimpanzees have prominent ears, and a prominent superorbital crest. This gives the brows a somewhat rigid and bony appearance. A sagittal crest may be present on very large individuals, but is not common. There is no nuchal crest. Cranial capacity of these animals ranges from 320 to 480 cc. The face is slightly prognathic. The lips protrude and are very flexible, allowing an individual to accomplish many tasks through labial manipulation.
Dentition is typical of primates. The dental arch is square in shape, and there is a prominent diastema. Canines are large, as are molars. Molars decrease in size toward the back of the mouth, and lack the enamel wrinkling seen in orangutans.
The face of adults is typically black, or mottled with brown. Hair is black to brown, and there is no underfur present. There may be some white hairs around the face (looking a bit like a white beard in some individuals). Infant chimpanzees have a white tuft of hair on their rumps, which identifies their age quite clearly. This white tail tuft is lost as an individual ages.
Individuals of both sexes are prone to lose the hair on the head as they age, producing a bald patch behind the brow ridge. Graying of hairs in the lumbar region and on the back is common with age, also.
Range mass: 26 to 70 kg.
Range length: 635 to 925 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
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