Temperature effects on frequency preferences and mating call frequencies in the green treefrog,Hyla cinerea (Anura: Hylidae)

Summary1.The frequency preferences of gravid females ofHyla cinerea for the low-frequency peak of bimodal synthetic mating calls shifted by about 400 Hz when the temperature of the animals was changed by about 7 °C. Changes in preference involving the high-frequency peak were much less dramatic (Table 1).2.The low-frequency peaks of the mating calls of four individual males ofH. cinerea changed only slightly (≦70 Hz) when they were recorded at high and low temperatures (Table 2, Fig. 1). The same acclimation times (around one hour) were used in testing female preferences and in recording male calls at different temperatures.3.Since shifts in female preference are not paralleled by concomitant changes in the spectral properties of the vocal signals, temperature coupling based on spectral information appears to be absent in the acoustic communication system of this species.4.Spectral properties are important for species recognition and at low temperatures females prefer calls with low-frequency peaks that are more similar to those of another, sympatric species (Hyla gratiosa) than to those of conspecific males. This implies that species isolation in nature could be jeopardized at low temperatures if females become responsive to mating calls under these conditions.5.Temperature effects on frequency preferences were predicted by a neurophysiological study of the auditory thalamic area inH. cinerea. The present results support the conclusion that this area is involved in processing biologically significant sounds.6.The results indicate, however, that resonance properties of the buccal cavity alone are not sufficient to match the mating call frequencies with the frequency sensitivity of the auditory system.

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