For the identification of insects and other fauna and flora of South Africa: please click on the following links:
Insects and related species: Antlions - Ants - Bees - Beetles - Bugs - Butterflies, Moths and Caterpillars - Centipedes and Millipedes - Cockroaches - Crickets - Dragonflies and Damselflies - Grasshoppers and Katydids - Mantis - Stick Insects - Ticks and Mites - Wasps - Woodlice
Plants, Trees, Flowers: (Note: Unless plants fall into a specific species such as Cacti, they have been classified by their flower colour to make them easier to find) Bonsai - Cacti, Succulents, Aloes, Euplorbia - Ferns and Cycads - Flowers - Fungi, Lichen and Moss - Grass - Trees
Animals, Birds, Reptiles etc.: Animals, Birds, Fish and Crabs - Frogs - Lizards - Scorpions - Snails and Slugs - Snakes - Spiders - Tortoise, Turtles and Terrapins - Whipscorpions
Other photography: Aeroplanes - Cars and Bikes - Travel - Sunrise - Water drops/falls - Sudwala and Sterkfontein Caves etc.

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Saturday, April 9, 2011

Monkey House - Part 3 - Spider Monkey

Spider Monkey Cebidae Ateles Geoffroyi geoffroyi

The spider monkey is considered a primitive new world monkey. They are called spider monkeys because they look like spiders when they are suspended by their tails.

Spider monkeys are usually all black, but some have flesh coloured rings around their eyes and white chin whiskers. Hair generally coarse and stringy. Lacks underfur.

Colors: golden, red, buff, brown or black, with hands and feet generally black.

Their brains are less complex, their thumbs are not opposable and their nostrils are further apart. These monkeys depend highly on their keen binocular vision. They have slender bodies and limbs with long narrow hands.

This arboreal monkey has a prehensile tail that is muscular and tactile and is used as an extra hand. The tail is sometimes longer than the body. Both the underside and tip of the tail are used for climbing and grasping and so the spider monkey uses it like a fifth hand. When swinging by the tail, the hands are free to gather food.

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. Hands are like hooks with long, narrow palms, long curved fingers, and no thumb. Head is small, muzzle prominent. Thumbs on feet only.

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.

Spider monkeys are generally found in lowland rain forests from Mexico to South America, along the coasts and the banks of the Amazon, south to Bolivia and the Matto Grosso in Brazil, and the mountain forest slopes of the Andes. They are restricted to arboreal habitats, mainly in the top of the tree canopy. They range from sea level to higher ground. Spider monkeys live in evergreen rainforests, semi deciduous and mangrove forests, lowland rainforests to mountain forests. In these forests they live mostly in the upper canopy, preferring undisturbed high forest, almost never coming to the ground. They prefer wet than dry forests.
Spider monkeys are frugivores preferring a diet of 90% fruit and seeds, feeding on the mature soft parts of a wide variety of fruits in which the seeds are swallowed along with the fruit. They also eat young leaves, flowers, aerial roots, sometimes bark and decaying wood, as well as honey. A very small part of the diet consists of insects, insect larvae and birds’ eggs. When feeding, they may hang by their tails and reach out for tidbits with their hands. They can also pick up things with their tails. They eat large quantities of food over a relatively short period of time and they tend to feed by suspension while hanging, climbing or moving. They do not pick fruit and carry it to another location to be eaten.

The lead female is often observed determining the forage route for the group; however if food is scarce they tend to divide into smaller groups. The largest groups of monkeys, sometimes up to 100 monkeys, are found in a big tree loaded with fruits. 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.

In the Zoo they are fed celery, bananas, raisins, apples, oranges, carrots, monkey chow, dog chow, lettuce, and wheat bread.

Spider monkeys live in medium-sized, loosely associated groups of about 30 individuals. The females have a more active leading role than males, so their social system is thought to be matriarchal. Within the group, adult males can coexist peacefully, although there is a clear hierarchy determined by age. The group is centered 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. When threatened, they make barking noises, but if that doesn’t scare intruders away, they fragment into subgroups and run. They prefer retreat, so fights are rare .

