The western gorilla is a great ape. They are generally lighter colored than eastern gorillas. Western lowland gorillas have black, dark grey or dark brown-grey fur with a brownish forehead. Measurements of wild individuals show that mature males average 5 ft 1 in in height, while mature females average 4 ft 5 in. Weights of captive western gorillas average 346 lb in males and 176 lb in females. Western gorillas live in groups that vary in size from two to twenty individuals. Such groups are composed of at least one male, several females and their offspring.
Mature male Western gorillas are known as 'silverbacks', and are named after silvery-white hair on their back, rump, and thighs.