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Accueil du site → Doctorat → États-Unis → 2013 → Linking climatic variability to behavior and fitness of herbivores : A bioenergetic approach

Idaho State University (2013)

Linking climatic variability to behavior and fitness of herbivores : A bioenergetic approach

Long, Ryan Andrew

Titre : Linking climatic variability to behavior and fitness of herbivores : A bioenergetic approach

Auteur : Long, Ryan Andrew

Université de soutenance : Idaho State University

Grade : Doctor of Philosophy (PhD) 2013

The heat-dissipation limit (HDL) theory challenges long-held views of endotherm energetics by emphasizing constraints that operate on the expenditure rather than the supply side of the energy-balance equation. Despite its broad ecological relevance, however, HDL theory rarely has been tested, and behavioral implications of the theory have not been fully articulated. We tested hypotheses derived from HDL theory about the interplay among climate, the energetic landscape (i.e., spatiotemporally explicit variation in costs versus supplies of energy), behavior, energy balance, and fitness of North American elk (Cervus elaphus) in two ecosystems with markedly different climatic regimes ; 1) a temperate montane forest ; and 2) an arid, high-elevation desert. At the population level, elk in the desert selected low-cost areas over those providing the highest-quality forage during spring-autumn. In contrast, costs imposed by the thermal environment were less pronounced in the forest, and patterns of selection were reversed. At the individual level, selection of low-cost areas by elk in the desert was state-dependent — individuals in the poorest condition at the end of winter showed the strongest selection for areas that reduced costs of thermoregulation during spring and summer, and also expended the least amount of energy on locomotion. Selection for forage quality by elk in the desert, however, did not vary with nutritional condition during spring and summer, and condition did not influence selection of low-cost areas or forage quality by elk in the forest. Nevertheless, female elk in the forest that consistently selected low-cost areas prior to parturition gave birth to larger young that had a higher probability of surviving until winter. In addition, lactating females that consistently selected high-quality forage during autumn in the forest accrued more fat and entered winter in better condition than individuals that were less selective. Our results are consistent with HDL theory, and highlight the importance of understanding the relative roles of energy expenditure versus intake in influencing patterns of behavior and energy balance. The capacity of endotherms to buffer themselves behaviorally against effects of climate change on fitness likely will determine thresholds beyond which changes in demography, population dynamics, or distribution occur.

Mots clés : behavior, biophysical model, climate change, ecosystem, elk, energy balance, large herbivores, movement, thermal environment,

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Page publiée le 13 avril 2014, mise à jour le 9 mars 2019