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, 63 (11), 1549-1562

Why Male Orangutans Do Not Kill Infants

Why Male Orangutans Do Not Kill Infants

Lydia H Beaudrot et al. Behav Ecol Sociobiol.


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.


Fig. 1
Fig. 1
Study site duration and all cumulative infanticides (i.e., male or female, within or between groups) reported for chimpanzees (C), mountain gorillas (G), and orangutans (O). Four out of six long-term chimpanzee study sites show a strong positive correlation between study site duration and cumulative number of infanticides observed. The other two long-term chimpanzee sites considered, Kanyawara and Tai, have reported only one and zero confirmed infanticides, respectively. Mountain gorilla observations at Karisoke show a similarly strong relationship, whereas no orangutan study sites have reported infanticide in spite of comparable study site durations at Ketambe and Tanjung Puting. Data sources: Chimpanzees (C), for reviews see Wrangham et al. and Wilson et al. ; more recent infanticides reported in Murray et al. 2007; Townsend et al. ; Sherrow and Amsler . Mountain gorillas (G): Fossey ; Watts ; Harcourt and Stewart . Orangutans (O): Gunung Palung, Mitani 1991; Knott et al. ; Ketambe, Wich et al. ; Kutai, Rodman ; Mitani 1985; Lokan, Horr ; Suaq Balimbing, van Schaik ; Sebangau, estimated; Tanjung Puting, Rodman and Mitani ; Galdikas pers. comm.; Tuanan, Jaeggi et al. ; Ulu Segama, MacKinnon

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