Infanticide exhibited by female mice: genetic, developmental and hormonal influences.

Approximately 25-40% of 25-45 day old C57BL/6J females killed young (1-3 day old Rockland-Swiss (R-S) albino mouse pups) while similarly aged DBA/2J females were parental or ignored neonates. Beyond 45 days of age C57BL and DBA females seldom killed young. When ovariectomized at weaning and tested for infanticide at 65 days of age, DBA females rarely killed neonates while 40% of C57BL females exhibited the behavior. In contrast to DBA females, significantly more C57BL females killed young in response to the adult administration of testosterone propionate (TP) and estradiol benzoate (EB), but not dihydrotestosterone propionate (DHTP). It is tentatively proposed that strain differences in spontaneous and steroid aroused infanticide in female mice may be related to differences in the prenatal hormone environment.