Why Do Wildebeest Migrate? The Science Behind the Great Migration

More than a million wildebeest, together with hundreds of thousands of zebra and gazelle, travel a rough circle through the Serengeti-Mara ecosystem every year. It is tempting to call it instinct, but the real reason is more specific.

Following the Grass

Wildebeest are grazers, and what they are really chasing is short, nutritious grass. Rain brings fresh growth, and the herds follow it. That is why the timing changes with the rainfall rather than following a fixed calendar.

The Southern Plains and Calving

From about December to March, the herds gather on the short-grass plains of the southern Serengeti and Ndutu. The volcanic soil there produces grass rich in the minerals pregnant wildebeest need. It is also calving season. Hundreds of thousands of calves are born within a few weeks, far more than predators can possibly catch, which helps the herds survive.

Why They Cross Rivers

Once the southern grass is eaten and dries out, the herds move north looking for fresh grazing. Their route crosses the Grumeti and Mara Rivers, creating the famous crossings. The river isn't the goal; it is simply in the way of better grass on the other side.

Nature Keeps Its Own Schedule

Because the rain decides the timing, nobody can promise an exact date or place in advance. That is why experienced local guides, who follow the herds year after year, make such a difference when planning your visit.