October 1, 2007—Scores of wildebeest washed up dead at a bend in Kenya's Mara River after some 10,000 of the animals drowned in a bizarre mishap there last week.

The deaths, which occurred over the course of several days, are said to account for about one percent of the total species population.

As the animals passed through southern Kenya during their annual migration, part of the herd attempted to cross the fast-moving Mara at a "particularly treacherous" point, according to Terilyn Lemaire, a conservation worker with the Nairobi-based Mara Conservancy who witnessed the incident.

"Once they jumped into the water, they were unable to climb up either embankment onto land and, as a result, got swept up by the current and drowned," she wrote in an email to National Geographic News.

Even as the first animals into the river struggled and failed to cross, thousands of others continued to stampede into the water behind them, Lemaire said.

Some 2,000 wildebeest drowned at the crossing in a single afternoon, she estimated.

Drowning deaths are not uncommon during the wildebeests' migration, but Lemaire said her organization has never witnessed fatalities on this scale.

"It is customary every year for the wildebeest to pick a particularly treacherous crossing point and for there to be a significant die-off," she said, "but the number of deaths during these crossings almost never exceeds one thousand."

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