New World Monkeys

The subfamily Atelinae includes the spider monkeys, the woolly spider monkeys, and the woolly monkeys. These monkeys are as large as howler monkeys but thinner.

Spider monkeys (Ateles) are found in approximately the same range as the howler monkeys, though spider monkeys occur farther north in Mexico and extend south to Brazil. Howler monkeys may eat slightly immature fruit, while spider monkeys wait until it is truly ripe. The arms of spider monkeys are longer than their legs, giving them an ungainly spider-like appearance. Spider monkeys are extremely agile and can walk along branches, hang upside down, leap sideways, and even leap long distances downward. Spider monkeys are very adroit at swinging from branches by arm to arm movements, also called brachiation, an ability that requires special flexibility in the shoulders. Their tails are quite thick toward the base but slender and with a naked patch with ridges toward the tip, which makes it quite sensitive.

The long tail is especially useful because, unlike many other monkeys, spider monkeys do not have an opposable thumb, meaning they are not very adept with their hands. Their skeletons show the remains of the thumb, and some individual animals have a slight protrusion where a thumb would be. Spiders live in large groups, though they often tend to break up into smaller family subgroups.

All spider monkeys have fairly long, shaggy fur, which is mostly dark brown or black. The fur on the head is brushed forward. The black-handed, or Geoffroy's spider monkey (A. geoffroyi) of Central America has golden, reddish, or bronze fur on its body and usually black hands and feet. The long-haired spider monkey (A. belzebuth) of the upper Amazon has chest and abdomen of a lighter color than the rest of its body. The brown-headed spider monkey (A. fusciceps) lives from Panama to Ecuador, between the ranges of the other two species.

In coastal parts of Brazil, the spider monkey's territory is taken over by the woolly spider monkey or muriqui (Brachyteles arachnoides). The woolly spider monkey is the heaviest monkey in Brazil, weighing 35 lb (16 kg); it has the chunky body and thick fur of the woolly monkey but lacks a thumb. It is lighter brown in color than most of its relatives.

The woolly spider monkey's social groups, which used to number about 30-40, are now down to typically 6-20. Within a group's territory, the individuals separate by gender and can frequently be seen hugging each other. There may be only a few hundred woolly spider monkeys left, reduced from half a million individuals when Europeans first arrived in South America. The large size and gentle nature of the woolly spider monkey makes them easy targets for hunting, and this species is now on the endangered species list.

The two species of woolly monkeys (Lagothrix) live in western South America, mostly at fairly high altitudes. Their thick fur makes the woolly monkeys look larger and stouter than they really are. The common woolly monkey (L. lagothricha), also known as Humboldt's monkey, is colored gray, black, or brown. The yellow-tailed or Hendee's woolly monkey (L. flavicauda) is deep red-brown with yellow fur along its tail and around its genitals. This monkey lives in a small mountainous area in northern Peru. The yellow-tailed woolly monkey was thought to be extinct from hunting for food and the pet trade, but a small wild population was rediscovered in the 1970s, and this endangered species is now being bred in captivity.