Perhaps no animal and phenomenon are as woven into the identity of the Serengeti as the wildebeest and the annual spectacle called the Great Migration. In its ecological significance and sheer magnificence, the movement across Serengeti of more than a million wildebeest—along with hundreds of thousands of zebras and Thomson’s gazelles—is like nothing else on the planet.

The western white-bearded wildebeest is a subspecies of the blue wildebeest, or brindled gnu. It is a large, bearded antelope with a deep chest, a short, thick neck, high shoulders, and thin legs. It has smooth, cow-like horns that are thicker and wider in males, a short, glossy, grey to dark brown coat with contrasting stripes, and a shaggy black mane and tail. Males can be as long as 2.4 metres from head to base of tail and weight up to 290 kilogrammes. Females have a lighter coat and are usually smaller.

The name “wildebeest” is derived from the impressions of Dutch settlers who thought that the animal resembled wild cattle. The blue wildebeest includes both migratory and nonmigratory populations and is widespread in grassy plains and open woodlands in much of southern and eastern Africa. The western white-bearded subspecies is the smallest blue wildebeest and is specific to northern Tanzania and southern Kenya.

The dependence of wildebeest on green grass and a steady supply of water exclude the wildebeest from the northern, drier regions of Africa. It is also the basis of the great Serengeti migration, as the wildebeest spend the early part of the year—the wet season—in the Ngorongoro Conservation Area in the southern Serengeti and, following available food and water, move northwest in (roughly) March through May, and arrive in Kenya’s Maasai Mara in late July or August. Except for a few small populations, the wildebeests in the Serengeti-Mara ecosystem are migratory. A closely related species, the black wildebeest, is more common in areas south of Tanzania and is nomadic rather than migratory.

Wildebeest are social grazers, tending to congregate where there is ample food and water. Wildebeest graze day and night, but are most active in the morning and late afternoon. They are often found in large herds with plains zebras, which feed on the upper, less nutritious grass canopy, exposing the lower, greener material that are preferred by wildebeest. The hyper-alert zebras, as well as other nearby animals, provide further benefit to wildebeest communities by giving early warnings about the presence of predators around the grazing areas. The wildebeest is a ruminant like other antelope and cattle-like animals, with a specialised stomach that allows it to consume vegetation that other animals might find inedible.

Wildebeest breed toward the end of the rainy season and produce offspring about 8 1/2 months later—around the beginning of the next rainy season. Females have one calf. Newborns can walk almost immediately after birth. Depending on environmental conditions, female offspring become fertile at 16 to 24 months. Males are sexually mature at about 2 years and are ready to assume territories at 4 to 5 years. Territorial bulls control mobile territories, holding onto cows and their young, while nursery herds move freely in and out. Young males forced out of such territories form bachelor herds that might include older and nonterritorial males. Wildebeest can live 20 years or longer in the wild

The primary predators of wildebeest include hyenas, leopards, cheetahs, and crocodiles. However, the wildebeest is not easy prey. Adults have a maximum running speed of around 65 km/h and are strong enough to injure even their largest predators. Predators focus on young and sick animals that they try to separate from the herd.

While the wildebeest is not considered endangered, its numbers have fluctuated dramatically from natural cycles of drought and famine. Human threats include land conversions, roads, fencing, and other barriers to migration. Poaching takes a further toll, as does disease. While wildebeests are often suspected of passing disease to cattle, it is also true that farm animals pass disease onto wildebeests. The most notorious such incident was the rinderpest epidemic of the 1950s, which reduced the wildebeest population in Serengeti from 1.5 million to fewer than 300,000.

The Serengeti-Mara ecosystem is home to 70 percent of blue wildebeests. Serengeti is critical for the wildebeest—and the wildebeest is critical for Serengeti. Tourism related to the Great Migration is essential to the economies of Tanzania and Kenya and essential for maintaining public support for the park. The abundant numbers of wildebeests—a result of their ability to access food resources unavailable to nonmigratory species—helps sustain a healthy population of predators and scavengers in Serengeti, while reducing predation pressures on vulnerable animals such as giraffes. Further ecosystem benefits include the grazing activities of wildebeests, which stimulates the productivity of grasslands and further assures the rich biodiversity of Serengeti.

Perhaps the most existential threat to the wildebeest is the prospect of a changing climate. Changes in temperature and seasonal rainfall could alter vegetation patterns and available food resources. This could affect the timing of migrations and possibly steer migrating herds away from protected areas and into more constant conflict with human settlements. The implications of this for wildebeests—and the health of the entire Serengeti ecosystem—are profound.