Saiga antelopes
Dead Saiga antelopes lie on a field in the Zholoba area of the Kostanay region, Kazakhstan, in this handout photo provided on May 20, 2015 by Kazakhstan's Ministry of Agriculture. About 20,000 endangered Saiga antelopes, killed by a suspected pasteurellosis infection, were found dead in Kazakhstan in a week, local media reported.REUTERS/Kazakhstan's Ministry of Agriculture/Handout via Reuters

Over one lakh critically endangered saiga antelopes in Kazakhstan died starting late May this year, baffling scientists and veterinarians on the cause of the sudden death. Now researchers have found clues as to why the animal died in large numbers in such a short span of time.

According to a report by Live Science, an entire herd of 60,000 saigas died within just four days shocking animal experts, conservationists and veterinarians. More than 1,34,000 saigas, which is more than half the population of the total herd (2,57,000 in 2014) in Kazakhstan, died in just two weeks before stopping suddenly in June.

Kazakhstan has witnessed mass death of saigas in the past, with a total of 4,00,000 saigas died in May 1988 and another 12,000 in May 2010.

"But since there happened to be die-offs of limited extent during the last years, at first we were not really alarmed," geo-ecologist Steffen Zuther, the international coordinator of the Altyn Dala Conservation Initiative, told Live Science.

Possible Reason Why Saiga Antelopes Died

Scientists could not find out the exact cause of Saiga's death in 2010 as they got sample of the animals only long after they died. They have apparently come to the conclusion that the death could have been caused by digestion problems due to abundance of grass that led to bacterial growth.

EJ Milner-Gulland, a conservation biologist at Imperial College London and chair of Saiga Conservation Alliance, had told The Guardian in June that "it's likely there is some kind of infection, but that there are predisposing environmental factors." 

"There are all sorts of possibilities. Saigas are moving further north now than they have done in the past and may be encountering different pastures. Large amounts of rainfall can pose a problem, with lush grasses causing bloat. We need to rule out the transmission of disease from livestock," he continued.

The situation is different this time around with Kazakhstan better prepared and researchers taking stock of the situation. Scientists not only take samples of water and vegetation saigas took weeks leading up to their death for study, but also tested the soil they walk on and insects that feed on them with the hope of finding the cause of their sudden death.

Researchers have now got clues on the cause of death of the endangered animal after detailed study. It found out that females with young calves die first, followed by their young ones, giving a hint that the disease could have been transmitted through the mothers' milk, said Zuther.

Zuther told Live Science that study of tissue samples revealed toxins produced by Pasteurella and possibly Clostridia bacteria cause bleeding in most animals but it still remains a mystery how "harmless microbes could take such a toll."

"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 added. "It's really unheard of."

One interesting fact about the mass death of saigas so far is that it happens only in the month of May, and it may help scientists find out the exact cause of death.