The enormous herd of wildebeest gives birth relatively all at once, usually over the course of three weeks between January and March when the short grass plains at the foot of the Gol Mountains offer the best grazing opportunities.

Because grass growth is influenced by regional conditions, the timing and direction of the Great Migration are rarely consistent. Thus, the wildebeest may leave the open plains earlier in one year and stay in the northern woodlands for a longer period the following year.

The timing of the wildebeest calving is probably linked to the timing of the rut at the end of the rains in May and June. The wildebeest move off the plains at this time to a smaller area, which is necessary to synchronise the rut. Interestingly, the rut itself appears to coincide with the full moon, suggesting that the mating peak is triggered by the lunar cycle.

Typically, the wildebeest migration heads northwest from the short grass plains to the Western Corridor of the Serengeti and its Grumeti River. This watercourse is their first real obstacle, and gigantic crocodiles are waiting for the hesitant wildebeest to stumble at the crossing. From Grumeti, the herds move north, often spilling over into the Klein’s Camp Concession, before crossing the Kenyan border into the Masai Mara. Here again, they must cross a river, this time the Mara, with its flotillas of hungry crocodiles. The masses of grunting wildebeest remain on the productive Mara grasslands until October or November. Then, as the storm clouds gather in the south, the vast herds return to their breeding grounds, which, by the time they arrive, are once again green and lush. As a result, the migration cycle begins again.