The effects of intrauterine position on competition and behavior in the mouse

The purpose of the present study was to examine the effect of intrauterine position on: (1) competition for limited food resources when the animals were previously deprived of food; (2) social preference for a male during various phases of the estrous cycle; and (3) social and sexual behavior when the animals were provided with like-treated females or receptive females, respectively. Females developing in utero between two males (2M females) and females developing between two females (0M females) were different on only one measure recorded during the competition for limited food, i.e., gaining control of the food pellet, with the 0M females outcompetiting the 2M females. When given a choice between a male or a female neither 2M or 0M females in estrus showed a preference for the male. The results also indicated that 2M females were significantly more aggressive and more likely to show male sexual behavior when compared to 0M females.