Caregiving in virgin mice (Mus musculus): Effects of biparental care and exposure to a second litter during preweaning development.

Abstract

I examined the effects of early family unit conditions on later parenting behavior in laboratory mice (Mus musculus). I challenge previous studies that claim to show enhancing effects of biparental care on offspring parental responsiveness by raising mice with a male parent either present (MPP) or absent (MPA) during preweaning development. The results of those studies are confounded because MPP mice also have a second litter present (SLP) and MPA mice do not (SLA). Thus, the findings may have been due to the presence of second litter and not to the presence of the male parent. In this experiment I show that when offspring raised in different family units are tested as virgins with stimulus pups, more SLP mice are parental than SLA mice, and fewer SLP mice bite newborn pups than do SLA mice. Thus, results of previous studies are due to second litter exposure and not biparental care.