Identifying resources driving long-term trends in predators is important to understand ecosystem changes and to manage populations in the context of conservation or control. The arctic fox population in Iceland has increased steadily over a period of 30 years, an increase that has been attributed to an overall increase in food abundance. We hypothesized that increasing populations of geese or seabirds were driving this growth. We analyzed stable isotopes in a long-term series of collagen samples to determine the role of these different resources. The isotopic signatures of arctic foxes differed consistently between coastal and inland habitats. While δ15N displayed a non-linear change over time with a slight increase in the first part of the period followed by a decline in both habitats, δ13C was stable. Stable isotope mixing models suggested that marine resources and rock ptarmigan were the most important dietary sources, with marine resources dominating in coastal habitats and rock ptarmigan being more important inland. Our results suggest that seabirds may have been driving the arctic fox population increase. The rapidly increasing populations of breeding geese seem to have played a minor role in arctic fox population growth, as rock ptarmigan was the most important terrestrial resource despite a considerable decrease in their abundance during recent decades. This study shows that a long-term population trend in a generalist predator may have occurred without a pronounced change in main dietary resources, despite ongoing structural changes in the food web, where one species of herbivorous birds increased and another decreased.

中文翻译：

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通过稳定同位素评估，冰岛北极狐（Vulpes lagopus）在30年内的饮食变化。

识别驱动捕食者长期趋势的资源对于了解生态系统变化和在保护或控制的背景下管理种群很重要。在过去的30年中，冰岛的北极狐种群数量稳步增长，这归因于食物丰富度的总体提高。我们假设鹅或海鸟数量的增长正在推动这种增长。我们分析了胶原蛋白长期样品中的稳定同位素，以确定这些不同资源的作用。在沿海和内陆栖息地之间，北极狐的同位素特征一直存在差异。尽管δ15N随时间呈非线性变化，但在期初略有增加，随后两个生境均下降，但δ13C稳定。稳定的同位素混合模型表明，海洋资源和雷鸟雷是最重要的饮食来源，海洋资源在沿海生境中占主导地位，雷鸟雷是内陆更重要的食物。我们的结果表明，海鸟可能一直在推动北极狐种群的增长。尽管近几十年来其种群数量大量减少，但雷鸟是最重要的陆生资源，而快速增长的繁殖鹅种群在北极狐种群的增长中似乎起了很小的作用。这项研究表明，尽管食物网中结构不断发生变化，但通吃性捕食者的长期种群趋势可能并未发生主要饮食资源的明显变化，其中一种食草鸟类增加而另一种减少。