Geoffroy's spider monkey (Ateles geoffroyi), also known as the black-handed spider monkey or the Central American spider monkey, is a species of spider monkey, a type of New World monkey, from Central America, parts of Mexico and possibly a small portion of Colombia. There are at least five subspecies. Some primatologists classify the black-headed spider monkey (A. fusciceps), found in Panama, Colombia, and Ecuador as the same species as Geoffroy's spider monkey. It is one of the largest New World monkeys, often weighing as much as 9 kg (20 lb). Its arms are significantly longer than its legs, and its prehensile tail can support the entire weight of the monkey and is used as an extra limb. Its hands have only a vestigial thumb, but long, strong, hook-like fingers. These adaptations allow the monkey to move by swinging by its arms beneath the tree branches. Geoffroy's spider monkey lives in fission–fusion societies that contain between 20 and 42 members. Its diet consists primarily of ripe fruit and it requires large tracts of forest to survive. As a result of habitat loss, hunting and capture for the pet trade, it is considered to be endangered by the IUCN.
Taxonomy Geoffroy's spider monkey belongs to the New World monkey family Atelidae, which contains the spider monkeys, woolly monkeys, muriquis and howler monkeys. It is a member of the subfamily Atelinae, which includes the spider monkeys, woolly monkeys and muriquis, and of the genus Ateles, which contains all the spider monkeys. The genus name Ateles means "imperfect", a reference to the vestigial thumb. The species name geoffroyi is in honor of French naturalist Étienne Geoffroy Saint-Hilaire. Agreement over the number of spider monkey species is not universal. Kellogg and Goldman (1944) based their classification on fur color, and Groves (1989) based his on fur color and geographic distribution. Kellogg and Goldman differentiated Geoffroy's spider monkey from other species by its dark black head, hands and wrists. Recent studies use mitochondrial DNA to help differentiate species. Such studies by Collins and Daubach (2000, 2001, 2006) indicate the Geoffroy's spider monkey is more closely related to the white-fronted spider monkey, A. belzebuth, and the brown spider monkey, A. hybridus, than it is to the red-faced spider monkey, A. paniscus. According to these studies, A. paniscus branched off from the other spider monkeys approximately 3.27 million years ago and the spider monkeys branched off from the woolly monkeys and muiriquis 3.59 million years ago. Older studies by Porter, et al. indicate the howler monkeys are believed to have branched off from the other Atelides over 10 million years ago. In 2005, mammalian taxonomy reference work, Mammal Species of the World, listed five subspecies:
Nicaraguan spider monkey, Ateles geoffroyi geoffroyi Hooded spider monkey, A. g. grisescens Ornate spider monkey, A. g. ornatus Mexican spider monkey, A. g. vellerosus Yucatan spider monkey, A. g. yucatanensis In 2015, a phylogenetic study recommended A. g. yucatanensis was a junior synonym of A. g. vellerosus. Some authorities also recognize A. g. azuerensis and A. g. frontatus as valid subspecies. The black-headed spider monkey, Ateles fusciceps, is considered by authorities such as Groves (1989) and Rylands et al. (2006) to be a separate species from Geoffroy's spider monkey. Other authorities, including Froelich (1991), Collins and Dubach (2001) and Nieves (2005), consider A. fusciceps to be synonymous with A. geoffroyi. Under this treatment, the two subspecies of the black-headed spider monkey represent additional subspecies of Geoffroy's spider monkey, A. g. fusciceps and A. g. rufiventris.
Distribution and habitat The range of this species extends over much of Central America, encompassing Panama, Costa Rica, Nicaragua, Guatemala, Honduras, El Salvador, Belize and the south and much of the eastern portion of Mexico. Observations by local people indicate the southernmost subspecies, the hooded spider monkey, A. g. grisescens, may also occur in the portion of Colombia near the Panama border. In western Colombia and northeast Panama, it is replaced by the black-headed spider monkey, A. fusciceps, which is considered by some primatologists to be a subspecies of Geoffroy's spider monkey. Geoffroy's spider monkey lives in various types of forest, including rainforest, semideciduous and mangrove forests. Higher densities of Geoffroy's spider monkeys are generally found in areas containing evergreen forest.
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+1⁄2 in). Males and females are approximately the same size. 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 and bare skin 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.
Behavior
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