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Behav Ecol Sociobiol (2009) 63:15491562 DOI 10.1007/s00265-009-0827-1
REVIEW
Why male orangutans do not kill infants
Lydia H. Beaudrot & Sonya M. Kahlenberg &
Andrew J. Marshall
Received: 23 December 2008 /Revised: 27 June 2009 /Accepted: 1 July 2009 /Published online: 21 July 2009 # The Author(s) 2009. This article is published with open access at Springerlink.com
Abstract Infanticide is widespread among mammals, is particularly common in primates, and has been shown to be an adaptive male strategy under certain conditions. Although no infanticides in wild orangutans have been reported to date, several authors have suggested that infanticide has been an important selection pressure influencing orangutan behavior and the evolution of orangutan social systems. In this paper, we critically assess this suggestion. We begin by investigating whether wild orangutans have been studied for a sufficiently long period that we might reasonably expect to have detected infanticide if it occurs. We consider whether orangutan females exhibit counterstrategies typically employed by other mammalian females. We also assess the hypothesis that orangutan females form special bonds with particular protector males to guard against infanticide. Lastly, we discuss socioecological reasons why orangutan males may not benefit from infanticide. We conclude that there is limited evidence for female counterstrategies and little support for the protector male hypothesis. Aspects of
orangutan paternity certainty, lactational amenorrhea, and ranging behavior may explain why infanticide is not a strategy regularly employed by orangutan males on Sumatra or Borneo.
Keywords Pongo . Infanticide . Sexual selection hypothesis . Female counterstrategies . Protector male hypothesis
Introduction
Infanticide, or the killing of an infant, is often hypothesized to be an adaptive behavior (Hrdy and Hausfater 1984; Janson and van Schaik 2000). Proposed benefits for male perpetrators include increased access to limited resources, prevention of misdirected parental care, nutritional benefits, or increased reproductive opportunities (Ebensperger 1998). Infanticide is widespread across invertebrates and vertebrates. In primates, infanticide is a widely employed male reproductive strategy in strepsirhines, New and Old World monkeys, and apes and has been invoked as a major determinant of primate socioecology (Sterck et al. 1997; van Schaik and Janson 2000). Among the great apes, sexually selected infanticide in the wild has been observed for chimpanzees (Pan troglodytes; for reviews, see Wilson et al. 2004; Wrangham et al....