The Udzungwa rainforest is a remnant of the ancient Eastern arc rainforest that stretched along the eastern rift. It has similarities with forests in Madagascar and West Africa . However, Madagascar split from the mainland 165 million years ago and the Udzungwa forests have remained isolated from those in West Africa for the last 5 million years so that there exists a high degree of endemism with 25% of the plant species unique, 4 species of endemic primate, and several recently discovered endemic bird species.