Like other atelines, they are found in tropical forests of Central and South America, from southern Mexico to Brazil.

Spider monkeys live in the upper layers of the rainforest and forage in the high canopy, from 25 to 30 m (82 to 98 ft).

[4] They can produce a wide range of sounds and will "bark" when threatened; other vocalisations include a whinny similar to a horse and prolonged screams.

Theories abound about the evolution of the atelines; one theory is they are most closely related to the woolly spider monkeys (Brachyteles), and most likely split from woolly monkeys (Lagothrix) in the South American lowland forest, to evolve their unique locomotory system.

[8] The genus name Ateles derives from the ancient greek word ἀτέλεια (atéleia), meaning "incomplete, imperfect",[9][10] in reference to the reduced or non-existent thumbs of spider monkeys.

[11][12] Disproportionately long, spindly limbs inspired the spider monkey's common name.

Their deftly prehensile tails,[13] which may be up to 89 cm (35 in) long, have very flexible, hairless tips and skin grooves similar to fingerprints.

[16] Their hair is coarse, ranging in color from ruddy gold to brown and black, or white in a rare number of specimens.

This urine is emptied at the bases of the clitoris, and collects in skin folds on either side of a groove on the perineal.

[21] Researchers and observers of spider monkeys of South America look for a scrotum to determine the animal sex because these female spider monkeys have pendulous and erectile clitorises long enough to be mistaken for a penis; researchers may also determine the animal's sex by identifying scent-marking glands that may be present on the clitoris.

The size of subgroups and the degree to which they avoid each other during the day depends on food competition and the risk of predation.

Males also cement bonds through "grappling": prolonged hugging, face greeting, tail intertwining, and genital manipulation.

If the pursuer continues to advance, the monkeys may break off live or dead tree limbs weighing up to 4 kilograms (8.8 lb) and drop them towards the intruder.

[29] Spider monkeys are diurnal and spend the night sleeping in carefully selected trees.

Groups are thought to be directed by a lead female, which is responsible for planning an efficient feeding route each day.

The slow development may also play a role: the monkeys may live from 20[34] to 27 years or more, and females give birth once every 17 to 45 months.

[35] Gummy, presumably the oldest spider monkey in captivity, is presumed to have been born wild in 1962, resided at Fort Rickey Children's Discovery Zoo located in Rome, New York,[36] and died at the age of 61, after living about twice as long as the average spider monkey.

Studies show the diet of spider monkeys changes their reproductive, social, and physical behavioral patterns.

[42] In present-day Maya religious feasts, spider monkey impersonators serve as a kind of demonic clowns.