Sexual behaviour and its olfactory control in the desert woodrat ( Neotoma lepida lepida)

Abstract

In studies 1 and 2 nine pairs of desert woodrats ( Neotoma lepida lepida) were observed for copulatory behaviour when the female was in a state of naturally occurring oestrus (study 1) and following ovariectomy and oestrogen and progesterone replacement (study 2). Males and females respond in a similar way under conditions of natural and hormone-induced oestrus. Males show a consummatory pattern involving multiple mounts and ejaculations, with ejaculations occurring after single intromissions. Females show the lordosis reflex accompanied by hop-and-dart and ear-wiggling responses. In addition, both sexes show appetitive precopulatory behaviours; the male emits an audible rasping vocalization as he trails and mounts the female, following a period of intense sniffing of the female's anogenital region. The female also frequently approaches and sniffs the male. In study 3, the role of female odours in the sexual behaviour of the male was examined in eight of the nine pairs used in studies 1 and 2. This was done by applying to the anogenital region of ovariectomized females a combination of urine and vaginal secretions taken from familiar and unfamiliar, and oestrogen-primed or non-oestrogen-primed females. The results show that odours from oestrogen-primed females are not sufficient to elicit male sexual behaviour, if the female is not sexually active. In study 4 the eight males were tested for their preferences for urine and vaginal secretion odours taken from females in different reproductive states and applied to cotton swabs. These males spent more time sniffing unfamiliar oestrous odours than unfamiliar non-oestrous odours and more time sniffing oestrous odours from a familiar female over those taken from an unfamiliar female. In study 5, 12 sexually active males were tested with oestrogen-primed females before and after either olfactory bulb removal or sham-surgery. Bulbectomized animals ceased copulating with females although females showed precopulatory approaches. Taken together, these studies suggest that normal sexual behaviour in the male woodrat requires that the female both possess the attractive odours (of oestrus) and that she engage in appetitive precopulatory behaviour.