SEARS, Michael W; HAYES, Jack P; GELUSO, Keith; O’CONNOR, Candace S; University of Nevada, Reno; University of Nevada, Reno; University if Nevada, Reno; University of Nevada, Reno: Physiological correlates of behavior: does maximal oxygen consumption influence activity in free-ranging deer mice?

Physiological performance likely affects behavior, but ecological and evolutionary physiologists know relatively little about how individual variation in physiological performance influences the behavior of animals in nature. We investigated whether thermogenic capacity (VO₂max, the maximal rate of oxygen consumption elicited during cold exposure) affects behavior of deer mice (Peromyscus maniculatus) living at high altitude (3800 m). We investigated the relationships between environmental conditions and aboveground activity of deer mice with known VO₂max. We measured hourly nocturnal activity during some of the coldest nights possible (i.e., immediately before the first heavy snows of the autumn when air temperatures were low, wind speeds were high, and there was little snow on the ground for insulation). We tested two hypotheses: 1) do thermal conditions affect activity at the population level, and 2) does individual variation in thermogenic capacity influence which deer mice are active during the coldest nights (i.e., can only mice with high VO₂max be active during the coldest nights). The influence of environmental conditions (standard operative temperature), thermogenic capacity, and body mass on activity were evaluated using both multiple regression and Pollock’s robust design to model recapture probabilities. The relative importance of competing models for different combinations of environmental conditions and individual physiology on activity were ranked using information-theoretic procedures. Our study represents one of the few attempts to document the links between physiology, behavior, and fitness in an ecological context.