A once-familiar sight on the grasslands and semi-arid deserts of central Asia, the critically endangered saiga antelope - with its distinctive tubular snout - has faced off many challenges in modern times, from habitat loss to poaching. Now, a new and mysterious threat to the species that is wiping out whole herds has scientists scrambling for answers.

In just two-and-a-half weeks in mid-May, something killed more than 120,000 saiga - or 35 percent of the global population. Males, females and newborn calves were all affected, with sick animals dying within hours of showing symptoms, including diarrhoea, breathing problems and frothing at the mouth.

While sudden mass die-offs are not unusual for the nomadic saiga, none of the previous events claimed such a huge proportion of the population. Contrary to other similar outbreaks, not a single animal in the affected herds survived. The death toll is particularly alarming in light of the animal's endangered status, say scientists.

"It is a very dramatic syndrome and very worrying for conservation," said Richard Kock, a wildlife veterinarian at the Royal Veterinary College in the UK, who flew to Kazakhstan to assist with an investigation into the deaths last month. "When a herd is affected, 100 percent die. That does not fit any natural, biological pattern. It's a sort of unnatural mortality."

Searching for answers

Following the outbreak, Kock led a team of international and Kazakh researchers on a visit to affected areas to figure out what could have triggered this "unnatural" disaster, and to prepare for future outbreaks.

According to the #link:http://www.unep.org/newscentre/Default.aspx?DocumentID=26816&ArticleID=35061&l=en:United Nations Environment Programme (UNEP)#, the research mission to Kazakhstan has identified two pathogens - specifically Pasteurella and Clostridia - as possible culprits behind the outbreak. But, according to Kock, these bacteria are only lethal to an animal if its immune system is compromised.

"The bacteria are opportunistic - they take their chance when the environment is conducive, and that's where resistance of the animal is important," said Kock. “These organisms are in the animal normally but can become a pathogen and kill the animal in certain circumstances."

The researchers are looking at a variety of factors - including environmental toxins from mines, forage, and other ecological factors to identify - for answers to how such typically benign bacteria could be taking out whole herds.

"We have climate change, we have agriculture, we have loss of species historically - so the ecological composition on the steppe is different. If you add them altogether, it might lead to this extraordinary sort of indicator of a problem," Kock said.

It will take weeks before the team gains a clear picture of what has happened, the wildlife veterinarian and conservationist told DW.

Species in jeopardy

The event is catastrophic for conservation. Large saiga herds have roamed the grassy Eurasian steppe since the last Ice Age - but numbers collapsed 95 percent in the 1990s, mainly due to poaching, for meat and for the animal's prized spiralled horns - used in Chinese traditional medicine. Only in recent years had numbers recovered from a global population of less than 50,000 animals, largely thanks to Kazakh and international efforts.

The particular herd affected in the outbreak is a large population in Kazakhstan's Betpak-dala region, and the one most secure from poaching - which is still the biggest threat saigas face.

"It's just so sad, because over the last few years this population has been doing so well," said E.J. Milner-Gulland, a UK-based scientist who heads the #link:http://www.saiga-conservation.com/home.html:Saiga Conservation Alliance# - an organization dedicated to protecting the antelope. "Because of good protection and management, it had been recovering really quite fast. This set us back quite a few years," Milner-Gulland told Deutsche Welle.

The organization has been engaged in a number of saiga conservation programs across the region, ranging from outreach and education in communities to helping government anti-poaching efforts.

Providing alternative sources of income is important too. The collapse of the saiga population mirrors the breakdown of the former Soviet Union: The resulting collapse in rural economies led to widespread unemployment and poverty, and saiga poaching brings in money, according to the alliance.

The Saiga Conservation Alliance runs an embroidery project for women in Uzbekistan, offering them training and an alternative source of income, so they can afford meat to feed their families and rely less on the saiga.

Milner-Gulland hopes that by finding the root causes of the huge scale of fatalities in the latest mass die-off, conservationists will be able to minimize future risks - or the "important" saiga will run the risk of extinction.

"Saigas are a very important part of the ecosystem in the central Asian steppes, and are also culturally really important as a nomadic species - they are symbols of the steppes for local people," said Milner-Gulland. "They are just really interesting and fascinating creatures as well."