The saiga antelope, an ice age relic, once roamed alongside woolly mammoths and saber-toothed tigers. Today, the population of this ancient species is in collapse. In just a 15-year period, their numbers have dropped by 95 percent, which represents the sharpest collapse for a mammal species ever recorded. Poaching and habitat loss are historically the main culprits, but in 2015 a new scourge arrived: a bacteria that wiped out more than 200,000 saiga in a matter of weeks, nearly half of the remaining worldwide population, reports NPR.

It's difficult to comprehend the loss that this species has suffered in such a short time. "Apocalyptic" is not too strong a word.

"You went from one or two animals to within three or four days — thousands," Professor Richard Kock of The Royal Veterinary College told NPR. "And then they were all dead by the seventh day."

So what could cause such a mass die-off?

Scientists revealed in a January 2018 study the dead saigas suffered from a bacterial disease, hemorrhagic septicemia, caused from Pasteurella multocida type B. However, the presence of the bacteria alone did not kill the animals. The same bacteria has been found in healthy, living saigas too. Environmental factors leading up to the days of the mass dying played a key role. The study showed the area had abnormally high relative humidity and temperatures.

Therefore, scientists believe the saigas were healthy with the bacteria Pasteurella multocida type B and didn't fall ill until exposed to changing weather.

"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," said Kock. "And that triggers them to start growing."

The disease strikes with alarming quickness. Animals typically die within hours of developing symptoms, which include depression, diarrhea and frothing at the mouth. The only good news is that the mass die-off appears to be over, as few new deaths have occurred since the initial collapse.

Recovering from the mass die-off

One reason for optimism is that the saiga is a resilient animal, and the species has survived population collapses in the past. Though not as severe as the recent die-off, similar events also occurred in 1984, 2010 and 2012, and the species was able to recover. Part of the reason the saiga is so well-adapted to such population collapses is that the animals have a high reproductive rate. They regularly produce triplets and have the highest fetal biomass of any mammal.

Still, it's a long uphill climb for a species that has been so utterly decimated in such a short period of time, and there are heavy hearts for the conservationists who have worked so diligently to protect this beautiful antelope.

The fossil record reveals that the prehistoric range of the saiga stretched from the United Kingdom to Alaska, though today their range is limited to pockets in Kazakhstan, Mongolia, Russia, Turkmenistan and Uzbekistan. The species is most recognizable for unusual noses, which look roughly like rudimentary elephant trunks. Though the noses look goofy, they represent remarkable adaptations. They act as filters, protecting the animals from breathing in rising dust from the dry ground in summer, and warming the air during the cold of winter.

“It’s a remarkable structure, really,” said Dr. Kühl-Stenzel, a saiga expert, to the New York Times. “In the rutting season, the male’s nose swells even more, and then they shake their heads and it makes a squishy sound.”

Editor's Note: This story has been updated since it was originally published in June 2015.