VARIATIONS IN THE SEXUAL PERFORMANCE IN OLD MALE-RATS

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