VARIATIONS IN THE SEXUAL PERFORMANCE IN OLD MALE-RATS

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 B and C. These results suggest that at least four qualitatively different types of male sexual performance exist in old rats.