In species with direct sperm transfer, copulation duration is a crucial trait that may affect male and female reproductive success and that may vary with the quality of the mating partner. Furthermore, traits such as copulation duration represent the outcome of behavioral interactions between the sexes, for which it is important-but often difficult-to determine which sex is in phenotypic contro...

Both male and female rats produce 50 kHz ultrasonic vocalizations (USVs) in the presence of a sexual partner and during copulation. Previous studies showed that USVs have no incentive value for rats. In this study, we evaluated the role of USVs in behavior during copulation. Three groups of rats were used: sham males paired with sham females, devocalized females paired with sham males, and sham...

Sexual selection can operate before and after copulation and the same or different trait(s) can be targeted during these episodes of selection. The direction and form of sexual selection imposed on characters prior to mating has been relatively well described, but the same is not true after copulation. In general, when male-male competition and female choice favor the same traits then there is ...

Intact, unanesthetized male rats were place in a supine position, with the penile sheath continuously retracted. Three forms of penile reflex were displayed: erections, cups, and flips. The reciprocal relation between copulation and the penile reflexes occurring in supine tests was explored in four experiments. In Experiment 1, sexual exhaustion depressed all penile reflexes, but the reflexes r...

Sperm release and sperm storage were examined in the spiny orbweaver, Micrathena gracilis. This species shares characteristics with other spiders that show a first-male advantage for egg fertilization. Male M. gracilis differentially released sperm to virgin females. Sperm release was not related to female age or copulatory duration. In this species, a complete mating between a pair requires tw...