Researchers at least have clues now as to why more than half of Kazakhstan's Saiga population, which once counted 257,000 antelope, died off within the space of a month. 

An entire herd of Saiga antelope, once 60,000 strong, died off in just four days. 

Antelope die offs aren't uncommon. So geo-ecologist Steffen Zuther and company weren't "really alarmed" when local veterinarians in Kazakhstan briefed the researchers about the dying antelope.

"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 told Live Science. "It's really unheard of." 

A similar Saiga die-off may have occurred last year. Veterinarians in the region weren't able to get their hands on the animals until the antelopes have been long dead.

Researchers have found more clues that point to rogue bacteria that went unchecked as it colonized the colons of the animals. It has been suggested that an abundance of available vegetation created problems inside of the animals' guts, which allowed the bacteria to spawn out of control.

As scientists puzzle over the Saiga die-offs, Live Science pointed out the fact that this isn't the worst the trunk-nosed antelope have had to endure. As many as 400,000 of the Saiga died in 1988, so there's a chance they're learning to adapt to whatever is really killing them.

But for now, the International Union for the Conservation of Nature lists Saiga antelopes as "critically endangered." That's a stage away from extinct in the wild and two steps away from extinct.  

"The population has shown an observed decline of over 80 percent over the last 10 years and the decline is continuing," explains the IUCN in its classification of the Saiga. "Severely skewed sex ratios are leading to reproductive collapse."

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