Every 2 – 3 years, a mother will give birth to one entirely black baby. No one else besides the mother looks after the baby. The baby is continuously carried by the mother, clinging to her and at about 5 months of age it will begin riding on her back, wrapping its tail around the mother's tail for additional security. It will be dependent on its mother's milk for 2 years. Juveniles at the age of 24 to 50 months old never ride on their mother's back but they will still stay close to her. They spend their time exploring, or chasing, grappling, and jumping on others. They will play with others their same age or with adults.

Spider monkeys have been called "the supreme acrobat of the forest." In the wild, the Spider monkey rarely comes down to the jungle floor. Acrobatic and swift, Spider monkeys move through the trees, with one arm stride covering up to 40 feet.

Spider monkeys are characterized by their long, slender limbs and great agility. They travel in small bands in forest trees, moving swiftly by making tremendous leaps, sprawling out like spiders, and grasping tree limbs with their prehensile tails.

Its tail and 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! When the animal is on the lookout, it stands or walks on two feet, using the tail to hold on to a support.

Spider monkeys use several different types of locomotion: quadrupedal, using all four limbs for locomotion as seen while walking or running; suspensory locomotion used when hanging, climbing or moving through the trees and bipedalism, using only two limbs when leaping. Quadrupedal locomotion is usually observed if the monkey is on a stable relatively substrate free of obstacles. When they are using suspensory locomotion they may be brachiating (swinging with their arms from one branch to another while often maintaining a tail hold). The most commonly used pattern of body movement while in a feeding pattern is that of quadrupedal, climbing and suspensory locomotion. While traveling they mostly employ quadrupedal walking and running, suspensory locomotion and climbing.

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.
Groups defend their ranges. Males will mark their territory with secretions from chest glands. Anyone stumbling into spider monkey territory receives an unpleasant ‘welcome’ of screams, barks, and rattling branches and thrown branches or feces. The interactions will often begin with males, often along with one or two females, calling, which will bring other group members into the area.

When 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 noisy sessions 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 occasionally scent mark branches by smearing saliva and a secretion that comes from a gland on his chest onto the branches, presumably to deposit his scent in the area.

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.

These calls are 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. The most frequently heard call resembles whinnying of a horse - probably a greeting or contact call. Like other primates, they have a wide range of facial gestures to express their moods. Both genders sniff and embrace when greeting.

The spider monkey travels in groups and the route they take through trees remain constant. During more abundant times of the year, the route shortens but does not change.

Spider monkeys are diurnal, which means they are active during the day. They are most active in the early morning. Feeding bouts are 1-15 minutes long.

At night they use sleeping trees which are usually tall enough so that the crown is free from the canopy beneath it having a broad open crown that has horizontally forked branches for prolonged resting postures. The sleeping trees are often chosen for their ability to provide a ready source of food. Sleeping high in a tree above the canopy also affords security from predators.

Since the thumb is absent, the Spider monkey's grooming is not as developed as in other primates. They scratch themselves with hands and feet, but most of their social grooming is mothers grooming their young.

Status: Critically Endangered
Their lifespan in the wild is about 27 years. Average 20 years in the wild, 33 years in captivity.

The spider monkey is critically endangered, which means it is facing an extremely high risk of extinction in the wild in the immediate future.

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. There is also a lucrative pet trade. They are also affected by habitat destruction, particularly logging, which removes the tall trees that they depend upon.

They are also vulnerable because they have low maturation and reproduction rates.

Three of the spider monkey species, the white-bellied spider monkey, brown-headed spider monkey, and white- whiskered spider monkey are listed as Endangered by either USESA or IUCN. This means that these species have at least a 20% chance of going extinct in the wild within 20 years or 5 of their generations. The black-handed and black spider monkeys are listed as Vulnerable by IUCN - there is at least a 10% probability of extinction within 100 years. Only the black-faced black spider monkey is considered at Lower Risk (CITES II.)
The population is estimated at 2,000 in isolated pockets.

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