Inhibition of infanticide after mating by wild male house mice

Abstract

The effect of mating on the behavior of male house mice (Mus musculus) toward young has been examined in numerous domestic stocks of mice, and the somewhat contradictory results led us to examine the effects of mating on the behavior of wild male mice toward young. The wild mice were the F 1-F 4 offspring of mice trapped in Missouri. Virtually all wild males exhibit infanticide prior to mating, but virrually all wild males were inhibited from exhibiting infanticide 3 weeks after mating whether they were placed into the cage of their former mate and her litter or into the cage of an unfamiliar female and her litter, similar to the effect of mating on the behavior of CF-1 male mice toward young. In contrast, wild males that had exhibited infanticide prior to mating were inhibited from exhibiting infanticide 3 weeks after mating when placed with their former mates and their 2-day-old young but not when placed with unfamiliar females and their 2-day-old young. When wild males were tested for their behavior toward young using the procedure of placing a single pup into each male's home cage, mating did not result in an inhibition of infanticide (about 90% of the males exhibited infanticide). Cohabitation with a female without mating also did not influence the behavior of wild males toward young. Wild males that exhibited infanticide when placed with a lactating female produced their own young more rapidly than did noninfanticidal males, thus providing further support for the hypothesis that under some conditions, infanticide can be an adaptive trait. But, virgin, infanticidal males took significantly longer to inseminate the females whose litters had been killed than did infanticidal males with prior sexual experience.