Vegetation varies in different areas of Senegal, depending on the average rainfall. The most tropical part of southern Casamance has mangrove swamps and remnants of high forest, including oil palms, bamboo, African teak, and the silk-cotton tree. The dry thornland of the northeast has spiny shrubs, especially acacia, including the gum-bearing species. Most of Senegal is savanna. Trees, which are widely spaced in this region, include the African locust bean, tallow tree, and gingerbread plum, along with cassias and acacias. The lion and leopard are occasionally found in the northeast, as are chimpanzees, elephants, hippopotamuses, and buffalo. The wild pig, hare, guinea fowl, quail, and bustard are widely distributed. Insects and birds are abundant, and there are numerous lizards, snakes, and other reptiles.