Infanticide and parental behavior in wild female house mice: effects of ovariectomy, adrenalectomy and administration of oxytocin and prostaglandin F2 alpha.

We have previously observed that about 60% of virgin, wild female house mice (Mus musculus), that were the offspring of wild mice trapped in Missouri, exhibited infanticide when a single 2-day-old pup was placed into each female's home cage. But, by the end of pregnancy, there was a significant increase (to 90%) in the proportion of wild female mice that exhibited infanticide. At parturition, infanticide was inhibited and parental behavior was induced in all females. In the present study we examined the influence of ovarian and adrenal hormones, as well as two hormones associated with pregnancy and parturition: oxytocin and prostaglandin F2 alpha (PGF), in regulating infanticide and parental behavior in wild female house mice. The presence or absence of gonadal and adrenal hormones did not influence the frequency of infanticidal behavior in adult female mice. Subcutaneous injections of either oxytocin or PGF inhibited infanticide in previously infanticidal pregnant females 1 hr after injection, but only oxytocin served to also facilitate parental behavior (most PGF-treated females left the pup untouched). Oxytocin, but not PGF, was effective in inhibiting infanticide in previously infanticidal virgin females. These findings suggest that, by themselves, ovarian and adrenal hormones do not mediate the exhibition of infanticide by wild female mice, but the lack of response to PGF in virgin females suggests that endocrine changes during pregnancy (possibly changes in steroids) may modulate the inhibitory effects of PGF on infanticide.