Mammals may disperse seeds through different mechanisms with endozoochory being the most important in large herbivores. Having wide home ranges, large herbivores play a key role in long-distance dispersal of plant seeds between and within habitats. Studying ungulates food habits is one of the most important steps in understanding their ecology and planning for their conservation. Seed dispersal studies can also complement the knowledge about food habits of the studied species. Persian wild ass or onager ( Equus heinous onager ) has been threatened by poaching, habitat degradation, insufficient protection and drought. Consequently, it is currently listed as Critically Endangered by IUCN. The aim of this study has been to investigate seasonal and spatial variation in dung seed content of onager as the only extant and originally largest ungulate species in Qatruiyeh National Park, South Central Iran. Identifying the dominant food plant species for onager has been the second aim of this study. Fresh pellet groups (n= 186) were collected from three different plains separated by mountain chains in July and October 2011 and were cultivated in a green house. Totally, 51 plant species (27 and 49 species from July and October samples, respectively) from 41 genera and 20 families germinated from dung samples. Species richness and relative frequency of seedlings varied not only between the seasons but also between the three plains ( p 0.001). Detrended Correspondence Analysis separated the three plains with regard to germinated plant species from dungs collected from each of them. In summer, the species composition of the germinated plant species from dung was more or less similar for Rig-Jamshid and Deh-Vazir plains, but was different for Einol-Jalal plain. In autumn, species composition was different for the three plains, although the similarity between Rig-Jamshid and Einol-Jalal plains was more than that between these two plains and Deh-Vazir plain. Lepidium vesicarium (Brassicaceae) and Astragalus podolobus (Fabaceae) were the most abundant plant species germinated from July and October samples, respectively. Simpson’s index of diversity had a range of 0.20 to 0.81 between the three plains in July samples, but was almost the same in all three plains for October samples. Microhistological analysis revealed the use of four plant species by onager including Stipa barbata, Tamarix ramosissima, Zygophyllum atriplicoides, and Achilla wilhelmsii . From these, the two annual plant species were also germinated from dung samples, but two woody species of Tamarix ramosissima and Zygophyllum atriplicoides were only recorded in microhistological analysis. Key words: Microhistological, diet, habitat mnagement, large herbivore, endozoochory
