Spider monkeys, Superb acrobats of the forest

You may have heard of varieties of spiders and monkeys, but spider monkeys? Perhaps not. Considered to be more primitive than the old world monkeys, these slender-bodied primates are found in tropical forests, semi-deciduous and mangrove forests, from southern Mexico to Brazil. They are indeed very fascinating creatures, so let's find out what they are like ...

Second only to gibbons (the lesser apes) in their agility, spider monkeys are famous for their acrobatic movements, especially the swift, tremendous leaps they make from one tree to another. In fact, it is these long acrobatic leaps they make with their long limbs and tails sprawling out like those of a spider's, that has resulted in them being called 'spider monkeys' and also earned them the title 'acrobats of the forest'.

Appearance

Their bodies are not in proportion at all. These spider monkeys have long limbs with hook-like narrow thumbless hands, elongated and re-curved fingers and slender bodies with long tails reaching up to 89 cm which are sometimes longer than their bodies.

The prehensile (capable of grasping) tail which is muscular and tactile (relating to the sense of touch) is used as an extra hand when climbing and gripping. These flexible tails, which are hairless at the tip, have skin grooves similar to fingerprints. When hanging by the tail, the spider monkeys have their hands free to forage (make roving search) for food.

These monkeys have coarse hair which is ruddy gold to brown in colour. The heads are small, nostrils are set wide apart and the faces are hairless. Some species have white chin whiskers and coloured rings round their eyes. The hands and feet are generally black.

The body length of adult spider monkeys who are generally larger than the females are about 15-26 inches (head and body), tail 20 to 35 inches, and the weight around 12-16 lbs (6-8 kg). Muzzle is prominent.

Locomotion

Spider monkeys rarely come down to the ground, and live mostly in the upper canopy of trees in the forests, jumping from branch to branch and tree to tree.

They use many ways to get from one place to another. When walking or running, they are quadrupedal (use all four limbs). When hanging, climbing or moving from tree to tree they usually use the suspensory method, and then they become bipedal (using only two limbs) when leaping.

Even when they are on the lookout for enemies or any danger, they usually walk on two feet, using the tail as support. They cover up to 40 feet, swinging from branch to branch on arm strides.

Species

It is believed that there are more than four basic species, even though some argue it is strictly four species. Anyway, these monkeys are classified according to the regions they live in and their physical differences.

The Black-handed or Geoffry's Spider Monkey, which is the least endangered, is either black, brown, silver or rust in colour. Then, there are the Red-faced spider monkey, White-fronted spider monkey, Brown-headed spider monkey, White-cheeked spider monkey, Black-headed spider monkey, Brown spider monkey and Hooded spider monkey.

Apart from the above mentioned, there are Mexican spider monkeys, Peruvian spider monkeys, Colombian spider monkeys and Yuctan spider monkeys. Three species of these monkeys are considered to be endangered.

Their diet...

Spider monkeys are frugivorous, meaning 90 per cent of their diet consists of fruits and seeds. As they eat the mature, soft parts of a wide variety of food, the seeds too are swallowed along with these fruits.

Apart from fruits, the spider monkeys also sometimes eat the barks of trees and also decaying wood, leaves, flowers, aerial roots as well as honey. It is a very small part of their diet that comprise insect larvae and bird eggs.

The spider monkeys eat a large quantity of food in a very short period of time. They search for food while on the move from branch to branch mostly on suspension (while hanging). Unlike most other primates, spider monkeys are not in the habit of carrying their food to another location to be eaten.

Behaviour and births

Spider monkeys live in medium sized, loosely associated groups of about 30 individuals and the sub-groups are no larger than four individuals. Females play an active role in the troop. In fact, they are better than males at planning the day's feeding routes which are highly economical and differ from day-to-day.

The female gives birth to a single infant once every three years. They are ready to become mums by the time they are 4-5 years of age and the baby is born after 226-235 days. The spider monkey's baby is born black and is dependent on the mother's milk up to two years.

The mothers continuously carry their young who cling to their ventrum (abdomen). At five months, the babies usually travel about on their mothers' backs. By this time they have already shed their black fur coats and started to grow their adult coats. Juveniles of 24-50 months do not climb on to their mothers' backs, but stay close to them at all times. They spend most of their time exploring, chasing, grappling and jumping on others of the same age or even play with adults.

The spider monkeys prefer to live in wet rather than dry forests. They are diurnal and at night use 'sleeping trees' to rest. They select tree branches high above the tree canopy which are forked and suitable for prolonged sleep. When threatened, both genders scare off the intruders with rough barking and wild behaviour displays. If this fails, they break into sub-groups and retreat because they dislike getting into fights.

Both genders sniff and embrace each other when greeting. Males scent-mark their territory, mixing saliva with a secretion produced from a gland on the chest. Spider monkeys are not so well groomed.

As the thumbs on their hands are missing, they do not go in for much grooming as other primates. They scratch themselves using both hands and feet. They have 'thumbs' on their feet only!