March – May
It’s mid March in the northern Tanzania, and thousands of animals are happily milling on the rolling plains of the Serengeti. The female wildebeest have just dropped their calves in a beautiful display of new life, as the youngsters stumble and stagger to their feet and are up and running within minutes. There’s still plenty of food to go around, and life must seem pretty idyllic for the wildebeest.
And yet, one, or two, or maybe a few hundred wildebeest sense something in the air.
For some reason, a few animals decide to start moving. They just get up and go, and the rest begin to follow.
Just like that: the largest terrestrial mammal migration on earth has begun.
It is a trek, a round trip, of some 1000 kilometers, over two countries (Tanzania and Kenya), across plains where predators—lion, cheetah and leopard—wait to pick off them off, over hills, and through rivers with crocodiles waiting; battling disease, starvation, thirst and fatigue; with around 250 000 animals perishing along the way.
Despite all this turmoil ahead, without fail, they go.
Why do they do it?
Why, when most wildebeest in Africa are non-migratory, do the animals of the Mara/Serengeti ecosystems risk it all in one mad trip?
No scientist or naturalist has yet been able to answer this question conclusively. But there are some theories.
Studies using aerial photography show a remarkable level of organization in the structure of the wildebeest herds as they start moving. The groups display a wavy front that snakes out like the head of a swarm. This amazing structure cannot be apparent to each individual wildebeest, which means that there is some degree of decision making that is happening between the animals. Is there some sort of leadership being displayed; maybe a form of communication we don’t yet know about?
Some scientists believe that the wildebeest are motivated by the chemistry of the grass. The herds are attracted to higher levels of phosphorus and nitrogen, which changes in response to the rains. So perhaps the wildebeest are merely following their taste.
It might simply be instinct. Fossil evidence suggests that wildebeest have been roaming the plains of East Africa for over one million years. In the same way their body tells them to run when a lion appears out of the grass, maybe the instinct to migrate has been coded into the DNA of the animals over many years of evolution.
Perhaps they just know—and so they just go!
Whatever the reason, over 1.5 million animals begin a journey that will undoubtedly cause death to many of their own, but will also bring life to many more animals as they follow the rains in search of green nutrient-rich fields that will sustain the next generation.
And so they charge onwards.
What Actually Happens?
During March the last of the babies appear and the wildebeest continue to nibble on the luscious grass. Following the localized rain showers, the wildebeest move across the Southern plains in search of the juiciest shoots and can wander as far as the northern reaches of the Ngorongoro (but never into the crater itself). Hungry predators follow their every move… The Southern Serengeti makes the best place to stay during March
The great migration continues to move constantly in April. Feasting complete and leaving behind a rather barren landscape in the south, the herds follow the rumblings of thunder northwards. Mega columns of wildebeest stretch from the south, through the Moru Kopjes in the central Serengeti and all the way to the Western Corridor.
During May, a few rogue wildebeest head even further north of the central region, but the masses make their way across to the Western Corridor. Here, they congregate in their heaving hundreds of thousands on the banks of the Mbalageti and Grumeti rivers and the first real challenge of the trek awaits: how to get to the other side…
By June, the herds begin to spill across the murky pools of the Mbalageti and Grumeti rivers. Although not quite as dramatic as the northern crossings, there’s plenty of drama in store as the crocodiles prepare for their annual wildebeest-banquet. Rutting season is also underway and the plains are alive with testosterone-fuelled males chasing their chosen ladies.