This past May, a large herd of saigas—a critically endangered antelope in Kazakhstan — completely died off in four days, and scientists had no idea why.

Geoecologist Steffen Zuther and his colleagues traveled to central Kazakhstan to monitor the calving of one herd of saigas. Local veterinarians reported dead animals on the ground, but since there had been die-offs before over recent years, the team was initially not alarmed.

Then within four days, the entire herd — 60,000 saiga — had died. They soon got word that more than 120,000 of these creatures had mysteriously died across the Central Asian country in two weeks. Scientists didn’t know what caused the mass dying then, but they have clues now.

Scientists believe that bacteria played a role in the saigas’ demise. However, they don’t know how exactly normally harmless microbes could cause such a cull.

“The extent of this die-off, and the speed it had, by spreading throughout the whole calving herd and killing all the animals, this has not been observed for any other species,” Zuther said. “It’s really unheard of.”

Zuther believes that an exceptionally cold winter followed by a very wet spring could have caused the bacteria to become widespread in the environment. He said that female saigas were hit the hardest and transmitted the bacteria to their calves through their milk.

Mass die-offs of the saiga have happened before. In 1988, 400,000 of them died and veterinarians reported similar symptoms. Scientists are concerned that another hit could devastate the entire saiga population. The species are listed as critically endangered by the International Union for the Conservation of Nature, and live in a few herds in Kazakhstan, one small herd in Russia and a herd in Mongolia. It’s estimated only 50,000 of them exist.

Saigas are vital to the ecosystem of the arid grassland steppe where they live. Their grazing helps to break down fallen plant material, recycling nutrients in the ecosystem and preventing wildfires fueled by too much leaf litter on the ground. They also provide meals for predators.

Though the cause of the massive death still remains a mystery, Zuther said he and his colleagues plan to continue their search.

The news comes just after the devastating news that the saiga’s distant relation, the Palestine mountain gazelle, has been recommended to be placed on the endangered list after finding that just 2,000 identified individuals of the species remain.

Source: 60,000 Endangered Antelopes Mysteriously Die in Four Days | Ecorazzi