WHITE-BELLIED SPIDER MONKEY

Ateles belzebuth

Geographic Distribution and Habitat
White-bellied spider monkeys, also known as white-fronted or long-haired spider monkeys, are native to the northwestern lowland and montane Amazonian forests of Colombia, Ecuador, Venezuela, Peru, and Brazil.

The Amazon rainforest, which has been in existence for at least 55 million years, is warm and moist. It is one of the richest places on earth for its biodiversity, with tens of thousands of plants, over 2 million insects, and more than 2,000 species of birds and mammals. It is composed of lowland and montane forests, flooded areas, bamboo and palm forests, and savanna. Although the temperature never exceeds 90 F (33 C), it feels very warm and stuffy because humidity is permanent.

White-bellied spider monkey range, IUCN 2019

Size, Weight, and Lifespan
There is a slight difference in body size and weight between male and female white-bellied spider monkeys. Males are about 17–19 inches (42–50 cm) tall, while females are about 13–23 inches (34–59 cm) tall. Tail length for both males and females averages 25–35 inches (65–90 cm)—longer than their entire body. They weigh between 13 and 20 pounds (6–10 kg).

Overall, spider monkeys can live 25 to 30 years in the wild and 40 or more in captivity. According to several published papers, females may have a longer lifespan than males.

Appearance
White-bellied spider monkeys’ limbs are long, muscular, and very strong. Their shoulders are such that the arms can fully rotate; the elbows allow the forearms to pronate and large carpal tendons make their wrists extremely flexible. Their hands are long, thin, and thumbless; their four long fingers form a perfect hook to help them swing on branches. Their torso is short. All of these features are perfectly adapted to the monkeys’ suspensory mode of locomotion.

Their long muscular tail is large at the base, thin at the tip, and able to bend, twist, and curl up. It is prehensile and tactile; the under part is bare with ridges like those found on the underside of hands and feet. Spider monkeys can use their tails to grab and hold onto branches. In fact, their tail is strong enough to sustain their full body weight and even propel them while in motion. It also allows the monkeys to hang still from a branch, with their torso at a sharp angle, while they use their hands to eat.

They have a narrow face with a tiny chin, a narrow snout, and large orbits in which almond-shaped brown eyes are set. The cranium is round and their ears look similar to ours. The upper palate is wider than the lower jaw. The incisor teeth are wide, the upper canines are long and curved (slightly shorter in females), and they are very sharp.

White-bellied spider monkeys living in lowland forest have blackish fur on the back and anterior limbs and yellow-creamy color fur on the belly; those in montane forests have more variety in color.

Photo Credit:Fábio Manfredini/Flickr/Creative Commons

What Does It Mean?

Angiosperms:
A large family of plants with flowers that produce seeds enclosed in the center part of the flowers.

Brachiation:
Also called arm swinging, is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. branches.

Brosinum:
Refers to a genus of American tropical trees.

Ficus:
Trees of shrubs that include figs and the rubber plant.

Liana:
A climbing plant that usually hangs on trees in tropical forests.

Mineral lick:
A natural area rich in minerals where animals can go lick the soil.

Prehensile:
Able to grasp or hold objects.
​​
Pronate:
Turn a hand or foot so that the palm or sole is facing down or back.

Virola:
Refers to a genus of South American forest trees with pale or reddish wood.​

Visit the Glossary for more definitions

Diet
White-bellied spider monkeys spend 20% of their time feeding. They eat primarily fruit and seeds, along with foliage, buds, and flowers. Of the many trees they feed on, they favor four tree species: ficus, cecropia, brosinum, and virola. They love the sugar-rich, small-seeded fruit of ficus and cecropia trees; the seeds from the fruit growing on brosinum trees; and the large oily seeds of virola fruit. In some locations, they also eat fruit from palm trees and even angiosperms, like Gustavia hexapetala, which has large white flowers.

Mineral licks (or saladeros), located at sites with eroded soil layers, provide the monkeys with nutrients and digestive enzymes found in the water or soil that they ingest.

Behavior and Lifestyle
These arboreal monkeys spend most of their time in the canopy. They rarely descend to the ground. When they do, it is to drink water, eat soil, cross an area with no trees, or run away from an aggressive opponent.

