Infanticide by female mammals: implications for the evolution of social systems

Abstract

The complexity and richness inherent in the social networks female primates forge for themselves has, too often, obscured a vital fact of their lives: that competition among females is central to primate social organization. ( hrdy 1981: 96) Introduction Female competition, especially female reproductive competition, is likely to play an important role in shaping the social systems of all mammals (Altmann 1997; Gowaty 1997b; Hrdy 1981). While this competition can often be subtle, it also can lead to what is perhaps the most extreme form of reproductive competition: infanticide. The chapters in this volume focus primarily, if not exclusively, on the phenomenon of infanticide by males and how it may be influencing the evolution of social systems. Generally, threats from conspecific males intensify under a specific context: the presence of an unrelated male, often following immigration into an established group (e.g., Hrdy 1974). But females and their young also face threats from conspecific females, including both unfamiliar intruders and fellow group mates. The threat of infanticide by females is likely to be taxonomically more widespread and, for group-living females, potentially a more constant threat than other forms of infanticide. The purpose of this chapter is to examine the phenomenon of infanticide by females other than the mother (hereafter “infanticide by females”) in a variety of mammalian taxa. How similar is this behavior to infanticide by unrelated males? What makes infants vulnerable to attack from female conspecifics, and what are the contexts in which female attacks on infants occur?