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The measurement of body composition in black bears (Ursus americanus), brown bears (U. arctos), and polar bears (U. maritimus) was investigated by means of isotopic water dilution and bioelectrical impedance analysis (BIA). The basic relationships between body lipid, water, protein, and ash were determined by direct chemical measurement of 13 black and 6 brown bears. Body water and lipid content as a percentage are highly correlated (r 2 = 0.98, standard error of the estimate (SEE) = 1.1%) and inversely proportional. The dry, lipid-free mass averaged 83.5 ± 1.6% protein and 16.5 ± 1.6% ash. Either isotopic water dilution or BIA can be used to estimate body lipid content of healthy, uninjured bears (r 2 = 0.93, SEE = 2.7% and r 2 = 0.96, SEE = 2.2%, respectively). Isotopic water equilibrated with body water by 150 min. Abscesses and recent injuries (i.e., gunshot or snare wounds) produced erroneous body composition estimates when BIA was used, but only when the injury was in the conductor path between the BIA electrodes. Dilution estimates were not affected by injuries. Currently, neither method can be used on dead bears.
Farley et al. (Tue,) studied this question.