Predicting nutritional condition in black bears and polar bears on the basis of morphological and physiological measurements

Abstract

Thirty-eight black bears (Ursus americanus) and 43 polar bears (Ursus maritimus) were dissected to determine equations for predicting body weight (BW) and nonfat body weight (NFBW). Nutritional condition was estimated by calculating a fat to nonfat (FNF) ratio, equalling (BW – NFBW)/NFBW. For each species, BW and NFBW were accurately predicted by multiple regression equations based on morphological measurements. The FNF ratio was independent of body size and thus comparable between sexes and among age-classes. The accuracy of predicting the FNF ratio is limited, and reliable comparisons of nutritional condition among individual bears will require the development of more accurate techniques. Physiological measurements of marrow and intramuscular percent lipid content were also evaluated as potential indicators of nutritional condition, but were determined to be unreliable.