The Zoo's African Savanna is dominated by open vistas and rolling grasslands. In this expansive space, Masai giraffes, bonteboks, ostriches, and zebras browse on scrub grass or tree leaves. The continent's fiercest predators - a pair of lions and a leopard - live nearby. African Savanna also features massive black rhinoceroses, which have distinctive prehensile upper lips for grasping food. Once the most numerous of all rhino species, black rhinos are critically endangered due to poaching. According to the International Rhino Foundation, there were 4,240 black rhinos left in the wild in 2011, and the International Species Information System estimates there are just 194 black rhinos in zoos worldwide. Next to the rhinos, some leaf-eating Colobus monkeys make their home on Monkey Island. These black-and-white monkeys, which are native to the forests of East Africa, are accomplished aerialists that navigate the treetops with ease. African Savanna also hosts a variety of bird species, including marabou and White storks, crowned cranes, spur-winged geese, and white-backed vultures.