Did you know there many different annual migrations in Africa? The most famous one is the annual wildebeest migration in East Africa, but there are numerous others. It is quite obvious if you think about it. Everywhere, animals need to migration to find water and grazing according to the seasons.
Here is another migration that happens in Botswana:
http://blog.sunsafaris.com/2012/11/14/a-migration-through-the-makgadikgadi/
The Great Wildebeest Migration moves through the Serengeti and Masai Mara National Parks. We track their progress. The migration path varies from year to year depending on weather and other environmental factors. The blog is the simpliest way to get an understanding of the movements based on recent past movement patterns.