Serengeti
The Serengeti ( ) ecosystem is a geographical region in Africa, spanning northern Tanzania. The protected area within the region includes approximately of land, including the Serengeti National Park and several game reserves. The Serengeti hosts the second largest terrestrial mammal migration in the world, which helps secure it as one of the Seven Natural Wonders of Africa, and as one of the ten natural travel wonders of the world. The Serengeti is also renowned for its large lion population and is one of the best places to observe prides in their natural environment. Approximately 70 large mammal and 500 bird  species are found there. This high diversity is a function of diverse habitats, including riverine forests, swamps, kopjes, grasslands, and woodlands. Blue wildebeest, gazelles, zebras, and buffalos are some of the commonly found large mammals in the region. The Serengeti also contains the Serengeti District of Tanzania. There has been controversy about a proposal to build a road through the Serengeti. The name "Serengeti" is often said to be derived from the word "seringit" in the Maasai language, Maa, meaning "endless plains". However, this etymology does not appear in Maa dictionaries. History. For eons, Serengeti was sparsely inhabited as species  of African wildlife have roamed freely across the vast rolling plains. However, this had all changed when nomadic pastoralists of the Maasai began to migrate to the area in the early 20th century. They were hurt by drought and disease. Thousands died in the 1880s from a cholera epidemic and in 1892 from smallpox. Rinderpest (a bovine viral disease) then wiped out the cattle which were their possessions. The Tanzanian government later in the 20th century re-settled the Maasai around the Ngorongoro Crater. Poaching, and the absence of fires (which had been caused by humans), allowed dense woodlands and  thickets to develop over the next 30–50 years. Tsetse fly populations now prevented any significant human settlement in the area. By the mid-1970s, wildebeest and Cape buffalo populations had recovered and were increasingly cropping the grass, reducing the amount of fuel available for fires. The reduced intensity of fires has allowed acacia to once again become established. In the 21st century, mass rabies vaccination programmes for domestic dogs in the Serengeti have not only indirectly prevented hundreds of human deaths, but also protected wildlife species such as the endangered African wild dog. Great migration. Each year around the same time , the circular great wildebeest migration begins in the Ngorongoro Conservation Area of the southern Serengeti in Tanzania and loops clockwise through the Serengeti National Park and north towards the Masai Mara reserve in Kenya. This migration is naturally caused, by the availability of grazing. The initial phase lasts from about January to March, when the calving season begins – a time when there is plenty of rain-ripened grass available for the 260,000 zebras that precede 1.7 million wildebeest and the following hundreds of thousands of other plains game, including around 470,000 gazelles. During February, the wildebeest are on the short  grass plains of the southeast part of the ecosystem, grazing and giving birth to approximately 500,000 calves in 2 to 3 weeks. Few calves are born ahead of time and of these, hardly any survive, largely because very young calves are more noticeable to predators when mixed with older calves from the previous year. As the rains end in May, the animals start moving northwest into the areas around the Grumeti River, where they typically remain until late June. The crossings of the Grumeti and Mara rivers beginning in July are a popular safari attraction because crocodiles are lying in  wait. The herds arrive in Kenya in late July / August, where they stay for the rest of the dry season, except that the Thomson's and Grant's gazelles move only east/west. In early November, with the start of the short rains, the migration starts moving south again, to the short grass plains of the southeast, usually arriving in December in plenty of time for calving in February. About 250,000 wildebeest die during the journey from Tanzania to the Maasai Mara National Reserve in southwestern Kenya, a total of . Death is usually from thirst, hunger, exhaustion, or predation including  by big cats. Ecology. The Serengeti has some of East Africa's finest game areas. Besides being known for the great migration, the Serengeti is also famous for its abundant large predators. The ecosystem is home to over 3,000 Lions, 1,000 African leopards, and 7,700 to 8,700 spotted hyenas ("Crocuta crocuta)." The East African cheetah are also present in Serengeti. African wild dogs are relatively scarce in much of the Serengeti. This is particularly true in places such as Serengeti National Park (where they became extinct in 1992), in which lions and spotted hyenas, predators that steal wild dog kills  and are a direct cause of wild dog mortality, are abundant. The Serengeti is also home to a diversity of grazers, including Cape buffalo, African elephant, warthog, Grant's gazelle, eland, waterbuck, and topi. The Serengeti can support this remarkable variety of grazers only because each species, even those closely related, has a different diet. For example, wildebeests prefer to consume shorter grasses, while plains zebras prefer taller grasses. Similarly, dik-diks eat the lowest leaves of a tree, impalas eat the leaves that are higher up, and giraffes eat leaves that are even higher.The governments of Tanzania and  Kenya maintain a number of protected areas, including national parks, conservation areas, and game reserves, that give legal protection to over 80 percent of the Serengeti. Near Lake Victoria, floodplains have developed from ancient lakebeds. In the far northwest, acacia woodlands are replaced by broadleaved Terminalia-Combretum woodlands, caused by a change in geology. This area has the highest rainfall in the system and forms a refuge for the migrating ungulates at the end of the dry season. Altitudes in the Serengeti range from with mean temperatures varying from . Although the climate is usually warm and dry, rainfall occurs in  two rainy seasons: March to May, and a shorter season in October and November. Rainfall amounts vary from a low of in the lee of the Ngorongoro highlands to a high of on the shores of Lake Victoria. The area is also home to the Ngorongoro Conservation Area, which contains Ngorongoro Crater and the Olduvai Gorge, where some of the oldest hominin fossils have been found.