Black spider monkeys (<i>Ateles fusciceps</i>) photographed at Omaha's Henry Doorly Zoo and Aquarium in Nebraska.
Black spider monkeys (Ateles fusciceps) photographed at Omaha's Henry Doorly Zoo and Aquarium in Nebraska.
Photograph by Joel Sartore, National Geographic Photo Ark

Spider monkeys

 

Common Name:
Spider monkeys
Scientific Name:
Ateles
Type:
Mammals
Diet:
Omnivore
Group Name:
Troop
Average Life Span In The Wild:
22 years
Size:
14 to 26 inches
Weight:
13.25 pounds

What are spider monkeys?

Spider monkeys are large New World monkeys that live in tropical rainforests from central Mexico in the north to Bolivia in the south. There are seven species of these agile primates, which get their name from the way their long limbs and tails resemble spider legs as they dangle from branches and swing through the treetops. Four long fingers on each hand help them grasp branches, too. (They also have thumbs but those are extremely short.) Their tree-to-tree locomotion, called brachiation, is how these swingers get around.

The spider monkey’s tail is prehensile, which means “capable of grasping.” It is generally longer than the animal’s body and acts as a fifth limb—an adaptation to life in the tree canopy. It can support a spider monkey’s full body weight and allows them to hang onto branches, freeing their hands so they can climb, forage, and eat.

Each of the seven spider monkey species differs in geographic range and appearance, although they do share some physical traits and behaviors. White-bellied spider monkeys, which range from Colombia to Peru, for example, have a coat of hair that ranges from black to auburn with a light patch on their foreheads and a chin-to-belly swath of white-to-beige hair. Red-faced spider monkeys are covered in longish black hair except for their bare faces, hands, and feet.

Diet and behavior

This animal’s diet consists mostly of fruits, plus leaves, nuts, seeds, and sometimes arachnids and insects. Spider monkeys are important seed dispersers for their rainforest homes. When animals eat fruit and nuts from trees and then go on their merry way, they eventually defecate the seeds and spread the tree species throughout the area. Between 50 and 90 percent of seed dispersal in tropical forests is done by animals.

Spider monkeys are social, living in groups of up to 40 members. Within that group, smaller subgroups will often splinter off to forage. A 2014 study of Mexican spider monkeys in Belize found that males and females spent their time differently, with females doing more eating and resting and males eating more ripe fruits and traveling. Males are likely on the move because they’re patrolling their borders and raiding other troops before returning to check on the females.

Reproduction

Spider monkey males and females are both known to have multiple sexual partners, but their reproductive behaviors are difficult to document, even in captivity, and weren't even observed until the 1970s.  

But there have been some discoveries: A 2010 study on the black-faced spider monkey found that males must scramble to find and mate with the few receptive females in a single mating period. It also noted that most trysts took place in secret. Like other primates, spider monkeys form consortships in which males and females pair up and leave the group for periods as short as a few days. (These ultra-rare monkey twins have different fathers.)

Spider monkeys have a long gestation period, from seven to 7.5 months. They don’t have a single breeding season, but an individual spider monkey will wait about two to four years before giving birth again. Infants are born with full body hair except for the bare skin around the eyes of their “baby face.” Mostly helpless, newborns cling to their mother, who provides parental care, and don’t wean for as long as two years.

Conservation

According to the International Union for Conservation of Nature, all spider monkey populations are decreasing. The most stable wild population—that of the Guiana spider monkey of Guyana, French Guyana, Surinam, and Brazil—is still vulnerable to extinction. Human activities including farming, ranching, and road construction are destroying the monkey’s habitat—even though much of its home range is protected.

The least stable population is the brown spider monkey, found in Colombia and Venezuela. These animals are critically endangered, a distinction that places them just two steps away from extinction. They are a favorite target of hunters, who shoot them for sport and to make medicine to treat a variety of maladies from rheumatism to snake bites.

Their forest homes are also being cleared for cattle ranching, agriculture, logging, and human settlements. Pockets of forest that are left may no longer be sustainable and only 20 percent of the species’ historical distribution remains. Some protections have been put in place for this species, including local awareness programs in Venezuela and ongoing surveys to find the species and forests that could potentially be protected in Colombia.

Human-driven habitat loss threatens other spider monkey species, too. The Central American spider monkey’s diet requires a lot of the fruit that is typically found in the forests that are rapidly diminishing. Another threat for this monkey is the illegal drug trade. 

Drug traffickers clear large swaths of forest for cattle ranchers or other operations as a money laundering front, using up 20 to 60 percent of the land in the species’ home region, which runs from Mexico south to Panama. It’s now one of the world’s 25 most endangered primates, according to the International Primatological Society’s 2019 report, Primates in Peril.

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