ABSTRACT
Field and laboratory-based experimental work examining protection and abuse of young has focused primarily upon the abusive behavior that adults can exhibit toward young and the reasons (both proximate and ultimate) for the emergence of this response strategy. A competing behavior which may have evolved as a counter strategy to infant abuse is that of maternal protection exhibited by pregnant and/or lactating female mice. As it is most often studied in the laboratory, this behavior consists of aggressive attacks exhibited by reproductively active females toward intruder males and females that threaten the nest site and the young. This aspect of maternal behavior is often referred to as maternal defense or maternal aggression and, in this chapter, these terms will be used interchangeably with that of maternal protection.
