![]() Spider monkeys possess a relatively rare social system with a high degree of fission-fusion dynamics, also typical of chimpanzees ( Pan troglodytes) and humans ( Homo sapiens). We examined wide-scale geographic variation in the behavior of spider monkeys ( Ateles geoffroyi) across five long-term field sites in Central America using a well established ethnographic cross-site survey method. These studies ensure behavior variants are considered within the context of a species' ecology and evolutionary adaptations. Copulation occurs with each in a sitting position facing the same direction, with the male seated behind.Cross-site comparison studies of behavioral variation can provide evidence for traditions in wild species once ecological and genetic factors are excluded as causes for cross-site differences. Prior to mating, the male and female both separate themselves from others in their group. After selecting her partner (mating is not restricted to dominant individuals, but dominant males mate more often than low-ranking males), the couple is given its privacy. The Geoffroy’s spider monkey has no specific breeding season however, the ritual of copulation is defined and conducted with a modicum of decorum. Home ranges for groups can exceed 2,200 acres (900 hectares), and the monkeys can cover 6,600 ft (2,000 metres) each day. Geoffroy’s spider monkeys forage over large tracts of forest in search of food. This phenomenon of splitting and merging for a defined purpose is known as “fission-fusion,” and Geoffroy’s spider monkeys inhabit fission-fusion societies. However, for groups as large as 100, the entire group might come together for only a few weeks of each year. Mornings are spent gorging themselves, while afternoons are reserved for rest.įor the purposes of foraging, particularly when food is difficult to find, larger groups will split into smaller subgroups-culinary search committees-and usually regroup in the evening. They spend this time in the forest canopy foraging for food. ![]() Geoffroy’s spider monkeys are diurnal, which simply put means that they are most active during the daylight hours. Group size varies with habitat type and depends largely on the available food sources in an area. Highly social animals, Geoffroy’s spider monkeys live in multi-male, multi-female groups averaging 30 individuals, although groups of up to 100 have been reported. By touching the females’ clitorises, then smelling their own fingers to detect olfactory cues, males are able to determine a female’s reproductive status. ![]() It allows the males to gauge a female’s sexual receptiveness. Primatologists believe that the enlarged clitoris of female Geoffroy’s spider monkeys helps the males decide which female to approach for mating. In what might be a case of primate penis envy, the female Geoffroy’s spider monkey is endowed with a protruding, oversized dangling clitoris (known as a “pendulous clitoris”) that resembles the flaccid penis of the male Geoffroy’s spider monkey-except the female’s organ is larger. Their expressive faces are hairless, with unpigmented skin framing the eyes and muzzle in a pale facial mask. Infants are born black, but their fur lightens in color during their first five months of life.Ī smallish head sits atop a lithe body. Their fur coats vary in color from light buff to reddish-brown or black. Like other monkeys and apes, Geoffroy’s spider monkeys have opposable big toes on their feet that can grab onto branches easily.Īs their name implies, the hands and feet of the Geoffroy’s spider monkeys are black. Long, hook-like fingers allow the monkeys to swing from tree to tree beneath the forest canopy with ease, with no help necessary from a vestigial thumb that evolution has rendered a functionless stub. The versatility and strength of this tail is most evident during suspensory feeding, when the monkeys hang, suspended from a tree branch around which they have wrapped their tail, while foraging for food. Their prehensile tail functions as a fifth limb, having adapted over the years to allow for grasping and manipulating objects. Spider monkeys are named for their extremely long, slender, “spidery” limbs.
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