There are two different subspecies of gorilla that are often lumped into one. There are distinct differences, though; the mountain gorilla is larger, with longer hair and shorter arms than their lowland gorilla cousins. Lowland gorillas are much more likely to be seen in the trees, and prefer a more heavily forested, flatter habitat than the mountain gorilla.
Mountain, or eastern gorillas, Gorilla beringei, are found in the Virunga volcanoes that separate the Democratic Republic of Congo from Rwanda and Uganda.
Western or lowland gorillas inhabit the forests of equatorial Africa from the western lowlands near the Cameroon coast through the Central African Republic, Equatorial Guinea, Gabon, Nigeria, Republic of Congo, Angola, and possibly the Democratic Republic of Congo.
As their names suggest, the two subspecies of gorilla have very different habitats. The lowland gorillas make their homes in the thick rain forests on the Atlantic Coast of Africa. They have a relatively small area that they still live in in the wild, including untouched wilderness in Congo, Equatorial Guinea, Central African Republic, and Cameroon. The mountain gorilla is found at much higher altitudes and much farther inland, surviving in a pocket of wilderness in Rwanda, Uganda, and the Democratic Republic of Congo. Most of their native habitats are the rocky slopes of once-active volcanoes, although they are known to venture into the high, alpine regions of the mountain ranges where they can face freezing temperatures.
Both subspecies live in family groups called “troops.” Large troops with as many as 30 individuals have been seen, but the usual makeup of these families is quite a bit smaller. A gorilla troop usually consists of one dominant male, a handful of his females, and their immature offspring. Adult male children will split off from their family unit to travel alone; around the age of 15, males will begin collecting their own harem of females and start their own family group. Between leaving their parents and collecting females of their own, immature lowland males will occasionally form their own troop, sometimes attached to a parent group.
There is some difference in the physical features between the two, although it can be hard to distinguish at a glance. Both have very long arms—their arm span is longer than they are tall—but mountain gorillas typically have shorter arms than their lowland cousin. They also have a larger nose and jaw, and larger teeth.
When stressed or upset, male mountain gorillas emit a strong odor from glands under their arms. Studies of lowland gorillas have so far shown that scent communication doesn’t play as large a role in their culture.