In 2015, 200,000 endangered antelope dropped dead in Kazakhstan. This is what killed them

Mary Bowerman | USA TODAY

Show Caption Hide Caption Why are so many antelopes dying? According to a study, a bacteria was present and harmless in the animals bodies before the massive die-off, but became deadly because of unusual changes in temperature.

In 2015, more than 200,000 endangered antelope died within three weeks in Kazakhstan, prompting worldwide interest in the massive die-off, and causing many to wonder: How did this happen?

At the time, researchers believed the saiga antelopes, which are critically endangered, died from hemorrhagic septicemia caused by a bacteria known as Pasteurella multocida type B. According to a study, published in Science Advances on Wednesday, that bacteria was present and harmless in the animals bodies before the massive die-off, but became deadly because of unusual changes in temperature.

The researchers believe that higher than usual humidity and warm temperatures in the days before the die-off caused the bacteria to grow.

"The fact that P. multocida infection in saigas ... appears strongly linked to high humidity and temperature is of concern going forward, given that a climate change–induced increase in temperature is projected for the region over the short to medium term," the researchers wrote.

For the study, the researchers compared the 2015 die-off, to two other similar events, one in 1981 and 1988, which were likely caused by hemorrhagic septicemia like the most recent event.

Richard Kock, a professor of Wildlife Health and Emerging Diseases at The Royal Veterinary College, told NPR that in the 2015 event, 30,000 saiga antelope, who were not in the same location as those that died, likely survived because they were in areas not affected by the high temperatures.

Kock told NPR that the herd has recovered and continue to breed, but if another weather event happens they could be wiped out.

"If we get a similar event, and all the animals are within a sort of weather envelope, it could be total extinction. It could happen in a week," says Kock.