Abstract
The nutritional state of animals is tightly linked to the ambient environment, and for northern ungulates the state strongly influences vital population demographics, such as pregnancy rates. Continuously growing tissues, such as hair, can be viewed as dietary records of animals over longer temporal scales. Using sequential data on nitrogen stable isotopes (δ15N) in muskox guard hairs from ten individuals in high arctic Northeast Greenland, we were able to reconstruct the dietary history of muskoxen over approximately 2.5 years with a high temporal resolution of app. 9 days. The dietary chronology included almost three full summer and winter periods. The diet showed strong intra- and inter-annual seasonality, and was significantly linked to changes in local environmental conditions (temperature and snow depth). The summer diets were highly similar across years, reflecting a graminoid-dominated diet. In contrast, winter diets were markedly different between years, a pattern apparently linked to snow conditions. Snow-rich winters had markedly higher δ15N values than snow-poor winters, indicating that muskoxen had limited access to forage, and relied more heavily on their body stores. Due to the close link between body stores and calf production in northern ungulates, the dietary winter signals could eventually serve as an indicator of calf production the following spring. Our study opens the field for further studies and longer chronologies to test such links. The method of sequential stable isotope analysis of guard hairs thus constitutes a promising candidate for population-level monitoring of animals in remote, arctic areas.
Highlights
Quantity and quality of forage is decisive for herbivore body condition and health, and may in turn affect vital population demographics, such as pregnancy rates and survival [1]
Stable isotope analyses constitute a valuable tool for unravelling animal diets, as stable isotopes in animal tissues and excreta reflect dietary preferences, and yield insight into the environmental conditions experienced by the animal [2, 3]
The length of the guard hairs used in this study ranged from 12–22 cm
Summary
Quantity and quality of forage is decisive for herbivore body condition and health, and may in turn affect vital population demographics, such as pregnancy rates and survival [1]. The ability to track animal diets as an indicator of changes in the environmental conditions, and thereby their likely consequences for animal population dynamics, are of great interest. Stable isotope analyses constitute a valuable tool for unravelling animal diets, as stable isotopes in animal tissues and excreta reflect dietary preferences, and yield insight into the environmental conditions experienced by the animal [2, 3]. Being able to understand the link between environmental conditions and animal diets, and to population dynamics, would greatly extend our understanding of the important drivers of changes in animal populations, and inform proper conservation and management initiatives. The analysis of stable isotopes in animal tissue or excreta may be a valuable, and often non-invasive, tool for species monitoring [10,11,12]
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