Total Body Electrical Conductivity (TOBEC) to Estimate Total Body Fat of Free-Living Birds

Abstract

Traditional methods to determine total body fat are undesirable under many circumstances because they require sacrificing individual birds. Walsberg (1988) recently introduced the total body electrical conductivity (TOBEC) method for total body fat to ecological studies. In this paper we expand on Walsberg' s (1988) seminal paper and show that: (1) TOBEC is accurate under a narrow array of body masses, and is therefore appropriate for intraspecific studies; (2) dead birds exhibit significantly different TOBEC than live birds; and (3) the use of metal bands does not affect TOBEC measurements. We conclude that TOBEC provides an accurate estimate of total body fat, that it is preferable to traditional methods because it does not require sacrificing the bird, measurements can be taken quickly in the field, and (most importantly to field ornithologists) body fat can now be tracked through time for individual, free-living birds.

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

“…Although there are several published validations of TOBEC for estimating body composition of wild birds (Walsberg 1988, Castro et al 1990, Roby 1991, Scott et al 1991, Asch and Roby 1995, there are few for wild mammals. Walsberg (1988) validated the EM-SCAN SA-1 TOBEC instrument by combining several rodent species, but failed to validate the technique on a single species.…”

Evaluation of the TOBEC Method for Calculating Fat Mass in Tree SparrowsPasser montanusand House SparrowsPasser domesticus

“…However, it depends on many factors, i.e. body shape (Fiorotto et al 1987, Castro et al 1990, Roby 1991 and body temperature (Scott et al 1991). Studies of live homoeothermic animals of a given species, or species of very similar body shape, can by convention assume constant body temperature and shapes throughout a sample.…”

“…However, because it allowed for estimates of amounts of fat in live vertebrates, it soon found application in scientific research on: human adult males (Presta et al 1983a, b) and infants (Cochran et al 1989), pigs (Fiorotto et al 1987, Cochran et al 1989), rabbits (Fiorotto et al 1987), rodents (Bracco et al 1983, Piasecki et al 1995, Koteja 1996, Zuercher et al 1997, fish (Fisher et al 1996) and birds (Walsberg 1988, Castro et al 1990, Morton et al 1991, Roby 1991, Scott et al 1991, Skagen et al 1993, Conway et al 1994, Asch & Roby 1995, Lyons & Haig 1995, Staudinger et al 1995, Burger 1997.…”

“…An apparatus operating on the basis of the TOBEC method is able to indicate a function for the lean body mass (LBM) of an organism, thereby allowing total body fat (TBF) to be calculated if total body mass (TBM) is known. However, as indications from the apparatus are influenced by an object's temperature (Scott et al 1991), and shape (Fiorotto et al 1987, Castro et al 1990, Roby 1991, there is no universal formula which would allow LBM to be calculated for all animals as a function of TOBEC.…”

Short‐term effects on body condition and size of immunocompetent organs in the hooded crow

“…This device estimates lean body mass, since the contribution of lipid tissue to conductivity is negligible (Walsberg, 1988;Castro et al, 1990). Each individual was placed in the detection chamber (152 mm diameter) of an SA-3000 Small Animal Body Composition Analyzer (EM-SCAN Inc., Springfield, Illinois) for 5-6 sec and the electrical conductivity index was recorded: TOBEC index = (S -E) / R, where S = measurement with the specimen, E = empty measurement, and R = reference number (detailed instructions in the EM-SCAN operator's manual).…”