In the forest canopy, white-bellied spider monkeys move freely between branches and can travel long distances quickly via a number of modes of locomotion. Their most common mode of arboreal locomotion is brachiation (or arm swinging)the monkey hangs from one branch,  swings forward, and hooks onto the next branch with another limb or tail. Another is the forelimb swing in which the monkey hangs from a branch with both arms, swings his or her body, and lets go before swiftly grabbing hold of another branch. Tail swinging is yet another form of locomotionthe monkey hangs from his or her tail as an intermediary step between branches. They may remain stationary while in this position to eat with both hands. Spider monkeys can also walk on branches using all four limbs or standing up on their hind limbs.

Daily Life and Group Dynamics 
White-bellied spider monkeys live in groups of 6 to 25 individuals, sometimes more. The group size varies with the environment, with larger groups found in undisturbed forest patches.

About one hour before sunrise (earlier between January and April) the group splits into sub-groups for foraging; they regroup at night to sleep. This is called a fission-fusion social structure. The make-up of individuals in each of these sub-groups change regularly. They can include males and females, only males, or only females. Some individuals prefer to forage on their own. Generally, female spider monkeys remain within core areas of the home territory while males travel longer distances and use areas that overlap with those of females or other males. This is not the case, however, for white-bellied spider monkeys in the Yasuni National Park in Ecuador, where both males and females use all areas within their home range equally.

On average, white-bellied spider monkeys travel 1–2 miles (1.5–3 km) per day to various feeding sites within a fairly large home range, which can be anywhere between 150 and 860 acres (60–350 ha). Their foraging patterns (distance traveled and time spent feeding) varies based on which fruiting trees are in season and how far apart they are.

Males patrol the borders of the group’s territory to chase away potential intruders and can inflict serious wounds if they bite an adversary.

About two hours past sunset, the group returns to their sleeping site, which is usually in a valley. The trees selected for the night are tall and never used for feeding. The monkeys settle for the night on branches about 80 feet (25 m) above ground level.

Fun Facts

Did you know that “Ateles” means “imperfect” and the reason naturalist Geoffroy Saint-Hilaire (1772–1844) named the spider monkey genus that way is because spider monkeys don’t have thumbs?

Plants and animals evolve together. In neo-tropical forests, for instance, plants and trees produce large yellow-orange, brown, or green fruit with a woody pericarp. These colors are easily perceived by New World primates who have dichromatic vision. The monkeys consume the fruit and transfer the seeds to a different area of the forest, thereby ensuring the propagation and survival of the plant species.  Interestingly, in Africa, fruit is mostly red or a bright color because the monkeys there have tri-chromatic vision.

When their limbs and tail are clinging to branches, these lanky creatures look like giant spiders, hence their name.

Communication
Spider monkeys use various vocalizations and body language to communicate.  

  • Whinnies allow group members to identify each other as well as locate one another.  
  • Loud calls are common and serve to alert the group about the presence of a predator or threat. When accompanied by the shaking of branches, they are meant to scare away enemies. 
  • Two-note squeals can be heard when spider monkeys are agitated or during conflicts. 
  • Infants make distress calls when they are away from their mothers or injured and the mothers vocalize back.

Affiliative behaviors include hugging, embracing, licking the wound of a friend, and grooming.

Spider monkeys also rub leaves on their body. It is possible the smells are used as natural insect repellent, but it is also possible that they could signal social status and attract a mate.

Reproduction and Family
White-bellied spider monkey females disperse when they reach their adult size (about 6 years old) to join other groups, but they don’t breed until they are 7 or 8 years old. Males become independent from their mothers at 5 years old and are then ready to begin courting females. They usually do so away from the prying eyes of the group. Females mate with several partners, thereby potentially blurring the lines of paternity.

Spider monkeys can reproduce all year long. Females give birth to one offspring after a gestation period of 7 months. Twins are rare. Rearing twins is, indeed, a lot more costly to the mother as she needs to rest longer than other adult females (with or without offspring) and is not able to spend as much time feeding or traveling to forage.

Although rare, infanticide has been observed. In each documented case, the targeted infants were males only a few weeks old. The attackers were adult males belonging to the same group as the mother of the victim. The reason is not known; hypothetically, infanticide could be explained because it significantly shortens the period needed for the bereaved mother to become pregnant again. Indeed, the normal interval between births is about 3 years and only some of the females in the group are receptive every year.

Mothers carry their newborn baby on their belly. After a few months, the offspring are able to spend time alone while their mothers forages or rests. They still ride on top of their mother when they need to travel long distances.

Photo credit: Ewa/Flickr/Creative Commons

Ecological Role
These primates are pollinators and seed dispersers. They play an important role in the regeneration of tropical forests by dispersing seeds from many different trees and lianas. They drop seeds far away from the sites at which they fed and large amounts of seeds can also be found underneath their sleeping area. It is estimated that each monkey spreads more than 230,000 seeds a year over a distance of 1600–3900 feet (500–1200 m), on average. Some of the seeds they spread also serve to feed other animals, like mice and peccaries.

