The only exception is the mountain gorilla subspecies, which is also critically endangered but saw its population increase to about 880 individuals in 2016.
The western lowland gorilla and the Cross River gorilla, the two western gorilla subspecies, inhabit tropical rain forests in Cameroon, the Republic of the Congo, Gabon and Equatorial Guinea.
They also occur in a small portion of Nigeria and the westernmost tip of the Democratic Republic of the Congo.
Eastern gorillas are herbivorous, with a heavily foliage based diet, due to lack of available fruit in their habitats.
They have smaller home ranges than western gorillas as foliage is more abundant than fruit.
Illegal hunting for bushmeat and destruction of their habitat as a result of intensifying forestry and the development of agriculture form the most important threats for the species.
Between 19, the eastern gorilla lost more than 70 percent of its population, and by 2016 the total population was estimated to be less than 6,000.This is why the older males are called silverbacks.Grauer's gorilla has a shorter, thicker, deep black fur, while the mountain gorilla has a more bluish color.They are diurnal but the majority of foraging occurs in the morning and late afternoon.At night, they build nests by folding over vegetation, usually on the ground.All gorilla species are listed as endangered by the International Union for the Conservation of Nature.