Except in years of exceptional drought, the Great Migration has reached the Southern plains of the Serengeti and the Ngorongoro Conservation Area, where pastures are fertile and rich in nutrients.
The herds spend the following months here until the calves, born in January and February, are strong enough to take their way, the pastures in the area are completely exploited and seasonal torrents and ponds have dried out.
Like in the following months, in December the herds move within this area, following sporadic downpours that make grass grow. 
Numerous predators gather here due to the presence of the Great Migration and also because they are waiting the births: 400,000 wildebeests and zebras are born in 2-3 weeks. This sort of “synchronised delivery” is a form of defence of the species: coming to light altogether the calves are more likely to survive the onslaught of predators.
The wildebeest is probably one of the most precocious mammals at birth: after 2-3 minutes after delivery, the calf can already stand up and after 5 minutes is ready to run.
The animals stay in these plains for the following months, the time it takes the mothers to wean their calves, so they are ready to migrate with the herds, thus beginning another cycle in the ecosystem of the Serengeti and continue a phenomenon that has occurred endlessly for thousands of years.
The Olduvai rock engravings depicting the Great Migration are tangible evidence of this phenomenon. 

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

Lake Ndutu and Lake Masek: around these reliable sources of water available throughout the time the animals stay here, there are marshy areas and fertile low-grass savannahs, that are the favourite by the wildebeests and zebras, as they are rich in nutrients. In addition to Great Migration animals, the area is inhabited by giraffes, elephants, different species of gazelles and antelopes, hippos, crocodiles, ostriches, spotted hyenas, lions, wild dogs, vultures and over 400 species of birds.
Moru Kopjes: this area links Ndutu to the Seronera valley. The presence of numerous kopje make the landscape very scenic. There is no lack of water here but the pastures are less fertile compared to the Southern Serengeti and the Ngorongoro Conservation Area. Here the herds scatter all around and move incessantly from one place to another.
Many animals live here, including lions, leopards, rhinos, buffalos, giraffes and various species of antelopes.
Seronera: in this area there is the highest concentration of cats, namely lions and leopards, thanks to the presence of a perennial river, the Seronera, and trees that offer the leopards a privileged position and a great hiding place for the ambushes. 

Discover the Great Migration map here

Discover the location of the Great Migration month by month