Meeting Abstract

S10.9  Friday, Jan. 7  Activity substitution for thermoregulation and the metabolic ecology of endotherms HUMPHRIES, Murray*; CAREAU, Vincent; McGill University; Sherbrooke University murray.humphries@mcgill.ca

If heat generated through activity can substitute for thermoregulatory requirements, then activity in cold environments may be energetically free for endotherms. Although the possibility of at least partial activity substitution has been long recognized, occasionally confirmed, and rarely refuted, its ecological implications have received little attention. We combine literature review, heat exchange modeling, and empirical evaluation to explore the implications of complete and partial activity substitution on the behavior and metabolic design of cold and warm-climate endotherms. We also model the extent to which activity substitution is likely to vary with body size and insulation to assess how differential activity substitution may inform macroecological patterns in body size, metabolism and activity. Activity substitution can account for several patterns in the metabolic ecology and activity patterns of endotherms, including narrower metabolic niches in cold climates and the scaling of activity rates. Activity substitution for themoregulatory requirements is an important and understudied aspect of endotherm thermal biology influencing the physiological, behavioral and ecological responses of free-ranging endotherms to temperature variation.