Beehner Jacinta C, Bergman Thore J
Department of Anthropology, University of Michigan, Ann Arbor, Michigan 48109-1043, USA.
Am J Primatol. 2008 Dec;70(12):1152-9. doi: 10.1002/ajp.20614.
Since Sugiyama's [1965] first observations of infanticide, empirical evidence from a multitude of primate species has supported the sexual selection hypothesis-the idea that males enhance their reproductive success by killing nonrelated, unweaned infants to hasten the mothers' return to fertility. Like other primates that live in social groups where paternity certainty is high, the social structure of geladas [Theropithecus gelada] suggests that infanticide by males could enhance their reproductive success. Nevertheless, empirical evidence for infanticide in this species is limited to anecdotal accounts. Using the timing of infant mortality and female reproductive and behavioral data collected across 26 months from a population of geladas living in the Simien Mountains National Park, Ethiopia, we test whether sexually selected infanticide occurs in this species. We also examine two additional hypotheses [noninfanticide hypothesis and generalized aggression hypothesis] for this population. Results suggest that sexually selected infanticide in geladas may, indeed, be a threat to females with dependent infants. First, male takeovers-the most likely time for infanticide-were associated with subsequently elevated rates of infant death [a 32-fold increase] comprising nearly 60% of all infant mortality. Second, females who lost infants during this period returned to fertility more quickly than if infants had lived [IBIs were 50% shorter], and third, all of these females were observed to mate with the new male. We found little to no support for other hypotheses. Finally, these results raise the possibility that anecdotal reports [from previous studies and this study] of pregnancy termination, accelerated weaning, and deceptive sexual swellings may represent female counterstrategies to male infanticide in geladas.
自杉山[1965年]首次观察到杀婴行为以来，来自众多灵长类物种的实证证据支持了性选择假说，即雄性通过杀死无血缘关系的未断奶婴儿来加速母亲恢复生育能力，从而提高自己的繁殖成功率。与其他生活在父系确定性较高的社会群体中的灵长类动物一样，狮尾狒[狮尾狒属]的社会结构表明，雄性杀婴行为可能会提高它们的繁殖成功率。然而，该物种杀婴行为的实证证据仅限于轶事记录。利用从埃塞俄比亚西米恩山国家公园的一群狮尾狒在26个月内收集的婴儿死亡率以及雌性繁殖和行为数据，我们测试了该物种是否存在性选择杀婴行为。我们还检验了针对该群体的另外两个假说[非杀婴假说和广义攻击假说]。结果表明，狮尾狒中的性选择杀婴行为可能确实对有依赖婴儿的雌性构成威胁。首先，雄性接管——最有可能发生杀婴行为的时期——与随后婴儿死亡率的升高相关[增加了32倍]，几乎占所有婴儿死亡的60%。其次，在此期间失去婴儿的雌性比婴儿存活时更快恢复生育能力[产婴间隔缩短了50%]，第三，观察到所有这些雌性都与新雄性交配。我们几乎没有找到支持其他假说的证据。最后，这些结果增加了一种可能性，即轶事报告[来自先前研究和本研究]中的妊娠终止、加速断奶和欺骗性性肿胀可能代表了狮尾狒雌性针对雄性杀婴行为的反制策略。
