Trade-off in short- and long-distance communication in tungara (Physalaemus pustulosus) and cricket (Acris crepitans) frogs

Abstract

Female phonotaxis in tungara (Physalaemus pustulosus) and cricket (Acris crepitans) frogs is biased toward male advertisement calls or call components of lower frequency. This behavioral bias might result in part from a mismatch between the spectral characteristics of the advertisement call and the most sensitive frequency of the peripheral end organ implicated in reception of these sounds. In both species, females are tuned to frequencies lower than average for the calls in their population. This mismatch, however, represents the situation during short-distance communication. Female frogs can also use the call to detect choruses at long distances, and the spectral distribution of call energy can vary with transmission distance. We used computer simulations to test the hypothesis that there is a better match between tuning and call spectral energy at long distances from the calling male than at short distances by comparing the performance (sound energy received) of the natural tuning curve relative to an optimal tuning curve (i.e., one centered at the call's dominant frequency). The relative performance of the natural tuning curve increased with distance in tungara frogs. For the two subspecies of cricket frogs, however, the relative performance decreased at longer distances. The performance did not equal the optimal tuning curve at the distances tested. The results indicate that the relationship between calls and auditory tuning cannot be optimal for both long and short distance reception. The relationship between female tuning and call dominant frequency may represent a compromise between short and long distance communication, and the bias toward short or long distances may vary among species. Key words: Acris crepitans, auditory system, communication, cricket frogs, Physalaemus pustulosus, sensory biases, sexual selection, tungara frogs. (Behav Ecol 11:102-109 (2000))