Selective phonotaxis to advertisement calls in the grey treefrog Hyla versicolor: behavioral experiments and neurophysiological correlates.

1. The significance of particular acoustic properties of advertisement calls for selective phonotaxis by the gray treefrog, Hyla versicolor (= HV), was studied behaviorally and neurophysiologically. Most stimuli were played back at 85 dB SPL, a level typically measured at 1-2 m from a calling male. 2. Females preferred stimuli with conspecific pulse shapes at 20 degrees and 24 degrees C, but not at 16 degrees C. Tests with normal and time-reversed pulses indicated the preferences were not influenced by the minor differences in the long-term spectra of pulses of different shape. 3. Pulse shape and rate had synergistic or antagonistic effects on female preferences depending on whether the values of one or both of these properties in alternative stimuli were typical of those in HV or heterospecific (H. chrysoscelis = HC) calls. 4. More auditory neurons in the torus semicircularis were temporally selective to synthetic calls (90%) than to sinusoidally AM tones and noise (< 70%). 5. Band-pass neurons were tuned to AM rates of 15-60 Hz. Neurons were more likely to be tuned to HV AM rates (< 40 Hz) when stimuli had pulses with HV rather than HC shapes. 6. Sharp temporal tuning was uncommon and found only in neurons with band-pass or low-pass characteristics. 7. Many neurons differed significantly in response to HV and HC stimulus sets. Maximum spike rate was more often elicited by an HV stimulus (74%) than by an HC stimulus (24%). 8. Differences in spike rates elicited by HV and HC stimuli were attributable to combinations of differences in the rise times and shapes of the pulses.