Every year a mass exodus occurs between the Serengeti in Tanzania and Maasai Mara in Kenya. More than 1 million wildebeest, zebras and antelope migrate in an almost circular tour as they look for fresh pastures for grazing.

It's a breathtaking spectacle that occurs between late July when the animals first go north and again in early October when the last group returns south.

Droves of animals cross the vast, crocodile-filled Mara River and run across plains teeming with predators like cheetahs, lions and other large wild cats. As the river swells, the trek becomes an ever-increasing test of survival.

The natural spectacle is considered an unofficial wonder of the world.

The wildebeest and other animals are on the move year-round, though these particular times of year and this section of the Maasai Mara National Reserve garner the most attention. As one site describes it: "…there is neither start nor finish to their endless search for food and water, as they circle the Serengeti-Mara ecosystem in a relentless sequence of life and death."

Ben Bolton looks at everything through a video lens.

Watch as hundreds of wildebeest cross a river during the Great Wildebeest Migration
Watch as hundreds of wildebeest cross a river during the Great Wildebeest Migration in Maasai Mara National Reserve.