Pethig Leonie, Ozgul Arpat, Heistermann Michael, Fichtel Claudia, Kappeler Peter M
Behavioral Ecology and Sociobiology Unit, German Primate Center, Leibniz Institute for Primate Research, Göttingen 37077, Germany.
Department of Sociobiology/Anthropology, Johann-Friedrich-Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Göttingen 37077, Germany.
Biol Lett. 2025 Feb;21(2):20240418. doi: 10.1098/rsbl.2024.0418. Epub 2025 Feb 26.
Most mammals, including humans, exhibit even or slightly male-biased birth sex ratios (BSRs) and female-biased adult sex ratios (ASRs) much later in life due to higher male mortality rates. The group-living primates of Madagascar are unusual in this respect because they lack female-biased ASRs, but it is unknown whether this is the result of skewed BSRs or sex-specific disappearance patterns. Using long-term demographic data from wild red-fronted lemurs (), we analysed their sex ratio dynamics across the lifespan. We assessed BSR via prenatal sex determination using maternal faecal oestrogen metabolite measurements during late pregnancy, confirming a visually determined equal sex ratio three months after birth, and indicating no early sex-specific mortality. Demographic analyses additionally disclosed higher female disappearance within the first 8 years of age, likely associated with reproductive effort early in life. Thereby, adult male survival had the greatest positive effect on the ASR. Our study offers a rare perspective on the dynamics of age- and sex-specific disappearance in a wild primate population, whose sex-reversed patterns may also contribute to a more general understanding of the mechanisms generating sex-biased mortality.
包括人类在内的大多数哺乳动物，出生时的性别比（BSR）呈均等或略偏向雄性，而成年后的性别比（ASR）则偏向雌性，这是因为雄性死亡率更高。马达加斯加的群居灵长类动物在这方面很不寻常，因为它们不存在偏向雌性的成年性别比，但尚不清楚这是出生性别比失衡还是特定性别的消失模式导致的结果。利用野生红额狐猴的长期人口统计数据，我们分析了其整个生命周期内的性别比动态。我们通过在妊娠后期测量母体粪便中的雌激素代谢物来进行产前性别鉴定，以此评估出生性别比，证实出生三个月后通过视觉确定的性别比是均等的，这表明不存在早期特定性别的死亡率。人口统计分析还显示，雌性在8岁前消失的比例更高，这可能与生命早期的生殖努力有关。因此，成年雄性的存活对成年性别比的影响最为显著。我们的研究为野生灵长类种群中年龄和性别特异性消失的动态提供了一个难得的视角。其性别反转模式也可能有助于更全面地理解导致性别偏向性死亡率的机制。
