education.nationalgeographic.org/resource/wildebeest-migration

More than 1.5 million wildebeest migrate in an enormous loop every year, from Tanzania to Kenya Masai Mara and back.
The annual migration northwest, at the end of the rainy season (usually in May or June) is recognized as one of the "Seven Wonders of the Natural World."

The search for greener pastures does not come without danger. Its migration route crosses many rivers with steep banks, most filled with giant Nile crocodiles.