Perinatal Testosterone Exposure has opposite Effects on Adult Intermale Aggression and Infanticide in Mice

In this chapter findings with house mice (now classified as Mus domesticus rather than Mus musculus 1 ) concerning the effects of sex steroid exposure during the perinatal period of sexual differentiation on adult infanticidal behaviour and intermale aggressive behaviour are reviewed. The perinatal period of sexual differentiation in mice begins with testicular differentiation on about Day 12 of foetal life (pregnancy typically lasts 18-19 days in mice) and continues through the first week of postnatal life 2 . During this time sex steroids influence the structure and function of numerous organs, including the brain and thus behaviour.