About the Migration
The 1.3 million strong wildebeest herd of Tanzania and Kenya trace a clockwise circuit of East Africa's great grassland plains, following the rain and the ripening grasses. Burchelli's Zebras infiltrate the black mass, perhaps seeking protection amid the numbers, while other hoofed species join the migration on its fringes, a colorful carnival of herbivores trudging, lurching, and leaping across the grasslands and woodlands. Africa's great predators are never far away from the menagerie.
The trek begins in the south, after the wildebeest-birthing season in February. The herd moves northwest, chasing rain and abundance, arriving at the northern end of the circuit in the Mara Triangle in July or August. Predicting where the wildebeest will be with any precision is impossible, but generally, the migration follows a regular pattern, although one ultimately dictated by the vagaries of wind, sun, and rain.
The wildebeest migration has followed its present circuit of the Serengeti Plain for hundreds of thousands of years. The wildebeest were joined on the plain by Maasai herdsmen 2500 years ago. The Maasai did little to disrupt the ancient patterns, but the activities of both the wildlife and pastoral herdsmen reshaped the landscape to better suit both. The traveling herds fertilized the soil and crushed nascent shrubs and trees and encouraged the grass to grow. The Maasai set fires to burn away stubble and shrubs, prompting new growth, and they rotated their cattle from pasture to pasture to prevent overgrazing. The Serengeti-Mara ecosystem we know today is the result of the complex interplay of geography, climate, wildlife, and people.
Disruption of one or more of elements of the ecosystem unbalances the larger system, often in unexpected ways. When European settlers arrived in East Africa in the 1890s, they brought with them cattle infected with rinderpest. In only a couple of decades, the virus reduced the continent's populations of wildebeest and buffalo and giraffe by 90%. The migratory Serengeti herds of a million and a half wildebeest were reduced to a few hundred thousand. Rinderpest decimated Maasai cattle herds too, of course, while European settlers claimed the most fertile land for themselves. In response to fewer wildebeest and fewer Maasai cattle, the grasslands began to change. Fire and a million stamping wildebeest had once controlled the advance of shrubs and trees; now nothing did. Denser bush led to a proliferation of tsetse flies; deadly to both livestock and people. Some early conservationists celebrated the emergence of the tsetse as "nature's game warden." The creation of game parks and reserves, and widespread rinderpest inoculation of cattle, allowed the Serengeti wildebeest herd to regenerate. By the 1970s the herd again numbered more than a million wildebeest. Post-colonial land-use practices have allowed the Maasai to return to many of their historic pastures, too.
The migration today is much like it has always been, but the balance is precarious.
The migration is threatened by encroaching human populations just as many of the world's wild places are. The complex of reserves and conservation areas that encompass most of the ecosystem - Serengeti National Park, Maasai Mara Reserve, Ngorongoro Conservation Area and associated wildlife corridors and buffer zones - is 10,000 square miles large, about as large as the state of Massachusetts. In times of drought the protected area may not be large enough for the herds as they push into the settlements on the fringes. In all times the protected area is too large for the growing number of people who live on its boundaries. Fences erected by farmers and ranchers restrict the animals' movements outside the parks. Bush meat hunters, often subsistence farmers living near the parks, illegally poach as many as 160,000 migratory herbivores each year. Arrests for illegal hunting in the Western Corridor rise and fall with the arrival of the migration. What is true for lions is true for bush meat hunters; predators tied to the land must wait for prey that is tied to the migration.
Climate change threatens the migration in a more fundamental way. The herds move over the plain based on the patterns of wet season and dry. When the rains do not fall as they normally do, whether heavier or lighter, the migration does not move as it normally does either. Heavy rains in the south have allowed the wildebeest to linger before beginning their trek, shortening their stay in the Mara Triangle, or eliminating it altogether. Several recent years of drought have trimmed the wildebeest population by several hundred thousand individuals. Continued drought will surely press the wildebeest population further. And should climate change significantly alter East Africa's historic rainfall patterns, the migration will surely change too.
The Serengeti ecosystem covers 10,000 square miles.
The roughly triangular route the migrants follow is about 300 miles from start to finish, as the crow flies. The trip can be considerably longer depending on which way the wildebeest wander.
Any given year, depending on the rain and other conditions, the Serengeti migratory wildebeest number between 1.2 to 1.5 million animals.
Wildebeest are also known as Gnu (pronounced 'nu').
The wildebeest are joined on their journey by up to 200,000 Burchelli's zebras.
A wildebeest consumes 3200 pounds of food in a year and a zebra consumes 4800 pounds.
A lion eats 7200 pounds of its neighbors each year, a leopard eats 3200 pounds, a cheetah eats 4015 pounds, and the cold-blooded crocodile eats just 1600 pounds of food each year.
An elephant consumes 69,000 pounds of food each year.
A human consumes 1950 pounds a food per year.
As many as 500,000 wildebeest are born each February.
Three percent of the wildebeest that begin the journey each year do not survive to finish it.
A lucky wildebeest can live as long as 20 years.