more than 50% of Uganda's tree species, and more than 100 fern species. The brown mahogany is a threatened plant species in the park. Bwindi Impenetrable National Park is important for the conservation of the afromontane fauna, especially species endemic to the Western Rift Valley's mountains. It is thought to have one of the richest faunal communities in East Africa, including more than 350 bird species and more than 200 butterfly species. There are an estimated 120 mammal species in the park, of which 10 are primates, and more than 45 are small mammals. Along with mountain gorilla, species in the park include common chimpanzee, L'Hoest's monkey, African elephant, African green broadbill, and cream-banded swallowtail, black and white colobus, red-tailed monkeys, vervets, the giant forest hog, and small antelope species. The fish species in the park's rivers and streams are not well known. There are also many carnivores, including the side-striped jackal, African golden cat, and African civet. Mountain gorillas The park is inhabited by about 459 individual mountain gorillas as per the last 2019 Gorilla Census (Gorilla Fund)(Gorilla beringei beringei), known as the Bwindi population, which makes up almost half of all the mountain gorillas in the world. The rest of the worldwide mountain gorilla population lives in the nearby Virunga Mountains. A 2006 census of the mountain gorilla population in the park showed that its numbers had increased modestly from an estimated 300 individuals in 1997, to 320 individuals in 2002 to 340 individuals in 2006, and 400 in 2018. Poaching, disease and habitat loss are the greatest threat to the gorillas. Research on the Bwindi population lags behind that of the Virunga National Park population, but some preliminary research on the Bwindi gorilla population has been carried out by Craig Stanford. This research has shown that the Bwindi gorilla's diet is markedly higher in fruit than that of the Virunga population, and that the Bwindi gorillas, even silverbacks, are more likely to climb trees to feed on foliage, fruits, and epiphytes. In some months, the Bwindi gorilla diet is very similar to that of Bwindi chimpanzees. It was also found that Bwindi gorillas travel farther per day than Virunga gorillas, particularly on days when feeding primarily on fruit than when they are feeding on fibrous foods. Additionally, Bwindi gorillas are much more likely to build their nests in trees, nearly always in Alchornea floribunda (locally, "Echizogwa"), a