Five-limbed monkey: The spider monkey is aptly named. Its prehensile tail is the most mobile and dextrous of any primate. As long and strong as its other limbs, with a hand-like naked portion at the tip, the tail forms a fifth limb both for locomotion and picking up things.
The spider monkey's arms and legs are particularly long too. It has hooked-shaped hands because its thumbs are either absent or reduced to a stump. These, together with its supple shoulder joints allows it to swing quickly under branches (brachiate) without fear of snagging thumbs. Its feet are greatly elongated and their big toe is prehensile, working like hands to grasp thinner branches, as well as for better grip as it walks upright on two legs on broad branches. It may even stand upright on a branch using its tail as a third limb in a tripod arrangement with its two legs!
Size: Male body length 38-48cm, tail 63-82cm, 9-10kgs. Female body length 42-57cm, tail 75-92cm, 6-8kgs. Males and females look the same.
Lifespan: Average 20 years in the wild, 33 years in captivity.
Babies: One young born. Gestation 226-232 days, no specific breeding season, females give birth once every 2-3 years, females mature in 4 years, males in 5 years.
Distribution: Only in South America, north of the Amazon and east of the Rio Negro.
Habitat: The canopy of lowland rainforests to mountain forests. They prefer wet than dry forests.
Classification: Family Cebidae. There are four species of spider monkey found between Mexico and the southern Amazon basin. Besides the black, the others are the Long-haired (A. belzebuth), Brown-headed (A. fuscipes), and the Black-handed/Golden (A. geoffroyi). But some researchers believe these are all just subspecies of A. paniscus.
Spider monkeys brachiate swiftly through the canopy, but not as well as gibbons of Asia. Where possible, they prefer to scuttle on all fives (including the tail!) over branches. They may also leap between trees and branches. On the rare occasions when they move on the ground, they may walk upright on two legs, their long tails held stiffly upright against the back. Spider monkeys are usually all black, but some have flesh coloured rings around their eyes and white chin whiskers.
At 13 kg, one individual, a wild male black spider monkey from Brazil, is the biggest known South American primate
Spider salad: The spider monkey’s diet is made up mainly of ripe canopy fruits (83%). They eat 171 species of fruit, in particular, figs. These monkeys specialise in the upper canopy, rarely foraging 20 metres below the canopy surface. Fruit is supplemented by leaves, flowers, bark. They also eat meat in the form of birds' eggs, caterpillars and arboreal termites. When feeding, they may hang by their tails and reach out for titbits with their hands. They can also pick up things with their tails. Spider monkeys are intelligent with a larger brain relative to its body size than any other New World Monkey. When threatened, they may break off branches and throw them at their attackers, some weighing up to 5kgs! They are most active in the early morning. Feeding bouts are 1-15 minutes long.
Social life: Fruits in the rainforest ripen unpredictably and fruiting trees are often widely spread out. Spider monkeys have evolved an extremely flexible society to cope with this. They move around the forest either singly or in groups of up to 20. These groups are not permanent, lasting for a few hours, or sometimes for a few days. Monkeys join or leave, alone or in smaller groups. This behaviour might give the impression that spider monkey society is fluid and unstructured. However, within any one area the monkeys are divided up into groups. A certain patch of forest might have 2 or 3 groups within it, moving around as smaller subgroups.
Whenever 2 subgroups meet, their reaction depends on whether they belong to the same permanent group. If they do, they mingle then divide up later, perhaps along different lines. But if they don't, then when the males are within 100m of each other, they will mutually threaten with a great deal of bluster. They chase about in the trees, shaking branches and whoop and growl at each other. These altercations can easily last for an hour or more but they seem to be strictly male affairs; females remain quietly in the background. But troops rarely come to blows. Sometimes a male will also smear saliva and a secretion that comes from a gland on his chest onto the branches, presumably to deposit his scent in the area.
Tree full of monkeys: The largest aggregations of monkeys are found when a big tree fruits, sometimes up to 100 monkeys. When they feed in a large tree, spider monkeys continuously adjust their positions so they are not too close to one another. Latecomers wait until earlier arrivals leave before entering the tree. It seems that spider monkeys can be quarrelsome feeders if they are too close to one another, and this spacing out saves them all trouble. During those months of the year when they have to depend on small, scattered sources of fruit, such as from palm trees, lone individuals and smaller aggregations are found moving through the forest. Thus, they avoid quarrelling at food sources with only enough ripe fruit at any one time to feed a few monkeys.
Within the group, adult males can coexist peacefully, although there is a clear hierarchy determined by age. The group is centred on the females and their young. Males are dominant over females, but it is the females that make the key decisions for the group. Males may forage in small groups. Females and offspring often forage alone.
Spider seduction: Female spider monkeys actively choose their mates. While some females may choose to mate with several different males in a single day, other female-directed pairings can last up to three days. Black spider monkeys mate face to face, as do gibbons, bonobos, orang-utans, capuchins and a few other primate species. The baby clings to mum's tummy for the first four months and later rides piggy-back, wrapping its tail around mum's tail for additional security. No one else besides the mother looks after the baby.
Spider talk: These monkeys have a variety of loud calls, audible for 800-1000m on the ground and 2,000m above the canopy. These "long" calls are used to help the groups space out in the forest and avoid unnecessary confrontations. It is also used to alert members of a group to a central feeding site. Juveniles develop their long call by trial and error. When they spot a predator on the ground, both males and females make a loud "ook-brak" bark, while throwing branches and shaking tree limbs by jumping up and down. Only males whoop. But when this fails to scare off the intruder, they scatter in smaller groups. Greeting and contact calls sound like horse whinnies. Like other primates, they have a wide range of facial gestures to express their moods. Both genders sniff and embrace when greeting.
Role in their habitat: As fruit eaters, spider monkeys are seed predators on about 20 tree species. But they may disperse the seeds of more than 135 tree species. They also pollinate some plants as they feed on nectar. They are also a source of food for other creatures. Their main predator is the harpy eagle, and they are also hunted as food by local tribes. They are alarmed by any flying bird of prey.
Status and threats: All are CITES 2, with A. geoffroyi frontatus and A. g. panamensis on CITES 1. Considered good to eat and because of their large body size, spider monkeys have been severely hunted throughout their range. They are easy to locate because they are noisy and travel in big groups. So spider monkeys are often extinct in areas easily accessible to people. They are also affected by habitat destruction, particularly logging, which removes the tall trees that they depend upon.
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