This species 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.

Ateles marginatus is endemic to the Brazilian Amazon, occurring between the Rio Tapajós (right bank) and its tributary, the Rio Teles Pires (right bank) and the Rio Xingu (left bank), south of the Rio Amazonas (Kellogg and Goldman 1944, Ravetta 2008, Ravetta 2009). This is the least known of the Amazonian spider monkeys. There are unconfirmed records of the species along the right bank of the rio Xingu. It is not possible, however, to be sure that the groups seen constitute a widespread population along the right bank of the Xingú (A. Ravetta, pers. obs.).

This species occurs in a number of protected areas in Brazil, including Tapajós National Forest (549,000 ha), Altamira National Forest (724,965 ha), Itaituba I National Forest (220,639 ha), Itaituba II National Forest (427,366 ha), Terra do Meio Ecological Station (3.373,133 ha), Trairão National Forest (257,526 ha), Crepori National Forest (741,244 ha), Jamanxim National Forest (1,301,683 ha), Jamanxim National Park (859,797 ha), Tapajós Environmental Protection Area (2.060,332 ha); Nascentes da Serra do Cachimbo Biological Reserve (342,192 ha ), Anfrísio River Extractive Reserve (736,135 ha) and Cristalino State Park (184,900 ha) (Ravetta 2008, Ravetta 2009, Ravetta, 2015, Buss et al.2017).

The species included in the national action plan for the middle and lower Xingú and the national action plan for Amazon primates.

It is listed on Appendix II of CITES.