19.2 Friday, Jan. 4 Resource needs and climate means contributing to a global heterothermic continuum in mammals THOMPSON, A.B.; BOYLES, J.G.*; MCKECHNIE, A.E.; MALAN, E.; HUMPHRIES, M.M.; CAREAU, V.; McGill Univ.; Southern Illinois Univ.; Univ. of Pretoria; Univ. of California, Riverside; McGill Univ. email@example.com
Thermoregulatory patterns are a defining characteristic of all animals, but endotherms have garnished special attention in this area, presumably because of the ecological and evolutionary success these species have gained from their ability to control body temperature (Tb) via metabolic thermogenesis. We evaluated ecological and evolutionary factors that affect Tb patterns in mammals using two complementary metrics that place variation in Tb on continuous scales (Thermoregulatory Scope, TS; and Heterothermy Index, HI). Body mass, season, latitude, and hoarding were important predictors of TS, a proxy of the variation in Tb a species is capable of displaying. Similarly, body mass, latitude, and average environmental temperature were important predictors of HI, a measure of the variation in Tb displayed under natural conditions. During winter, there was a strong positive relationship between latitude and heterothermy, suggesting species at high latitudes are more likely to display large fluctuations in Tb. However, during summer, HI values were negatively related to latitude, suggesting that factors other than temperature (e.g. water or food availability) more strongly affect Tb patterns. Phylogenetically older taxa exhibited high TS values, suggesting they are capable of allowing Tb to fluctuate more than phylogenetically young taxa. However, the phylogenetic pattern was less clear in HI values, suggesting that although older taxa may be more capable of displaying heterothermy, Tb patterns in the wild are strongly controlled by ecological factors.