HAYES, JP*; SEARS, MW; BANTA, MR; O’CONNOR, CS; University of Nevada, Reno: Out in the cold: Physiological performance affects behavior of deer mice
Physiological performance (e.g., summit metabolism (VO2max) or basal metabolic rate (BMR) is often thought to be ecologically significant. If VO2max (which describes the upper limit to heat production) and BMR (which describes the lower limit to heat production for a normeothermic endotherm) are ecologically significant, they may act by influencing behavior, particularly in the cold. We conducted a laboratory study to test whether BMR or VO2max was correlated with behavior of 48 deer mice exposed to a series of cold temperatures. Each mouse had a warm nest box connected via a tube to an environmental chamber that contained food, ice chips, and a running wheel. Behavior was monitored while temperature in the environmental chamber was -5, -10, or -15 C for two days each. BMR was measured before and VO2max was measured before and after cold exposure. We used a linear mixed-model with repeated measures to analyze the data. Total time active in the cold was negatively correlated with temperature. Bout length (when mice were out of the nest box) decreased at colder temperatures, but number of bouts did not. Bout length increased with change in VO2max (post VO2max – pre VO2max). Food consumption decreased at colder temperatures resulting in loss of body mass. Mice with greater increases in VO2max ate more and lost less mass. Even though BMR is only part of the overall demand for energy, mice with higher BMR lost mass more rapidly under cold stress than mice with lower BMR. Our study suggests that mice with low BMR and larger capacity to increase VO2max may be best able to tolerate cold environments. In summary, physiological performance can affect behavior in response to environmental conditions. Supported by NSF IBN 9410693.
