Validation of two new total body electrical conductivity (TOBEC) instruments for estimating body composition of live northern red-backed voles Clethrionomys rutilus

Total body electrical conductivity (TOBEC) is a method for non-destructively estimating body composition. We sought to monitor seasonal changes in total body fat in northern red-backed voles Clethrionomys rutilus (Pallas, 1779), a microtine (10-45 g). We validated two new TOBEC instruments: the SA-3000 by EM-SCAN Inc. and the ACAN-2 by Jagmar Inc. Both instruments explained 94% of the variation in lean body mass and total body water. However, accuracy of fat estimates generated from lean mass predictions was poor for both instruments (± > 100%). Two instrument-specific multiple regression models and a TOBEC-free multiple regression model were used to estimate total body fat. All three improved the ability to predict total body fat in C. rutilus. These two TOBEC instruments can not be used to measure changes in total body fat of individual C. rutilus due to the small amount of fat reserves and lack of seasonal variation.