Digestive and metabolic efficiencies of grizzly and black bears

Abstract

Digestive and metabolic efficiencies of black bears (Ursus americanus) and grizzly bears (Ursus arctos) were determined in 7-day total collection trials using seven single foods and four mixed diets. No significant interspecific differences in digestive or metabolic efficiencies were observed. Dry matter and energy digestibilities were inversely related to the dietary fiber content, whereas digestible protein was directly correlated with dietary protein content. Mean retention time for hair in a meat diet was 13 h, whereas the retention time for clover was 7 h and did not differ between species. Giant pandas (Ailuropoda melanoleuca), grizzly bears, and black bears appear to have very similar digestive efficiencies and passage rates. The relationships between diet composition and digestive efficiency can be used to begin evaluating the nutritional quality of diets consumed by free-ranging bears.