Data from: Macronutrient signature of dietary generalism in an ecologically diverse primate in the wild

A question of considerable importance is why some animals are able to succeed on a wide range of diets while others are more tightly constrained. Theory predicts that generalists should show a flexible response for macronutrient acquisition in the face of ecologically-driven constraint on the nutritional balance of available foods, which in the modelling framework of nutritional geometry has been quantitatively characterized as an “equal distance” regulatory model. This prediction, which has empirical support from several laboratory studies on insects, has not been tested for any generalist animal in the wild, nor for any vertebrate. We performed the first such test, using 281 dawn-to-dusk focal animal observations over three years (2013-2015) of Rhesus macaques monkeys (Macaca mulatta tcheliensis), a primate that is second only to humans in ecological generalism. Results showed, as predicted, that macronutrient regulation conformed closely to the equal distance pattern, and differed markedly from the other, ecologically more-specialized primate species that have been studied to date. The same was independently true for lactating and non-lactating macaques, but lactating females had substantially higher intake of macronutrients, as well as the non-nutritional food components, indigestible fiber and tannins. This demonstrates that equal distance regulation by non-lactating monkeys was not an artefact of constraint such as restricted food availability or an upper limit to the ingestion of dietary fiber or plant tannins, but a strategic regulatory response to variation in dietary macronutrient balance. We discuss implications of our results for the most generalist primate of all, humans.

一个极具研究价值的核心问题在于：为何部分动物能够适应多样化的饮食结构，而另一些动物的饮食范围则受到更为严格的限制。相关理论预测，当可获得食物的营养平衡受到生态因素驱动的限制时，广食性动物应在宏量营养素（macronutrient）获取方面表现出灵活的调节策略；在营养几何学（Nutritional Geometry）的建模框架中，这种调节模式已被定量表征为‘等距’（equal distance）调节模型。该预测虽已在多项昆虫实验室研究中获得实验证据支持，但尚未在野生广食性动物或任何脊椎动物类群中得到验证。本研究开展了此类验证的首次尝试，以2013至2015年三年间累计281次从黎明至黄昏的定点猕猴（Macaca mulatta tcheliensis）观察数据为基础——该非人灵长类在生态广食性方面仅次于人类。研究结果与理论预测一致：猕猴的宏量营养素调节模式与‘等距’模型高度契合，且与迄今已被研究的其他生态特化灵长类物种存在显著差异。该规律在哺乳期与非哺乳期猕猴中均独立成立，但哺乳期雌性的宏量营养素摄入量以及不可消化膳食纤维、单宁等非营养性食物组分的摄入量均显著更高。这表明非哺乳期猕猴的等距调节模式并非由食物可获得性受限、膳食纤维或植物单宁摄入存在上限等约束条件所导致的人为假象，而是针对膳食宏量营养素平衡变化的战略性调节响应。最后，我们讨论了本研究结果对广食性程度最高的灵长类——人类的研究启示。