Do Gorillas Live in Families?

Gorillas are social animals who usually form harems: One silverback male lives together with several adult females and their offspring. However, in mountain gorillas about 40% of groups contain several adult males who are closely related.
As groups contain more females than males, many males are 'left over'. They roam the forests on their own. Such loners make up 5-10% of the gorilla population. Mountain gorilla males occasionally form all-male groups.
The size of gorilla groups is very variable. An average gorilla group contains four to ten members. The biggest gorilla group known to date was found in Rwanda: It consisted of 65 individuals for a short period.
When the group leader dies, the group dissolves or a subordinate silverback male, usually the son of the dead leader, takes over.