A Comparative Nutritional Analysis of Przewalski’s Horses and Asiatic Wild Asses

Abstract

In 1992, the, then critically endangered, Przewalski’s horse (Equus przewalskii) was re-introduced into the Great Gobi B Protected Area in southwestern Mongolia, in an effort to re-establish the species within its historic range. This semi-desert region also sustains relatively large populations of the closely-related, threatened Asiatic wild ass (Equus hemionus). Though the extensive ranges of both species once overlapped, it is unclear whether or not the same overlap in a much smaller area will cause competition between the two for food. The goal of this study was to compare the equids’ nutritional niches and see if they overlapped. Captive individuals from each species were given four different mixtures of hay, with the amount consumed daily recorded. The species-specific dietary decisions were then visualized and characterized using the Geometric Framework proposed by Stephen Simpson and David Raubenheimer. The results suggest that the Przewalski’s horse consumes more water and energy per kilogram body weight than the Asiatic wild ass, and that the wild ass tended to shift towards the more protein-rich food options than the Przewalski’s horse. The study ultimately concludes that the two species occupy two distinct nutritional niches, and, unnatural pressures withstanding, are likely capable of co-existing in the Great Gobi B.