Longitudinal Study of Saguaro National Park’s Gila Monsters

Tullis, Martha Resource Management Saguaro National Park, Tucson, Arizona, USA martha_tullis@partner.nps.gov

Perkins, Nic Resource Management Saguaro National Park, Tucson, Arizona, USA

Swann, Don Resource Management Saguaro National Park, Tucson, Arizona, US

Saguaro National Park (Tucson, AZ) has a large population of Gila monsters (Heloderma suspectum), many regular visitors, and a database of over 700 photos of Gila Monsters, dating to 2001. Univ. of Arizona researchers photographed ~100 animals in 2009-2011 during a study focused on radio telemetry and genetics. Since then Park staff, visitors and neighbors have continued to contribute both old and new photos. At the end of 2019, we had over 600 voucher photos of some 500 individual animals. Goals for this low-cost project are to explore Gila Monster life history, longevity, habitat use and home ranges, and to engage visitors. We’ve observed that tail damage is not unusual, and can heal over. Small changes in body coloration patterns of young animals can be used to estimate age, which in subsequent years can help set a lower limit on lifespan: Several individuals are at least 14 years old. Both reticulated and banded body patterns occur in the Park, and the most common pattern appears to be a mix of the two. One individual was photographed at 2,118 m (6,950 ft) elevation in the Rincon Mountains. Repeat sightings have been within a ~1km home range, as reported for other locations. Citizen Scientist photographers have been quite enthusiastic, and appreciate getting feedback on the photos they submit.