Effect of carrying a radiocollar on expenditure of energy by meadow voles

We compared the daily expenditure of energy of meadow voles (Microtus pennsylvanicus) with and without dummy radiocollars. Daily expenditure of energy was estimated by doubly labelled water, while voles were kept in large outdoor cages. Carrying a radiocollar (6.7-9.0% of body mass) had no effect on daily expenditure of energy. Metabolism of caged animals was not inferior to that of free-ranging ones, suggesting that caging did not reduce locomotory costs and that radiocollars do not influence energy budgets of voles in natural conditions. Subsequently, we remove a potential argument against the use of telemetry on mammals of small size. We also validate the simultaneous use of radiotelemetry and doubly labelled water in small running mammals, which should offer new opportunities to investigate ecological energetics of these species.