Habitat alteration and poaching have reduced populations of large herbivores in Iran to levels at which they now need to be actively conserved. Asiatic wild ass Equus hemionus is one of the seven extanct species of the horse family, which is categorized as Endangered (EN) by IUCN. As the most threatened (CR) suecies of Asiatic wild ass, the Persian wild ass Equus hemionus onager is now confined to only two isolated populations in Touran National Park and Protected Area and Qatrouiyeh National Park and the surrounding Bahram-e-Goor Protected Area in Iran. Knowledge on abundance and habitat associations of this taxon is urgently required for its conservation. In this study, the distribution of onager herds with foals (maternal) and without foals (herd constituted mainly of males) in Qatrouiyeh National Park was separately modelled in winter 2013 using Maxent. Habitat suitability modelling was also performed based on all the sighted onager groups both in summer and winter 2013. The effect of group size on the obtained habitat suitability maps was scrutinised by iterative run of the Maxent program applying different group size thresholds. Line transect distance sampling was used to estimate abundance of the species in the study area. Mean density of onager in the study area was estimated at 1.1 km 2 (95% CI: 0.69-1.7). The estimated density seems low considering the figures given in previous studies and the growth rate of the population. Rigjamshid and Dehvazir plains were recognised as suitable habitats for both maternal and male herds, but Einoljalal plain showed a lower suitability particularly in winter. Maternal herds preferred foothills located in 1500 to 1700 altitudes. Overall, maternal herds seem to use more limited ranges of environmental conditions. Altitude, distance to Salsola-Atriplex and Artemisia-Stippa vegetation types, and slope were the most important factors determining habitat suitability of onager. Keywords : Persian wild ass, Habitat suitability modelling, Maxent, Abundance estimation, Maternal
