Effect of reciprocal cross-fostering on aggression of female mice toward lactating strangers.

Reciprocal cross-fostering of mice was carried out between an inbred strain (C57 BL/6) in which the female showed a particular form of aggression toward lactating female intruders, and a strain (C3H/He) which proved to lack totally this type of attack. In adulthood, cross-fostered females of the 2 strains and their controls were submitted to a series of aggression tests. They encountered in the test situation either a strange lactating female of their own strain of the foster strain. No differences in aggression measures were found between cross-fostered animals and controls, indicating that experimental factors (viz., cross-fostering) were without effect.