DATE: January 17, 2018

SNIP: Over the span of three weeks in 2015, more than 200,000 saiga antelope suddenly died in central Kazakhstan.

Scientists knew that bacteria called Pasteurella multocida type B caused the mass death. Now, new research suggests that the bacteria was already present in the animals; it was triggered and became harmful because of a period of unusual weather.

Richard Kock, a professor of Wildlife Health and Emerging Diseases at The Royal Veterinary College, witnessed the “rapidly accelerating death.”

“You went from one or two animals to within three or four days — thousands. And then they were all dead by the seventh day,” Kock tells NPR. “The animals were showing normal behavior, normal signs, normal grazing and then suddenly they’d start looking a little bit unhappy and stop feeding. Within about three hours they were dead.”

But the bacteria alone were not enough to explain the mass fatalities, which only 30,000 of the area’s critically endangered saigas survived.

In a paper published today in Science Advances, the scientists say that they believe “virtually 100 percent of adults” already had the organism present in their bodies. An environmental factor must have triggered the bacteria to proliferate and kill these animals at the same time.

The culprit, Kock says, is a period of unusual heat and humidity in the ten days leading up to the mass death.

And while they are now recovering and breed quickly, it’s not clear whether they could survive another event like this. “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.

There’s evidence that unusual weather patterns could be having similar impacts in other animal populations, such as reindeer and musk ox. “We may be looking at a much more global effect,” he adds.