Assessing dual hair sampling for isotopic studies of grizzly bears

Comparison of methanol and isopropanol as wash solvents for determination of hair cortisol concentration in grizzly bears and polar bears

Methodological differences among laboratories are recognized as significant sources of variation in quantification of hair cortisol concentration (HCC). An important step in processing hair, particularly when collected from wildlife, is the choice of solvent used to remove or "wash" external hair shaft cortisol prior to quantification of HCC. The present study systematically compared methanol a...

Mama Grizzly and the polar bears.

A recent paper on the matrilineal population history of two sister species, Ursus maritimus (polar bears) and Ursus arctos (brown bears), based on mtDNA sequence analysis, reveals a comparatively recent introgression. The authors propose that it represents a signature of environ mental stress in marginal habitats [1]. In a nutshell, it means that all modern polar bears probably belong to a mate...

Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods?

This is a Forum article commenting on: Ripple, W. J., Beschta, R. L., Fortin, J. K., & Robbins, C. T. (2014) Trophic cascades from wolves to grizzly bears in Yellowstone. Journal of Animal Ecology, 83, 223-233. Comparisons Ripple et al. (2014) used to demonstrate increased fruit availability and consumption by grizzly bears post-wolf reintroduction are flawed and tenuous at best. Importantly, a...

Den selection by grizzly bears on a managed landscape

Trophic cascades from wolves to grizzly bears in Yellowstone.

We explored multiple linkages among grey wolves (Canis lupus), elk (Cervus elaphus), berry-producing shrubs and grizzly bears (Ursus arctos) in Yellowstone National Park. We hypothesized competition between elk and grizzly bears whereby, in the absence of wolves, increases in elk numbers would increase browsing on berry-producing shrubs and decrease fruit availability to grizzly bears. After wo...