Gorillas are the largest living primates. They are ground-dwelling apes that are majorly herbivorous. Gorillas are divided into two species; the western gorillas and the eastern gorillas. Both species are critically endangered and have about 4 sub species. The DNA of gorillas is highly similar to that of humans, from 95 to 99% depending on what is included, and they are the next closest living relatives to humans after the chimpanzees and bonobos.
Gorillas live in tropical and subtropical forests in sub-Saharan Africa. Gorillas cover a wide range of elevations although their range covers a small percentage. The mountain gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2,200 to 4,300 metres. Lowland gorillas live in dense forests and lowland swamps and marshes as low as sea level, with western lowland gorillas living in Central West African countries and eastern lowland gorillas living in the Democratic Republic of the Congo near its border with Rwanda.
Western lowland gorillas
The western lowland gorilla (Gorilla gorilla gorilla) lives in montane forests and lowland swamps in central Africa in Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. It is the nominate subspecies of the western gorilla, and the smallest of the four gorilla subspecies. These gorillas remain far uncommon than their relatives, the mountain gorillas.
This species of gorillas exhibits pronounced sexual dimorphism. They possess no tails and have jet black skin along with coarse black hair that covers their entire body except for the face, ears, hands and feet. The hair on the back and rump of males takes on a grey coloration and is also lost as they get progressively older. This coloration is the reason why older males are known as “silverbacks”.
Western lowland gorilla groups travel within a home range averaging 8–45 km2. Gorillas do not display territorial behavior, and neighboring groups often overlap ranges. The group usually favours a certain area within the home range but seems to follow a seasonal pattern depending upon the availability of ripening fruits and, at some sites, localised large open clearings. The group of gorillas is led by one or more adult males.
As primarily herbivores, the main diet of western lowland gorilla groups is roots, shoots, fruit, wild celery, tree bark and pulp which is provided for in the thick forests of Central and West Africa. During the wet season gorillas commonly consume fruits. While in the dry season, there is a decrease in the consumption of fleshy fruits, but they still continue to eat other kinds of fruits.
Cross river gorillas
The Cross River gorilla (Gorilla gorilla diehli) is populated at the border between Nigeria and Cameroon, in both tropical and subtropical moist broadleaf forests.
This subspecies of the western gorilla is very similar in appearance to the more numerous western lowland gorilla, but subtle differences can be found in the skull and tooth dimensions.
Cross River gorillas are scattered in at least 11 groups across the lowland montane forests and rainforests of Cameroon and Nigeria, an area of 3,000 square miles. The groups of Cross River gorillas consist mainly of one male and six to seven females plus their offspring. The Cross River gorilla’s diet consists largely of fruit, herbaceous vegetation, liana, and tree bark. Much like their nesting habits, what they eat is contingent on the season.
Cross River gorillas have certain nesting behaviors that depend on things such as their current habitat, climate, food source availability and risk of attack or vulnerability. From April up until November, Cross River gorillas are more likely to build their nests within a tree, and from November on they are more likely to build it on the ground.
The eastern low land gorilla (gorilla beringei graueri) is a subspecies of the eastern gorilla endemic to the mountainous forests of eastern democratic republic of Congo. These gorillas live in the Kahuzi-Biega and Maiko National Parks and their adjacent forests, the Tayna Gorilla Reserve, the Usala forest and on the Itombwe Massif.
The eastern low land gorilla is the largest of the 4 sub species and has shorter hair on its body. Males have an average weight of 210 kilograms, females of 100 kilograms. The maximum standing height for males is 1.85 metres, while females reach 1.6 metres.
Gorillas spend long hours feeding on plant matter every day. Groups are stable apes as they stay together for months and years at a time, much like the structure of a family. Groups of eastern lowland gorillas are usually larger than those of western gorillas.
The eastern lowland gorilla has the widest altitudinal range of any of the gorilla subspecies, being found in mountainous, transitional and lowland tropical forests. One of the most studied eastern lowland gorilla population lives in the highlands of Kahuzi-Biega, where habitats vary between dense primary forests to moderately moist woodland, to Cyperus swamp and peat bog.
Eastern lowland gorilla has a varied plants diet including fruits, leaves, stems and bark as well as small insects such as ants and termites. They rarely eat ants and insects.
Eastern lowland gorillas are highly sociable and very peaceful, living in groups of 2 to over 30 individuals. A group usually consists of one silverback, several females and their offspring. Silverbacks are strong and each group has one dominant male leader. These males protect their group from danger. Young silverback males will slowly begin to leave their natal group when they reach maturity, and will then attempt to attract females to form their own group.
A female will give birth to a single infant after a gestation period of about 8½ months. They breastfeed for about three years. The baby can crawl at around nine weeks old and can walk at about 35 weeks old. Infant gorillas normally stay with their mother for three to four years.
The mountain gorilla (gorilla beringei beringei) is one of the subspecies of the eastern gorilla. It is an endangered species and comprises of about 10004 individuals as of 2018 census. One population lives in the Virunga Mountains which are made up of 3 mountains; Virunga national park (D.R Congo), Mgahinga national park (Uganda) and volcanoes national park (Rwanda) and the other population lives in Bwindi impenetrable national park in Uganda.
Mountain gorillas live in the forests of the albertine rift valley and Virunga volcanoes. The altitude of this habitat ranges from 2,200-4,300 meters. Most are found on the slopes of three of the dormant volcanoes; Karisimbi, Mikeno, and Visoke. The vegetation is very dense at the bottom of the mountains, and sparser at higher altitudes. Mountain gorillas live in cloudy, misty and cold forests. The home range size is influenced by availability of food sources.
The mountain gorilla diet is mostly composed of the leaves, shoots and stems. It also feeds on bark, roots, fruit and some flowers. The mountain gorilla spends most of its time in the Hagenia forests, where galium vines are found year-round. All parts of this vine are consumed: leaves, stems, flowers, and berries. It travels to the bamboo forests during the few months of the year fresh shoots are available, and it climbs into subalpine regions to eat the soft centers of giant senecio trees.
Gorillas live in groups consisting of 6-7 individuals up to 35 individuals. The group is usually led by one dominant male who is accompanied by several females and young ones.