ORNATE SPIDER MONKEY
Ateles geoffroyi ornatus
Geographic Distribution and Habitat
Ornate spider monkeys are a subspecies of the Geoffroy’s spider monkey. They are endemic to Costa Rica and Panama, as well as to the southernmost part of Nicaragua, close to the border with Costa Rica. A population was also introduced to the island of Barro Colorado, Panama.
Most ornate spider monkeys live at altitudes ranging from sea level to 7,500 feet (2,200 m), in varied habitats. In Costa Rica, for instance, the national parks they inhabit offer a mosaic of tropical forests. Corcovado National Park, on southwest Costa Rica’s Osa Peninsula, is covered in primary forest, mangrove, and lowland tropical forest. It is one of the richest region for its biodiversity. The monkeys also live in Monteverde Cloud Forest Reserve, in the rainforest of La Selva Biological Station and in the Santa Rosa National Park, on the North Pacific coast, which consists mostly of tropical dry forest.
Spider monkeys are fairly large New World primates. They weigh 15–18 pounds (7–8 kg), with no significant difference in size between males and females. They are about 16–22 inches (42–57 cm) tall and their tail measures 29–36 inches (75–92 cm).
They can live up to 25 years in the wild and up to 40 in captivity.
Although lanky, with long limbs, a bulbous torso, and a small rounded head, ornate spider monkeys are handsome monkeys. They have a golden back and underside but their head, face, forearms, and outer legs are black. Their big round eyes are encased in two large orbs that contrast sharply with their narrow snout and chinless mouth. They have large incisors as well as thin and sharp canines perfectly suited to their frugivorous diet. Males have canines that are a bit longer and wider than those of females.
Their arms are much longer than their legs; their shoulders are very flexible and fully rotate forward and backward; the tendons of their wrists are long and their hands (which lack a thumb) form hooks around branches. Their trunk is short and their lower spine has evolved to enable their prehensile tail to twist, bend, and curl—thereby providing these animals with the suspensory support they need to hang in place while foraging, or propel their body from branch to branch. Their tail is covered in fur on the outside but the inside is bare and the skin has ridges allowing the monkeys to feel surfaces just like they do with their hands. Their muscular feet have bare soles and have an opposable digit.
Ornate spider monkeys have a diet rich in easily digested carbohydrates and lipids. They forage in the canopy and eat mostly both ripe and unripe fruit (75%). They supplement their diet by munching on young leaves (12%), stems, aerial roots, and flowers. When fruit is scarce, though, they increase their intake of young leaves. The fruit and vegetal matter they consume originates from many different plants, but 50% belong in the Ficus and Brosimum families, which grow all over South America.
They get their water needs met by eating fruit, but they also drink from tree holes. Occasionally, they descend to the ground to drink and eat soil from salt licks. It is thought that the soil is a good source of minerals (especially phosphorus) that they may be lacking from their regular diet.
Ornate spider monkeys follow a social model called “fission-fusion.” This means they live in large groups of 16–55, composed of males and females, that split into smaller units during the day. Subgroups are usually made up of 4 to 5 individuals of the same gender, but they are not static. Monkeys move in and out of these groups as they please. This strategy allows individual members to avoid conflict over food resources.
Relationships are rich and complex. Grooming is a way to keep friendships intact. It is practiced in all age groups, but males groom each other more than they groom females, or than females groom each other. There doesn’t seem to be a very strong dominance hierarchy among female spider monkeys in general. However, females that have been with the group the longest are dominant over the newcomers. Males remain within their native groups. They form strong and lasting alliances. Such bonds are especially important during intergroup encounters, when they need to support one another. Intruders may try to steal females and food resources, so male spider monkeys regularly patrol the borders of their territory. Females, on the other hand, especially those with infants and juveniles, don’t approach the borders.
Ornate spider monkeys are also referred to as “brilliant,” or “common” spider monkeys.
In Corcovado National Park, Costa Rica, entire groups of ornate spider monkeys died between September and November 2005. The trigger may have been heavy rains that resulted in a drastic fruit shortage and caused starvation of the groups, although an epidemic outbreak was never ruled out.
In the early morning, the monkeys split up in small groups to go foraging. They select trees with large trunks and wide branches. They feed for about 10 minutes before moving to another area of the forest. They can travel quite far—especially when fruit is scarce. Their home range is fairly large at 120–500 acres (50–200 ha) on average. It is usually greater for males than for females.
They spend most of their time in the forest canopy and travel like skilled acrobats, using a variety of locomotive techniques. When crossing gaps between trees, they leap and drop. When traveling across on horizontal branches, they sometimes run on two legs using their tails for balance, or crouch on all fours holding on with their feet and hands. They use feet, hands, and tail when climbing up a tree, or sometimes lying horizontally across two branches. They swing using their body and legs to propel themselves from one branch to another. They also grab onto one branch after another when suspended from their arms. As they forage, they can hang from a hand, a foot and tail, or just from the tail—which is strong enough to support their body weight for a long time. When resting, they lie down or crouch, holding their knees to their chest with folded arms around their legs and chin resting on their wrists.
In the early evening, all members of the troop regroup before dividing up once again into their sleep units, which are larger than the foraging units. They then settle into wide tall trees for the night.
Like their brethren all over South America, ornate spider monkeys have a rich vocal repertoire to communicate with each other. Long calls give out the location of individuals in a group and bring them back together. Barks are general warnings. Chitters are indicators of a nearby disturbance. Alarm calls are warnings that are specific to predators. Whinnies are used by monkeys to identify themselves, to let others know where a food resource is located, and to help spider monkeys stay in touch as they separate to forage. Tee-tee sounds are greetings, whereas ook-ook-ak-aks are invitations to play. Growls communicate hostility. Screams convey annoyance, anger, and frustration.
