Data and scripts for Apodemus metabolism-behaviour covariation analyses

Energy is a central resource for life, but animals’ energy budgets are limited by their ability to collect, process and redistribute energetic assets to diverse functions, including behavior. Yet none of the existing bioenergetic models unequivocally explain behavioral variation, suggesting that they are not mutually exclusive, or that they are incomplete and overlook important processes. To describe a means by which an endotherm regulates its metabolism and behavior in varying environments, we simultaneously analyzed several components of energetic budgets. To accurately assess the costs of body maintenance and thermoregulation, and activity and shyness of wild mice, we measured resting metabolism at different temperatures, and repeatedly estimated basal metabolic rate (BMR) and behavior. Contrary to expectations of the ‘performance’ or ‘allocation’ models, which predict that high BMR aids or limits the energy available for investment, we found no evidence of strong covariation between BMR and shyness or activity. Instead we found that individuals that can invest more energy in thermoregulation, above obligatory maintenance, expressed higher levels of activity, pointing to other mechanisms of behaviour-metabolism covariation. Our results also suggested that females may save energy to compensate for high thermoregulatory costs by reducing activity, but that males may substitute metabolic heat with muscular heat production. Those relationships were only evident under environmental conditions which do not induce high thermoregulatory costs – pointing to both environmental and sex dependent bioenergetic mechanisms of behavioral expression.