Individual variation in amphibian metabolic rates during overwintering: implications for a warming world

Abstract

AbstractMetabolic rates (MRs) vary consistently among individuals within a population, providing raw material for natural selection. Although individual energy demands may play an increasingly important role for ectotherm survival under warmer and more variable winter conditions, whether individual variation in MRs persists during overwintering is virtually unknown. Here, we repeatedly measured MR in wintering Alpine newts Ichthyosaura alpestris to (1) confirm the consistent individual variation in this trait; (2) test whether the individual differences in MR affect body mass loss during overwintering. The individual identity of newts explained 72% of variation in mass‐and‐activity‐corrected MR. Newts with a high MR lost a higher proportion of their initial body mass than individuals with lower metabolic demands. We conclude that the consistent individual variation in MR during overwintering is an important predictor of spring body condition in newts. This provides a new perspective on intraindividual variation in MRs as a mediator of winter climate change on the dynamics of ectotherm populations.