Female presence during postejaculatory interval facilitates penile erection and 22-kHz vocalization in male rats

During the postejaculatory interval (PEI), male rats exhibit prolonged immo bility, 22-kHz vocalization, and penile erections. To test whether females modulate these behaviors, females were removed after the first or second ej aculation or left in the test chamber. Female presence during the PEI delay ed exploratory behavior and facilitated vocalization and erection. Female s timulation of vocalization is consistent with the hypothesis that vocalizat ion has a communicative function, not just a thermoregulatory one. The timi ng of the effect of females on erection suggests that males are sexually ar ousable well before they resume copulation. Therefore, erection may be bett er than vocalization as an indicator of the male's sexual refractoriness. T he findings also challenge the conventional view that the PEI comprises abs olute and relative sexual refractory periods marked, respectively, by the p resence and absence of 22-kHz vocalization.