There have been small die-offs of Saiga antelopes over the past few years. But according to geo-ecologist Steffen Zuther, the entire Saiga herd he had traveled to Kazakhstan to monitor died within a four-day span. All 60,000 of them. This is a die-off in size and speed never seen before.
NBC News:
Now, the researchers have found clues as to how more than half of the country's herd, counted at 257,000 as of 2014, died so rapidly. Bacteria clearly played a role in the saigas' demise. But exactly how these normally harmless microbes could take such a toll is still a mystery, Zuther said.
"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."
The real cause is still a mystery. They studied the parts of the population hit the hardest: mothers and newborn calves. One clue is it is bacterial in origin. Since the calves were too young to eat vegetation, whatever was killing them transfers through the mother's milk.
Tissue samples revealed that toxins, produced by Pasteurella and possibly Clostridia bacteria, caused extensive bleeding in most of the animals' organs. But Pasteurella is found normally in the bodies of ruminants like the saigas, and it usually doesn't cause harm unless the animals have weakened immune systems.
Environmentally, there is still a lot of research to be done.
Another possibility is that such flash crashes are inevitable responses to some natural variations in the environment, he said. Zuther said he and his colleagues plan to continue their search for a cause of the die-off.