Serengeti Migration

The Serengeti Migration In 1996, I went on a safari to the Serenegti National Park, Tanzania, to see lions. We saw a big pride of lions, but what was most impressive was the 'migration.' We were on the Serenegti short-grass plains, and as far as the eye could see were wildebeest, with the odd zebra family mingling in the massing herds. The view was framed by the Ngorongoro Crater to the South, the Gol Mountains to the East, and the Moru Kopjes to the West. This was in late March, and the wildebeest herds were massing on the short grass plains for the long trek North to the Maasai Mara in Kenya. Since then, I have had the pleasure and privilege of working in Serengeti for three years from 2003 to 2006 - the annual migration is still the most impressive thing I have ever seen. What is the Migration? The 1.4 million wildebeest, plus a million other ungulates, in the Serengeti ecosystem represent the world's greatest remaining aggregation of large mammals (Estes, 1991). Every year, in search of fresh pastures, 1.4 million wildebeest and 250,000 zebra move creating the spectacle of the Serenegti migration. The system is driven by annual rainfall patterns. The Serengeti short-grass plains are rich in minerals necessary for lactation, but lack water for most of the year. The short rains may fall anytime between October to December. While the long rains generally fall between January to April (with the majority falling in March and April). The short rains are highly variable, there are years when they fail, but typically you get one or two weeks of rain. The variability of the rainfall, make predicting where the migration will be difficult. But typically, the migration is on the short grass plains in Southern Serengeti from December to April. Typically the wildebeest give birth to their calves in February or March on the short grass plains. In April, the herds start massing for the long trek north to their dry season refuges. From May to July, the herds are generally in the Serengeti Western Corridor along the Grumeti River. If the year is particularly dry, the herds may by-pass the Western Corridor and head directly toward Northern Serengeti and the Maasai Mara. From the Western Corridor, the migration moves north, and by September the herds are in Northern Serengeti/Maasai Mara. The Mara River and its tributaries provide the herds with water during this dry period. In November, the herds again start massing for the long trek South to the Serengeti short grass plains. And the cycle begins again. Over the year the Wildebeest will cover over 400km. The Wildebeest and Zebra The wildebeest population has changed with time. A rinderpest epidemic swept across Africa at the start of the 1900s, which led to a marked decrease in the Serengeti wildebeest population. For much of the 20th centuary the Serengeti wildebeest population hovered around the 300,000 mark. In the 1960s, the cattle around the Serengeti were vaccinated against rinderpest. This freed the wildebeest population of rinderpest, and within a decade the wildebeest population had reached the 1.3 million mark. The Zebra population on the other hand has remained largely static around the 250,000 mark - this remains one of the great scientific mysteries (why has the zebra population not varied over time?). Other Animal Movements Other Serengeti animals also commute long distances. The eland and thompson gazelle are also migratory. The eland moves from Eastern Serengeti to Northern Serengeti, while the thompson gazelle moves from Southern Serengeti to central Serengeti. However, other species are more sedentary. These are year round residents: impala, warthog, buffalo, topi, kongoni and Grant's gazelle. Wildebeest Behaviour Wildebeest females give birth around the same time; few tropical mammals have such a restricted birth season, with 80%-90% of calves dropped during a 3 week period (Estes, 1991). At this time of year, wildebeest herds are at their most structured, with groupings of pregnant cows and of cows that have calved, groups of yearlings, and bachelor herds. During the breeding season or rut, bulls defend territories and attempt to herd females in these territories and keep out intuding males. This is quite a difficult task as the cows are migrating, so the bulls have to constantly move and set up new territories. During the rut, the bulls are constantly calling, creating a distinctive humming sound. The timing of calving and rutting is geared to rainfall in such a way that both occur under favourable conditions. The rut occurs at the end of the rains when the animals are in peak condition. While, calving occurs at the begining of the period of most reliable rain - thus ensuring an abundance of fresh pastures for the lactating cows. Zebra Behaviour Zebra's in Serengeti have a harem system. A stallion herds and defends 2-5 mares and his offspring by them from against other malesand against predators. Though unrelated, harem females spend their adult lives together, and continue to associate together even if the herd stallion is replaced. The Migration and Carnivores Hyenas commute large distances on a weekly basis, covering up to 100km from their den sites to the migration. Lions on the other hand tend to defend their territories and not move as much. However, during the rainy season, lion prides from central Serengeti will move south to the short grass plains to feed on the abundant herds of wildebeest. Lions in Serengeti have a period of gluttony when the migration is in town, followed by a period of starvation when the herds leave their territories. Cheetahs feed on smaller prey (e.g. Thompson gazelle), but have a feeding frenzy during the calving period. Leopards are similar to lions in that they have territories. Other species that are reliant on the migration for survival include crocodiles and the various species of vulture. The crocodiles are adapted to surviving for long periods without food, and feeding when the migration passes their territories. Vultures on the other hand employ the same technique as hyenas and cover large distances in search of food . For more information visit Wild Things

About the Author

Roy J Hinde M.Sc. is a former research scientist who now is a director of Wild Things Safaris Ltd Wild Things