Evaluation of the risk of trophic overlap among wild herbivores in Coahuila, Mexico

Abstract

Understanding the annual and seasonal composition of herbivore diets is essential for effective population management and habitat conservation. This study aimed to evaluate the annual and seasonal dietary composition and diversity of four wild herbivores in a desert scrubland of Coahuila, Mexico, during the dry season (October 2018 and February 2019) and the wet season (May and August 2019). The research was conducted at the Rancho San Juan Wildlife Management Unit (UMA) using captive populations of desert bighorn sheep (Ovis canadensis mexicana), aoudad (Ammotragus lervia), white-tailed deer (Odocoileus virginianus texanus), and mule deer (O. hemionus). A total of 280 fecal group samples per species (140 per season) were collected and analyzed using microhistological techniques. Dietary diversity was estimated using Hill numbers by season. Differences in dietary composition were assessed with the Kruskal–Wallis test and principal component analysis. Aoudad exhibited the highest dietary diversity (64 species), followed by desert bighorn sheep (50), white-tailed deer (49), and mule deer (43). Shrub species predominated in all diets. No significant differences were detected between seasons, although grouping patterns were observed in plant occurrence frequencies. Principal component analysis indicated that 55% of the consumed plant species constituted the common dietary base of the four herbivores. White-tailed deer and mule deer, as browsing ruminants, showed greater selectivity for shrubs, while mule deer stood out for including lechuguilla (Agave lechuguilla), a dominant species in the rosetophyllous desert scrub. These findings underscore the importance of incorporating dietary diversity into wildlife management strategies and highlight the need for long-term studies to better understand patterns of plant resource use in arid ecosystems.