1. In ecological niche theory, diet is a trait frequently used to place species along a continuum from specialists to generalists. A multidimensional approach to investigating species’ niches has been developed to incorporate nutrition. We apply the concepts of multidimensional nutritional niche theory to the dietary patterns of a widespread, large herbivore, the American bison Bison bison, at various levels of its nutritional niche.
2. Specifically, we sought to estimate dietary niches for female bison at the levels of the forage items they consume and the macronutrients they acquire from those forage items. We assessed how these dietary niches changed seasonally and explored physical and climatic mechanisms that contribute to observed differences in the dietary niches. We also examined dietary differences between the two bison subspecies: wood bison Bison bison athabascae and plains bison Bison bison bison.
3. We compiled data for 16 bison subpopulations using 26 peer‐reviewed publications, government reports, conference proceedings, and graduate theses that described the dietary composition of female bison for analysis of dietary niches.
4. We found that the diets of female bison were, as expected, dominated by graminoids throughout the year, but during the growing season (spring and summer), dietary niches had greater breadth. Their diets were relatively high in carbohydrates, but percentages of dietary lipid and protein increased during the growing season. Further, we found significant increases in consumption of browse items, lipids, and proteins with increasing latitude (†N), and differences between American bison subspecies.
5. Our study provides insight into the fundamental macronutrient niche of the American bison and also provides a framework for the nutritional targets of bison. We show that bison are able to adapt to availability of local forage and that they may consume different items in different proportions in order to regulate nutritional composition of their diet.

中文翻译：

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美洲野牛野牛野牛日粮的经纬度和季节性可塑性

1. 在生态位理论中，饮食是一种特征，通常用于将物种沿着从专家到通才的连续体放置。已经开发了一种多维方法来研究物种的生态位，以纳入营养。我们将多维营养生态位理论的概念应用于各种规模的营养生态位的广泛的大型食草动物美国野牛野牛野牛的饮食模式。
2. 具体而言，我们试图估计雌性野牛在其所消耗的草料和从这些草料中获取的大量营养素水平上的饮食优势。我们评估了这些饮食生态位如何随季节变化，并探索了造成饮食生态位差异的物理和气候机制。我们还检查了两个野牛亚种之间的饮食差异：野牛野牛野牛athabascae和野牛野牛野牛野牛。
3. 我们使用26种经过同行评审的出版物，政府报告，会议记录和研究生论文，为16个野牛亚种汇编了数据，这些论文描述了女性野牛的饮食组成，以分析饮食生态位。
4. 我们发现，正如预期的那样，雌性野牛的饮食全年都以类固醇为主，但在生长季节（春季和夏季），饮食生态位的宽度更大。他们的饮食中碳水化合物含量较高，但在生长季节中饮食中脂质和蛋白质的百分比增加。此外，我们发现随着纬度（†N）的增加以及美国野牛亚种之间的差异，浏览项目，脂质和蛋白质的消耗量显着增加。
5. 我们的研究提供了对美洲野牛基本宏观营养素生态位的见解，还为野牛的营养目标提供了框架。我们表明，野牛能够适应当地草料的供应，并且他们可能会以不同比例食用不同的食物，以调节其饮食的营养成分。