The Great Migration

To be precise, there isn't a beginning nor an end to the Great Migration, it's a circular, never-ending pilgrimage that starts again and again. Animals will follow the circular clockwise route year after year, back and forth from the Serengeti National Park, in northern Tanzania, to the Masai Mara National Reserve, in southern Kenya.

However, for the sake of setting a starting point, we could say that the Great Migration begins from late January to mid-March, that is, when things always begin: with birth. Indeed, several hundred thousand wildebeest calves are born each year during this period, though many will be shortly hunted by hyenas, jackals, and other predators.

The animals set off in April, when the Southern Serengeti plains have dried up and become increasingly worn out. The herds gather and start the trek, following a North West direction, into the Western Corridor (near Lake Victoria), where they'll find fresh tall grasses. Although the herds include many different herbivores, the big numbers are made by Wildebeest, of course, Thomson's gazelle, and Zebra: respectively, 1.3 million, 360 thousand, and 191 thousand. Integration among the migration companions is highly accomplished. On the one hand, each species eats a different part of the grass sward and so do not compete. On the other, a larger number provides a greater safety for individuals, as there are more targets for predators.

Unfortunately, gazelles and zebras aren't the wildebeest's only companions. Several gangs of carnivores -most notably lions and hyenas- march along, closely following an irresistible and fairly convenient-to-catch protein source. Hunting is not strictly necessary: many animals will fall to the fatigue of the trip, making an easy lunch for the meat-eaters.

By the end of May the herds move to the northern Serengeti plains and woodlands. After finishing its mineral-rich pastures, the herd continue to the Masai Mara National reserve, usually between the last week of June and the first of July. At this point, the groups coming from the Serengeti meet the resident ones that inhabit the Loita Plains and Hills.

The migration route is cut again and again by the rivers that run into Lake Victoria -Mara, Grumeti, and Mbalangeti- and their tributaries. Rivers are most feared by gnus and their co-migrants, not only for the steep banks and harsh torrents, but also because of the crocodile populations that lie in wait, impatient to sink their teeth on the warm meat. This is what happens during July, when the gnus and company cross the Mara river and its tributary, the Talek.

From late July to the first days of October, the animals that got through the stressing river fording can graze peacefully on the Masai Mara grasslands, though their tranquillity is repeatedly cut by the tireless predators: lions, cheetahs (who prey on calves only), and hyenas.

By mid to late October, rains leave the Mara for the Serengeti, and the migratory animals make the reverse route, heading for the southern Serengeti plains once again, where the wildebeest will graze, give birth to a new generation of calves, and wait for the cycle to start all over again.