Time-contingent change in infanticide and parental behavior induced by ejaculation in male mice.

About 50% of sexually-naive male CF-1 mice (Mus musculus) commit infanticide (kill young). But, 80-90% of male mice commit infanticide between 1-4 days after mating. Between 12 and 50 days after mating infanticide is inhibited and most males (80-100%) behave parentally toward young (they build a nest, retrieve and groom the young, and hover over the young to keep them warm). Beginning at 60 days after mating, infanticide is again facilitated and parental behavior is inhibited (70-80% of males commit infanticide). The facilitation and inhibition of infanticide as a function of time after mating is mediated by the act of ejaculating rather than by mounting and intromitting during mating or by cohabiting with a female either before or after mating. The experience of committing infanticide either prior to mating or within the first 4 days after mating does not influence the facilitation of parental behavior that occurs 12 days after mating. But, repeated contact with young after males become parental serves to maintain parental behavior for an extended period of time. The age of the young (newborn-20 days old) utilized as stimulus animals does not influence these time-dependent changes in the behavior of male mice after ejaculation. This phenomenon is unique in that a response (infanticide) to a novel stimulus (young) is facilitated, then inhibited, and then facilitated again as a function of time between an event (ejaculation) and exposure to the novel stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)