Why Zebra & Wildebeest do Migration Wildebeest herding and following Zebra in the Serengeti National Park (Tanzania). During these migrations, wildebeest spend 10 months per year in the Serengeti National Park and two months in the Masai Mara, (Kenya). Not all wildebeest are migratory. Black wildebeest herds are often nomadic or may have a regular home range of 1 km2 (11,000,000 sq ft). Bulls may occupy territories, usually about 100 to 400 m (328 to 1,312 ft) apart, but this spacing varies according to the quality of the habitat. In favorable conditions they may be as close as 9 m (30 ft) or as far apart as 1,600 m (5,200 ft) in poor habitat. Female herds have home ranges of about 250 acres (100 ha; 0.39 sq mi) in size. Herds of non-territorial bachelor males roam at will and do not seem to have a home range. In the Masai Mara game reserve, there is a non-migratory population of blue wildebeest which had dwindled from about 119,000 animals in 1977 to about 22,000 in 1997. The reason for the decline is thought to be the increasing competition between cattle and wildebeest for a diminishing area of grazing land as a result of changes in agricultural practices, and possibly fluctuations in rainfall. Each year, some East African populations of blue wildebeest have a long-distance migration, seemingly timed to coincide with the annual pattern of rainfall and grass growth. The timing of their migrations in both the rainy and dry seasons can vary considerably (by months) from year to year. At the end of the rainy season (May or June in East Africa), wildebeest migrate to dry-season areas in response to a lack of surface (drinking) water. When the rainy season begins again (months later), animals quickly move back to their wet-season ranges. Factors suspected to affect migration include food abundance, surface water availability, predators, and phosphorus content in grasses. Phosphorus is a crucial element for all life forms, particularly for lactating female bovids. As a result during the rainy season, wildebeest select grazing areas that contain particularly high phosphorus levels. One study found, in addition to phosphorus, wildebeest select ranges containing grass with relatively high nitrogen content. Wildebeest in Masai Mara during the Great Migration Numerous documentaries feature wildebeest crossing rivers, with many being eaten by crocodiles or drowning in the attempt. While having the appearance of a frenzy, recent research has shown a herd of wildebeest possesses what is known as a swarm intelligence, whereby the animals systematically explore and overcome the obstacle as one. Major predators that feed on wildebeest include the lion, hyena, cheetah, leopard, and crocodile, which seem to favor the wildebeest. Wildebeest, however, are very strong, and can inflict considerable injury even to a lion. Wildebeest have a maximum running speed of around 80 km/h (50 mph). The primary defensive tactic is herding, where the young animals are protected by the older, larger ones, while the herd runs as a group. Typically, the predators attempt to cut out a young or ill animal and attack without having to worry about the herd. Wildebeest have developed additional sophisticated cooperative behaviors, such as animals taking turns sleeping while others stand guard against a night attack by invading predators. Wildebeest migrations are closely followed by vultures, as wildebeest carcasses are an important source of food for these scavengers. The vultures consume about 70% of the wildebeest carcasses available. Decreases in the number of migrating wildebeest have also had a negative effect on the vultures. In the Serengeti ecosystem, Tanzania, wildebeest may help facilitate the migration of other, smaller-bodied grazers, such as Thomsons gazelles (Eudorcas thomsonii), which eat the new-growth grasses stimulated by wildebeest foraging.
Posted on: Mon, 13 Oct 2014 08:04:55 +0000
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