The Geoffroy's spider monkey is a type of New World monkey, from Central America. 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 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.
The range of Geoffroy's spider monkeys extends over much of Central America, including 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 (Hooded spider monkey) may also occur in the portion of Colombia near the Panama border. Geoffroy's spider monkeys live in various types of forest, including rains, semideciduous and mangrove forests.
Geoffroy's spider monkeys are arboreal and diurnal. They mostly inhabit the upper portion of the forest and come to the ground frequently. They live in fission-fusion societies, large groups that include 20-42 members. These groups split into smaller subgroups to forage during the day. Subgroups typically number 2-6 members, and sometimes the subgroups remain separate from the main group even through the night. Geoffroy's spider monkeys move around by walking or running on four limbs and climbing. They also use brachiation, or swinging from the arms with assistance from the prehensile tail. The most common method to cross between trees is "bridging", in which they grasp for a branch from the new tree and pull it towards itself so they can climb onto it. Airborne leaps are used when necessary. These monkeys communicate with the help of barks, whinnies, squeals, squeaks, and screams. Barks are typically alarm calls. Whinnies and screams can be used as distress calls, and are also made at dawn and at dusk.
Little is known about the mating system in Geoffroy's spider monkeys. They breed year-round. Females give birth to a single infant every two to four years. The gestational period lasts around 7.5 months. The young are born dark in color and begin taking on the adult coloration at the age of 5 months. They are carried on their mothers' chests for the first month and a half to two months, at which point they can ride on their backs. They nurse until they are about 1 year old, but begin eating solid foods and moving independently at about 3 months. Even when they move independently, they cannot always cross gaps in the canopy that adults can manage. To help them, an adult will stretch across the gap, forming a bridge over which the young can cross. Females become reproductively mature at about 4 years, and males at about 4 years. Upon reaching maturity, females leave their natal group, but males do not. As a result, the males in the groups are typically related, while the females are not.
The main threat to Geoffroy's spider monkeys is the loss of the habitat. They require large tracts of primary forest to survive, so they are vulnerable to deforestation and are sometimes hunted by humans and captured for the pet trade. Because of their low reproductive turnover, Geoffroy's spider monkeys cannot quickly replenish their numbers when affected by these events. As a result, this species has disappeared from some areas where it was once common.
According to the IUCN Red List, the total population size of the Geoffroy's spider monkey is unknown. However, there are estimated populations of some subspecies: Azuero spider monkey: 112 - 116 individuals; Yucatan spider monkey: 648 individuals and Black-browed spider monkey: 110-160 individuals. Currently, the Geoffroy's spider monkey is classified as Endangered (EN) on the IUCN Red List and its numbers today are decreasing.
As frugivores, Geoffroy's spider monkeys act as important seed dispersers of the plants they consume, thus benefiting the local ecosystem.