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Body mass and mast abundance influence foraging ecology of the American black bear (Ursus americanus) in Maine

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We studied nutritional ecology of American black bears (Ursus americanus Pallas, 1780) in Maine, including active and hibernating bears during 5 years, across three study areas, using nitrogen stable isotope analyses of blood samples (n = 152). Our central finding, in two study areas, is positive correlation between body mass and δ15N. This suggests use of large body size to acquire or guard food resources that have relatively high δ15N, consistent with importance of ungulates as food for the largest bears in Maine. In these two study areas, hibernating bears across the spectrum of body mass showed greater δ15N during 2 years of beechnut (Fagus grandifolia Ehrh.) scarcity compared with 2 years of beechnut abundance. Adiposity, measured by serum leptin, was greater in hibernating bears following a season of beechnut abundance compared with one of beechnut scarcity. Total litter mass correlated positively with maternal serum leptin and negatively with maternal δ15N, supporting the importance of mast, including beechnuts, to reproductive success of bears in Maine. In the third study area, bears across the spectrum of body mass had greater δ15N in all years, consistent with food resources relatively high in 15N that were available to bears of all sizes.

Keywords: American black bear; Ursus americanus; abondance du paisson; alternate-year cycle; beechnuts; body mass; carnivore; cycle biennal; faînes; isotope stable d’azote; masse corporelle; mast abundance; nitrogen stable isotope; ours noir

Document Type: Research Article


Affiliations: 1: University of Maine, Department of Animal and Veterinary Sciences, 130 Hitchner Hall, Orono, ME 04469, USA. 2: University of Maine, Department of Wildlife Ecology, 210 Nutting Hall, Orono, ME 04469, USA. 3: Maine Department of Inland Fisheries and Wildlife; 650 State Street, Bangor, ME 04401, USA. 4: University of Missouri, Division of Animal Sciences, 160 Animal Sciences Research Center, 920 East Campus Drive, Columbia, MO 65211, USA.

Publication date: April 16, 2013

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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