WEATHER VARIABLES HELP PREDICT FIELD SIGHTINGS OF GILA MONSTERS (HELODERMA SUSPECTUM) AT SAGUARO NATIONAL PARK

picture of Victoria Farrar presenting his/her poster: WEATHER VARIABLES HELP PREDICT FIELD SIGHTINGS OF GILA MONSTERS (HELODERMA SUSPECTUM) AT SAGUARO NATIONAL PARK

Victoria Farrar , Kevin Bonine

WEATHER VARIABLES HELP PREDICT FIELD SIGHTINGS OF GILA MONSTERS (HELODERMA SUSPECTUM) AT SAGUARO NATIONAL PARK

The Gila monster (Heloderma suspectum) is a large and venomous lizard native to the Sonoran Desert. For these ectothermic reptiles with tropical ancestry, the activity patterns and behavior of individuals are influenced by environmental conditions. We hypothesized that climate and weather information could predict the observed activity (i.e whether or not an individual was sighted) of Gila monsters in the field. Daily weather data from a two year (2011-2012) field study of Gila monsters in Saguaro National Park (Rincon Mountain District), east of Tucson, was compared to reported observations of active Gila monsters in the same study. Considering reptile physiology and previous observations, we expected that humidity (positive correlation), temperature (positive correlation for intermediate temperatures), and wind speed (negative correlation) would be the most predictive variables for observed Gila monster activity. Our data indicated that humidity had no significant effect on sightings in this study. However, temperature (at 1 cm above the ground surface), amount of cloud cover, and average wind speed (measured over 60 seconds) best predicted observed Gila monster activity across multiple models. Contrary to what was expected, all three of these measurements were positively correlated with sightings, perhaps indicating interactions between weather variables. Moreover, the predictive utility of the weather variables changed seasonally. Understanding how the abiotic environment influences Gila monsters can better inform future research, tracking studies, and the implications of climate change. 

This research project was supported in part by funding from the UA Provost's Office, and The Friends of Saguaro National Park. 

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