Smaller does not mean worse: variation of roe deer antlers from two distant populations in their mechanical and structural properties and mineral profile

Antler size, structure, composition and mechanics have been shown to reflect nutrition, climate and body effects in red deer, but studies have only assessed effects on size in the roe deer (Capreolus capreolus). Roe deer show little sexual dimorphism, lower inter-male fighting and could form groups during part of the year but does not form harems, in contrast to red deer. Thus, it is interesting to assess how nutrition and habitat affects investment in antlers as compared to red deer. Antlers were collected from adult males of two game estates differing in location, climate and management: 13 from the south-east of Spain (mild winter, hot summer, dry habitat and rich supplementary feeding), and 10 specimens came from central-southern part of the Czech Republic (snowy winter, mild summer, humid habitat and limited supplementary feeding). After measuring whole-antler parameters, a destructive sampling was performed to obtain a full-transversal section and cortical bone samples from two sampling position along the main beam. Then bone structure, mechanical properties (three-point bending test, impact test) and the mineral profile were studied. Roe deer from Spain had heavier and longer antlers than Czech roe deer. Their bone material had a higher mechanical quality, although Czech roe deer compensated by developing antlers with thicker walls. Mineral composition also differs, particularly by greater contents in Czech antlers in 3 minerals associated with nutrient stress: Fe, K and Zn. We concluded that the differences found between populations may be caused by differences in habitat quality and diet, in a similar way as reported for red deer, despite interspecific differences. Our study suggests that habitat affects antler parameters and, as previous results in red deer, suggests that improving diet quality may affect size, composition and mechanical quality of antler material. Certainly, antlers of roe deer provide information useful for population management.