Investigating the relationship between standard metabolic rate and calling behavior in Hyla chrysoscelis

Individual variation in behavior is common and often has an effect on fitness. However, there is a lot of debate on the mechanisms that produce this variation. One hypothesis is that an individual’s maintenance metabolic rate affects the amount of energy they can put into behavior, thus causing variation in behavior if individuals differ in metabolic rate. Indeed, in previous studies, highly energetically costly behaviors had a strong relationship with maintenance MR. To test this hypothesis, I examined the relationship between standard metabolic rate (SMR) and highly energetically costly acoustic sexual signals in male Cope’s grey treefrogs (Hyla chrysoscelis). Additionally, I examined factors affecting SMR, the repeatability of SMR, and if the time between SMR recordings affected the consistency of SMR to determine the implications of the relationship between SMR and calling behavior. I recorded individual acoustic advertisement calls from wild populations in the field during the breeding season. The following day, I recorded individual SMR in the lab using a push mode respirometry system. I found that in H. chysoscelis SMR does not influence calling behavior and thus is not unlikely to be a target of selection by females. Additionally, SMR decreased across the breeding season, potentially due to depletion of energy stores. While SMR was significantly repeatable, it does not explain consistent individual variation in calling because SMR and calling behavior weren’t related. Lastly, SMR was less consistent when there was more time between SMR measurements, suggesting that, while repeatable, SMR is somewhat plastic.