Corticosterone: a costly mediator of signal honesty in sand lizards

The mechanisms underlying honest signal expression remain elusive and may involve the integration of social and physiological costs. Corticosterone is a socially modulated metabolic hormone that mediates energy investment and behavior and may therefore function to deter dishonest signal expression. We examined the relationship between corticosterone and green badge coloration in male sand lizards (Lacerta agilis), hypothesizing that physiological and behavioral costs resulting from elevated baseline glucocorticoids function in maintenance of honest signal expression. We found that large-badged males had higher corticosterone titer, with this relationship apparent at the end of the season and absent early in the season. Large-badged males also suffered higher ectoparasite load (number of tick nymphs), despite being in better condition than small-badged males. Ectoparasite load was positively related to corticosterone titer early in the season at the time of badge formation. High-conditio...