Assessing Nutritional Parameters of Brown Bear Diets among Ecosystems Gives Insight into Differences among Populations

Abstract

Food habit studies are among the first steps used to understand wildlife-habitat relationships. However, these studies are in themselves insufficient to understand differences in population productivity and life histories, because they do not provide a direct measure of the energetic value or nutritional composition of the complete diet. Here, we developed a dynamic model integrating food habits and nutritional information to assess nutritional parameters of brown bear (Ursus arctos) diets among three interior ecosystems of North America. Specifically, we estimate the average amount of digestible energy and protein (per kilogram fresh diet) content in the diet and across the active season by bears living in western Alberta, the Flathead River (FR) drainage of southeast British Columbia, and the Greater Yellowstone Ecosystem (GYE). As well, we estimate the proportion of energy and protein in the diet contributed by different food items, thereby highlighting important food resources in each ecosystem. Bear diets in Alberta had the lowest levels of digestible protein and energy through all seasons, which might help explain the low reproductive rates of this population. The FR diet had protein levels similar to the recent male diet in the GYE during spring, but energy levels were lower during late summer and fall. Historic and recent diets in GYE had the most energy and protein, which is consistent with their larger body sizes and higher population productivity. However, a recent decrease in consumption of trout (Oncorhynchus clarki), whitebark pine nuts (Pinus albicaulis), and ungulates, particularly elk (Cervus elaphus), in GYE bears has decreased the energy and protein content of their diet. The patterns observed suggest that bear body size and population densities are influenced by seasonal availability of protein an energy, likely due in part to nutritional influences on mass gain and reproductive success.

Diet and macronutrient niche of Asiatic black bear (Ursus thibetanus) in two regions of Nepal during summer and autumn

“…We predict that the macronutrient proportions of diets will be relatively high in nonprotein macronutrients (combinations of carbohydrate and lipid) compared to protein, given that previous studies of Asiatic black bear document them as consuming high proportions of both soft and hard mast during summer and autumn. This prediction is also in keeping with diet studies of brown bear (Coogan et al, ; López‐Alfaro, Coogan, Robbins, Fortin, & Nielsen, ) and American black bear ( Ursus americanus ; Beeman & Pelton, ). In addition to providing regional knowledge of Asiatic black bear nutritional ecology, this research will contribute to the nascent comparative nutritional ecology literature.…”

Estimating the seasonal energy balance in Asian black bears and associated factors

“…Using the study by López‐Alfaro et al. () as a reference, we determined digestible energy content by multiplying the proportion of digestible energy (%) to gross energy content (kcal/g). The proportions of digestible energy have only been examined for some foods (e.g., ants, 18.7%), so we substituted values of similar foods for items that had no values available.…”

Dietary protein supplementation and its consequences for intake, digestion, and physical activity of a carnivorous marsupial, Sminthopsis crassicaudata

“…Dietary nutrient balance has been shown to strongly influence many life history traits of animals, including growth, reproduction, and lifespan (Koch, Ganzhorn, Rothman, Chapman, & Fichtel, ; López‐Alfaro, Coogan, Robbins, Fortin, & Nielsen, ; Simpson & Raubenheimer, ). There is wide variation in the availability and nutritional composition of foods in nature, and thus animals are often faced with deficient or imbalanced diets.…”

“…Dietary imbalances can have significant consequences for animal health and fitness depending on which nutrients are over‐ or underabundant. Hence, animals may respond to imbalanced diets by a combination of changes in total food intake, activity, and digestive efficiency (Irwin, Raharison, Raubenheimer, Chapman, & Rothman, ; Lindsay, Allen, & Major, ; López‐Alfaro et al., ; Raubenheimer, Simpson, & Tait, ).…”