This species prefers high primary forest (Stevenson et al. 2000), generally associated with terra firma clay soil forests (absent in the white sand forest of the Guainía-Atabapo forest of Venezuela (B. Urbani, unpubl. data)). They visit flooded forests when fruit productivity is high (Stevenson et al. 2000), and the highest densities seem to be found in places where both terra firme and flooded varzeas co-occur (Ahumada et al. 1998), but it has not been found in the floodplains near the Amazon river.

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 (Stevenson and Quiñones 1993), and populations in western Amazonia frequently visit specific areas in the forest ground (mineral licks) where they feed of soil (Link et al. 2011; Link and Di Fiore 2013). 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 ripe and fleshy fruits, which comprise approximately 80% of their diet (Stevenson et al. 2000), consuming preferentially common plants and fruits rich in lipids (Stevenson and Link 2010). They feed mainly in the emergent trees and upper part of the forest canopy (Van Roosmalen and Klein 1988, Stevenson and Quiñones 1993, Di Fiore et al. 2008). The spider monkeys respond to seasonal periods of fruit scarcity by concentrating at places in the forest with high fruit supply (Mourthé 2014). Additionally, they complement their diet with young leaves and flowers (both especially at times of fruit shortage) (Stevenson et al. 2000, Stevenson 2005), and less often with young seeds, floral buds, pseudobulbs, aerial roots, decaying wood, honey, and very occasionally small insects such as caterpillars (Link 2003, Di Fiore et al. 2008, Mourthé 2012). They play a significant role as seed dispersers, as they swallow seeds from hundreds of species of different trees and lianas (Suarez 2006, Di Fiore et al. 2008) and disperse them away from parental sources (Link and Di Fiore 2006). The absence of these primates and other atelines can reduce plant diversity in seedlings and saplings (Stevenson 2011). The population decline of spider monkeys can have negative effects in the forest dynamics in the absence of other large seed dispersers (Pacheco and Simonetti 2000).

Spider monkeys live in groups of up to 15-55 individuals (for review see Shimooka et al. 2008). 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 (McFarland Symington 1990, Stevenson et al. 1998) that show a high degree of fission fusion dynamics (sensu Aureli et al. 2008). Each female in the group has a core area of the group’s home range which she uses most (Symington 1987, Link and Di Fiore unpubl. data), while males use the group´s home range more evenly. Subgroup size is most frequently of 1 to 4 individuals (Klein and Klein 1976, Link and Di Fiore 2013, Mourthé and Barnett 2014), and only rarely will the entire group coalesce in a single area. Home ranges vary from 150 ha in Tinigua Park, in Colombia and in El Caura basin, in Venezuela, to over 400 ha at the Tiputini Biodiversity Station in eastern Ecuador (Castellanos 1997,,Spehar et al. 2010; Link et al. 2012).

Field studies of the behaviour and ecology of this species have been carried out by Izawa et al. (1979), Klein and Klein (1975, 1976, 1977), Ahumada (1989, 1992), Ahumada et al. (1998), Stevenson et al. (1998, 2000), and Link et al. (2006) in La Macarena, Colombia; by Nunes (1988, 1995, 1998),  Mourthé (2011, 2012 2014) and Mourthé and Barnett (2014) at Maracá Ecological Station, Brazil; by Pozo (2001, 2004a, 2004b, 2004c), Suarez (2006), Spehar et al. (2010), Link and Di Fiore (2006), and Di Fiore et al. (2009) in the Yasuní National Park, Ecuador. Additionally, Castellanos (1995, 1997; Castellanos and Chanin 1996) studied the feeding ecology of Ateles belzebuth along the middle and lower reaches of the Río Tawadu, a tributary of the Río Nichare, a tributary of the Rio Caura. Since 2005, Link and Di Fiore (2013 and refs therein) have studied the behavioral ecology and social behavior of white bellied spider monkeys continuously at the Tiputini Biodiversity Station (TBS) in Ecuador.

Six estimated birth dates given by Klein (1971) for A. belzebuth, were spread throughout the year (December, January, April, September, October and November). Nonetheless, in more than 30 births recorded at TBS, Ecuador, births have been restricted to the period between May and December suggesting some reproductive seasonality (Link and Di Fiore unpubl. data). Spider monkeys have been suggested to reach sexual maturity at 4-5 years of age (Klein 1972) but recent studies have found that females leave their natal groups after 6 years of age and do not give birth until after 2–3 years of being in their new groups. Thus, age at first reproduction for females may well be around 7 to 9 years of age (Link and Di Fiore unpubl. data). They give birth to single offspring after a long gestation period of 226-232 days, with interbirth cycles that range between 32 and 36 months. Late maturation and long inter-birth intervals make it difficult for them to recover from hunting and other threats.

Size
H&B 46-50 cm; TL 74-81 cm (Defler 2003)

Adult male weight mean 8.3 kg (n=10), adult female weight mean 7.9 kg (Smith and Jungers 1997).
Adult male weight 7.3-9.8 kg (mean 8.5 kg, n=12), adult female weight 5.8-10.4 kg (mean 8.1 kg, n=15) (Ford and Davis 1992).

The geographic distribution of Ateles belzebuth includes the lowland forests (generally below 1,000 m asl) of western Amazonia in Colombia, Ecuador, and Perú, northern Amazonia in southern Venezuela, and northwestern Brazil, reaching east as far as the Rio Branco. The distribution of this species is not well known, and defies an easy description. There are at least three discontinuous areas of occurrence of White Bellied Spider Monkeys: [1] north-western Amazonian rainforests in Colombia; [2] western Amazonian populations in eastern Ecuador (south of the Río Napo) and northwestern Perú; and [3] those populations living in the easternmost part of the distribution in Venezuela and northwestern Brazil. At least in the last case, such gaps could be partly explained by the occurrence of savannas (a habitat formed by low and sparsely distributed shrubs) that are not used by spider monkeys.

