At this time of year, the northern Serengeti teems with wildebeest. This alone is an unforgettable sight – when the herds mass along the riverbanks in readiness to cross, the tension is palpable. Ahead lies the lure of fresh grazing – yet to reach it they must risk their lives in these treacherous waters where monstrous crocodiles lie in wait. If they survive the crocodiles, they still face the dangers of cliff-like river banks slick with mud and churned by the frantically scrambling wildebeest crushed together. Ever-present predators add to the dangers, and you can be sure of drama all round.

Our second day along the Mara had already provided some incredible sightings of other wildlife, and we were excited by the prospect of a potential river crossing. Mid-morning, we headed towards a likely spot, and were rewarded with the sight of several thousand wildebeest gathering along the far bank. This was a promising sight, and it was clear that they were building up the courage to literally take the plunge in their constant search for new grass. We waited just half an hour or so until the bravest animals led the charge down the bank and into the brown waters. This was the signal for the rest to follow, and soon we were watching the entire herd pour down the steep slopes into the river.

It’s one of the most spectacular sights imaginable, and the sheer noise and tension of this mass of tightly-packed animals swimming across and scrambling up the other side is unforgettable. Fortunately for these wildebeest, none of the crocodiles were feeding here, and the entire herd crossed unscathed. Often in these crossings of several thousand or so, some individuals are taken by the crocodiles and many more drown in the crush of bodies and flailing hooves so typical in the chaos. Further upstream we saw the surreal aftermath of such a crossing – hundreds of carcasses drifted with the currents and wedged up against the rocks, swirling in the eddies, with far too many casualties for the predators and scavengers to consume.