The Annual Migration of the WildebeestsDubbed the ‘Greatest Wildlife Show on Earth', the annual wildebeest migration is one of the most vivid, tragic and splendid illustrations of the concept of ‘the survival of the fittest'. It happens twice a year, propelled by the rains, and involves 1.3 million wildebeests, 200,000 zebras and 300,000 Thomson's gazelles, all of which gather together to undertake a roughly triangular 800 km trek in search of the fresh grass upon which their survival depends.
Typically, during the rainy season (between December and May), the herbivores graze the lush grass of the southern sections of the Serengeti and the Ngorongoro Conservation Area. During this time, the wildebeests have their calving season, which is typically in February, and during which more than 8,000 wildebeest calves are born per day. However, because irrigation is scarce in these areas of the Serengeti ecosystem, as the land dries out so does the grass.
Gradually the herbivores are forced to mass together to feed on the few areas of green grass that remain. Eventually, as the herds swell to create massive groups of over a thousand increasingly hungry animals, the decision is made to migrate out of the Serengeti, north-west into the Masai Mara, where there is more chance of fresh grass. The precise timing of the migration varies but generally, the mass movement begins around the end of May: sometimes it takes a few weeks, sometimes only a few days. In the very dry years, the herds may decide to move northwards sooner, in which case they often either avoid or skirt the Western Corridor of the Serengeti.
As long as the dry season lasts, which is typically between July and October, the wildebeests, their fellow herbivores and the predators that track their movements, remain in the Masai Mara. Technically in Kenya, the Mara is contiguous with the Serengeti and an integral part of the same eco system. Only when the dry season ends, do they begin to move south again in anticipation of the rains in the Serengeti.