Unheard of' Mass Death That Wiped Out 60,000 Endangered Antelope in Four Days Still Baffles Scientists

Back in May, an already critically endangered species of antelope suffered a devastating blow as a mass death hit the population as a whole. Scientists have some clues as to what might have caused the rapid die-off of saiga antelope in Kazakhstan, but much of it still remains a mystery.

According to Nature, within a short period of time half of the saiga antelope population in the country — about 134,000 head — died. The species has been subject to unexplained die-offs in the past, but this one in particular raised eyebrows.

“I have worked in veterinary diseases all my career and I have never seen 100 percent mortality,” wildlife veterinarian Dr. Richard Kock with the Royal Veterinary College told Nature at the time. “We had a herd of 60,000 aggregated and they all died. That is extraordinary.”

"The death of Saiga antelopes in such large numbers is almost a personal loss to all those who work in researching and protecting this steppe species," the Association for the Conservation of Biodiversity of Kazakhstan, which is investigating the death, said in a statement.

Live Science more recently reported that this herd of 60,000 specifically was wiped out within four days, the green landscape dotted with the tan carcasses of dead antelope.

We know what killed all those saiga antelope back in May. But we don't why. https://t.co/bpUKIpmMxH

— E. Van Every (@E_VanEvery) September 4, 2015

Scientists took samples form the animals and the environment and have since been analyzing them, hoping to figure out the cause.

So far, geoecologist Steffen Zuther with the Altyn Dala Conservation Initiative told Live Science that toxins associated with Pateurella and possible Clostridia bacteria were seen in the samples from the animals, which suffered extensive bleeding from their organs.

Pasteurella, Live Science noted, is common in ruminants like these antelope and is not usually harmful when the animal is otherwise healthy.

"There is nothing so special about it. The question is why it developed so rapidly and spread to all the animals," Zuther told Live Science.

Scientists know the saiga antelope died after suffering bleeding from their organs, but they're still trying to determine why. (Photo credit: Shutterstock)

Here's more on the speculation:

So far, the only possible environmental cause was that there was a cold, hard winter followed by a wet spring, with lots of lush vegetation and standing water on the ground that could enable bacteria to spread more easily, Zuther said. That by itself doesn't seem so unusual, though, he said.

Another possibility is that such flash crashes are inevitable responses to some natural variations in the environment, he said. Zuther said he and his colleagues plan to continue their search for a cause of the die-off.

Zuther told Live Science the saigas play a role in keeping vegetation at bay, thus helping prevent some wildfires, and perform other ecological services. He noted that where saigas are observed, other species are more abundant as well, some using the antelope species as a food source.

Based on its 2014 estimates, prior to the die-off, the Association for the Conservation of Biodiversity of Kazakhstan had said saiga antelope numbers were around 256,700.