In Colombia, Defler (2003, 2004) reported that the taxon was recorded in the piedmont and Cordillera Oriental as far north as the Río Upía drainage in the department of Boyacá. However, a population was recently discovered west of Yopal, at 1,100 m asl in a forest patch from 1,000 to 1,800 m asl (A. Barrera pers. comm). It occurs in the region of the Sierra de La Macarena, eastern Caquetá and the Coehmaní rapids in the South East of the department of Caquetá. It is rare west of the Río Yarí. It was reported from the upper Río Mesay, opposite of the mouth of the Río Pirá-Paraná on the right bank of the Río Apaporis, and on the lower right bank of the Río Apaporis at a salado (clay-lick) site near the Estrella rapids (Defler 2003, 2004). According to Defler (2003, 2004), there is no evidence for its occurrence between the Ríos Caquetá and Putumayo, except on the most western, upper reaches. Ateles belzebuth extends south along the piedmont into Ecuador, but is evidently absent south of the middle and lower Putumayo (Province of Sucumbíos) and is restricted to the South of Río Napo (De la Torre 2000, Tirira 2007). From there it occurs throughout the Ecuadorian Amazon into northern Peru. The distribution map of Aquino and Encarnación (1994, p.120) shows the occurrence of A. belzebuth throughout northern Peru, between Río Putumayo and Río Amazonas, along the left bank of the Río Ucayali, including the basins of the Ríos Napo, Tigre, Marañón, Pastaza, Pacaya and Samiria, and south as far as the Río Cushabatay, a tributary of the Río Ucayali (with Ateles chamek replacing it south of the Cushabatay). The range in Peru extends through the Putumayo/Napo interfluvium up to the Ecuadorian border, but it seems to end near the mouth of the Río Aguarico, not extending into Ecuador (Tirira 2007). Its occurrence between Putumayo and Amazonas Rivers in Peru would indicate that it occurs in the Colombian Trapezium, but this still warrants confirmation (Defler 2003, 2004). In Brazil, Ateles belzebuth occurs throughout the region north of the Rio Negro and west of the right bank of the Rio Branco in Roraima, extending into Venezuela north towards the Río Orinoco (limited by the llanos/forest interface) and in the East to the left bank of the Río Caura (Bodini and Pérez-Hernández 1987). Although widely distributed in Brazil, the species does not occur continuously, being absent or very rare in large areas of campina and campinarana habitats in the westernmost part of the state of Amazonas and in the savannas in the Northeast of the state of Roraima. It seems there are no known localities which connect the Brazilian/Venezuelan populations with those of south-western Colombia, Ecuador and northern Peru. The occurrence of this species between the Ríos Putumayo and Amazonas-Napo requires further field research. The species has been observed at altitudes up to 1,300 m on the eastern slopes of the Cordillera Oriental (Hernández-Camacho and Cooper 1976).

This species is confirmed, or may occur, in a number of protected areas:

Brazil:

• Pico da Neblina National Park (2,298,154 ha)
• Maracá Ecological Station (103,995 ha) (Nunes et al. 1988))
• Juamí-Japurá Ecological Station (832,078 ha) (in range)
• Serra da Mocidade National Park (373,130 ha) (in range)
• Niquiá Ecological Station (282,830 ha) (in range)
• Amazonas National Forest (1,573,100 ha) (in range)
• Caracaraí Ecological Station (Ravetta 2008)
• Roraima National Forest (2,664,685 ha) (in range)

Colombia:

• Cordillera de los Picachos Natural National Park (286,600 ha) (Defler 2004)
• La Paya Natural National Park (442,000 ha) (reported by interview Palanco-Ochoa et al. 1999)
• Tinigua Natural National Park (201,875 ha) (Ahumada 1989, 1992; Stevenson et al. 2000)
• Serranía de la Macarena Natural National Park (630,000 ha) (Klein and Klein 1976)
• Nukak Natural National Reserve (855,000 ha) (in range: Defler 2004)
• There is potential occurrence of A. belzebuth in the following parks (Defler 2004):
• Puinawai Natural National Reserve (1,092,500 ha)
• Cahuinarí Natural National Park (575,500 ha)
• Serrania de Chiribiquete Natural National Park (1,280,000 ha)

Ecuador
Podocarpus National Park (146,280 ha) (Tirira 2007)
Sumaco-Napo Galeras National Park (205,249 ha) (Tirira 2007)
Yasuní National Park (982,300 ha) (Pozo 2001; Tirira 2007)
Cayambe-Coca Ecological Reserve (403,100 ha) (Tirira 2007)
Cofán-Bermejo Ecological Reserve (55,451 ha) (Tirira 2007)

Peru
Pacaya-Samiria National Reserve (2,080,000 ha) (in range: Aquino and Encarnación 1994a). Soini et al. (1989) informed that it exists in low numbers in the Pacaya-Samiria basin. Neville et al. (1976) reported one sighting of Ateles chamek in the reserve.

Venezuela
Serrania de la Neblina National Park (1,360,000 ha) (in range)
Parima Tapirapecó National Park (3,420,000 ha) (in range)
Duida-Marahuaca National Park (210,000 ha) (in range)
Jauá-Sarisarinama National Park (330,000 ha) (in range)
Yapacana National Park (320,000 ha) (in range).

It is listed on Appendix II of CITES.