Max-Planck-Institute for Evolutionary Anthropology, Leipzig, Germany.
Aggress Behav. 2019 May;45(3):300-309. doi: 10.1002/ab.21819. Epub 2019 Feb 2.
The selective advantage of male infanticide is enhancement of reproductive success of the aggressor. This implies that aggression is directed at individuals sired by others, infant loss shortens the mother's inter-birth interval, and the aggressor has a greater likelihood of siring the next offspring of the victims' mother. As these conditions are not always met, the occurrence of male infanticide is expected to vary, and hominoid primates offer an interesting example of variation in male infanticide. Infanticide has been reported in gorillas and chimpanzees but appears to be absent in orangutans and bonobos. One argument for the absence of infanticide in bonobos is reduction of male aggression. However, given that male aggression against immature individuals occurs and that females engage in behavior that is considered to be counterstrategy against male infanticide, the risk of male infanticide may pose a potential threat. Here, we explored whether aggression by male bonobos fits predictions of male infanticide. Male aggression toward immature individuals was rare and did not have lethal consequences, but the majority of observed cases exposed targets to risks of injury. Males did not target their own offspring less frequently than unrelated immatures, and the risk of being the target of male aggression increased with the targets' age. Overall, these results do not match the predictions of the adaptive male infanticide hypothesis. Instead, aggression by males may promote the emigration of the targets and older males may reinforce their superior status toward individuals that will soon compete for the same resources.
杀婴的选择优势在于提高了攻击者的生殖成功率。这意味着攻击是针对其他雄性所生育的个体，而幼仔的死亡会缩短母亲的生育间隔，并且攻击者更有可能成为受害者母亲的下一胎后代的父亲。由于这些条件并不总是满足，因此预计杀婴行为会有所变化，而类人猿提供了杀婴行为变化的有趣例子。在大猩猩和黑猩猩中已经报道了杀婴行为，但在猩猩和倭黑猩猩中似乎不存在。关于倭黑猩猩不存在杀婴行为的一个论据是雄性攻击性的减少。然而，鉴于雄性对不成熟个体的攻击行为以及雌性采取被认为是对抗雄性杀婴行为的对策行为，雄性杀婴行为的风险可能构成潜在威胁。在这里，我们探讨了雄性倭黑猩猩的攻击性是否符合雄性杀婴行为的预测。雄性对不成熟个体的攻击行为很少见，也没有致命后果，但大多数观察到的案例使目标面临受伤的风险。雄性不会比不相关的不成熟个体更频繁地针对自己的后代，而且成为雄性攻击目标的风险随着目标年龄的增长而增加。总的来说，这些结果与适应性雄性杀婴假说的预测不符。相反，雄性的攻击性可能会促使目标个体迁移，而年长的雄性可能会加强他们对即将为争夺相同资源而竞争的个体的优越地位。
