Data from: Functional implications of omnivory for dietary nutrient balance

Captive experiments have shown that many species regulate their macronutrient (i.e. protein, lipid, and carbohydrate) intake by selecting complementary food types, but the relationships between foraging strategies in the wild and nutrient regulation remain poorly understood. Using the pine marten as a model species, we collated available data from the literature to investigate effects of inter-annual, seasonal and geographic variation in diet on dietary macronutrient balance. Our analysis showed that despite a high variety of foods comprising the diet, typical of a generalist predator, the macronutrient energy ratios of pine martens were limited to a range of 50-55% of protein, 38-42% of lipids and 5-10% of carbohydrates. This broad annual stabilisation of macronutrient ratios was achieved by using alternative animal foods to compensate for the high fluctuation of particular prey items, and sourcing non-protein energy (carbohydrates and fats) from plant-derived foods, particularly fruits. Macronutrient balance varied seasonally, with higher carbohydrate intake in summer-autumn, due to opportunistic fruit consumption, and higher protein intake in winter-spring. In terms of their proportional dietary carbohydrate intake the pine marten's nutritional strategy fell between that of true carnivores (e.g. the wolf) and more omnivorous feeders (e.g. the European badger). However, in terms of energy contributed by protein pine martens are equivalent to obligate carnivores such as the wolf and domesticated cat, and different to some omnivorous carnivores such as the domesticated dog and grizzly bears.圈养实验已证实，诸多物种会通过选择互补性食物类型来调控宏量营养素（macronutrient，即蛋白质、脂质与碳水化合物）的摄入，但野生觅食策略与营养调控之间的关联仍有待深入阐明。本研究以松貂为模式物种（model species），整合已发表的文献数据，探究了日粮的年际、季节及地理变异对日粮宏量营养素平衡的影响。分析结果显示，尽管松貂作为广食性捕食者（generalist predator），其日粮食物种类繁多，但松貂的宏量营养素能量占比被限定在特定范围：蛋白质50%-55%、脂质38%-42%、碳水化合物5%-10%。松貂通过利用替代性动物性食物来弥补特定猎物资源的剧烈波动，并从植物源食物（尤其是果实）中获取非蛋白能量（碳水化合物与脂肪），从而实现宏量营养素占比的年度稳态维持。宏量营养素平衡存在季节变异：夏秋季因机会性采食果实，碳水化合物摄入占比更高；冬春季则蛋白质摄入占比更高。从日粮碳水化合物摄入占比来看，松貂的营养策略介于专性食肉动物（true carnivore，如狼）与高度杂食性动物（omnivorous feeder，如欧洲獾）之间。但从蛋白质贡献的能量占比来看，松貂与狼、家猫等专性食肉动物并无差异，却与家犬、灰熊等杂食性食肉动物有所不同。