Consistent individual differences (CIDs) in behavior are a widespread phenomenon in animals, but the proximate reasons for them are unresolved. We discuss evidence for the hypothesis that CIDs in energy metabolism, as reflected by resting metabolic rate (RMR), promote CIDs in behavior patterns that either provide net energy (e.g. foraging activity), and/or consume energy (e.g. courtship activity). In doing so, we provide a framework for linking together RMR, behavior, and life-history productivity. Empirical studies suggest that RMR is (a) related to the capacity to generate energy, (b) repeatable, and (c) correlated with behavioral output (e.g. aggressiveness) and productivity (e.g. growth). We conclude by discussing future research directions to clarify linkages between behavior and energy metabolism in this emerging research area.
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