The mountain gorilla (Gorilla gorilla beringei), is listed in Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora and in class A of the African Convention on the Conservation of Nature and Natural Resources as ‘vulnerable to extinction’. Human activities such as forest clearance for agriculture and poaching are the main threats to the mountain gorillas. Mountain gorillas have few natural predators such as leopards. Of the 3 sub-species of gorilla, the mountain gorilla (Gorilla gorilla beringei) is the most endangered.

A study on the home range, group size and composition of 10 groups of mountain gorillas in Bwindi Impenetrable National Park (BINP) was conducted for about 14 months (November 1991 to January 1993). Five groups were studied at lower-medium altitude (Buhoma, 1600-2000m), and 5 groups at higher altitude (Ruhija, 2000-2500m).  Each team of 2-4 park rangers moved in a predetermined direction until a gorilla trail of less than 1 week old was found. The trails were then followed until the nest sites were located. Mountain gorilla searches were made for at least 7 hours per day. All nest sites and trails encountered were recorded.

A total of 5207 nests at 407 nest sites were examined. The total number of nests encountered was less than the expected (5307) because only adults build their own nests. Infants -and sometimes juveniles- do not build nests. A total of 133 mountain gorillas were tracked. Group size varied from 9-24 individuals with a mean size of 13.3. There was no significant difference between group size of gorillas at lower and higher altitudes.  Each group was composed of at least one dominant male (silverback) and a dominant female.  Silverbacks, juveniles and adult females accounted for 18.8%, 28.6% and 52.6% respectively. Group composition varied from place to place. The correlation between the group size and the number of silverbacks indicated that the larger the group the more the silverbacks it has.  

Daily travel distance varied from 148-2036m, with an average distance of 1000metres per day. Daily distance travelled was affected by the presence of human beings and other gorillas, with the largest distance covered by habituated groups and those undergoing habituation.

Home range size varied from 9-26km². Group size affects the home range size. Home range size of mountain gorillas at lower altitudes was larger compared to those at higher altitudes. 3] 

The home range sizes of the 10 Bwindi mountain gorilla groups were generally smaller than those of mountain gorillas in Kabara (in the Democratic Republic of Congo) and larger than those of Visoke, in the Virunga mountains straddling the border of Congo and Rwanda. However it fell within the mountain gorilla’s yearly range across.