Energetics and behavior: unrequited needs and new directions

•A growing number of studies investigate links between metabolic rate and behavior.•A common assumption is that metabolic rate is a proxy for energetic constraints.•We outline why this is false and provide guidelines for testing this assumption.•We conclude by highlighting exciting directions for future work in this field.

The number of studies investigating links between among-individual differences in metabolic rate (MR) and behavior has grown dramatically in the past several years. A major and often untested assumption of these studies is that the selected measure of MR is a valid proxy for energetic constraints. We argue that without explicitly testing this assumption, observed patterns between MR and behavior are uninterpretable. We provide guidelines for evaluating how a given measure of MR relates to constraints on the acquisition or expenditure of energy. The approach we advocate will allow researchers to develop and test a priori predictions relating energy metabolism and behavior. We conclude by highlighting several exciting directions for future work in this rapidly growing field.