Occurs in primary lowland rain forest.

Spider monkeys travel and forage in the upper levels of the forest. They spend much time in the canopy and also use the middle and lower strata but are rarely seen in the understorey. In accordance with their use of the highest levels of the forest, they are highly suspensory. When travelling they spend more time hanging from branches, moving by brachiation and arm swinging, and climbing than they do walking or running on all fours. They are highly frugivorous and feed largely on the mature, soft parts of a very wide variety of fruits, which comprise 83% of their diet and are found mainly in the emergent trees and upper part of the forest canopy (Van Roosmalen and Klein 1988). They also eat young leaves and flowers (both especially at times of fruit shortage during the beginning of the dry season), and besides such as young seeds, floral buds, pseudobulbs, aerial roots, bark, decaying wood, and honey, and very occasionally small insects such as termites and caterpillars. They play a significant role as seed dispersers. Van Roosmalen (1985; Van Roosmalen and Klein 1988) found that A. paniscus was dispersing the seeds of at least 138 species (93.5% of all fruits species used) through their ingestion and subsequent defecation (endozoochory). A further 10 species were being dispersed by the monkeys carrying them off some distance from the tree before dropping them (exozoochory). In only 23 species were the seeds being ruined or eaten (seed predation).

Spider monkeys live in groups of up to 20-30 individuals (for review see Van Roosmalen and Klein 1988). However, they are very rarely all seen together, and nearly always to be found travelling, feeding and resting small in groups of varying size and composition (most usually 2-4), the only persistent association being that of a mother and her offspring (McFarland Symington 1990). Group members will also travel on their own. Each female in the group has a “core area” of the group’s home range which she uses most. Ateles are rarely seen in association with other primates and mostly they are occasional and ephemeral, resulting from the simultaneous occupation of fruiting trees.

Spider monkeys apparently reach sexual maturity at 4-5 years of age (Klein 1971; Eisenberg 1973, 1976). They give birth to single offspring after a long gestation period of 226-232 days, with a minimum theoretical interbirth interval in captivity of 17.5 months, but in the wild probably as long as 28-30 months (Eisenberg 1973, 1976). Late maturation and long inter-birth intervals make it difficult for them to recover from hunting and other threats.

Red List Category

Red List Criteria

Version

2008

Mittermeier, R.A., Boubli, J.-P. & Di Fiore, A.

Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)

Justification

History

• 2003
  Endangered
  (IUCN 2003)
• 2000
  Endangered
• 1996
  Endangered
• 1996
  Endangered
• 1994
  Endangered
  (Groombridge 1994)

There are no published population densities available.

Decreasing

Although it occurs south as far as the north of the state of Mato Grosso, its range is relatively small, cut by major highways such as the Transamazon and the Cuiabá-Santarém, and in many parts subject to active and widespread deforestation (especially in the south), and, as in all spider monkeys, A. marginatus is particularly susceptible to hunting. Accelerated expansion of the agricultural frontier in northern Mato Grosso, with the ongoing establishment of enormous areas of soy bean plantations accompanying the paving of the Cuiabá-Santarém highway are additional and major threats.

This species occurs in a number of national forests in Brazil, including Tapajós National Forest (545,000 ha), Xingu National Forest (252,790 ha), Alatmira National Forest (689,012 ha), Itaituba I National Forest (220,034 ha), and Itaituba II National Forest (440,500 ha). More strictly protected areas are needed for the conservation of this species.

Surveys are currently ongoing throughout the range of the species (Ravetta 2005; A. L. Ravetta pers. comm.).

It is listed on Appendix II of CITES.