Locomotor activity in newborn mice: II. Existence and influence of a male pheromone

In a previous paper it was observed how locomotor activity of newborn mice raised by both parents decreases significantly compared with that shown by young raised by the mother alone. In the present experiment the sire’s presence was simulated by placing near the nest urine from adult males. In this way, it was possible to note that male urine has the same effect on infant activity as the father’s presence. So, for the first time, the existence of a masculine pheromone, which acts in the parental situation and which influences the litter from birth, is revealed. Its function is evident: to maintain the family cohesion, limiting the activity of the newborn mice.