Sexual Selection and Calling Behavior in the American Toad (Bufo americanus)

Abstract

Mating system structure, variation in advertisement and release calls, and calling behavior were investigated during a three-year period in Bufo americanus in east-central Maine. Although the breeding season was relatively brief, chorus size was small, and males participated in chorus activity for an average of six or seven nights within a season. Pulse rate and duration of the advertisement call were significantly correlated with temperature, but neither frequency nor call rate was influenced by temperature over a 10 C range. Dominant frequency was the only advertisement call variable significantly (negatively) correlated with snout-vent length in one of two years for one of two populations studied. Similarly, dominant frequency was the only release call variable significantly (negatively) correlated with male size (snout-vent length and mass). Males exhibited consistency in both call rate and call duration as measured over a series of nights of chorus activity: repeatability (intraclass correlation coefficient) was 0.52 for call duration and 0.24 for call rate. Females did not discriminate between high and low frequency calls in discrimination experiments; however, females did prefer calls broadcast at relatively high call efforts (rate x duration).