title: 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.
authors.affiliation: Department of Renewable Resources, University of Alberta, 751 GSB, Edmonton, T6G 2H1, AB, Canada; Departamento de Ciencias Ambientales y Recursos Naturales Renovables, Universidad de Chile, Av. Santa Rosa, 11315, Casilla 9206, Santiago Chile.
authors.forename: Claudia
authors.initials: C
authors.lastname: López-Alfaro
authors.affiliation: Department of Renewable Resources, University of Alberta, 751 GSB, Edmonton, T6G 2H1, AB, Canada; School of Biological Sciences and the Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Sean C P
authors.initials: SC
authors.lastname: Coogan
authors.affiliation: School of the Environment and School of Biological Sciences, Washington State University, Pullman, WA, United States of America.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Robbins
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, WA, United States of America.
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Fortin
authors.affiliation: Department of Renewable Resources, University of Alberta, 751 GSB, Edmonton, T6G 2H1, AB, Canada.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D004032:Diet; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology; D008297:Male; D008962:Models, Theoretical; D009656:North America; D009749:Nutrition Surveys; D012621:Seasons; D001503:Ursidae / Q000502:physiology*