Amid the fertile short-grass plains of the southern Serengeti, Ndutu, and the Greater Mwiba Protected Wildlife Area, around 8,000 calves take their first unsteady steps every day. Nearly half a million are born within the space of three weeks — and the predators (lions, cheetahs, leopards, and hyenas) are never far behind.

Darkening skies at the end of March herald the arrival of the long rains, triggering the herds’ journey northwest. This marks the start of the rutting season, where males clash in competition for females, their aggressive grunts echoing across the plains.

The fast-flowing waters of the Mara River in the north set the stage for the herds’ desperate dash to reach the rain-soaked plains of Kenya’s Maasai Mara. The crossings are not a single event — they unfold over months, at multiple points along the riverbank, sometimes several times a day. When the megaherds move, thousands of hooves thunder into the churning water at once. When they don't, handfuls of stragglers can be seen picking their way across.

Short rains summon the herds back to the Serengeti. To get there, they face the danger of the Mara River once more, crossing in waves as they flow south toward the calving grounds where the cycle begins anew.