The Great Wildebeest Migration – also called the Gnu Migration, Serengeti Migration or Masai Mara Migration – is one of the world’s last great wildlife spectacles. Every year, more than two million animals move across the Serengeti–Mara ecosystem, following ancient instincts in search of rain-fed pastures.

It’s the number one reason why thousands of travelers choose a Kenya and Tanzania safari, especially around mid-year when dramatic river crossings take place.

But the Migration is also one of nature’s biggest mysteries: we know the herds will move, but not exactly when. We know they’ll cross the Mara River, but nobody – not even the wildebeest – knows the precise moment. That unpredictability is part of what makes this journey so remarkable.

How the Migration Works

The herds are driven by survival:

• Food & Water: They follow the rains and the growth of new grass.
• Breeding & Calving: Wildebeest synchronize births with the lush green season to give calves the best chance of survival.
• Instinct & Movement: Some experts suggest they are triggered by storms and distant lightning, but the truth is still debated.

Because this is a year-round cycle, there’s no real beginning or end – just a continuous clockwise movement through Tanzania and Kenya.

How the Migration Works

• January – Southern Serengeti: Herds gather near Ndutu and Lake Masek. This is calving season, with mega-herds breaking into smaller groups.
• February–March – Ndutu Plains: Around 8,000 calves are born daily. Predators thrive, making this a dramatic time for safari.
• April – Central Serengeti: As the long rains begin, wildebeest drift northwest. Rutting season (breeding) brings fierce battles between males.
• May – Western Serengeti: Huge columns stretch for miles. Stronger calves mean the pace quickens.
• June – Grumeti Region: The herds prepare for dangerous river crossings where massive crocodiles lie in wait.
• July – Northern Serengeti: The Mara River crossings begin. This is safari’s most sought-after moment – powerful, chaotic, and unforgettable.
• August – Masai Mara (Kenya): Considered the best month to witness crossings and vast herds grazing on the Mara plains.
• September – Split Herds: Some wildebeest remain in the Serengeti, others dominate the Mara. Excellent game-viewing in both countries.
• October – Mara Conservancies: Herds linger in Kenya before rains call them back south. Private conservancies offer fewer crowds and exclusive safari experiences.
• November – Returning South: Short rains trigger the movement back toward the Serengeti. Smaller groups gather in the north and east.
• December – Eastern Serengeti: Fresh grass draws the herds south, completing the circle before calving begins again.

Can the River Crossings Be Predicted?

In a word: no. Some wildebeest plunge in immediately, others wait days, and some turn back entirely. If you want the best chance of seeing a crossing, allow several days in the northern Serengeti or Masai Mara, ideally staying in a mobile camp that moves with the herds.

Best Time to See the Migration

• Calving: February–March in the Southern Serengeti.
• Rutting (breeding): April–May in Central & Western Serengeti.
• Grumeti Crossings: May–June in the Western Corridor.
• Mara Crossings: July–August in Northern Serengeti & Maasai Mara.
• On the Move: November–January as herds travel south again.

Key Things to Remember

• The Migration is a year-round cycle – you can see it at any time, depending on where you go.
• River crossings are unpredictable; patience is essential.
• The herds are not one single group, but many mega-herds spread across vast distances.
• The Serengeti holds the bulk of the migration, but the Mara offers spectacular viewing mid-year.