Wildebeest are serious herd animals. They come into the Mara by the thousands, and reach several million during the summer. They are not the brightest, or most alert, so they normally follow the grevy zebra, and hope for the best. The zebra eat different parts of the grass, so they can live together without competition. In order to make it into the Mara from Tanzenia the wildebeest have to cross a couple of crocodile-infested streams and rivers. They tend to let momentum push them through and only a few of the thousands at each crossing actually get eaten! Wildebeests are prime cat-food.