Functions of Vocalization in Sociosexual Behaviors in Rats (Rattus norvegicus) in a Seminatural Environment

Abstract

Both male and female rats produce vocalizations in the presence of a potential sexual partner. In this study, we evaluated the role of vocalizations in sociosexual behaviors in an ecologically valid procedure. Three males and 4 females were housed in a seminatural environment. In each group, 1 or 2 males and females were devocalized, and the other subjects were sham operated. Sociosexual interactions between males and females were recorded for a period of 1 hr when all 4 females were receptive so that the males had the choice to interact either with vocalizing or with silent females. Devocalized and sham-operated males displayed very similar behavioral patterns. There was no difference in any of the male sexual behavior patterns nor in male-initiated nonsexual social interaction. Female vocalizations do not contribute to the regulation of sociosexual interaction. Devocalized males received as much attention from females as sham-operated males, with the exception of paracopulatory behaviors with short duration, which were more frequently directed toward the sham-operated males than to the devocalized males. This was the case for both silent and vocalizing females. It appears, then, that devocalized males are inferior to sham males with regard to the capacity to induce female paracopulatory behaviors. However, this has no consequence for sexual interaction because devocalized and sham males copulated equally based on the number of mounts, intromissions, and ejaculations. In sum, these data show that vocalizations play a very limited role in rat sociosexual behavior in a seminatural environment. Furthermore, this indicates that vocalizations have no evident function during copulatory interactions.