Features of Fodder Vegetation as a Possible Cause of Saiga Die-Offs on Steppe Pastures

Résumé fourni par la source

Abstract Modern climatic changes, weakening of the anthropogenic pasture load, and an increase in steppe fires have led to the expansion and dominance of grasses (graminoids) vegetation on the steppe pastures of Russia and Kazakhstan since the end of the 20th century. This resulted in deterioration of the forage quality of pasture vegetation, a factor in the depression of the saiga population that may have affected the increase in cases of saiga die-offs. A die-off occurred in Kazakhstan in 2015, when about 200 000 animals died. A large number of different versions have been put forward about the reasons for these deaths: an infectious disease (hemorrhagic septicemia), toxic forage plants, unfavorable weather conditions, and the destructive effect of rocket fuel. In this article, we consider a different version of death associated with the negative effect of low-quality food on the sites of saiga death. It is shown that the food supply for saigas on steppe pastures consistently decreases with an increase in the abundance of grasses in forage vegetation. Suitable, nutritious food for breeding saigas include pastures in which the share of grasses in the aboveground phytomass is no more than 30%. If this level is exceeded, the pastures do not provide the necessary level of nutrition for breeding saigas and are unsuitable for them. It is possible that the saigas found themselves during spring migration in steppe regions with a predominance of turf grasses (65–75%), which exceeds their permissible (threshold) abundance (30%). This pasture condition did not provide the necessary nutrition, caused a weakening of animals during the rearing period, and promoted the activation of infectious septicemia in breeding saigas, which, with the combined action of both factors, may have led to their die-off.

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