ACTIVITY PATTERNS IN RELATION TO BODY-MASS AND AMBIENT-TEMPERATURE AMONG OVERWINTERING COTTON RATS (SIGMODON HISPIDUS)

We examined mass-specific activity patterns among overwintering cotton rats (Sigmodon hispidus) in northeastern Kansas. We livetrapped anima ls for a 24-h period, checking traps every 2 h. Trapping occurred ever y 2 weeks for 5 months. We estimated probability of capture for each m ass class, time class, and date, then tested for differences in probab ility of capture (i.e., activity levels) using a General Linear Model with temperature as a covariate. Large cotton rats were significantly less active than small and intermediate-sized cotton rats. Activity of small cotton rats increased with decreasing temperature, whereas larg er cotton rats were less responsive to temperature. Finally, activity levels of large and small cotton rats did not vary significantly with time of day, but intermediate-sized cotton rats were significantly les s likely to be captured during the night than at dusk.