BLACK-FACED BLACK SPIDER MONKEY

Ateles chamek

Geographic Distribution and Habitat
Black-faced black spider monkeys are also commonly known as Peruvian spider monkeys. Despite their alias, they are actually found in Bolivia and Brazil, as well as in Peru. They inhabit areas in northeast Peru, northern Bolivia, and the western Amazon rainforest in Brazil. They are primarily found in lowland forests but also live in a range of other habitats.

A recent study found groups of black-faced black spider monkeys living north of the river previously thought to be the northern boundary of its range in Brazil. Although rivers often act as barriers that separate species, these monkeys are able to swim; it is thought that members of this species crossed the Solimões river at some point and expanded their range. 

Black-faced black spider monkey range, IUCN 2020

Size, Weight, and Lifespan
Black-faced black spider monkeys are relatively large-bodied monkeys who show some sexual dimorphism in size. Their heads and bodies measure around 17.7–23.6 in (45–60 cm) long for males and 15.7–20.5 in (40–52 cm) long for females. Their long tails reach around 31.5 in (80 cm) in both sexes. Males weigh more than females at around 15.4 lb (7 kg), compared to females’ average weight of 11 lb (5 kg).

In captivity, spider monkeys can live upwards of 30 years.

Appearance
Black-faced black spider monkeys have longs arms and legs, long tails, and thick, silky black pelage. The skin around their eyes and mouths is pinkish-gray skin. Their feet are also pink. A silvery genital patch extends down their inner thighs. Infants are born with a more grayish-black pelage that becomes darker with age.

Their long tails are prehensile, which means that they are able to hang from them—this helps them move through the canopy. Unlike most other primates, they only have a vestigial thumb, which allows them to swing more easily among the trees.

What Does It Mean?

​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.

Diurnal:
Active during daylight hours.

Fission-fusion society:
​A society in which the members of a social group break off into smaller groups and then rejoin as a larger group.

Frugivorous:
Having a diet that consists of fruits.

Pelage: 
The fur, hair, or wool of a mammal.

Prehensile tail: 
The tail of an animal that has adapted to be able to grasp or hold objects.

Sexual dimorphism:
Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves.

Vestigial:
A part of the body that in the course of evolution, has degenerated and become functionless; the last small part that remains of something that once existed.

Visit the Glossary for more definitions

​Diet
This species, like other spider monkeys, is highly frugivorous. Fruits make up around 85% of their diets. In some areas, figs can make up almost 50% of their diet and these are eaten year round, even when unripe. While fruits are their preferred source of food, they also eat leaves and, to a lesser extent, flowers and insects to supplement their diets.

Behavior and Lifestyle
Black-faced black spider monkeys are diurnal and spend their time in the higher levels of the forest. They are skilled climbers and, aided by their long arms and prehensile tails, spend more time brachiating and hanging from branches than they do walking or running quadrupedally.

Home ranges of groups are estimated to be around 642–964 acres (260–390 ha) and each female has a core area of the home range that she uses more than other areas. Around 30% of their day is spent feeding, usually on fruits that occur at the top of the canopy. The rest of their time is spent resting and traveling and individuals can range up to 2.5 miles (4 km) in one day.

Daily Life and Group Dynamics 
Groups vary in size, but can be up to around 40 individuals. However, this species has a fission-fusion social system, which means that members of the same group often split up into much smaller subgroups, often just 2–4 individuals. The whole group is rarely seen together and the only stable grouping is that of a mother and her infant.

There are generally more adult females than adult males in a group; males stay in their natal groups to reproduce, whereas females disperse to new groups.

Fun Facts

Black-faced black spider monkeys live in fission-fusion societies and members are often split into smaller subgroups.

They are highly frugivorous and fruit accounts for around 85% of their diet. 

Despite their alternate common name, Peruvian spider monkeys, they are actually found in Bolivia and Brazil, as well as in Peru. 

Communication
Due to their fission-fusion social structure, group members are often separated. It is thought that spider monkeys use “whinny” vocalizations to stay in contact with other group members that they cannot see. They also use a range of other vocalizations, such as barks that are produced during encounters with other groups or when humans approach. Spider monkeys also use a range of visual and tactile gestures to communicate with one another, including a head shaking gesture that encourages friendly interactions and embracing one another during a reunion.

Reproduction and Family
​Females likely reach sexual maturity at around 4–5 years of age and disperse from their natal group in order to reproduce.  The gestation period is thought to be around 230 days, after which they will give birth to a single infant. Females seem to isolate themselves from the rest of the group when they give birth, much like female chimpanzees do. This may be because of the threat of infanticide by adult males, which has been observed in this species. Inter-birth intervals are thought to be over two years and infant mortality has been estimated at around 30%. This high level of mortality combined with relatively slow reproductive rates makes this species even more vulnerable to population decline. 

Photo credit: Miguelrangeljr/Creative Commons

Ecological Role
The highly frugivorous nature of the black-faced black spider monkey means that they are important seed disperser for many trees in the Amazon rainforest and other habitats. It is estimated that these monkeys disperse seeds of over 120 different species of plants.

Conservation Status and Threats
The black-faced black spider monkey is currently classified as Endangered by the International Union for Conservation of Nature (IUCN, 2015).

It is estimated that their total population has declined by at least 50% over the past 45 years. This is primarily due to hunting and habitat loss. This species is hunted locally for meat and hunting remains one of its biggest threats. Habitat loss is also a major threat; huge amounts of deforestation for cattle farming, agriculture, mining, and logging has resulted in severe habitat loss across this species’ range. Planned highways across the southern part of their range adds yet another threat to this species’ survival by threatening habitat and also opening up the area to further hunting.

Conservation Efforts
Black-faced black spider monkeys occur in a number of protected areas within their range and are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that their trade is restricted. However, their populations are still decreasing and more information is needed about their distribution and threats in order to adequately protect them.

​References:

  • ​Dubreuil, C. J. (2014). Sex Differences in the Use of Whinny Vocalizations in Spider Monkeys (Ateles geoffroyi). (Unpublished master’s thesis). University of Calgary, Calgary.
  • Felton, A. M., Felton, A., Wood, J. T., & Lindenmayer, D. B. (2008). Diet and feeding ecology of Ateles chamek in a Bolivian semihumid forest: the importance of Ficus as a staple food resource. International Journal of Primatology29(2), 379-403.
  • Ramos-Fernández, G. (2005). Vocal communication in a fission-fusion society: do spider monkeys stay in touch with close associates?. International Journal of Primatology26(5), 1077-1092.
  • Symington, M. M. (1988). Demography, ranging patterns, and activity budgets of black spider monkeys (Ateles paniscus chamek) in the Manu National Park, Peru. American Journal of Primatology15(1), 45-67.
  • Wallace, R. B. (2005). Seasonal variations in diet and foraging behavior of Ateles chamek in a southern Amazonian tropical forest. International Journal of Primatology26(5), 1053-1075.
  • Wallace, Robert (2006). Seasonal Variations in Black-Faced Black Spider Monkey (Ateles chamek) Habitat Use and Ranging Behavior in a Southern Amazonian Tropical Forest. American Journal of Primatology68 (4): 313–332.
  • Wallace, R.B., Mittermeier, R.A., Cornejo, F. & Boubli, J.-P. 2008. Ateles chamek. The IUCN Red List of Threatened Species 2008: e.T41547A10497375.
  • www.alltheworldsprimates.org

Written by Jennifer Bottin, PhD, June 2020