Comparative Demography and Dietary Resource Partitioning of Two Wild Ranging Asiatic Equid Populations

Abstract

Tooth wear signatures allow inference on the dietary traits of herbivorous ungulates. Comparing dietary regimes of taxonomically closely related populations further allows inference on habitat structure and food availability. The mesowear method of tooth wear evaluation has opened up a pathway to reconstruct subtle differences in dietary behavior and resource partitioning based on skeletal material as the only source of information. Eighty cheek dentitions of Asian wild asses (Equus hemionus) from the Southern Gobi (Mongolia) and 61 dentitions of African free ranging donkeys (Equus asinus) from the Emirate Sharjah (United Arab Emirates) were investigated for their mesowear signatures. It is tested if sexes and age classes of individuals are different in their mesowear signatures. Cluster analyses and principal components analyses are applied in order to test hypotheses using 27 ungulate species with known diets as a reference. The wild asses from the Gobi are found to classify as typical grazers within this spectrum and have a more abrasion-dominated signature then the donkey population from the United Arab Emirates (UAE). The diet available to the latter population is thus considered to be more heterogeneous. This indicates that the donkey habitat in the UAE is a more diverse mosaic of feeding resources compared to the wild ass habitat of the Mongolian desert. In both populations there are more intraspecific differences in the diet between sexes then there are interspecific differences between the two African zebra species E. burchelii and E. grevyi. The dietary signal is further interpreted as to reflect the social structure of the animals as associated with specific environmental conditions. Between the two sexes of Asian wild asses and UAE donkeys, one would expect a more pronounced segregation in the diet when male territories are small and poor in resources at the same time. This condition would best characterise the habitat inhabited by the UAE donkey population. The data suggest that the male territories of this population are comparatively small and thus provide highly abrasive forage only.