Gila Monster Project Results

Gila Monster
Gila Monster

NPS Photo

Research Highlights
What have we learned from the science so far? How are Gila monsters doing in Saguaro National Park?

Based on photographs, observations, and genetic analysis, Gila monsters are more common in the park than was once thought. Since 2005, we have received more than 660 photographs and identified about 500 different individuals. Using mathematical models, we estimate that more than 80 Gila monsters live in the area of the 8-mile Cactus Forest Loop Road. DNA results* indicate that the population is healthy and robust, with high genetic diversity.

Of the 500 individuals identified in photos, at least 100 have been photographed more than once. Two Gila monsters have been captured by cameras as many as 11 times.

How long do Gila monsters live in the wild? In time, we hope to use these collected photos to answer that question, but one adult Gila monster that was first photographed in 2001 was still alive and healthy 12 years later in 2013.
gila monster
Gila Monster

NPS Photo/N Perkins

What are the threats to Gila monsters? We know that one problem is cars -- visitors and park staff have sent in photos of more than 25 dead Gila monsters found on roads in and next to the park.

Probably the most important result of nearly 15 years of citizen science research in Saguaro National Park is that although Gila monsters are seldom seen, they are not rare. The population is very healthy, which suggests that National Park and Arizona regulations to protect this spectacular animal have been successful.

*Victoria Sophia Farrar , Taylor Edwards and Kevin Edward Bonine. 2017. Elusive does not always equal rare: genetic assessment of a protected Gila monster (Heloderma suspectum) population in Saguaro National Park, Arizona. Amphibia-Reptilia 2017. 38:1–14.

Last updated: May 19, 2020

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