bioRxiv preprint doi: https://doi.org/10.1101/383679; this version posted August 2, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Title: Torpor duration, more than temperature, is key to hummingbird nighttime energy savings Authors: A Shankar*1, RJ Schroeder*2,3 , SM Wethington4, CH Graham1,5, DR Powers2 * Equal and corresponding authors 1 Stony Brook University, Stony Brook, NY 11794, USA 2 George Fox University, Newberg, OR 97132, USA 3Current Address: 2721 Kingsway Dr. Homedale, ID 83628 4 Hummingbird Monitoring Network, Patagonia, Arizona 85264 USA 5 Swiss Federal Research Institute (WSL), Birmensdorf, CH-8903 Switzerland Page | 1 *Emails:
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[email protected] bioRxiv preprint doi: https://doi.org/10.1101/383679; this version posted August 2, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. ABSTRACT 1. Torpor is an important energy saving strategy in small endotherms, but it has been insufficiently studied in natural field conditions. Building on what we know from laboratory studies, we compared torpor use across hummingbird species and different natural temperature regimes to explore predominant hypotheses about torpor use and evaluate the possible effects of environmental variation on energy management. 2. We found that the probability of an individual entering torpor was correlated with mass and unrelated to nighttime temperature, and that hummingbirds at both warm tropical and cooler temperate sites used torpor.