Ecogeographic Variation in Physical Traits of White-Tailed Deer

Abstract

A growing body of work has revealed that differences in body size of ungulates follow ecoregion and soil boundaries and that these size differences are nutritionally influenced. Currently, it is unclear if these patterns of body size result from differences in quantity or quality of forage produced. We quantified differences in white-tailed deer (Odocoileus virginianus Zimm.) body mass and antler size captured at four sites in South Texas, United States. We sampled available forage to determine if long-term differences in average body and antler size could be explained by forage quantity or quality, or some combination of the two. Data collected from 2011 to 2019 indicated female body mass was > 3 kg smaller on the eastern edge of the Coastal Sand Plain ecoregion as compared with those from the western transition zone of the Coastal Sand Plain and Tamaulipan Thornscrub ecoregions. Similarly, male body mass and antler size were > 6 kg and > 20 cm smaller, respectively, in coastal habitats compared with more interior sites. We found that forb biomass, browse and forb diversity, and the nutritional landscape, quantified using digestible energy, crude protein, phosphorus, and neutral detergent fiber, differed between sites. However, differences between sites were inconsistent with predictions that would have supported our hypothesis. Overall, we found no support for the hypothesis that forage quantity drives ecogeographic variation in physical traits of white-tailed deer but were unable to fully refute or support the hypothesis that forage quality, specifically plant diversity, drives ecogeographic variation in physical traits of ungulates.