Animal migration is the relatively long-distance movement of individuals, usually on a seasonal basis. It is a ubiquitous phenomenon, found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The trigger for the migration may be local climate, local availability of food, the season of the year or for mating reasons. To be counted as a true migration, and not just a local dispersal or irruption, the movement of the animals should be an annual or seasonal occurrence, such as birds migrating south for the winter, or a major habitat change as part of their life, such as young Atlantic salmon leaving the river of their birth when they have reached a few inches in size.
The wildebeest (pron.: // WIL-də-BEEST or // VIL- , plural wildebeest or wildebeests, wildebeesties (juv)), also called the gnu (pron.: // NOO or // NEW ) is an antelope of the genus Connochaetes. It is a hooved (ungulate) mammal. Wildebeest is Dutch for "wild beast" or "wild cattle" in Afrikaans (beest = cattle), while Connochaetes derives from the Greek words κόννος, kónnos, "beard", and χαίτη, khaítē, "flowing hair", "mane". The name "gnu" originates from the Khoikhoi name for these animals, gnou.