Spider monkeys also express themselves through gestures in specific contexts. For instance, male friends embrace and sniff each other’s chests. Interactions between males of different ages are cautiously carried out—one male approaches the other, then retreats. The two then embrace, or wrap their tails together and face greet.
Very often throughout the day, males growl and show threatening faces while chasing females—sometimes physically hurting them. This is how they assert their dominance over females. Finally, when encountering other groups, males shake branches and scream to scare off outsiders.
Spider monkeys are ready to start a family around the time they are 7 or 8 years old. Males of reproducing age stay with their native group but females migrate.
Once they integrate into a new group, females choose their partners and give birth to one offspring after a gestation period of 7–7.5 months. They typically do not give birth again for at least three years. In Costa Rica, most births occur between May and July when fruit is most abundant. Infants are totally dependent on their mothers during the first six months of life. Then, they learn to forage on their own and start eating solid food, but mothers continue to nurse them for at least one year and sometimes up to two years.
Ornate spider monkeys are great seed dispersers—mostly through their feces. They eat rapidly and can ingest large quantities of fruit in a short time. Their digestive tract is adapted to this type of diet and allows them to quickly absorb nutrients while evacuating all the seeds they can’t process as they travel to new feeding sites. The only time they spit out seeds in place is when consuming fruit in the family of two specific palm plants, and only because the seeds easily detach from the flesh of the fruit—otherwise they swallow them whole.
These monkeys feast on fruit from many plant species, so the seeds they disperse vary in size—from very small (0.03 in / 1 mm) to very large (0.7–1.1 in / 20–30 mm). Because not many other mammals are able to disperse large seeds, ornate spider monkeys play an extremely important role in forest regeneration.
The International Union for Conservation of Nature classifies the ornate spider monkey as Vulnerable (IUCN, 2020), appearing on the IUCN’s Red List of Threatened Species.
The main threats they face are deforestation and human encroachment on their habitat. Experts forecast that by the middle the twenty-first century, these beautiful animals will have lost about 20% of their habitat. This is a serious issue because these monkeys need connected forests to travel. A slow birth rate combined with an inability to travel can far increases the vulnerability of the species by limiting population growth and the gene pool. These animals usually need access to large foraging areas to stay healthy. Therefore, their survival depends on their ability to diversify their diet and adjust to the smaller number of plant species available in disconnected forest patches.
Furthermore, dramatic weather events induced by climate change are more prevalent worldwide than in the past decades. These can have a devastating effect on neo-tropical primates, including the ornate spider monkeys. Droughts, for instance, are responsible for the disappearance of important trees and drastically reduce ripe fruit availability—especially during the dry season. Fragmented forests don’t have many large trees that produce abundant crops, so monkeys living in disturbed habitats are most impacted. Undernourished mothers aren’t able to provide infants the nutrients they need.
Ornate spider monkeys are rather large so they are also hunted for meat. Hunting spider monkeys is not only motivated by the needs of humans to add protein to their diet, it is also fueled by beliefs attributing medicinal or magical powers to these creatures. Indeed, spider monkeys are often thought to be beneficial to treat arthritis or snake bites.
Finally, the lucrative illegal pet trade still fuels the abduction of wild animals—including spider monkeys.
Natural predators of the ornate spider monkeys are pumas, crested eagles, harpy eagles, and jaguars—although in Costa Rica, populations of jaguars and harpy eagles have been dwindling.
National parks in Costa Rica play an important role in the conservation of spider monkeys. They are financed through eco-tourism and offer a wide array of opportunities for tropical fauna and flora research and study. For instance, the Barro Colorado Island has been used for scientific research into tropical forest, animal behavior, species interaction, and conservation since the creation of the Panama Canal in 1914. Studies there are conducted by the Smithsonian Tropical Research Institute, which has set the standard for tropical research around the world.
Since habitat fragmentation is a huge threat, forest restoration and the creation of corridors are important to allow free movement of spider monkeys and thereby ensure gene flow and reproduction opportunities, as well as a way out in case of food shortages. Several organizations are leading conservation efforts that will greatly help in the survival of the ornate spider monkeys and other species. Costa Rica’s Osa Conservation nonprofit, for instance, started a project to understand how spider monkey droppings under specific trees can be used to help forest restoration efforts.
- IUCN Red List 2020
- ticotimes.net – The Taco Times – “Monkey Death Investigation Continues in Corcovado Park – (march 2006)
- news.bbc.co.uk Earth News – Folk medicine poses global threat to primate species – Matt Walker (2010)
- Differential impact of severe drought on infant mortality in two sympatric neotropical primates (2020) – Fernando A. Campos, Jeremy D. Hogan, Saul E. Cheves, Even Murillo-Chacon, Adrián Guadamuz, Monica S. Myers, Colleen M. Schaffner, Katharine M. Jack, Filippo Aureli, and Linda M. Fedigan
- Spider Monkeys – Behavior, Ecology and Evolution of the Genus Ateles – Edited by Christina J. Campbell (2018)
- Distribution, ecology, life history, genetic variation, and risk of extinction of nonhuman primates from Costa Rica – Maria E. Zaldivar, Oscar Rocha, Kenneth E.Glander, Gabriel Aguilar, Ana S. Huertas, Ronald Sánchez & Grace Wong (2004)
Written by Sylvie Abrams, February 2021