Wildebeest are well known for their annual migration to new pastures. Many wildlife documentaries have featured this event, in which vast numbers of wildebeest can be seen crossing rivers, such as the Mara River and dying in large numbers as they attempt to reach the other side, because many of them are eaten by crocodiles while others simply drown. Although it is commonly assumed that this is simply a frenzy and that the wildebeest cross blindly, recent research has shown that a herd of gnu possesses what is known as a “swarm intelligence”, whereby the animals systematically explore and overcome the obstacle as one. Wildebeest have an apparent maximum running speed of around 64 km/h (40 mph).