Thousands of wildebeest die every year [P 012 & P013 / crossing rivers] and lakes. Most drownings occur in the Mara and Grumeti Rivers of the woodlands. The wildebeest in the front portion of the herds slow down when they approach the banks of the river. The momentum from behind pushes them into the river and they are often swept away by the currents.
The dense vegetation along the river banks provide cover for lions. Feeling threatened, the animals push forward causing a chain reaction of wildebeest plunging into the river trampling and drowning the individual in front. The weaker and more vulnerable are often swept away by the currents or fall prey to crocodiles.
By the time the rear of the herd reach the opposite side, the banks of the river are muddy and difficult to climb. Many slip back into the water and drown while other are swept off the banks by crocodiles and pulled under. Predators also ambush the exhausted animals when they emerge from their struggle up the river banks.
The losses from the river crossings varies from year to year depending on the height of the river, number of animals crossing at one time and the crossing locations.
Hundreds of calves die each year in the unexplainable [V 003 / crossing of Lake Lagarja] on the plains. Every year, some females attempt to cross the lake with their young calves while most walk around the lake and never cross it. In addition to accidents at river and lake crossings, wildebeest are often trampled and fall into gullies during night stampedes.
