Senegal is a country in West Africa, known as the "Gateway to Africa". The area known today as Senegal was long part of the ancient kingdoms of Ghana and Djsolof, and a major hub on the trans-Saharan caravan routes. The country lies on an ecological frontier where semi-arid grasslands meet ocean coast and tropical rainforest, a diverse environment that has endowed Senegal with a wide variety of flora and fauna. Senegal's larger animal species are now largely confined to national parks. These include the Guinea Baboon, the Senegal Hartebeest, the Western Hartebeest, the Scimitar Oryx, the Roan Antelope and several gazelle species. Because of habitat destruction, the populations of the Western Red Colobus, elephants, lions and many other species have been severely reduced. The Giant Eland's western subspecies is critically endangered, with the only known extant population in Niokolo-Koba National Park. The fast reduction in antelope numbers is blamed on poaching. Among the other mammals found in the country are the Green Monkey, the Guinea Gerbil and the Senegalese One-Striped Grass Mouse. The country has recorded some 674 species of birds, the most spectacular of which are species such as the Red-Billed Tropicbird, the Arabian Bustard, the Egyptian Plover, the Golden Nightjar, the Red-Throated Bee-Eater, the Chestnut-Bellied Starling, the Cricket Warbler, the Kordofan Lark and the Sudan Golden Sparrow. The Djoudj National Bird Sanctuary, on the southern side of the Senegal River Delta, is an important site for migratory and wintering waterbirds.