More than 200,000 saiga antelope died suddenly over the course of a couple weeks in 2015. Scientists blamed bacteria called Pasteurella multocida type B. But new research suggests the antelope already contained the organism in their bodies, and that unusual heat and humidity released the bacteria, causing them to multiply rapidly in the days leading up to the event.
Over several hundreds of miles of central Kazakhstan, antelope began showing symptoms of blood poisoning, called hemorrhagic septicemia. Suddenly, they stopped eating. At first, one or two antelopes would die. But by the end of the seventh day, they were all dead.
Pasteurella multocida type B is so toxic that an infected animal doesn’t have time to show many symptoms. It normally lives in the antelope’s tonsils, but during the event, they quickly spread to the bloodstream, causing the hemorrhaging.
The presence of bacteria alone is not enough to explain the mass death. So, Richard Kock from The Royal Veterinary College and his team developed models that looked into two other extinctions (1981 and 1988) caused by hemorrhagic septicemia. They analyzed environmental conditions like temperature, rainfall, wind, and vegetation. Here’s Merrit Kennedy reporting for NPR:
“You have unusually high levels of humidity each day over that 10 day period. And by doing that we could really tease it out and get a significant correlation,” says Kock. That makes sense, he says, “because the bacteria in the tonsils, they’re quite close to the environment of the air and they then basically, presumably, respond to that change in atmosphere. And that triggers them to start growing.”
Only 30,000 saigas in the region survived, and while they are rapidly recovering and breeding, scientists don’t believe they could survive another event like this.
What’s more, evidence suggests that animals like reindeer and musk ox face similar risks due to abnormal weather patterns.