The species occurs in lowland terra firme unflooded forest, semi-deciduous forest, riparian and flooded forest (várzea and igapó forests) with little or no hunting pressure (van Roosmalen and Klein 1988; Konstant and Rylands 2013). They are also found in transitional forest (forest to savanna) in southwestern Amazonia. In Bolivia, in the Noel Kempff Mercado National Park, Wallace et al. (1998) recorded A. chamek most often in tall forest (4.42 encounters per 10 km), followed by so-called saternejal forest (along the forest–savanna border, in the vicinity of small forest streams that undergo periodic flash floods; 2.49 encounters per 10 km). Garcia and Tarifa (1988) found A. chamek to be restricted to high forest in the Beni Biological Station. Otherwise, Alves (2013) recorded A. chamek in both unflooded terra firme and open/dense igapó clear-water flooded forests, but not in cerradão dense savanna woodland. This taxon is restricted to primary forest. The population decline and local extinction of Ateles in most areas with human activity are the result of hunting pressure that is often associated with habitat destruction and degradation (van Roosmalen and Klein 1988; Peres 1997; Parry et al. 2007). The species of the genus are present in altered/fragmented areas but generally do not persist for long periods (Peres 1990, 1997). In the state of Rondônia (Brazil), A. chamek occurs in some forest fragments without hunting pressure (Ferrari et al. 1996; Iwanaga and Ferrari 2001, 2002), indicating a relative flexibility of the taxon to habitat disturbances in the absence of hunting.

Spider monkeys travel and forage in the upper levels of the forest. They spend most time in the upper canopy, sometimes using the middle and lower strata but are rarely seen in the understory. Due to the use of the highest levels of the forest, they spend more time hanging from branches, moving by brachiation, arm swinging, and climbing, than 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 about 80-90% of their diet and are found mainly in the emergent trees and upper part of the forest canopy (van Roosmalen and Klein 1988). In the state of Rondônia (Brazil), Iwanaga and Ferrari (2001) recorded a diet consisting of 97.1% fruits, of which the Moraceae and Caesalpinaceae families account for 53.3% of the species exploited by A. chamek. Similar findings were presented by Felton et al. (2008) for the Guarayos Forest Reserve in Bolivia, where Moraceae was the most important plant family in the diet, both in terms of number of species and time spent feeding. They also eat young leaves and flowers (especially during periods of fruit shortage at the beginning of the dry season), but occasionally also young seeds, floral buds, pseudobulbs, aerial roots, bark, decaying wood, honey, and at rare occasions small insects such as termites and caterpillars. They play a significant role as seed dispersers. Van Roosmalen (1985) and van Roosmalen and Klein (1988) found that A. paniscus was dispersing the seeds of at least 138 species (93.5% of all fruits species consumed) through their ingestion and subsequent defecation (endozoochory). Another 10 species were dispersed by carrying them off some distance from the tree before dropping them (exozoochory). Only in 23 species the seeds were ruined or digested (seed predation).

Spider monkeys live in large, territorial, multi-male/multi-female groups of 37-55 individuals (Wallace 2005; Konstant and Rylands 2013). However, they are rarely seen together, and almost always found travelling, feeding and resting in subgroups of varying size and composition (usually 2-4 individuals). The only persistent association is that of a mother and her offspring (McFarland Symington 1990). Iwanaga and Ferrari (2002) recorded a mean (± SE) group size of 3.34 ± 2.60 individuals (n = 219 sightings) at a number of localities in the state of Rondônia in Brazil. At Lago Uauaçú, in the lower Rio Purús region, Haugaasen and Peres (2005) observed a mean groups size of 6.0 individuals/group in terra firme forest, but 12.6 individuals/group in várzea forest. Often single group members travel on their own, and each female occupies a preferred “core area” within the group’s home range. Klein and Klein (1976, 1977) estimated 259-388 ha home ranges with 20-30% overlap between groups for A. belzebuth in La Macarena National Park in Colombia. Ateles species are rarely seen in association with other primates, and if, they are occasional and ephemeral, resulting from the simultaneous occupation of fruiting trees.

Six estimated birth periods, spread throughout the year, were given by Klein (1971) for Ateles belzebuth (i.e., December, January, April, September, October and November). Spider monkeys apparently reach sexual maturity at 4-5 years of age (Klein 1971; Eisenberg 1973, 1976). They give birth to a single offspring after a long gestation period of 226-232 days, with a minimum birth interval of 17.5 months (in captivity) or 28-30 months in the wild (Eisenberg 1973, 1976). Late maturation and long inter-birth intervals make it difficult for the species to recover from hunting and other threats.