DAVIS, J. R.*; DENARDO, D. F.; MATTLIN, A. K.; GALLARDO, L. I.; Arizona State University: Daily and Seasonal Activity Patterns of the Gila Monster, Heloderma suspectum

The hot, arid conditions of temperate deserts provide considerable physiological challenges. Therefore, despite the dependence on surface activity for foraging and reproductive behaviors, many desert species have restricted periods of surface activity, which is often influenced by environmental conditions (e.g., temperature, humidity, rainfall). Understanding the relationship between environmental conditions and surface activity provides valuable information regarding behavioral modifications used by desert organisms to maintain homeostasis despite the physiological challenges they face. We used implanted temperature data loggers to assess both body temperature and surface activity of Gila Monsters Heloderma suspectum over four periods of the active season (spring, dry summer, monsoon, and post-monsoon). Our results indicate that both the timing and duration of surface activity is influenced by temperature and rainfall. As ambient temperatures increase, surface activity shifts from crepuscular to nocturnal without a significant difference in activity duration. However, the onset of the monsoon season leads to a 7-fold increase in surface activity. Therefore, the monsoon season likely plays a critical role in the survival of this species, thus the existence of a reliable summer rainy season is probably a limiting factor in its distribution.