Gorillas are the largest species amongst all primates. They are ground dwelling chiefly herbivorous mammals inhabiting the forests of central Africa. They are placed in two species and four or five subspecies. The DNA of gorillas bears 95-99% similarity with humans and is believed to be very close to humans just after two species of chimpanzees. They are found in the tropical and subtropical forests in Africa. The Mountain Gorilla dwells in Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2,200-4,300 metres. The lowland gorillas inhabit the dense forests and lowland swamps. They have derived their name from a Greek word.
The closest relatives of gorillas are humans and chimpanzees. All these three share the same family Hominidae and same ancestor that evolved around 7 million years ago. Human genome differs only 1.6% from that of the gorilla’s genome. At present three species of these primates are known namely Western Lowland Gorilla, the Eastern Lowland Gorilla and the Mountain Gorilla. They move by knuckle walking and use bipedal locomotion only while feeding or defending themselves from the predators. Adult males attain a height from 1.65-1.75 meters and weigh about 140-200 kg. Adult females are generally 1.4m in height. Animals kept in captivity have attained a body weight of about 270 kg also. They have a specific facial structure known as mandibular prognathism and the mandible protrudes more than that of maxilla.
Mountain Gorilla is darkest in colour followed by Eastern and Western Gorillas. Mountain Gorilla bears thickest hairs. The Western Lowland Gorilla has reddish-brown forehead and are more bulky. A silverback is an adult gorilla that is more than 12 years of age and can be identified by the presence of a silver patch of hair at the back. It also bears large canines when it is fully mature. Blackbacks are sexually mature adult males of about 11 years of age. Silverbacks are strong and dominant troop leaders. Silverback takes all the decisions of troop, mediates conflicts and determines the movements of the group. Blackbacks may serve as backup protection. Adult females tend do not tend to participate in these matters.
Male gorillas tend to leave their paternal groups when they are 11 years old. Sometimes a male remains in his father’s troop and inherits the control as the father grows old. Adult females also leave their parental troop when they attain sexual maturity. As they leave the troop they search for a nearby silverback male. They prefer a male who has a better fighting prowess and access to quality of habitat. Once a female starts reproducing she becomes a permanent member of a troop. The infants remain with their mothers for about 3-4 years and silverbacks will also take care of them. When chased by an outsider gorilla the silverback screams, beats his chest, breaks branches, bares his teeth, and then charges forward. If the leader of the troop dies either by disease, fighting or by accident the group gets split and it searches a male to be the leader. There is a possibility that the infants of the dead silverback may be killed by the new troop leader.
Gorillas are herbivores feeding on fruits, leaves and shoots. They can sometimes ingest small insects also. They spend most of their day by eating. Their large sagittal crest and long canines help them to feed on hard plants like bamboo also. Lowland gorillas mainly feed on fruits while the Mountain gorillas feed on roots, herbs and leaves. They have a gestation period of eight and a half months. There is typically a gap of 3-4 years between the births of infants. The infants tend to remain associated with their mothers for about 3-4 years. A female becomes sexually mature at the age of 10-12 years while a male is sexually mature when he is 11-13 years of age. They have an average lifespan of 30-50 years. They are considered to be closely related to humans are believed to be highly intelligent.
Both the species of gorillas are now placed in the category of endangered because of the poaching practices since time immemorial. Threat to their survival includes habitat destruction and bushmeat trade. They are now under conservation programmes of various agencies.