WHY DO ANIMALS MIGRATE?
There is combinations of factors that cause animals to migrate. The main reason however, is to ensure enough food and water throughout the year. In the Serengeti Ecosystem animals basically alternate between the Short Grass Plains in summer and the wooded, tall grass areas in winter. The short grass plains have a low rainfall and lack surface water, except for the temporary pans during the wet season. The tall grass woodland in the north and west has a higher rainfall with perennial rivers.
WHICH ANIMALS SPECIES MIGRATE?
Form the bulk of the migration, being the numerous. They prefer short grasses but they do eat tall grasses, especially after these have been “trimmed” by Zebra and Buffalo. They thrive on the new shoots of grasses.
Form the second largest group of migratory animals and largely follow the same route as the wildebeest. They congregate on the plains during the rainy season when food is abundant. AS soon as becomes scarce, they break up and disperse in the family units. Their dispersal minimizes grazing pressure in the low production tall grasses areas.
They have the ability to browse [eat leaves] as well as graze [eat grass] and are very well adapted to almost any environment from lowlands mountains. Although they do not follow the same migratory route as Wildebeest, they also alternate between the plains and woodland.
They have a much shorter route than the Wildebeests. They feed only on short grasses, herbs and forbs. They are the first to arrive on the plains and the last to leave.
They do not really need to migrate as they are water independent, but they do move to a limited extent, mainly locally. Their route is in some cases opposite to that of migratory species, spending the rainy season in open patches within the woodland and the dry season on the plains.
THE ANNUAL MIGRATION PATTERN IN THE SERENGETI ECOSYSTEM.
Early dry season [July to October]
This is when the bulk of the migratory herds find itself in the western corridor, where they cross the Grumenti River in about May/June. Some reaches the Mara River already in early July. During September and October, some of them spill into the Masai Mara game Reserve.
Some of the herds never go as far north as the Masai Mara Game Reserve.
Late wet season [April to June]
During this time there is a general movement to the northwest of the plains along the Simiyu, Mbalageti, Seronera and Nyabogati Rivers to the western corridors which they reach in about June. Part of the population moves directly north through Seronera and a smaller section moves north in the eastern side of Serengeti, through the Loliondo area.
Late dry season to early wet season [October to December]
In the late dry season, bulk of the migration herds starts trek south through the lobo area and along the eastern boundary. Some move straight south through Seronera. Most of the herd will have reached the short grass plains by the middle of January. They have their young in January and February. After which they move around on the plains, following local rainstorms.
Early wet season [December to April]
During this time the animals are mainly on the short grass plains west of Gol Mountain in the Ngorongoro Conservation Area, at Gol Kopjes, Barafu Kopjes, Naabi gate and Lake Ndutu. If there is a dry spell in between, they move west into the Maswa Game Reserve and to the Mbalageti Valley. At the first signs of rain, they move back on the Serengeti Plains because instant availability of new growth.
Note that; This Migration pattern is not fixed. It depends with climatic condition of the respective year.