The great migration month by month: what the calendar knows and what it only promises

The great migration calendar is reliable on place and season and unreliable on the two things that sell best: the day of a river crossing and the number of animals. The herds circle between the southern Serengeti and the Masai Mara behind the rain, so every row of the table shifts by a few weeks; they are in Kenya from July to October and in Tanzania all year. And the number in the brochures is an aerial estimate that has not moved since the 1970s — a satellite count in August 2022 and 2023 found fewer than six hundred thousand.

GuideThe Serengeti beyond the calendar — camps, prices, how many days?Serengeti →

One table, two countries

Kenya — July to October; Tanzania has herds all year. A shift of a few weeks either way is the rule, not the exception: the herds follow the rain, not the date.

How many there really are

The figure of more than 1.3 million wildebeest comes from counts made from aircraft and has barely changed since the 1970s; in the 1950s there were about 250,000. A research team counted the herds on satellite images of the northern Serengeti and south-western Kenya in August 2022 and 2023, over more than four thousand square kilometres, with two artificial-intelligence methods: about 330,000 in the first year and 500,000 to 530,000 in the second — and those figures include zebra, which a satellite cannot tell from wildebeest. The paper, published in PNAS Nexus in 2025, leaves two explanations: aerial counts take a sample and extend it over ground nobody flew, or there really are fewer animals, through lost habitat, climate and predators. Neither has been ruled out.

For a traveller it means the number in the brochure is an inheritance, not a measurement — and the same goes for the number of calves, worked out from the same estimate. The calendar does not change: in August the herds are where they always were, only nobody knows exactly how many.

Of everything in the loop, the calving is closest to a timetable. The females give birth almost together — within a window of about three weeks, according to a study published in Scientific Reports in 2018 — on the short grass of the southern Serengeti and around Ndutu, in late January and February. The window repeats every year on the same stretch of plain, so February is booked by date.

The Mara crossing is the opposite case. From August to October the herds are along the river on both sides of the border and cross it in both directions, but nobody can sell the day or the place — an operator who guarantees it is selling something they do not have. So a crossing is bought not with a date but with nights by the river.

When to goHow many nights and which camp for a crossing, on the Kenyan side:The best time to visit Masai Mara →

The decision by goal

• A sure sight on a date: late January or February, the southern Serengeti and Ndutu — Tanzania.
• A river crossing: August or September, the northern Serengeti or the Mara; plan by nights, not by day.
• Kenya outside July–October: the Mara has its own animals then, but not the migrating herds — a safari, not the migration.

When to goThe Serengeti month by month, with rain and prices:The best time to visit Serengeti →