A fatal miscalculation appears to be responsible for a tragic mishap that killed about 10,000 migrating wildebeest attempting to cross Kenya's Mara River in late September.

The deaths occurred at Kenya's Maasai Mara National Reserve as the herd was beginning to swing toward the east on its way back to the Serengeti. Conservationists estimate the fatalities account for about one percent of the total number of the species in East Africa.

Terilyn Lemaire, a conservation worker with the Mara Conservancy who witnessed the incident, wrote in her blog that the deaths occurred as the wildebeest tried to cross the waterway, "at a particularly steep and treacherous point."

After the first animals fell into the river and drowned, thousands more continued to stampede into the water on top of them, according to Lemaire.

She points out that many of the animals die in similar incidents during each migration, but not on such a tragic scale.

"Every year, there are one or two days where the wildebeest pick a terrible crossing point and, regardless, throw themselves into the Mara River to their drowning deaths. It is unusual, however, for the number of single die-offs to exceed one thousand," Lemaire wrote.

She added that Kenyan wildlife authorities considered blocking off the lethal crossing point when the number of fatalities began to mount, but they later decided to let nature take its course.

"The crocodiles, storks, and vultures have not had to worry about where to find their next meal," Lemaire concluded.

Photo: Terilyn Lemaire - Lara Conservancy/Wildlife Direct