Male mice that live with their mates help to nurture pups, whereas virgin males attack them, owing to differences in neural signalling. Kashiko Tachikawa and her colleagues at the RIKEN Brain Science Institute in Saitama, Japan, compared how sexually naive males and cohabiting fathers reacted to pups displaced from their nests, and found that their behaviour was mediated by the pheromone-detecting vomeronasal organ located at the base of the nasal cavity. Most of the virgin males attacked the pups, and the neural pathways that link the vomeronasal organ to other areas in their brains were highly activated in these animals. Cohabiting fathers, however, carried pups back to their nests and displayed little activation in these neural pathways. Sexually naive males showed parental behaviour if their vomeronasal organ had been removed.

J. Neurosci. 33, 5120–5126 (2013)