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. 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 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