To lose 60,000 of one animal in the space of four days is always catastrophic. But when 60,000 members of an endangered species have died, the situation becomes even more grave. That's what has happened to the saiga antelope of the Eurasian steppe -- and scientists are only now beginning to understand why.
In late May, the mysterious die-off began. Geoecologoist Steffen Zuther and colleagues were in Kazakhstan to study the unusual antelope, but soon, they started to see dead animals, Live Science reported. Only four days later, 60,000 of them had died.
"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. It's really unheard of."
Neighboring herds also died off, and by the end of two weeks, 134,000 died before the strange population crash stopped suddenly, Science Alert added. And scientists were left scratching their heads.
Right now, the species is limited to just a few herds. There are a few in Kazakhstan -- including the 60,000-strong herd that just died off -- one in Russia, and one in Mongolia. That's it. The reason for that is the same reason so many animals around the world are disappearing -- poaching. In this antelope's case, the Chinese prize its horn for medicine, giving poachers a lucrative business: one horn costs $150. This Chinese demand has decimated the population of the antelope a disturbing 95 percent in just 15 years.They are an unusual-looking creature: a light shade of brown, the antelope has a small, banded horn and a short, trunk-like nose. They play an important role in the ecosystem of the Eurasian steppe, which runs from Moldavia, across Ukraine and Siberia, and into Hungary. There, they eat plant material that can't decompose in the region's cold winters; by eating it, this antelope actually prevents wildfires.
After the 60,000 animals died, scientists sampled everything in their path they may have eaten or touched -- water, vegetation, even the rocks and dirt they walked across. And they may have identified the problem -- a bacteria that naturally lives in the antelope's gut and is usually completely harmless. But they found a toxin -- produced by the common bacteria -- in their bodies.
This toxin caused widespread organ bleeding, killing the antelope in mass numbers.
But what could make a normally harmless bacteria cause mass death? That's the part of the puzzle scientists still haven't figured out. A cold winter followed by a wet spring may have caused the bacteria to spread more than usual is one theory, and so is subtle environmental changes that make the bacteria's toxins more deadly to the antelope.
Another hint lies in the way the antelope congregate, which at least explains how 60,000 died so suddenly. Separate herds join during the winter and when they migrate; they split when they have their young. During the die-off, the mothers died first, then their calves, which could mean that whatever killed them was transmitted via the mom's milk.
Since the antelope has died en masse before -- 270,000 in 1988 and 12,000 in 2010 -- scientists worry that one more crash could wipe out the saiga entirely.
[Photos Courtesy Victor Tyakht, BBH/Shutterstock]