The great migration of wildebeest, zebra, topis and Thomson’s gazelles is the ceaseless pursuit of green grass produced by the rains as they move across the savannah. As the rains move north, the herds cross from Tanzania into Kenya’s Maasai Mara, and face the biggest challenge of the migration – crossing the mighty Mara River.
The Mara river cuts deep into the red savannah soils, creating sheer cliffs ten meters high on either side. Its bends are home to grumpy hippos, and its length is patrolled by marauding monster crocodiles. The crocodiles can grow to over twenty feet in length, and weigh more than a ton, yet lie absconded beneath the muddy waters, watching the places where the banks slope more gently into the river creating opportunities for crossings.
Living up to one hundred years, they are the most experienced hunters on the savannah, using guile, surprise and brute strength to grab animals and drag them into the deep waters for horrifically violent deaths. They have survived 200 million years of evolution, designed as the perfect hunters. For many animals in the migration, it is their first sight of such a river, definitely their first attempt at crossing one, and they cannot imagine that the emotionless reptilian eyes they see approaching are just the small visible part of one of the most frightening killing machines nature has ever created.
The herds approach the river in great winding lines mimicking the river itself. They perch on the shores, the zebra scanning the waters for danger, and the wildebeest standing in vacillation, awaiting one to emerge as a leader. The energy of the herd waxes and wanes. As they push closer to the water, the nasal honking of the wildebeest surges, and they jostle each other to the water’s edge.
Any one animal can lead, and similarly, if any animal is startled, it can retreat back up the banks, and either way the entire herd mindlessly follows. This creates commotion and circular trips up and down the banks, and in doing so, other herds are drawn in, thirsty from grazing in the sun all day, wanting a drink and smelling green grass across the river.
Then the herd’s energy crescendos, and one frantically lunges forth into the river, and as if on autopilot, the whole herd plunges in behind it. Hundreds of thousands of hooves beat down on the soil, and huge clouds of dust rise-up over the savannah. The dust veils the herds, and animals leap out from it, as ghosts from crossings past, suspended in mid-air before splashing into the muddy waters below. The crocodiles inch forward through the ripples, patient, observing, carefully choosing a target among the masses.
The herds form a line as they cross, sometimes single file, and sometimes four or five animals abreast depending on their numbers. The line bends down river with the current, and in the frenzy, animals kick, and leap over each other, breaking backs, legs, and hooves, and drifting down river into the jaws of waiting giants.
After a couple weeks of crossings, the rivers are littered with bloated bodies, which crocodiles store in strategic locations, vultures pick on from above, and hyenas drag from the shores back to their dens. One would think — given the danger — that crossings would happen fairly infrequently. Once as animals cross to the plains of the northern Mara, and again as they return south to the Serengeti to calve. However, this is not the case, and it is fairly common to even see animals crossing in different directions at the same time.
The beacon which the migration follows are the thunderclouds on the horizon and the wafting smells of green grass, but those can be erratic, and make animals constantly think the grass is greener on the other side of the river. Further, crossings are often disrupted, commonly by a monster crocodile that swims into the herd, ripping one from the ranks, and spooking the rest of the herd. Mothers can be separated from their young, leaving animals calling each other across the river, and sometimes a reverse crossing occurs to reunite family units.
The waters of the Mara River give life to the surrounding ecosystem but their depths also take it violently away. These swirls of motion are eddies in the flow of the migration. The crossings add chaos and disorder to the grazer’s lifecycle, creating opportunities for predators, which in turn keep the herds strong by culling the weak. It is the pinnacle of excitement in one of the greatest natural spectacles on earth, inciting a migration of travelers to the shores of the Mara every year, a herd that everyone should aspire to join at least once.