An automated temperature-based option for estimating surface activity and refuge use patterns in free-ranging animals

Accurately assessing free-ranging animals’ patterns of surface activity and refuge use is critical, yet fundamentally challenging for biologists and wildlife managers. We evaluate the accuracy of an automated technique—temperature-based activity estimation (TBAE)—in estimating surface activity and refuge use patterns of two sympatric reptiles, the western diamond-backed rattlesnake (Crotalus atrox) and the Gila monster (Heloderma suspectum) in the Sonoran Desert. TBAE derived from a comparison of body temperature to shaded air temperature was effective in estimating the overall percent surface activity for both rattlesnakes (observed surface activity 51.8%, TBAE estimated surface activity 48.2%) and Gila monsters (observed 22.3%, TBAE 24.5%). There was, however, considerable interspecific difference in the effectiveness of TBAE in predicting surface activity at specific time points; TBAE was far more accurate for Gila monsters than for rattlesnakes (96% vs. 66% time point-specific accuracy, respectively). We assert that, when validated, TBAE can be used to yield concurrent and accurate body temperatures and activity estimates for multiple free-ranging animals, particularly in arid environments, which improves our understanding of animal biology and can be used to inform management decisions.