Effects of temperature on spectral preferences of female gray treefrogs (Hyla versicolor)

Males of many animal species produce conspicuous signals to attract mates; male treefrogs produce loud and persistent acoustic signals called advertisement calls. Frogs face an interesting challenge in that temperature can differentially impact signal production and perception, leading to a mismatch between sender and receiver. For instance, female Green Treefrogs (Hyla cinerea) exhibit temperature-sensitive preferences for the frequency of the advertisement call, potentially resulting in interspecific hybridization at low temperatures. Considering climate predictions by the Intergovernmental Panel on Climate Change, we investigated whether, and by how much, temperature modifies female preferences for natural variation in spectral properties of male advertisement calls. The mate-choice preferences of the Gray Treefrog (H. versicolor) have been extensively studied; females prefer calls with standard bimodal frequency peaks of 1100 and 2200 Hz over calls with higher and lower frequencies. These preferences were determined at 20° C, but the dominant frequency of calls is positively correlated with temperature. Using two-speaker choice experiments, we tested the hypothesis that acoustic preferences of female H. versicolor for the frequency of male advertisement calls vary based on ambient temperatures (15, 20 and 25° C). We found that female preferences based upon frequency are, at best, only moderately temperature dependent. We discuss the possible neurophysiological basis for the seeming lack of temperature coupling in this aspect of the Gray Treefrog communication system, and conclude that mate-choice decisions based on frequency will not be significantly impacted by modest (2° C) changes in environmental temperatures.