The rainy season, especially in the second half of the month, draws to a close and the showers and storms become less frequent.
The marching herds leave the central part of the Serengeti to head North-West, towards the Western Corridor.
Endless rows of wildebeests and zebras walk ceaselessly along two main ways: the first route starts West of the Seronera region and along the river Mbalageti further on to Kirawira; the second one starts North of Seronera and follows the river Grumeti.
It’s also the time of mating: half a million wildebeests mate in less than a month. The peak of pregnancies seems to be influenced by the May/June moon.
This phenomenon is at the origin of the “synchronised deliveries” in January, when the Great Migration will be back to Southern Serengeti and the Ngorongoro Conservation Area.
Fighting among dominant males for the supremacy on the territory and for the right of mating are quite frequent.
Usually fights are not violent and the species do not suffer serious wounds or injuries. 
Quite curious is the fact that although males fight for the females, the last choice lies with the females, who decide with which to mate. 

Where is possible to spot the herds of Great Migration in May

The Musabi and Mbalageti plains: here you can also find the highest concentration of Topi antelopes and, with a bit more luck, you can spot the patas monkey.
The Ndabaka plains: South of the river Grumeti in the direction of Lake Victoria. Here you can spot buffalos, elephants, giraffes, Topi antelopes, waterbucks, lions and cheetahs. If you are lucky, here you can also see patas monkeys.
The circuit along the river Grumeti: zebras and wildebeests arrive here from the Ndabaka plains and gather on the South bank of the river, they are so many and some are forced to cross the river infested with Nile crocodiles and reach the opposite bank, where they find new pastures.
Black-and-white colobus monkeys find shelter on the branches of the trees in the forests lining the banks of the river, and it is quite easy to spot leopards.
The Ruwana plains: North of the river Grumeti, the animals that successfully cross the river come here where they find fresh grassy plains.
Giraffes, elephants, buffalos, various species of antelopes, lions and cheetahs reside here.

Discover the Great Migration map here

Discover the location of the Great Migration month by month