Closely linked by DNA, gorillas (family Hominidae) are one of the four species of great apes that are the closest living relatives of humans – the other three are chimpanzees, bonobos and orangutans. Great apes are different from monkeys for a variety of reasons: they are larger, walk upright for a longer period of time, don’t have tails and have much larger, more developed brains.
There are four subspecies of gorillas: the eastern lowland or Grauer’s gorilla (Gorilla beringei graueri); the mountain gorilla (Gorilla beringei beringei); the western lowland gorilla (Gorilla gorilla gorilla); and the Cross River gorilla (Gorilla gorilla diehl).
Like all great apes, gorillas have arms that are longer than their legs and tend to walk on all four limbs at certain times – a movement that is called knuckle walking. Adult males are known as 'silverbacks' due to the distinctive silver-colored hair on their backs.
Gorillas' appearances can vary based on sub-species, but for the most part, the western subspecies tend to be brownish gray in color, while the eastern and mountain gorillas tend to have a more blackish coat. Mountain gorillas also have longer and thicker fur which is adapted to their colder mountainous habitat. The three lowland subspecies of gorillas sport short, fine hair. Eastern lowland gorillas are the largest of the four subspecies.
Gorillas are herbivores and eat leaves, shoots, roots, vines and fruits.
Eastern lowland gorilla numbers have rapidly declined to below 5,000 today. Critically endangered, there are fewer than 300 Cross River gorillas. Mountain gorillas, another endangered subspecies, number at around 700. A recent survey has shown that there are around 150,000-200,000 western lowland gorillas.
Eastern lowland gorillas are found in part of the eastern Democratic Republic of Congo (DRC), Uganda and Rwanda, while mountain gorillas are only found within the Virunga mountain region straddling the DRC, Rwanda and Uganda borders, as well as the Bwindi Impenetrable National Park in Uganda. Western lowland gorillas inhabit Cameroon, Nigeria, the Central African Republic, the Republic of Congo, eastern DRC, Equatorial Guinea, Gabon and Angola. Cross River gorillas are confined to a small region in Nigeria and Cameroon.
Gorillas are ground-dwelling and live in groups of 6-12 with the oldest and largest silverback leading a family of females, their young and younger males called blackbacks. The silverback makes the decisions on when his group wakes up, eats, moves and rests for the night. Because he must protect his family at all times, the silverback tends to be the most aggressive. In such situations, he will beat his chest and charge at the perceived threat.
Gorillas are shy animals that are most active during the day. At dusk, each gorilla constructs a ‘nest’ of leaves and plant material in which it will sleep. Mothers usually share their nests with nursing infants.
Young males may leave their family groups as they become older and either live as solitary silverbacks or create their own family groups. The silverback has the exclusive rights to mate with the females in his group.
Mating Season: Throughout the year.
Gestation: 8.5 months.
Litter size: 1 baby.
Gorilla infants are helpless at birth and weigh about 3-4 lbs. They learn to crawl at about 2 months and are walking by the time they are around 8 or 9 months. Mother gorillas nurse their babies for about 3 years, following which the young become more independent.
Gorillas are threatened by habitat loss  due to increasing human populations, poaching for the bushmeat trade and diseases like ebola. Species that live in higher elevations, like mountain gorillas, are also affected by climate change , which has the potential to impact gorillas directly by altering their habitat, and indirectly by affecting agriculture yields in nearby communities, which in turn puts more pressure on remaining habitat.