Metabolic Correlates of Anuran Behavior

Abstract

Frogs exhibit extensive diversity in their repertoires of social, reproductive, defensive, and predatory behavior, and in the metabolic processes that support these activities. Three aspects of anuran biology (foraging mode, post-metamorphic ontogenetic changes in ecology, and reproductive behavior) are analyzed for their correlations with metabolic capacities. Anurans that forage widely for prey have greater capacities for aerobic ATP production than do sedentary foragers. This relationship appears to extend to intraspecific analyses; significant differences in aerobic capacity among populations of a species of dart-poison frog are associated with differences in feeding ecology. Ontogenetic change in metabolic capacity is directly coupled with ontogeny of behavior. The magnitude of post-metamorphic changes in physiology, behavior, and ecology appears to be related to differences in life history. A relatively short larval stage and small body size at metamorphosis, such as that found in American toads, are associated with extensive post-metamorphic changes in oxygen carrying capacity of the blood, cardiac muscle mass, and aerobic capacity of predispersal juveniles. In contrast, predispersal juveniles of species with long larval periods and large body size at metamorphosis possess adult physiological and behavioral features. Anuran reproductive activities, especially calling to attract mates, are energetically demanding, suggesting that the behavior of male frogs at a breeding pond may be limited by their metabolic capacities. However, the only study that has attempted to relate individual variation in reproductive behavior to individual variation in aerobic capacity found no correlation between those characteristics. The complexity of anuran biology ensures that physiological characteristics of anurans reflect many aspects of ecologyand behavior, some of which act independently, others in concert. Carefully designed experiments that incorporate both field and laboratory data are required to assess these interlocking features.