The mountain gorillas are found in the Virunga Mountain range which stretches along the borders of Rwanda, Uganda and DRC. The best places to see them are Bwindi Forest in Uganda or Parc des Volcans in Rwanda.
About 300 gorillas live in the Virungas. Lowland species of gorillas were first described in the mid 18th century but the mountain gorilla was not known to the western world until 1902. The first detailed study of them was undertaken by George Schaller in the 1950s and was the starting point for the most famous research done by Dian Fossey in Rwanda. Mountain gorillas are bulkier than other species of gorilla, weighing up to 200kg. They are very sociable moving in troops of anything up from 5 - 50 individuals.
A troop typically consists of a silverback male (the males back turns silver grey when he becomes sexually mature around 13 years old) and his 3 or 4 'wives' with several young animals. A silverback usually acquires a harem when he is around 15 years old, normally attracting a young female from another troop. The silverback leaders can lead their troops well into the forties. Females become sexually mature around 8 years after which they often move between troops. One a female has given birth she normally stays with the same silverback until he dies. Gorillas have the same gestation period as humans at around 9 months and if they live to old age would normally have had around 6 babies. Gorillas have a mainly vegetarian diet and are known to eat nearly 60 different species of plants. They also eat insects particularly ants. Troops spend most daylight hours on the ground, moving into the trees at night when each individual builds a temporary nest. They usually move less than 1km each day making tracking them day to day fairly easy for experienced guides. Having few natural enemies they often live up to 50 years in the wild but their livelihood is threatened by poaching, deforestation and increased exposure to human diseases.
In Uganda there are gorillas in Mgahinga and Bwindi but currently the habituated group in Mgahinga are not being trekked as their territory also includes Congo and Rwanda and they often move over the borders to feed.
In Bwindi there are two areas for gorilla trekking - Buhoma which is most popular and frequently used with access to three habituated groups and at Nkuringo which is at the far west end of the park and accessed from Kisoro. This is more difficult and has a long steep hill that can only be walked (not driven to) for access.
In the Buhoma area there were two main families of gorillas - the Habinyanja and Mubare groups. The first of these has split into two smaller groups, one of which (the Rushegara group) is now habituated to visitors.