The Great Migration isn't a single event but a continuous, year-round movement of roughly two million wildebeest, zebra and gazelle following the rains in search of fresh grazing. Where they are depends heavily on the month.
Between December and March, herds gather on the short-grass plains of the southern Serengeti for calving season, which is also when predator activity peaks, as lion and hyena take advantage of the vulnerable young calves.
By April and May the herds begin moving north and west through the central Serengeti, and by June and July they're pushing toward the Grumeti River, where smaller but still dramatic crossings occur.
The Mara River crossings, the image most people associate with the migration, usually happen from July through September as herds push into the northern Serengeti and across into Kenya's Maasai Mara, before turning back south again around November.
