Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
PLoS One. 2012;7(4):e35610. doi: 10.1371/journal.pone.0035610. Epub 2012 Apr 26.
Climate and weather conditions, such as the North Atlantic Oscillation, precipitation and temperature influence the birth sex ratio (BSR) of various higher latitude species, including deer, elephant seals or northern human populations. Although, tropical regions show only little variation in temperature, climate and weather conditions can fluctuate with consequences for phenology and food resource availability. Here, we evaluate, whether the BSR of chimpanzees, inhabiting African tropical forests, is affected by climate fluctuations as well. Additionally, we evaluate, if variation in consumption of a key food resource with high nutritional value, Coula edulis nuts, is linked to both climate fluctuations and variation in BSR. We use long-term data from two study groups located in Taï National Park, Côte d'Ivoire to assess the influence of local weather conditions and the global climate driver El Niño Southern Oscillation (ENSO) on offspring sex. Côte d'Ivoire has experienced considerable climate variation over the last decades, with increasing temperature and declining precipitation. For both groups we find very similar time windows around the month of conception, in which offspring sex is well predicted by ENSO, with more males following low ENSO values, corresponding to periods of high rainfall. Furthermore, we find that the time spent cracking and feeding on Coula nuts is strongly influenced by climate conditions. Although, some of our analysis suggest that a higher proportion of males is born after periods with higher nut consumption frequency, we cannot conclude decisively at this point that nut consumption may influence shifts in BSR. All results combined suggest that also chimpanzees may experience climate related shifts in offspring sex ratios as response to climate fluctuation.
气候和天气条件，如北大西洋涛动、降水和温度，影响着各种高纬度物种的出生性别比（BSR），包括鹿、象海豹或北方人类。虽然热带地区的温度变化很小，但气候和天气条件可能会波动，从而影响物候和食物资源的可获得性。在这里，我们评估了生活在非洲热带森林中的黑猩猩的 BSR 是否也受到气候波动的影响。此外，我们还评估了一种具有高营养价值的关键食物资源——Coula edulis 坚果的消耗变化是否与气候波动和 BSR 变化有关。我们使用来自科特迪瓦泰伊国家公园的两个研究小组的长期数据来评估当地天气条件和全球气候驱动因素厄尔尼诺南方涛动（ENSO）对后代性别的影响。科特迪瓦在过去几十年经历了相当大的气候变化，气温上升，降水减少。对于两个群体，我们都发现了与受孕月份非常接近的时间窗口，在这个时间窗口内，ENSO 很好地预测了后代的性别，低 ENSO 值对应于高降雨量时期，雄性比例较高。此外，我们发现，黑猩猩花在破解和食用 Coula 坚果上的时间受到气候条件的强烈影响。尽管我们的一些分析表明，在坚果食用频率较高的时期，雄性出生的比例较高，但我们不能在此刻得出决定性的结论，即坚果食用可能会影响 BSR 的变化。所有结果综合表明，黑猩猩也可能会经历与气候相关的后代性别比例变化，以应对气候波动。
