Geoffroy's Spider Monkey - Physical Description

Physical Description

Geoffroy's spider monkey is one of the largest New World monkeys. Its length measures between 30 and 63 cm (12 and 25 in) and it weighs between 6 and 9 kg (13 and 20 lb). The tail is longer than the body at between 63 and 85 cm (25 and 33 in). Males are slightly larger than females.

Its body color varies by subspecies and population, and can be buff, reddish, rust, brown or black. The hands and feet are dark or black. The face usually has a pale mask around the eyes and muzzle.

Its arms and legs are long and slim. The arms are about 25% longer than the legs. The thumb is only vestigial, but the fingers are long and strong, making the hands hook-like. The long arms and hook-like hands allow Geoffroy's spider monkey to brachiate, that is, swing by its arms beneath the tree branches.

The prehensile tail is very strong and has a palm-like pad at the end. The tail acts as an extra limb, and is used for locomotion, as well as to pick fruits and to scoop water from holes in trees. Geoffroy's spider monkey can support its weight suspended by its tail and often does so when feeding.

The clitoris of female Geoffroy's spider monkeys is large and protrudes, looking like a penis. This organ, called a pendulous clitoris because of the way it dangles externally, is actually larger than the male flaccid penis. As a result, females are sometimes mistaken for males by human observers. The enlarged clitoris is believed to aid males in determining sexual receptiveness, allowing them to touch the clitoris and smell their fingers to pick up chemical or olfactory cues to the female's reproductive status.