The disproportionately long limbs and long prehensile tail makes them one of the largest New World monkeys and gives rise to their common name. 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). They primarily eat fruits, but will also occasionally consume leaves, flowers, and insects. Due to their large size, spider monkeys require large tracts of moist evergreen forests and prefer undisturbed primary rainforest.[2] They are social animals and live in bands of up to 35 individuals but will split up to forage during the day.
Recent meta-analyses on primate cognition studies indicated that spider monkeys are the most intelligent New World monkeys.[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.
They are an important food source due to their large size and are widely hunted by local human populations; they are also threatened by habitat destruction due to logging and land clearing.Spider monkeys are susceptible to malaria and are used in laboratory studies of the disease. The population trend for spider monkeys is decreasing; the IUCN Red List lists one species as vulnerable, four species as endangered and two species as critically endangered.
Evolutionary history
There are many theories about the evolution of the atelines; one theory is that spider monkeys are most closely related to the woolly spider monkeys (Bractyteles), and most likely split from the woolly monkeys (Lagothrix and Oreonax) in the South American lowland forest, to evolve their unique locomotory system. This theory is not supported by fossil evidence. Other theories include Brachyteles, Lagothrix and Ateles in a non-resolved trichotomy,and two clades, one composed of Ateles and Lagothrix and the other of Alouatta and Brachyteles. More recent molecular evidence suggests that Atelinae split in the middle to late Miocene (13 Ma), separating spider monkeys from the woolly spider monkeys and the woolly monkeys
spider monkey drinking water
spider monkey cryingAnatomy and physiologySpider monkeys are among the largest New World monkeys; Black-headed Spider Monkeys, the largest spider monkey, have an average weight of 10.8 kg (24 lb) for males and 9.66 kg (21.3 lb) for females. Disproportionately long, spindly limbs inspired the spider monkey's common name. Their deftly prehensile tails, which may be up to 89 cm (35 in) long, have very flexible, hairless tips and skin grooves similar to fingerprints. This adaptation to the spider monkey's strictly arboreal lifestyle serves as a fifth hand. When the monkey walks, its arms practically drag on the ground. Unlike many monkeys, they do not use their arms for balance when walking, instead relying on their tail. The hands are long, narrow and hook like, and have reduced thumbs. The fingers are elongated and recurved.The hair is coarse, ranging in color from ruddy gold to brown and black; the hands and feet are usually black. Heads are small with hairless faces. The nostrils are very far apart, which is a distinguishing feature of spider monkeys.
Spider monkeys are highly agile, and they are said to be second only to the gibbons in this respect.
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spider monkey blackSpider monkeys form loose groups of 15 to 25 animals. During the day, groups break up into subgroups of 2 to 8 animals. This social structure ('fission-fusion') is found in only two other types of primates, chimpanzees and Homo sapiens. 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. The average subgroup size is less than four animals.[14] Also less common in primates, females rather than males disperse at puberty to join new groups. Males tend to stick together for their whole life. Hence males in a group are more likely to be related and have closer bonds than females. The strongest social bonds are formed between females and their young offspring.
Spider monkeys communicate their intentions and observations using postures and stances, such as postures of sexual receptivity and of attack. When a spider monkey sees a human approaching, it barks loudly similar to a dog. When a monkey is approached, it climbs to the end of the branch it is on and shakes it vigorously to scare away the possible threat. It shakes the branches with its feet, hands, or a combination while hanging from its tail. It may also scratch its limbs or body with various parts of its hands and feet. Seated monkeys may sway and make noise. Males and occasionally adult females growl menacingly at the approach of a human. If the pursuer continues to advance, the monkeys often break off live or dead tree limb weighing up to 4 kg and drop them towards the intruder. They do not actually throw the branches, but twist to cause the branch to fall closer to the threat.[clarification needed] The natives of the area know very well of this risk. The monkeys also defecate and urinate toward the intruder.
Spider monkeys are diurnal and spend the night sleeping in carefully selected trees. Groups are thought to be directed by a lead female who is responsible for planning an efficient feeding route each day. Grooming is not as important to social interaction, owing perhaps to a lack of thumbs.
Spider monkeys have been observed avoiding the upper canopy of the trees for locomotion. One researcher speculated that this was because the thin branches at the tops of trees do not support the monkeys as well.
At 107 grams, the spider monkey brain is twice the size of a howler monkey brain of equivalent body size; this is thought to be a result of the spider monkeys' complex social system and their frugivorous diet, which consists primarily of ripe fruit from a wide variety (over 150 species) of plants. This requires the monkeys to remember when and where fruit can be found. The slow development may also play a role: the monkeys may live 20 years or more, and females give birth once every 3 to 4 years.
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