Hormonal stimulation necessary for elicitation of maternal nest-building in the mouse ( Mus musculus)

Abstract

Summary Nest-building behaviour in sixty-one male and sixty-four female 9-week-old white mice was studied over a period of 8 weeks. The effects on nest-building of castration, impregnation, and castration with hormonal implantation were tested. It was found that treatment with oestradiol significantly decreases nest-building in spayed females. Progesterone treatment, however, significantly increases nest-weight and ‘maternal character’ in spayed females. Oestradiol and progesterone implanted together also results in a significant decrease in nest-building. Progesterone treatment of intact females produces an even greater increase in both nest-weight and ‘maternal character’ than that observed in spayed females treated with progesterone alone. It is concluded, therefore, that a state of high progesterone and very low oestrogen is probably the hormonal situation eliciting ‘maternal’ nest-building in pregnant mice. Male mice implanted with progesterone show a trend towards increased nest-building and with oestradiol a trend towards decreased nest-building. Thus it may be concluded that the male is probably not genetically different from the female in regard to response to these hormones. Instead it appears that the male is merely less responsive to them than the female.