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2 March 2020 State-dependent foraging by caribou with different nutritional requirements
Kristin Denryter, Rachel C. Cook, John G. Cook, Katherine L. Parker, Michael P. Gillingham
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Abstract

Foraging by animals is hypothesized to be state-dependent, that is, varying with physiological condition of individuals. State often is defined by energy reserves, but state also can reflect differences in nutritional requirements (e.g., for reproduction, lactation, growth, etc.). Testing hypotheses about state-dependent foraging in ungulates is difficult because fine-scale data needed to evaluate these hypotheses generally are lacking. To evaluate whether foraging by caribou (Rangifer tarandus) was state-dependent, we compared bite and intake rates, travel rates, dietary quality, forage selection, daily foraging time, and foraging strategies of caribou with three levels of nutritional requirements (lactating adults, nonlactating adults, subadults 1–2 years old). Only daily foraging times and daily nutrient intakes differed among nutritional classes of caribou. Lactating caribou foraged longer per day than nonlactating caribou—a difference that was greatest at the highest rates of intake, but which persisted even when intake was below requirements. Further, at sites where caribou achieved high rates of intake, caribou in each nutritional class continued foraging even after satisfying daily nutritional requirements, which was consistent with a foraging strategy to maximize energy intake. Foraging time by caribou was partially state-dependent, highlighting the importance of accounting for physiological state in studies of animal behavior. Fine-scale foraging behaviors may influence larger-scale behavioral strategies, with potential implications for conservation and management.

© The Author(s) 2020. Published by Oxford University Press on behalf of American Society of Mammalogists. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
Kristin Denryter, Rachel C. Cook, John G. Cook, Katherine L. Parker, and Michael P. Gillingham "State-dependent foraging by caribou with different nutritional requirements," Journal of Mammalogy 101(2), 544-557, (2 March 2020). https://doi.org/10.1093/jmammal/gyaa003
Received: 20 May 2019; Accepted: 10 January 2020; Published: 2 March 2020
KEYWORDS
bite rate
diet quality
diet selection
energy maximizing
foraging time
intake rate
lactation
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