Dead Saiga antelopes lie on a field in the Zholoba area of the Kostanay region, Kazakhstan. (Reuters/Kazakhstan's Ministry of Agriculture)

As a species, saiga antelopes have endured a lot. They once roamed the Earth with Wooly Mammoths during the last Ice Age and but were almost driven to extinction by a loss of habitat and hunting during the late-20th century. Now the distinctive animals, easily distinguished by their large noses and prized for their meat and horns, are considered an endangered species and protected by the government of Kazakhstan.

Around May 10, however, they began dying en masse. Now, in just a few weeks, vast numbers of the species been found dead – Kazakhstan officials have said that almost 121,000 carcasses have been counted, according to Reuters, a number officials from the United Nations Environment Program (UNEP) have confirmed.

For an endangered species, this is dramatic, if not catastrophic. Kazakhstan's has around 90 percent of the world's saiga population, which was estimated to be around 250,000 before the deaths began. Experts are clearly shocked. "It is very painful to witness this mass mortality," Erlan Nysynbaev, vice minister of the Ministry of Agriculture of Kazakhstan, said.

"It's very dramatic and traumatic, with 100 per cent mortality," Richard Kock of the Royal Veterinary College told the New Scientist this week from Kazakhstan. "I know of no example in history with this level of mortality, killing all the animals and all the calves," Kock added, noting that the animals die after respiratory problems and extreme diarrhea.

Saiga antelope with a baby grazes next to carcasses of dead antelopes lying on a field, in the Zholoba area of the Kostanay region, Kazakhstan. (Reuters/Kazakhstan's Ministry of Agriculture) Saiga antelope with a baby grazes next to carcasses of dead antelopes lying on a field, in the Zholoba area of the Kostanay region, Kazakhstan. (Reuters/Kazakhstan's Ministry of Agriculture)

The huge scale of the deaths initially left some scientists baffled, and some unusual theories spread – the Kazakhstan's Space Agency have said that they could see no link between the deaths of the animals and a number of Russian space rocket launches near the area they live, though they could not yet rule it out (these launches have already caused some controversy in Kazakhstan). On Thursday, researchers working with the UNEP say that two pathogens, Pasteurella and Clostridia, appeared to be contributing to the die off, but that the animals appear to have already had their immune systems weakened by another unknown factor.

Whatever is causing the deaths, experts are fearing the worst. "The death of the saiga antelope is a huge tragedy," zoology scientist Bibigul Sarsenova told Reuters. "Should this happen again next year, they may simply disappear." But the hope is that if the deaths can be controlled or stopped, the animals can bounce back, again.