Date of this Version
Total body electrical conductivity measurements and lipid composition were determined for the deer mouse (Peromyscus maniculatus) to derive species specific calibration equations for use with EM-SCAN estimates of lean and fat tissue. For each individual, total body electrical conductivity was measured by EM-SCAN, and actual lipid content was determined by chemical extraction. Then, using estimated and actual lipid values, separate calibration equations were generated for freshly captured (lean) and laboratory maintained (fat) individuals, and a combined equation was derived for all individuals. These equations were variable in the accuracy of lipid estimates; the lowest relative error estimate (percent body fat) was obtained with the equation for fat individuals while the highest error (percent body fat) was associated with the lean condition. Although high average error rates for lipid might preclude the use of this approach when absolute accuracy is necessary with lean individuals, estimates of lean tissue were very accurate regardless of body composition condition. When removed from the field and maintained in the laboratory, body composition changed significantly and quite rapidly with relative body fat doubling in six weeks. Thus, maintenance under laboratory conditions might affect physiologic and behavioral parameters in such subjects.