In the Old World tropics, hornbills form a group of specialist canopy-top frugivores. This niche is filled in America by toucans, slightly smaller in size but with similar beak construction, which evolved independently to feed on the same sorts of fruit . Tropical America is also much the richest region in bats, and the Amazon has about half all known species of freshwater fish. For many rainforest vertebrates, fruits are an important component of the diet. For example, at the Cocha Cashu rainforest in Peru, mammal and bird biomass was about 2 tonne per sq km, whereas it can reach 12 tonne per sq.km in African savanna.
Many fruit eating species eat other foods as well.
Besides differences among the three tropical regions, there are other differences within them. One major pattern is that, within the African and American rainforests there are certain areas that are especially rich in species. In Africa, for example, some parts of the forest have a large number of bird species, while in America some forests are expecially rich in birds and butterflies. In Asia, the major pattern is set by Wallace's Line , which divides the continental Asian faunas from the Australasian ones. Finally, in all parts of the tropics, there are generally fewer and fewer species as altitude increases, from lowland to mountain forest .