COPULATORY-BEHAVIOR OF THE VLEI RAT OTOMYS IRRORATUS

Laboratory experiments were undertaken to describe and quantify the co pulatory behaviour in 10 pairs of the vlei rat Otomys irroratus. Mean mount latency from the beginning of testing was 39.9 s (SE = +/- 10.2) , and males achieved first intromission at a mean time of 181.1 s (+/- 30.3). Mean duration of tests was 64.8 min (+/- 2.4), and males ejacu lated a mean of 6.8 (+/- 0.4) times during tests. The copulatory patte rn was characterized by no lock, intra-vaginal thrusting, multiple int romissions and multiple ejaculations. All females had sperm in the vag inal tract at the end of testing, and some developed a copulatory plug . Analysis of the pre-copulatory behaviour indicated that females were significantly more aggressive than males, and were less inclined to p articipate in sexual activity. In contrast to females, males displayed more amicable behaviour towards females, and readily participated in tactile and olfactory investigations of their mates. The copulatory be haviour of O. irroratus appears to be related to the ecological circum stances and the social organization of the taxon.