Functional macronutritional generalism in a large omnivore, the brown bear

Area of Science:

• Ecology
• Zoology
• Nutritional Science

Background:

• Omnivory is a key dietary strategy in many species.
• Understanding macronutrient composition is crucial for assessing dietary breadth and adaptation.
• Brown bears (Ursus arctos) are widely distributed omnivores with diverse diets.

Purpose of the Study:

• To analyze macronutrient proportions (protein, carbohydrate, lipid) in brown bear diets.
• To investigate the influence of food availability and anthropogenic subsidies on bear diets.
• To assess brown bear omnivory as an adaptation to varied environments and resources.

Main Methods:

• Utilized a framework for dietary generalism and compositional data analysis.
• Analyzed literature data to estimate macronutrient proportions in wild brown bear diets.
• Compared macronutrient profiles between populations consuming natural versus anthropogenic food sources.

Main Results:

• Brown bear diets varied significantly in macronutrient proportions across their range, indicating a broad macronutrient niche.
• Carbohydrate proportion was the most variable macronutrient, while protein and lipid were more interdependent.
• Populations consuming anthropogenic foods showed higher carbohydrate and lower protein content compared to those relying on natural diets.
• Seasonal variation was observed, with autumn diets being higher in carbohydrate and lower in protein than spring diets.

Conclusions:

• Brown bear omnivory is a functional adaptation allowing them to exploit diverse habitats and cope with food resource variability.
• Anthropogenic food subsidies lead to distinct dietary macronutrient profiles in brown bear populations.
• Dietary flexibility, particularly in carbohydrate intake, is a key factor in brown bear's ecological success.