INTRAUTERINE POSITION AND ANOGENITAL DISTANCE IN-HOUSE MICE - CONSEQUENCES UNDER FIELD CONDITIONS

Intra-uterine position is related to anogenital distance in female hou se mice, and possibly male house mice. Consequences of intra-uterine p osition as tested in the laboratory include effects on aggression, rep roductive behaviour and hormone biology. The behavioural and reproduct ive consequences of variation in intra-uterine position, using anogeni tal distance in young mice as a bioassay, were tested using wild house mice, Mus domesticus, in eight 0.1-ha field enclosures. Male mice wit h larger anogenital distances were more aggressive as adults, had larg er mean home range size and were more likely to disperse than males wi th smaller anogenital distances. Female mice with smaller anogenital d istance were more likely to attain reproductive status, had a higher r ate of pregnancy and had more pregnancies on average than females with smaller anogenital distance. Survival was not related to anogenital d istance for either sex. These findings indicate that intra-uterine pos ition has consequences for behaviour and reproduction in mice. In uter o exposure to higher levels of testosterone apparently enhances behavi our patterns related to reproductive success for males and decreases r eproductive success for females. Differences in exposure to oestrogen in utero may also be a possible mechanism for some of these effects in males. (C) 1996 The Association for the Study of Animal Behaviour