Progressively reduced copulatory behavior with age has been reported for male rats. In the present study, the sexual behavior of 197 old male rats (18-19 months) was investigated and four types of behavioral performance observed. Some subjects (16%) displayed the complete copulatory patterns, including mounts, intromissions, and ejaculations (Group A). Others (36%) exhibited mounts and intromissions but no ejaculation (Group B). Only 6% of the subjects exhibited mounts and did not show intromission or ejaculation (Group C). Most subjects (42%) did not exhibit any copulatory behavior (Group D). Comparisons of observed behavioral items among the four groups rendered significant differences (p < 0.005). An exception to this was the first mount data of Groups Band C. These results suggest that at least four qualitatively different types of male sexual performance exist in old rats.
Sexual behavior, Male rat, Age
