Meeting Abstract
Despite a large body of knowledge on the thermoregulation of temperate and cold-climate endotherms, our functional knowledge of endotherms in warmer climates remains incredibly scarce. In particular, their use of facultative heterothermy, lowering or raising body temperatures to conserve energy and/or water, has been chronically understudied. Small endotherms (<5kg) are often assumed to live predominantly at temperatures below thermoneutrality. Tropical and subtropical mammals, however, routinely experience temperatures above the lower critical limit of their thermoneutral zones. Therefore, unlike temperate species that must consistently generate heat to maintain an elevated body temperature, low latitude species spend more time at thermoneutrality and therefore can spend the energy elsewhere. As well as providing a general overview of some of the forms of heterothermy observed in warm climates, I will review the results of field studies on a highly heterothermic nocturnal mammal (the greater hedgehog tenrec, Setifer setosus) and a homeothermic (yet thermally labile) diurnal mammal (the large treeshrew, Tupaia tana). I discuss the costs and benefits of the body temperature variability in warm climates, the evolution of homeothermy in mammals, and the links (or lack thereof) between basal metabolic rates and life histories in mammals.
