What to eat in a warming world: do increased temperatures necessitate hazardous duty pay?
Contemporary climate change affects nearly all biomes, causing shifts in animal distributions and resource availability. Changes in resource selection may allow individuals to offset climatic stress, thereby providing a mechanism for persistence amidst warming conditions. Whereas the role of predation risk in food choice has been studied broadly, the extent to which individuals respond to thermoregulatory risk by changing resource preferences is unclear. We addressed whether individuals compensated for temperature-related reductions in foraging time by altering forage preferences, using the American pika (Ochotona princeps) as a model species. We tested two hypotheses: (1) food-quality hypothesis—individuals exposed to temperature extremes should select higher-quality vegetation in return for accepting a physiologically riskier feeding situation; and (2) food-availability hypothesis—individuals exposed to temperature extremes should prioritize foraging quickly, thereby decreasing selection for higher-quality food. We quantified the composition and quality (% moisture, % nitrogen, and fiber content) of available and harvested vegetation, and deployed a network of temperature sensors to measure in situ conditions for 30 individuals, during July–Sept., 2015. Individuals exposed to more extreme daytime temperatures showed increased selection for high-nitrogen and for low-fiber vegetation, demonstrating strong support for the food-quality hypothesis. By contrast, pikas that experienced warmer conditions did not reduce selection for any of the three vegetation-quality metrics, as predicted by the food-availability hypothesis. By shifting resource-selection patterns, temperature-limited animals may be able to proximately buffer some of the negative effects associated with rapidly warming environments, provided that sufficient resources remain on the landscape.
KeywordsThermoregulatory risk Climate change Forage choice Resource selection Ochotona princeps
The Wyoming Game and Fish Department, in cooperation with the Meg & Bert Raynes Wildlife Fund, Natural Resource Conservation Service, University of Wyoming-Office of Research, University of Wyoming-Program in Ecology, University of Wyoming-Zoology and Physiology Department, U.S. Geological Survey, and Louise & Ralph Haberfeld, funded our work. We are grateful to C. Tarwater, T. Robinson, J. Ceradini and J. Carlisle for advice on statistical analyses, along with colleagues in the Quantitative Analysis of Field Data course at the University of Wyoming. G. Barille and L. Sanders provided helpful comments on our preliminary findings. We thank E. Beever, M. Ben-David, J. Merkle, J. Shinker, C. Whelan and two anonymous referees for insightful feedback on an earlier draft of the manuscript. Field and data support were provided by: S. DuBose, S. Gaddis, J. Henningsen, R. Jakopak, A. Ruble, C. Tappe and M. Wallace. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
LEH formulated the idea, LEH and ADC developed hypotheses and designed the study, LEH conducted the fieldwork, completed the analyses and drafted the manuscript, ADC provided critical feedback on manuscript drafts as well as essential intellectual input throughout the entirety of the study.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable institutional and/or national guidelines for the care and use of animals were followed.
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