From BBC Earth's Arj Singh:
You could say it is the best of times and the worst of times for the herbivores of the Serengeti.
The arrival of the rains in the south is a precursor to one of the world's largest migrations.
One and a half million animals, including wildebeest, buffalo, gazelles and zebras, come together to take advantage of the bountiful food in the fast-growing lush grasses.
[You can see all sorts of videos and images of other migrating animals including humpback whales, Monarch butterflies and more over on our Facebook page, where you can also enter a photo competition and win DVDs.]