Yin Lijie, Jin Tong, Watanabe Kunio, Qin Dagong, Wang Dezhi, Pan Wenshi
Center for Nature and Society, School of Life Sciences, Peking University, Beijing, China; Chongzuo Biodiversity Research Institute, Peking University, Chongzuo, Guangxi, China.
Integr Zool. 2013 Dec;8(4):365-77. doi: 10.1111/1749-4877.12022.
Infanticide was first observed in langurs nearly 50 years ago, and this rare phenomenon has been inferred to have either an evolutionarily adaptive function or to be a pathological and non-functional behavior. In this study, we report 5 male takeover events in one-male groups of white-headed langurs in the Nongguan Karst Hills, Guangxi, China from 1998 to 2006. We recorded 13 attacks on 9 infants by extra-group males or new resident males. During the male takeovers, all of the infants younger than 6 months (with an average age of 3.6 months [N = 11]) in the groups disappeared. The infant death rate during the 4.2 months after takeover by a new male was significantly higher than the infant death rate calculated for most of the year. Older infants that were still nursing (with an average age of 14.1 months [N = 7]) were often attacked and seriously wounded by the extra-group males or new resident males, but all of them survived. The interbirth intervals of females whose infants were assumed to be killed by males were significantly reduced relative to those of females in groups with stable male tenure (mean = 10 months vs 25 months). Our data suggest that males kill unrelated and unweaned infants during the takeover period to decrease the time until the infants' mothers resume fertility. Thus, infanticide would support sexual selection theory in white-headed langurs. The data also show that infanticidal behavior was directed toward the infants, especially those who were still nursing. Female dispersal may function as a counter-strategy to avoid infanticide.
近50年前，人们首次在叶猴中观察到杀婴行为，这种罕见现象被推断要么具有进化适应性功能，要么是一种病态的、无功能的行为。在本研究中，我们报告了1998年至2006年期间在中国广西弄官喀斯特山区白头叶猴单雄群体中发生的5起雄猴接管事件。我们记录了群外雄猴或新迁入雄猴对9只幼猴的13次攻击。在雄猴接管期间，群体中所有6个月以下（平均年龄3.6个月 [N = 11]）的幼猴都消失了。新雄猴接管后的4.2个月内幼猴死亡率显著高于一年中大部分时间计算出的幼猴死亡率。仍在哺乳的较大幼猴（平均年龄14.1个月 [N = 7]）经常遭到群外雄猴或新迁入雄猴的攻击并受重伤，但它们都存活了下来。其幼猴被认为被雄猴杀死的雌性的产仔间隔相对于雄猴任期稳定的群体中的雌性显著缩短（平均为10个月对25个月）。我们的数据表明，雄猴在接管期杀死无亲缘关系且未断奶的幼猴，以缩短幼猴母亲恢复生育能力所需的时间。因此，杀婴行为在白头叶猴中支持性选择理论。数据还表明，杀婴行为针对的是幼猴，尤其是那些仍在哺乳的幼猴。雌性扩散可能作为一种反制策略来避免杀婴行为。
