Eppley Timothy M, Donati Giuseppe, Ganzhorn Jörg U
Department of Anthropology, University of Texas at Austin, 2201 Speedway Stop C3200, Austin, Texas, 78712.
Department of Animal Ecology and Conservation, Biozentrum Grindel, University of Hamburg, Martin-Luther-King Platz 3, Hamburg, 20146, Germany.
Am J Phys Anthropol. 2016 Oct;161(2):328-42. doi: 10.1002/ajpa.23034. Epub 2016 Jun 27.
The proximate and ultimate determinants that may have prompted some primates to shift from an arboreal to terrestrial feeding niche, whether due to environmental change, seasonality, and/or predation pressure, are poorly understood. Within a fragmented littoral forest in southeast Madagascar, an arboreal strepsirrhine population spends a large proportion of time on the ground, thus we aimed to identify which factors influence terrestrial feeding.
From January to December 2013, we conducted 103 full-day focal follows on three social groups of southern bamboo lemurs H. meridionalis. We continuously recorded feeding time on all arboreal and terrestrial items, as well as whether the focal individual was under the canopy or exposed, and the distance to their nearest conspecific neighbor. All observed food items were collected and analyzed for macronutrient content. Daily climatic variables (temperature, precipitation), resource seasonality, daily path length (DPL), along with dietary and predation risk proxies, were used as fixed effects in a linear mixed model, with the daily proportion of terrestrial feeding as the dependent variable.
Our model indicated that daily terrestrial feeding increased at cooler temperature, was associated with reduced DPL, and the intake of dietary metabolizable energy increased as terrestrial feeding increased. All other fixed effects were not significant predictors.
Our study provides a window into the ultimate determinants of niche expansion: ancestral primates, in absence of their primary resources, may have initially descended to the ground in peripheral population range areas where the benefits (e g., nutritional pay-off) out-weighed the costs.
对于可能促使一些灵长类动物从树栖觅食生态位转向陆地觅食生态位的直接和最终决定因素，我们了解得还很少，这些因素可能是由于环境变化、季节性和/或捕食压力导致的。在马达加斯加东南部一片碎片化的沿海森林中，一个树栖的狐猴种群在地面上花费了大量时间，因此我们旨在确定哪些因素影响陆地觅食。
2013年1月至12月，我们对南方竹狐猴（H. meridionalis）的三个社会群体进行了103次全天的焦点跟踪。我们持续记录在所有树栖和陆地食物上的进食时间，以及焦点个体是在树冠下还是暴露在外，以及到其最近同种邻居的距离。所有观察到的食物都被收集起来并分析其宏量营养素含量。每日气候变量（温度、降水量）、资源季节性、每日路径长度（DPL），以及饮食和捕食风险指标，被用作线性混合模型中的固定效应，以陆地觅食的每日比例作为因变量。
我们的模型表明，在较凉爽的温度下，每日陆地觅食增加，这与DPL的减少有关，并且随着陆地觅食的增加，饮食可代谢能量的摄入量也增加。所有其他固定效应都不是显著的预测因子。
我们的研究为生态位扩展的最终决定因素提供了一个窗口：在没有主要资源的情况下，祖先灵长类动物可能最初在边缘种群范围区域下到地面，在那里好处（例如营养回报）超过了成本。
