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. Behavior Geoffroy's spider monkey is arboreal and diurnal, and mostly inhabits the upper portion of the forest. However, it comes to the ground more frequently than other spider monkey species. It lives in fission–fusion societies, large groups with a typical 20 to 42 members, which split into smaller subgroups to forage during the day. Subgroups typically number two to six members, and sometimes the subgroups remain separate from the main group even through the night. Geoffroy's spider monkey forages over large tracts of forest in search of food. Home ranges for groups can exceed . Monkeys can range about each day. Males tend to cover a larger day range than females, and dominant individuals tend to have larger day ranges. Geoffroy's spider monkey sometimes rubs a mixture of saliva and ground lime tree Citrus aurantifolia leaves on its fur. This is believed to act as an insect repellent. In some locations, Geoffroy's spider monkey interacts with the white-headed capuchin. These interactions can include mutual grooming. In addition to walking or running on four limbs and climbing, Geoffroy's spider monkey uses several forms of suspensory locomotion. Brachiation, or swinging from the arms with assistance from the prehensile tail, is the most common form of suspensory locomotion. Less common forms include swinging while suspended by the tail, and walking on four limbs under a branch. Studies have indicated