Postpubertal isolation decreases infanticide and elevates parental care in C57BL/6J male mice

Postpubertal (60 days of age) but not prepubertal (21 days of age) isolation reduced the normal tendency of C57BL/6J male mice to kill newborn pups (infanticide) and instead dramatically elevated their exhibition of parental care (retrieving of young). These effects were time-dependent in that longer durations of isolation (60 days) were more effective than shorter durations (20 days) of individual housing. Postpubertal isolation of male mice with previous killing experience also resulted in a reduction in infanticide and an elevation in parental care, but these effects were not as dramatic as those observed in naive, nonexperienced animals. The findings are discussed in terms of endocrine and neurochemical changes known to accompany isolation in mice.