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Region: Africa Class: Mammalia Order: Primates Family: Hominidae Genus: Gorilla Scientific Name: Gorilla gorilla gorilla
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Description:
Gorillas are the largest of the primates. Western lowland gorillas are the lightest of the four sub-species of gorillas. The males, on average, weigh approximately 135-220 kg and the females weigh about half of that at around 70-90 kg. Captive gorillas tend to weigh more. The male is very stocky and powerful in the body, with wide shoulders and chest. The females are much smaller and slimmer.
There are two species of gorilla: the western gorilla (Gorilla gorilla) and the eastern gorilla (Gorilla beringei). Within each species there are two subspecies. The eastern gorilla subspecies are the mountain gorilla (Gorilla beringei beringei) and the eastern lowland gorilla (Gorilla beringei graueri). The western gorilla subspecies are the western lowland gorilla (Gorilla gorilla gorilla) and the cross river gorilla (Gorilla gorilla diehli). The gorillas at the Toronto Zoo are western lowland gorillas.
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Distribution:
Congo River basin of Western Africa.
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Habitat:
Lowland rain forests.
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Food:
Mainly juicy plant stems, vines and leaves. Bark, roots and fruits are also taken, the choice parts being selected, the remainder discarded. There is a definite preference shown in plant selection, wild celery, thistles, nettles, bamboo shoots and bedstraw (Gallium) are among those chosen.
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Reproduction and Development:
Females mature sexually around 8 years of age and are fully grown at 8-10 years of age. Males are sexually mature at about 10 years of age and fully grown at 12-15 years. Females begin breeding as soon as they are sexually mature, but male gorillas need to physically mature so they can attain silverback status and lead a group of gorillas. This usually occurs between the ages of 15 and 20. In male apes, including humans, potency (the ability to sire offspring) is continuous until it is lost through senescence. Female gorillas have a menstrual cycle similar to that in humans, the average length being 30-31 days. In the wild, copulation is normally dorso-ventral, in captivity both dorso-ventral and ventro-ventral copulations occur. The average gestation period is 265 days. A single young is born weighing approximately 2 kg. The baby gorilla is completely dependent on its mother for food and protection. At birth they appear to lack the strength to grasp their mother's hair, so she will support her infant with both hands. When on the move, she cradles the infant to her breast with one hand. The infant stays with the mother for the first three years of its life. It begins to eat vegetable matter at about 6 weeks of age, but nursing continues for another year and a half to two years. By one month, the infant clings to its mother unaided; by three months it rides on its mother's back; by four or five months it can walk unaided, by six months it can climb and is very active. Young gorillas are incredibly playful. Juveniles climb more frequently and with greater ease than the adults. Very often other females will play the role of "aunt" to a baby and participate in its care, playing with it and carrying it around. Gorillas live in fairly stable groups of 5 to 15 individuals. Larger bands consist of an adult male, several younger males and a large number of females with their young. Smaller groups may consist of only one adult male with a few females and their young. The oldest gorilla in captivity was "Jenny" who died at the age of 55 in the Dallas Zoo.
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Adaptations:
Gorillas are strictly diurnal in habit, building nests to rest in each night. Day nests are built as well. Both types of nests may be built on the ground or in trees. When they build in trees, they are seldom more than 9 metres from the ground. The adult male because of his size does not build nests in trees. Nests are occupied for one night only. Gorillas collect their varied foods mainly on the ground. Gorillas are quiet most of the time and they enjoy dozing and sunbathing in the mid-morning between bouts of feeding. Postures, gestures, facial expressions and vocalizations are all used in communication within the group. Only one or two sounds carry far enough to reach other groups; one of them is the sound of chest beating and the other is the sound heard during the intimidating display that gorillas frequently give among themselves or to an intruder. This display includes rising on its legs, throwing vegetation in the air, leg kicking, running sideways, slapping and tearing nearby vegetation, and thumping the ground. Many variations occur, and some acts may occur alone. Aggressive charges rarely result in serious physical combat. The gorilla avoids conflict until extremely hard pressed, with the dominant male always acting in defence of his group.
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Threats to Survival:
As is the case with many species, humans are the primary threat to the survival of gorillas. Gorillas are widely hunted for "bushmeat" and the young are collected for sale to the pet trade, a practice that is now illegal. Habitat loss also significantly jeopardizes gorilla populations. The main reasons for habitat loss are mining for charcoal and coltan which is used in cell phones and other electronics, logging for timber and fuel wood, and agricultural expansion. Civil wars occurring in gorilla habitat are also a serious threat. Outbreaks of disease, in particular, Ebola virus are contributing factors to declining gorilla populations and young gorillas are susceptible to predation by leopards.
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Status:
Critically endangered (IUCN 2008).
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Zoo Diet:
Fruits and vegetables, monkey chow, gelatin cake, and assorted treats like coconut and browse.
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