Every year, up to 1.5 million wildebeests as well as hundreds of thousands of other animals, including zebra and gazelle, migrate between Tanzania's Serengeti and Kenya's world-famous Maasai Mara National Reserve.

The year-long, continuous cycle sees the animals travelling thousands of kilometres, in one of the greatest wildlife spectacles on earth.

The migration has a spot on Africa's Seven Natural Wonders list and is a major draw for wildlife enthusiasts and tourists from around the world. This photograph, from the "Make It Kenya" tourism and commerce public relations campaign, shows a large herd of wildebeests breaking into a run after crossing the Mara River in Kenya on Tuesday.

The wildebeests, which earned their Afrikaans name meaning "wild beast" for their menacing appearance, begin their spectacular northward migration in search of greener pastures. The journey is dictated by weather patterns but usually begins in May or June, and features impressive crossings of the Mara River where the animals risk their lives to stampede through the water and are often attacked by crocodiles.

A wildebeest can weigh up to 272kg and live up to 40 years - that is, if it survives the hazardous journey.