8 Surprising Facts About Spider Monkeys

Spider monkeys are New World monkeys found in the tropical and subtropical rainforests of Central and South America. Their name is the result of their spiderlike appearance when they hang by their extra long prehensile tails from the bow of a tree. 

There are seven species and seven subspecies of spider monkeys, and all are at risk of extinction due to habitat loss and hunting. Spider monkeys are primarily herbivores and frugivores that are quite social and tend to live in large groups. From their lack of opposable thumbs to their ability to cover large distances with a single swing, discover the most fascinating facts about spider monkeys.

1. Spider Monkeys Have Strong Tails

One of the most defining characteristics of the spider monkey is its long prehensile tail. The spider monkey’s tail is strong and well-developed for arboreal life — and is often described as an extra limb. The tail is designed for gripping: It lacks hair on the underside so that the monkey can more easily grasp branches with its tail while gathering fruit with its hands.

The tails of spider monkeys are longer than their bodies — some are as long as 35 inches.

2. They Don’t Have Thumbs

A unique adaptation of spider monkeys as compared to other primates is their lack of opposable thumbs on their hands. Their hands have only vestigial thumbs, the tiny nub left over from their ancestors, who did have thumbs. The absence of this extra digit gives the spider monkey a more hooklike hand with long, slender fingers, providing a better grip to swing from branch to branch in its arboreal abode.

3. The Females Take the Lead

Spider monkey troops are matriarchal, meaning the females play a leadership role. Females actively choose their mates when breeding, which, in the case of white-bellied spider monkeys, leads to less aggressive behavior among males. The alpha female of the troop also tends to be the decision-maker, leading the group to feeding areas and determining the ultimate size of the group.

Female spider monkeys are also more likely to leave the nest, moving on to join a new troop when they reach puberty. 

4. They Are Swinging Specialists

Rather than leap from tree to tree, spider monkeys are specialists at swinging from limb to limb, and can clear great distances in a single swing. Spider monkeys can cover as much as 30 feet of distance with a single powerful swoosh of their arms. Their hook-like hands, powerful tail, and mobile shoulder joints assist spider monkeys with their impressive moves.

These agile acrobats can pause between swings to stand up or hang from their tail to eat with both hands.

5. Spider Monkeys Are at Risk 

There are seven species of spider monkey, and all of them are under threat of extinction. The variegated or brown spider monkey, Ateles hybridus, is critically endangered. Found in Columbia and Venezuela, their biggest threats are degradation and fragmentation of their forest habitat and illegal hunting. Much of the brown spider monkeys’ habitat is used for agriculture, and their population is anticipated to be reduced by as much as 80 percent over the next 45 years.

Five additional species: Geoffroy’s spider monkey, brown-headed spider monkey, white-cheeked spider monkey, white-bellied spider monkey, and the black-faced black spider monkey are all endangered, while the Guiana spider monkey is listed as vulnerable by the IUCN. Throughout their range, the spider monkey population is in decline primarily due to loss of suitable habitat and hunting.

6. They Are Social Animals

Spider monkeys are highly social primates. They are diurnal, with most of their activity occurring during the day. Some species, like the Geoffroy’s spider monkey, congregate in groups as large as 100 individuals, while others, like the brown spider monkey, sometimes live in groups of only two or three. Many spider monkey groups consist of multiple males and multiple females.

The group dynamic of spider monkeys is described as fission-fusion. When food is scarce, foraging is usually completed within smaller subgroups, and when food is abundant, the group size and composition is larger and more stable.

7. Spider Monkeys Reproduce Infrequently

The slow reproductive rate of spider monkeys is a challenge to the conservation efforts for the species. After a gestation period of around seven months, female spider monkeys generally give birth to one offspring every two to four years. The baby receives a high level of parental care from the mother, who also teaches her young social behaviors and how to forage.

Females keep their young offspring with them, even when traveling to other groups. Baby spider monkeys are weaned at between 12 and 20 months of age.

8. They Add Nutrients to the Forest

Spider monkeys create rich nesting sites by pooping below where they sleep. Scientists have found a direct correlation between the abundance of food on the forest floor and the sleeping patterns of spider monkeys.

The monkeys are drawn to areas that have a significant food supply, but they also add to it. When large groups of spider monkeys converge in a region, the feces they leave behind is rich in seeds and nutrients to help grow more trees. This pattern not only creates more food for the spider monkeys, it improves the tropical ecosystem for all creatures in the area.