Mongolian gerbil fathers avoid newborn male pups, but not newborn female pups: olfactory control of early paternal behaviour

We examined effects on the parental behaviour of male Mongolian gerbils, Meriones unguiculatus, of the sex and number of pups in a litter. Recent fathers interacting with foster litters consisting entirely of newborn males decreased the time that they spent in contact with a litter the greater the number of pups it contained. However, fathers that interacted with litters composed entirely of newborn females showed no change in the time they spent in contact with a litter as a function of its size. Fathers responded similarly to litters of 1- and 3-day-old female pups, but their responses to male pups changed from avoidance to approach as the age of males increased from 1 day to 3 days, and fathers made anosmic by intranasal administration of zinc-sulfate solution did not avoid neonatal litters. Results of a correlational study revealed that the more time males spent with newborn young during a 30-min test, the greater their latency to mate with their partners in postpartum oestrus and the shorter the duration of their mating effort during the 24 h immediately after parturition. We discuss these findings as consistent with the view that androgen-mediated olfactory stimuli produced by newborn male Mongolian gerbils make them unattractive to fathers, possibly functioning to increase the time that recent fathers mate-guard while their partners are in postpartum oestrus.