Credit: Provided/Joint Saiga Health Monitoring Team

Scientists have discovered that the sudden death of more than 200,000 saiga antelopes in 2015 was likely due to environmental factors that triggered a deadly bacterium.

These critically endangered antelopes live in the remote steppe grassland of Central Asia. The deaths amounted to more than 60 percent of the global population of the species. A paper published Jan. 17 in Science Advances describes how the healthy animals died of blood poisoning caused by the Pasteurella multocida bacterium. The mass deaths occurred while they were calving.

“Saiga gather en masse every spring to deliver their calves within a short period of time,” said paper co-author Wendy Beauvais, a postdoctoral researcher in the lab of Renata Ivanek, associate professor of population medicine and diagnostic sciences. “During that time, they are susceptible to disease, and since they are gathered together so closely, the whole population becomes vulnerable.”

The pathogen was likely living in the antelopes’ tonsils without causing harm to the animals until increased humidity and elevated air temperatures triggered an opportunistic invasion by the bacterium into animals’ blood streams, according to the paper.

This species has seen a handful of mass mortality events in the last 50 years, from two in the 1980s to this incident in 2015. The paper calls the occurrence unprecedented among other large mammal species. A subspecies of this antelope in Mongolia suffered similar losses in 2017 after a virus infection spilled into their herd from livestock.

The saiga antelope has been critically endangered since 2002. They are known for their long migrations and how they give birth to the largest calves, in proportion to their size, of any ungulate species. In addition to natural dangers like wolves and extreme temperatures, man-made threats like poaching and infrastructure development have depleted herds in Kazakhstan and Russia.

“They were already considered critically endangered before this event,” said Beauvais. “Although the outlook is worrying, they are capable of repopulating quickly and it’s possible their previous levels could be restored relatively soon.”

Local groups such as the Association for the Conservation of Biodiversity of Kazakhstan have propelled ongoing efforts to catch and prosecute poachers, monitor the remaining populations and educate local citizens about the saiga antelopes and their conservation needs.

“We are working toward gathering enough information to predict and prevent these occurrences,” said Beauvais. “Our research team has already contributed to guidelines for such investigations, and now we will review them and hopefully improve them further.”

The paper is titled “Saigas on the brink: multi-disciplinary analysis of the factors influencing mass mortality events.”

Melanie Greaver Cordova is a staff writer for the College of Veterinary Medicine.