Dietary Macronutrient Profiles of Free-Ranging European Brown Bears Differ Between Climate Regions

Whether climate region affects macronutrient intake in species is unknown. Because of their wide variety of habitats with varying environmental conditions and local food availability, the free-ranging European brown bear was used as a model species to study the dietary macronutrient profile in relation to climate region (using the Köppen-Geiger climate classification system), season and supplemental feeding of anthropogenic foods. Climates included were cold (regions in Norway, Sweden, Estonia and Slovakia), temperate (regions in Slovenia and Spain) and warm (regions in Croatia and Greece). Regardless of climate region, protein content was higher, and carbohydrate content was lower in spring and summer diets compared to autumn and winter diets. Diets in warm climate regions were marked by a high (digestible) carbohydrate content compared to cold climates and a low protein content compared to cold and temperate climates. A low protein to non-protein ratio, close to the optimum reported for brown bears (0.2 ME basis), was found in autumn in every climate type, and was present all year round in warm climates. At supplemented feeding sites, high (digestible) carbohydrate and low protein contents were observed compared to natural feeding sites. Supplementation also decreased seasonal variation in macronutrient composition. Fat content did not vary across seasons, climate type or with supplemental feeding. Fibre contents varied with season, climate type and supplemental feeding; however, differences were very small. Although seasonal fluctuations of macronutrients follow similar patterns across climate regions, macronutrient profiles differ between climate regions, corroborating that external conditions can influence macronutrient balance in species.