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Spider monkey
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Found in tropical forests from southern Mexico to Brazil, spider monkeys belong to the genus Ateles; the closely related woolly spider monkeys, are in the genus Brachyteles.
They require large tracts of undisturbed forest and specialize on ripe fruits, spider monkeys may be considered an indicator species. They are threatened by habitat destruction and are also highly vulnerable to hunting owing to their large size and slow reproduction.
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Encyclopedia
Found in tropical forests from southern Mexico to Brazil, spider monkeys belong to the genus Ateles; the closely related woolly spider monkeys, are in the genus Brachyteles.
They require large tracts of undisturbed forest and specialize on ripe fruits, spider monkeys may be considered an indicator species. They are threatened by habitat destruction and are also highly vulnerable to hunting owing to their large size and slow reproduction. Consequently, the lowest threatened status assigned to a spider monkey is Vulnerable for the Red-faced Spider Monkey, the remaining all being Endangered or Critically Endangered.
A recent comparative intelligence study gives spider monkeys a value a little above gorillas, so it is reasonable to believe that spider monkeys are among the most intelligent New World monkeys. The maximum recorded age of a spider monkey in the wild is 33 years.
Physical description
Disproportionately long, spindly limbs inspired the spider monkey's common name. Their deftly prehensile tails, which may be up to 89 cm (35 inches) 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. Adults reach an average body length of 50 cm (20 inches) and a weight of 6.4 kilograms (14 pounds).
Spider monkeys move through the trees, with one arm stride covering up to 12 m (40 feet).
The arms are very thin and very long, while the legs are shorter. 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 hooklike, and have no thumbs. The fingers are elongated and recurved.
The hair is coarse, ranging in colour 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.
There is speculation that the alleged Loys's Ape is a large spider monkey, but this is still intensely debated by cryptozoologists.
Behavior
Spider 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 one other primate species, the Chimpanzee. 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. 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 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 small 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 they twist so the branch causing it to fall closer to the threat. 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.
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.
Feeding
The diet of spider monkeys consists of about 90% fruits and nuts. They can live for long periods on only one or two kinds of fruits and nuts. They eat the fruits of many big forest trees, and because they swallow fruits whole, the seeds are eventually excreted and fertilized by the feces. Most feeding happens from dawn to 10 am. Afterward, the adults rest while the young play. Through the rest of the day they may feed infrequently until around 10 pm. If food is low they may eat insects, bark or rotting forest, and honey.
Spider monkeys have a unique way of getting food: a lead female is responsible for feeding. If she cannot find enough food for the group, it splits into smaller groups to find food easier. The traveling groups have four to nine animals. Each group is closely associated with its territory. If the group is big, it spreads out while eating.
Reproduction
Spider monkeys mate year-round. The female chooses a male from her group with whom to mate. Both males and females sniff their mates to check their readiness for copulation. This process is known as “anogenital sniffing”. The gestation period ranges from 226 to 232 days. Each female bears only one offspring on average, every 3 to 4 years.
Until age six to ten months, infants rely completely on their mother. Males are not involved in raising the offspring.
A mother carries her infant around her belly for the first month after birth. After this she carries it on her lower back. The infant wraps its tail around its mother’s and tightly grabs her midsection. Mothers are very protective of their young and are generally attentive mothers. They have been seen grabbing their young and putting them on their backs for protection and to help them navigate from tree to tree. They help the more independent young to cross by pulling branches closer together. Mothers also groom their young.
Classification
External links
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