Ecological flexibility within animal populations can allow for variation in resource use and foraging decisions. We estimated brown bear (Ursus arctos) diet composition in Gates of the Arctic National Park and Preserve, Alaska from 2013 to 2015 to evaluate how variation in foraging behavior influences body condition and size. We used stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of sectioned brown bear hair samples to evaluate assimilated diet. We then developed a set of a priori linear models to evaluate differences in the diet composition of brown bears (n = 80) in relation to body fat (%) and mass. The proportion of meat (salmon [Oncorhynchus keta] and terrestrial meat combined) in the diet from July through late September varied between male and female bears, with males (x-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\stackrel{-}{x}$$\end{document} = 62%, SD = 30) assimilating significantly more meat than females (x-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\stackrel{-}{x}$$\end{document} = 40%, SD = 29). Most of the meat consumed came from marine-derived resources for males (53% of the total diet or 86% of the meat) and females (31% of the total diet or 77% of the meat). As we found the range of observed diets was unrelated to physiological outcomes (i.e., percentage body fat), we suggest that ecological flexibility within populations may provide an adaptive advantage by allowing individuals to reduce competition with conspecifics by foraging on alternate food resources. Identifying variable foraging behaviors within a population can allow for a better understanding of complex behaviors and, ultimately, lead to more informed management decisions related to habitat use, development, and harvest.

中文翻译：

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膳食可塑性以及鲑鱼对北极低生态系统中棕熊 (Ursus arctos) 体型和状况的重要性

动物种群内的生态灵活性可以允许资源利用和觅食决定的变化。我们估计了 2013 年至 2015 年阿拉斯加北极国家公园和保护区盖茨的棕熊 (Ursus arctos) 饮食成分，以评估觅食行为的变化如何影响身体状况和体型。我们使用对切片棕熊毛发样本进行稳定碳 (δ13C) 和氮 (δ15N) 同位素分析来评估同化饮食。然后，我们开发了一组先验线性模型来评估棕熊 (n = 80) 的饮食成分与体脂 (%) 和质量之间的差异。7 月至 9 月下旬的饮食中肉类（鲑鱼 [Oncorhynchus keta] 和陆生肉的总和）的比例因雄性和雌性熊而异，男性 (x-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength {\oddsidemargin}{-69pt} \begin{document}$$\stackrel{-}{x}$$\end{document} = 62%, SD = 30) 吸收的肉明显多于雌性 (x-\documentclass[ 12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\stackrel{-}{x}$$\end{document} = 40%，SD = 29）。消耗的大部分肉类来自男性（总饮食的 53% 或肉类的 86%）和女性（总饮食的 31% 或肉类的 77%）的海洋衍生资源。由于我们发现观察到的饮食范围与生理结果（即体脂百分比）无关，我们建议种群内的生态灵活性可以通过允许个体通过寻找替代食物资源来减少与同种物种的竞争来提供适应性优势。识别种群中可变的觅食行为可以更好地理解复杂的行为，并最终导致与栖息地使用、开发和收获相关的更明智的管理决策。