Saiga Population Grows After Mysterious Epidemic

http://www.nytimes.com/2016/06/21/science/saigas-kazakhstan.html

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It was a silent spring for saiga antelopes last year.

Within a few weeks in May in Kazakhstan, a mysterious illness claimed the lives of more than 200,000 of the endangered animals, or over 60 percent of the species.

This spring scientists and conservationists around the world waited anxiously to see whether the die-off would be repeated. Not only has May come and gone with no epidemic, but newly published results from an April census revealed that the saigas are making modest gains in population.

In particular, the Betpak-Dala saiga population in central Kazakhstan, which was hit hardest by the epidemic, grew from 31,000 after the die-off to 36,000 by April, said Steffen Zuther, who coordinates the Altyn Dala Conservation Initiative, a large-scale conservation program in central Kazakhstan.

“It’s fantastic news,” said Stephanie Ward, a representative of Britain’s Royal Society for the Protection of Birds, a partner in the conservation program. She attributed the population growth to the Kazakh government’s effort to combat poaching for meat and male saiga horns, which are prized in Chinese traditional medicine.

“Some of us were worried initially that the saiga horn would go up in value and really put pressure on the remaining antelope,” Ms. Ward said, “but the Kazakh government has risen to the challenge.”

The apparent success of antipoaching and conservation measures, however, has done little to expose the roots of last year’s disease outbreak, which in some cases killed off entire herds.

Research in the past year has pinned the die-off on Pasteurella multocida, a bacterium that commonly causes disease in water buffalo, cattle and bison (though not at such a deadly rate).

Still, the mystery remains. The bacteria naturally occur in the antelopes without causing a problem, said Richard Kock, of the Royal Veterinary College in London, who has been studying last year’s die-off.

What caused the bacteria to suddenly become virulent last year is unclear. One possibility was weather, Dr. Kock said. Increased rainfall, he said, “seems to create conditions where the pathogen can thrive, or the host is stressed in a way that makes it easier for the pathogen to invade.”

Another possibility: Changes in vegetation as a result of reduced grazing by wild horses and, later, livestock kept by nomads on the steppes as that way of life declined. The changes might have created environmental stressors that are not yet well understood.

For now, conservationists say, the international community needs to continue protecting saigas through proven strategies like cracking down on poaching and expanding protected areas.

Before the die-off, there were more than 240,000 Betpak-Dala saiga. To ensure that a future disaster doesn’t wipe out the species, the population should be closer to a million, said Michael Brombacher, who heads the Frankfurt Zoological Society.

Mr. Zuther, of the conservation initiative, is optimistic. “These animals were around in the Pleistocene, thousands to millions of years ago, with woolly mammoths,” he said. “The saiga has this really good capability of bouncing back.”