Exploring the Desert Survival Strategies of Gila Monsters – 20 Years and Counting

DeNardo, Dale F. School of Life Sciences Arizona State University Tempe, Arizona USA denardo@asu.edu

The Gila Monster (Heloderma suspectum) has been widely popularized for more than a century and is seen as an icon of the American Southwest. Despite this attention and interest, surprisingly little was truly known about this species. In fact, it has previously been suggested that Gila Monsters are poorly adapted to living in the desert. However, this is not sensible since Gila Monsters have resided in the Sonoran Desert for as long as it has existed in its current state. The misconception likely reflects the fact that Gila Monsters do not use survival strategies that are typical of desert lizards. Instead, they use a suite of behavioral and physiological adaptations that are rarely seen in other lizards yet are convergently represented in a scattering of other desert vertebrates. These include large home range size, seasonal shifts in foraging activity, low preferred body temperature, specialized cooling mechanisms, parenteral water storage, and the production of venom. Together, this unique assemblage of traits enables Gila Monsters to have an otherwise unachievable specialized diet – the contents of vertebrate nest. Surviving on such a seasonally-limited and widely dispersed resource clearly demonstrates that the Gila Monster is extremely well adapted to its environments and the niche that it fills.