White-bellied spider monkey  (Ateles belzebuth)

Classified as Endangered (EN) on the IUCN Red List (1). Listed under Appendix II of CITES (3).

Like all spider monkeys, the white-bellied spider monkey, also known as the long-haired spider monkey, has long, slender limbs and very mobile shoulder joints that aid in swinging hand-over-hand below branches (2) (4). The thumbs are either absent or reduced to a small stump, resulting in a hook-like hand structure that facilitates fast swinging below the branches (5). A further adaptation to this arboreal lifestyle is the extremely flexible prehensile tail that is used as an extra limb (2). The coat is black or brown, while the underparts, hindlimbs and the base of the tail are paler brownish-white (2). In one-third of the population, there is a yellowish-brown or white triangular patch on the forehead (2).

This New World monkey is found in Colombia, Brazil, Ecuador, Peru and Venezuela (1). Its range in Colombia has previously been greatly overestimated; it is found in the lowlands where there has been massive colonisation by humans, as well as in the piedmont forests of the north. It is currently the most threatened species in the Colombian Amazon (6). In Ecuador, the population has declined by 30% in the previous three generations (1). In Brazil, this monkey is found to the north-west of the Amazon (1).

Inhabits subtropical or tropical lowland and montane forests (1).

The white-bellied spider monkey is active during the day and spends most of its time in the canopy (2). It feeds mainly on ripe fruit; the composition of the diet changes depending on what fruits are available at a given time (7). Group size varies throughout the year, becoming larger when fruit is particularly abundant (2). Males cooperate to defend the boundaries of the territory against other groups (2).

Mating occurs throughout the year. Females give birth to a single young following a gestation period of around 225 days. Upon reaching maturity, young females disperse from their natal group, whereas males remain (2).

The most serious threats facing this spider monkey are hunting and deforestation for agriculture and for logging (1).

The white-bellied spider monkey occurs in a number of protected areas in Colombia (La Macarena, Tinigua and Picachos) but there has been extensive human colonisation around these parks and so there is a need for hunting to be controlled in these areas. Unfortunately, the presence of insurgents in some areas complicates park management (6). There is a substantial subpopulation of this species in Colombia between the Rios Caguan and Yari. This area is, at the present time, relatively isolated, but developments that may enable colonists to move into the area will quickly endanger this subpopulation (6).

For more information on this species see:

• The Primata:
  www.theprimata.com/factsheets.html

Authenticated (24/10/2005) by Matt Richardson, independent primatologist and writer.

• Arboreal: living in trees.
• Gestation: the state of being pregnant; the period from conception to birth.
• Montane forests: forest occurring in the montane zone, a zone of cool upland slopes below the tree line dominated by large evergreen trees.
• Natal: site of birth.
• Prehensile: capable of grasping.

1. IUCN Red List (January, 2009)
   http://www.iucnredlist.org
2. Macdonald, D. (2001) The New Encyclopedia of Mammals.Oxford University Press, Oxford.
3. CITES (September, 2008)
   http://www.cites.org/eng/resources/species.html
4. The Primata (March, 2004)
   http://www.theprimata.com/ateles_belzebuth.html
5. Kavanagh, M. (1983) A Complete Guide to Monkeys, Apes and Other Primates.Jonathan Cape, London.
6. Defler, T.R., Rodrigues, J.V. and Hernaandez-Camacho, J.I. (2003) Conservation Priorities for Columbian Primates. Primate Conservation, 19: 10 - 18.
7. Nunes, A. (1998) Diet and feeding ecology of Ateles belzebuth belzebuthat Maraca Ecological Station, Roraima, Brazil. Folia Primatology, 69: 61 - 76.