by J. D. Heyes
(NaturalNews) A critically endangered species of antelope has been driven further to the brink of extinction following a mysterious and substantial die-off of its herd over the summer.
The herd of saigas, which are native to regions of Kazakhstan, Russia and Mongolia, began dying during their calving period in May, reports Newser, and scientists are at a loss to figure out why.
According to reports, some 12,000 saigas died from a still-unexplained digestive issue after scientists speculated that there might have been too much greenery, reports Live Science.
However, the death rate quickly accelerated to 120,000 animals, or about half of the population in Kazakhstan, by June, including a herd of 60,000 that died off in about four days.
"Extraordinary" occurrence"I have worked in veterinary diseases all my career and I have never seen 100% mortality," Richard Kock, a wildlife veterinarian at the Royal Veterinary College in Hatfield, UK, who flew out to Kazakhstan last month to assist with efforts to make sense of the devastation, told Nature. "We had a herd of 60,000 aggregated and they all died. That is extraordinary."
Saigas are a nomadic antelope species that live in large herds, sometimes comprising thousands of individuals, on the steppe grasslands and semi-arid deserts of central Asia, Nature reported. Fossil records note that in prehistoric times, their range stretched from the United Kingdom to Alaska. However, over the past few centuries, the herds have been dramatically reduced; the population in Mongolia is actually considered a sub-species of saiga.
So far, scientists are stumped as to what has caused such a mass die-off, the largest since the loss of hundreds of thousands of saigas in 1988, or 67 percent of the population in the Ural Mountains at the time.
"Epidemiologically, you cannot get a directly transmitted disease to kill a whole population in seven days," Kock said. "I'd say it's a polymicrobial disease."
Scientists studying the die-off have found that mothers died first, followed by their calves. However, that observation was followed by a mystery: they discovered toxins from usually harmless Pasteurella and possibly Clostridia bacteria often found in the animals' bodies were causing extensive bleeding in their organs, reports UPI.
The problem is that no one is certain what changed in the bacteria to suddenly make it deadly.
"There is nothing so special about it. The question is why it developed so rapidly and spread to all the animals," geoecologist Steffen Zuther told Live Science.
Experts are still investigating. Some say that the recent die-off could be another "flash crash" like the 1988 loss of about 400,000 saigas. Again, some people think that the bacteria believed to be responsible could have simply spread more easily this year from standing water after a wet spring. Another theory is that the Pasteurella and Clostridia might have simply reacted unexpectedly on their own.
Critical to ecosystemsScientists say that saigas play a crucial role in the ecosystem of arid grassland steppes, where exceptionally cold winters tend to prevent fallen plant material from decomposing. Grazing of the dog-sized, Gonzo-nosed antelopes helps to break down the organic materials, thereby recycling nutrients back into the ecosystem while preventing wildfires that can be fed by too much leafy material on the ground. Finally, the animals provide meals for steppe predators, said Zuther.
"Where you find saiga, we recognize also that the other species are much more abundant," Zuther told Live Science.
Nature also reported:
Towards the end of the nineteenth century, widespread hunting brought the species close to extinction. There was some recovery in the twentieth century, but the end of the Soviet era brought about a dramatic collapse.
Rural poverty coupled with a market for meat and horns in China and not much in the way of law enforcement or conservation, saigas were killed in massive numbers.
"Those three things together caused a 95 percent decline over a ten-year-period," E. J. Milner-Gulland, a conservation biologist at Imperial College London and chair of the Saiga Conservation Alliance, told Nature.
The last count, in April 2014, put the saiga population at around 262,000, up from about 200,000 at the lowest point in the early 2000s. Much of the increase came from growth in the population that has just been devastated, scientists said.