Copulatory behaviour of the vlei rat Otomys irroratus

Abstract

Laboratory experiments were undertaken to describe and quantify the copulatory 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 ejaculated a mean of 6.8 (± 0.4) times during tests. The copulatory pattern was characterized by no lock, intra-vaginal thrusting, multiple intromissions and multiple ejaculations. All females had sperm in the vaginal 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 participate 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 behaviour of O. irroratus appears to be related to the ecological circumstances and the social organization of the taxon.

S. Afr. J. Zool. 1997,32(3)