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From Tissues to Landscapes: How Thermal Physiology, Water Use, and Climate Influence Patterns of Landscape Use in Elephants

  • Author(s): Dunkin, Robin Christine
  • Advisor(s): Williams, Terrie M
  • et al.
Abstract

In the following chapters the interaction between large body size and climate and the resulting influence of this interaction at the level of the tissue, the whole body, and at the landscape level are investigated. In chapter one, tissue level adaptations of Asian (Elephas maximus)(Loxodonta africana)oC range of ambient temperatures were used to construct climate dependent thermal and water budgets. In chapter three, these budgets were used to construct a coupled biophysical and dynamic programming model to investigate how climate together with thermal, water, and energy demands, interact to produce landscape level patterns of habitat use. At the tissue level, the integument of elephants has a high water and low lipid content and its thermal conductivity (0.19±0.01 to 0.23±0.13 W m--10C) approaches the upper limit of previously measured mammalian values. The integument's resistance to water loss is also low and is comparable to or less than that of some amphibians. At the whole body level, low integumental resistance results in high rates of cutaneous evaporative water loss (E.m.: 0.31 and 8.9 g min-1m-2; L.a.: 0.26 and 6.5 g min-1m-2) and at temperatures between 28-30oC, elephants are fully dependent on evaporative cooling to dissipate heat produced from resting metabolism. At the landscape level, simulations under six combinations of climate and primary productivity demonstrated that under cool and moderate climates, primary productivity was the strongest determinate of home range size, however, at temperatures above 24-27oC, ambient temperature was limiting as elephants were more tightly tethered to water with less access to food. Climate appears to have a non-linear influence on landscape use because evaporative cooling increases exponentially with ambient temperature. Although the drivers of landscape use by large herbivores are complex, the results of this work demonstrate the importance of interactions between body size and climate spanning three levels of biological organization, in setting the fundamental spatial and temporal patterns of landscape use reported for elephants.

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