Factors influencing maternal attack on conspecific intruders by lactating female “TO” strain mice

Factors regulating maternal attack in “TO” strain mice were investigated to determine 1) optimal conditions for inducing this behaviour and 2) the likely utility of this activity. Lactating females were more likely to attack male intruders than female intruders. The mate's presence reduced maternal attack in this strain, or (putting it conversely) aggression was generated in the male's absence. Removal of the mothers from their litters for four to five hours also suppressed maternal attack. Investigation of the bite targets in the maternal attack suggested that it is a defensive, rather than an offensive, response.