Resting metabolic rate is repeatable, but does not affect call characteristics, in the gray treefrog Hyla chrysoscelis Open Access

Consistent among-individual variation in behavior is widespread and often has consequences for fitness. However, the mechanistic basis of repeatable variation in behavior is less understood. Metabolic rate is a likely candidate to drive repeatability in behavior because energy metabolism can limit behavioral expression. There are competing hypotheses for the relationship (or lack thereof) between levels of maintenance metabolism such as resting metabolic rate (RMR) and the expression of behaviors. On the one hand, RMR may show a negative relationship with behavior if higher RMR limits energy that can be allocated to other processes. On the other hand, RMR may positively correlate with behavior if high RMR leads to greater energy production ability. To test these hypotheses, we examined the relationship between RMR and repeatable, highly energetically costly sexual signals in male Cope's grey treefrogs (Hyla chrysoscelis). We recorded individual male acoustic advertisement calls in the field and measured their RMR the following day. We made repeated measurements of RMR across multiple captures of the same individuals to assess the repeatability of metabolic rates, and whether consistency in RMR decreases over time. There was no evidence that RMR affected call characteristics in H. chrysoscelis. Nevertheless, RMR was significantly repeatable. We found that RMR decreased across the breeding season, which reduced the consistency in RMR measurements of the same individual over time. We conclude that calling in H. chrysoscelis does not provide information to mates or rivals on male RMR, although other aspects of metabolism may still drive individual variation in calling.