When there is enough food for wildebeests to remain relatively sedentary, herds form in the typical fashion of social ungulates: bachelor herds and territorial males with a group of females and offspring. As the dry season deepens, more animals congregate on available grazing lands and thus lose separate herd identities. Wildebeests are continually on the move as they seek favorable supplies of grass and water.
The famous Serengeti population of wildebeest is a very large nomadic group. Each year around 1 million wildebeest make a migratory circle of 500 to 1,000 miles. Beginning right after the calving season in January and February on the southeastern Serengeti plains, they move west toward Lake Victoria, then turning north into the Maasai Mara. They are relentless in their advance and many are injured, lost (especially calves) or killed. By the end of the dry season, the wildebeest have almost exhausted the grazing lands and return south to the Serengeti plains as the rains begin.