Conservation Status and Threats
The white-bellied spider monkey is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2019), appearing on the IUCN Red List of Threatened Species. These primates are extremely affected by changes in their natural habitat. Deforestation for agriculture, cattle ranching, logging, fruit or resins harvesting, and even oil drilling are all contributing factors. As the monkeys become displaced, the groups become smaller in degraded forests, where they are also more at risk of being hunted by humans, both for food and the pet trade. This is especially true in lowland forests and anywhere illegal logging is practiced. In fact, in some areas they have been over-hunted and the species has totally disappeared, as in the lowland forests of the Peruvian Amazon, where the last sighting reports date back to 2007. Nowadays, most of the groups in Peru can be found in the montane regions of the Área de Conservación Privada Los Chilchos. Some groups are also present in the Región San Martín and Región La Libertad in Peru.

Natural predators of white-bellied spider monkeys include jaguars, pumas, and eagles.

Conservation Efforts
Several initiatives and regulations aim at protecting the forest and its inhabitants, including the white-belied spider monkey. However, the situation is still dire. Deforestation has not decreased in spite of the Amazon Deforestation Monitoring Project, which started in 1988. Hunting is prohibited in protected areas, like the Área de Conservación Privada Los Chilchos in Peru, but it is still legal in Colombia, for instance.

Fortunately, all Latin American countries are members of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival, and the trade of primates and other wild animals has decreased over the years. The white-bellied spider monkey is listed on Appendix II of CITES.

References:

  • ​Costs of twins in free-ranging white-bellied spider monkeys (Ateles belzebuth belzebuth) at Tinigua National Park, Colombia – Andres Link, Ana Cristina Palma, Adriana Velez, Ana Grabriela de Luna
  • Conservation Status and Threats to Atelids in the Northeastern Peruvian Amazon – Rolando Aquino, Luis López, Gabriel Garcia, Elvis Charpentier, Iris Arévalo
  • Use of Mineral Licks by White-Bellied Spider Monkeys (Ateles bezebuth) and Red Howler Monkeys (Alouatta seniculus) in Eastern Ecuador – John G. Blake, Jaime Guerra, Diego Mosquera, Rene Torres, Bette A. Loiselle, David Romo
  • Current status of Ateles belzebuth in Montane Forests of the Peruvian Amazon – Rolando Aquino, Luís López, Hugo Gálvez and Silvia Diaz 
  • Multi-Forest Comparison of Dietary Preferences and Seed Dispersal by Ateles spp. – Sabrina E Russo, Christina J. Campbell, J. Lawrence Dew, Pablo R. Stevenson, Scott A. Suarez
  • Fruit Preferences of Ateles belzebuth in Tiniga Park,Northwestern Amazonia – Pablo R. Stevenson, Andrés Link
  • Initiation of feeding by four sympatric Neotropical primates (Ateles belzebuth, Lagothrix lagotricha poeppigii, Plecturocebus (Callicebus) discolor, and Pithecia aequatorialis) in Amazonian Ecuador: Relationships to photic and ecological factors – D. Max Snodderly, Kelsey M. Ellis, Sarina R. Lieberman, Eduardo Fernandez-Duque, Anthony Di Fiore
  • IUCN Red List www.iucnredlist.org 
  • Male-directed infanticide in spider monkeys (Atels spp) – Sara Álvarez. Solas, Anthony Di Fiore, Andrés Link
  • Male and Female Range Use in a Group of White-Bellied Spider Monkeys (Ateles belzebuth) in Yasuní National Park, Ecuador – Stephanie N. Spehar, Andrés Link, Anthony Di Fiore
  • Suspensory locomotion of Lagothrix lagothricha and Ateles belzebuth in Yasuní National Park, Ecuador – John G. H. Cant, Dionisios Youlatos, Michael D. Rose
  • Morphology and evolution of the spider monkey, genus Ateles – Aflred L. Rosenberger, Lauren Halenar, Siobhán B. Cooke and Walter C. Hartwig.
  • Terrestrial Behavior of Ateles spp. – Christina J. Campbell, Filippo Aureli, Colin A. Chapman, Gabriel Ramos-Fernández, Kim Matthews.
  • A literature review of the spider monkey, Ateles sp., with special focus on risk for extinction – Julia Takahashi

Written by Sylvie Abrams, May 2020