Selectivity in the responses of hamsters to conspecific vocalizations.

Lordosis responses by estrous hamsters were triggered by brief manual stimulation. Lordosis durations then were timed, as manual stimulation was discontinued, and subjects were exposed to tape-recordings of conspecific vocalizations reproduced at intensities of 0-60 dB SPL. Relative to the durations observed in the presence of ambient noise alone, recordings of stress-elicited screams failed to facilitate lordosis regardless of stimulus intensity. In contrast, ultrasounds by male or female hamsters did prolong lordosis, and to extents that were directly related to intensity but unrelated to the sex of the caller. The very different responses to screams and ultrasounds suggest that the ability to facilitate sexual behavior is at least somewhat specific to ultrasounds and is not shared by all vocalizations reflecting states of high general arousal. On the other hand, the similar responses elicited by male and female ultrasounds suggest that these calls convey similar messages and that structural differences between them effect changes in call localizability, not meaning.