Female rats, like many other rodents, are capable of producing large litters of pups. While developing in utero, these pups are exposed to testosterone produced not only by their own developing testes (if male), but also to testosterone produced by the testes of neighboring male fetuses. This exposure to testosterone can cause masculinization of both females and males in terms of their underlying morphology, physiology, and behavior. Several experiments were done examining the effects of intrauterine-position effects on the reproductive and parenting behavior of Mongolian gerbils (Meriones unguiculatus). These experiments showed that increasing testosterone exposure over the course of a male’s development:.