Is Pasture Structure and Plant-Composition the Key to Explaining the Mass Die-Off of the Saiga Antelope in the Borsy Region of Kazakhstan?

V. Pinion

In the post-calving periods of 2010 and 2011, mass die-offs of the critically endangered Saiga antelope, Saiga tatarica tatarica, occurred in a sub-population in West Kazakhstan. The investigation into the phenomenon, which resulted in the death of more than 12,000 and 400 individuals respectively, led to the official diagnosis of pasteurellosis. Despite this, with a full review of the evidence, alternative, more likely hypotheses present themselves.

The die-offs were very location specific and individuals from the same sub-population who grazed elsewhere suffered no mortality event. Adult antelope died suddenly whilst grazing, and calves died subsequently, apparently as a result of starvation.Acute pulmonary oedema and emphysema (APE), or fog fever, results from sudden expose to lush vegetation and is proposed as the cause of this die- off due to the observed acute and pasture-related nature of the mortality events.

Using historical data on the location of calving and post-calving pasture, this study investigates the pasture composition and nutritional quality where the die-offs occurred and compares this to areas where Saiga calved. Furthermore, it incorporates a discussion of historical meteorological and remotely-gathered data.

Pasture analysis was limited due to severe time restrictions in situ, but the data gathered appears to illustrate a similarity in community composition between the die-off sites in both years, with the 2011 calving area showing some similarity and the 2010 calving area the most dissimilar. Species richness seems higher in micro-depressions than in plateau and micro-hills and appears higher in the death zones of both years than the calving areas. L-tryptophan, involved in the development of APE, was detected in all areas tested.