The Great Wildebeest Migration is the biggest animal herd movement on earth. In fact, the vast columns of wildebeest may be observed from orbit with up to 1,000 animals per km2.It occurs between the month of June and September every year.
The figures are staggering: in quest of nourishing grass and water, nearly 1.2 million wildebeest, 300,000 zebra, topi and other animals migrate continuously through the Serengeti-Mara habitat. Each wildebeest will travel 800 to 1,000 miles on its own over historic migration routes, guided by instincts for survival. In this natural display, also referred to as “the greatest show on Earth,” hungry predators like lions, leopards, cheetahs, hyenas, wild dogs, and crocodiles ensure that only the strongest survive.
The circuit transports the animals from Tanzania’s southern Serengeti, the Ngorongoro Conservation Area (though not into the Crater itself), across the Serengeti, across into Kenya’s Masai Mara, and back again. The trek is fraught with peril: crocodiles take their fair share of the stragglers, newborn calves are stolen by predators, the slow are brought down by lion prides, daring animals break legs on steep river slopes, and the weak and tired drown.
As one group consumes the top of the tallest grass, the following group will begin to consume some of the medium-height grass. This process continues until the grass is almost fully consumed, at which point the herds move on. This indicates that each group stays within its own kind, with their distributions seldom overlapping. In the entire Serengeti, the grasses of the plains have the highest concentration of calcium and protein.
Although it is unclear how the wildebeest choose their route, it is generally accepted that they respond to the weather by moving in the direction of rain and the development of new grass. Although there is no scientific evidence for it, some professionals think that the animals respond to distant lightning and thunderstorms. Even the idea that wildebeest can detect rain from more than 50 km distant has been floated.