DAVIS, J.R.*; DENARDO, D.F.; TAYLOR, E.N.; MALAWY, M.; Arizona State Univ.: The use of implanted semicontinuous temperature loggers to estimate surface activity of ectotherms

Automated systems have proven reliable and effective for collecting data on the thermal biology of organisms. For ectothermic vertebrates, body temperature (T_b) data collected with such systems can also be used to estimate the timing and duration of activity bouts when compared to air temperature (T_a). For example, the T_b of a surface-active ectotherm is predicted to be similar to or higher than T_a (as a result of radiant heat gain), whereas the T_b of an ectotherm in a refuge would tend to be relatively stable and lower than T_a on a hot day. Based upon these generalizations, one could estimate the timing and duration of surface activity on nearly any temporal scale. However, environmental conditions and behavioral patterns of a species might greatly influence the validity of these assumptions. We assessed the efficacy of this technique in two free-ranging ectothermic vertebrates native to the Sonoran Desert: an active forager, the Gila Monster (Heloderma suspectum), and a sit-and-wait predator, the Western Diamond-backed Rattlesnake (Crotalus atrox). We implanted temperature data loggers and radiotelemeters in all animals used in this study. We used our field notes to compile a list of dates and times that specific animals were tracked using radiotelemetry and noted whether the animal was surface active or inactive when tracked. We plotted T_b and T_a on the same y-axis and by comparing the two, generated an estimate of activity for each individual tracked. Visual confirmations of activity and inactivity made during tracking episodes were then compared with estimates of activity made using automated systems. The results of this study will yield useful information regarding the applicability of this technique for estimating activity in free-ranging desert ectotherms.