There are two main species determined mainly by their geographic location, each containing 2 sub-species:
The western gorilla species which are situated in Central West Africa include the western lowland gorilla and
the cross river gorilla.
The eastern gorilla species which are situated in Central East Africa include the eastern lowland gorilla and the mountain gorilla.
Eastern gorillas have the darkest fur compared to western gorillas which tend to have a brown grayish color. Mountain gorillas are rather bulky due to their lack of activity in the mountainous terrain they inhabit. Lowland species, on the other hand, travel more and sport a slender physique.