Unusually high temperatures helped contribute to the dramatic sudden death of more than 200,000 "critically endangered" saiga antelopes in Central Asia's remote steppe grassland in 2015, according to a new study.

Over the course of three weeks in May 2015, a bacterial disease caused blood poisoning and wiped out more than 80 percent of the saiga population in Kazakhstan's Betpak-Dala region. In some herds, not a single animal survived.

Read more: Mass antelope deaths baffle scientists

Researchers already believed the disease was caused by the pathogen Pasteurella multocida, but they were baffled by the die-off because the bacteria had likely been living harmlessly in the saigas' tonsils up to that point. This led researchers to wonder why the bacteria suddenly became deadly on such a vast scale among the nomadic animals with the distinctive pendulous nose.

The international and interdisciplinary team of researchers studied previous die-offs — two similar events occurred in the 1980s — in saiga populations, uncovering patterns that showed an increased likelihood of such events when the weather is unusually humid and warm, as was the case in the days leading up to the deaths in 2015. This triggered an opportunistic bacterial invasion of the blood stream.

While the team of vets, botanists, lab scientists and ecologists did not examine the link between climate change and warmer weather during their research, Richard Kock, who helped carry out the study, speculated that there may be a connection. The Professor in Emerging Diseases at London's Royal Veterinary College said there is a trend of rising temperatures — and warmer and wetter weather over the past 40 years, adding that a similar event could happen again.

"I think it (the saiga) is an indicator of environmental change — a sensitive indicator that doesn't have the privilege of air conditioning," Kock told DW. "It tells us about the planet and is an indicator of things at a biological level, which is very concerning."

Other threats

Saigas are an ancient species that have wandered the Eurasian steppe since the last Ice Age. They're also culturally important animals in the steppe and are a symbol of nature's resilience. The steppe environment is extreme. Temperatures range from minus 40 degrees Celsius (minus 40 Fahrenheit) winter to above 40 in summer, food and water are scarce and predators, like wolves, are lurking around the corner. 

The animals have evolved a number of features to survive the tough conditions. One example is their noses, which filter out dust and heat up air as they breathe. The saigas also invest much energy in reproduction to survive. Saiga calves are exceptionally large, which allows them to develop quickly and migrate with the herd. However, their unusual size puts added physiological stress on the mothers during pregnancy. The evolutionary strategy makes them more vulnerable to mass mortality events during calving. 

Poaching is another threat. Numbers had already collapsed by 95 percent in the 1990s due to demand for their spiraled horns, which are used in Chinese traditional medicine. Only in recent years had the global population bounced back thanks to international and Kazakh conservation efforts. But poaching is still a danger, as is habitat fragmentation and disruption to migration pathways due to increasing levels of infrastructural development.

Saving saigas

Scientists fear that these challenges, coupled with another mass die-off could reduce saiga numbers to such a degree that recovery is not possible.

"The triggering of such MMEs (mass mortality events) in saiga through weather conditions shows that not much can be done to prevent them occurring," said Steffen Zuther, project manager for Kazakhstan at the Frankfurt Zoological Society, which was also involved in the study, "and therefore how important it is to maintain saiga populations of sufficient size for the species to survive such catastrophes."

Transferring the saigas to drier and higher areas might be one way of maintaining their numbers, said Kock. The animals are moving to wetter areas where there is more food but such environments may possess a higher risk of disease.  During the 2015 outbreak, one set of rangers protecting the steppe and its animals moved saiga away from wet, swampy locations with good results.

"There is a high risk in some of these landscapes for the animals so you may want to encourage animals away from those areas," said Kock. "I think once we understand the geographical and topographical aspects, then we might be able to influence protected area management."

To find out more about the researchers' work, check out DW's multimedia story "Saigas in distress."