AbstractA time‐sampling procedure was employed to examine the caretaking behavior of male mice housed with lactating females and their litters, and to investigate the effects of the male's presence on the behavior of the female. The incidences of 14 categories of behavior were recorded over 20 hr distributed throughout the period of lactation. The development of litters was monitored by regular weighing. The results show, contrary to earlier findings, that males display just as much caretaking behavior as females. Differences in other forms of behavior can be related to the increased nutritional needs of the nursing mothers. The presence of the male seems to have very little influence on the behavior of the female and no effect at all upon the physical development of the litte