Mice Reared with Rats: Effects of Mother on Adult Behavior Patterns

Abstract

Litters of four male and two female mice were fostered, at four days of age, to lactating rat mothers whose own litters (two to six days of age) were removed at the time of fostering. Control mouse litters (four males, two females) remained with their natural mothers. Rat-reared mice had a higher mortality rate between birth and weaning but the survivors weighed more at weaning than did mouse-reared mice. Rat-reared mice were less active in an open field on the first day of testing and were less aggressive than mice reared by mouse mothers. The data definitely implicate the mother as a critical determiner of adult behavioral patterns.