Team DeNardo

Jon Davis

Education:

B.S. Biology, Northern Arizona University, 2002

Research Interests:

Current Work:

Because of aridity and relatively low productivity, temperate deserts pose significant physiological challenges to organisms found there. However, many organisms persist despite these challenges. Of vertebrates, reptiles are often thought of as the best suited to desert environments. This notion provides the foundation of my research interests.

I am interested in the ways in which an organism's physiologic needs influence its behavioral ecology. The primary question my research addresses is: given the relatively arid environment of the Sonoran desert, how does an ectothermic vertebrate maintain water balance over the long-term (i.e., months to years)? Specifically, my research focuses on water balance in a desert-adapted lizard, the Gila Monster, Heloderma suspectum. My approach incorporates both laboratory and field experiments to address the following:

(1) morphologic attributes and physiologic processes that allow Gila Monsters to conserve water when it's readily available for later use during prolonged periods of drought,
(2) hormonal control of physiologic processes related to water conservation,
(3) costs and benefits of specific morphologic attributes,
(4) effect of season on hydration state in free-ranging animals, and
(5) effect of hydration state on activity levels and ultimately, energy acquisition.

Ultimately, I will use any understanding of water balance garnered to better understand the interplay between water, thermal, and energy balances. Of special interest is the dynamic hierarchy that exists between these physiologic processes and the factors (i.e., environmental condition, reproductive state) that influence the hierarchy. Finally, I will use my research to reevaluate the concept of homeostasis in a desert-adapted squamate reptile. For example, do Gila Monsters defend well-defined physiologic boundaries whenever possible or alternatively, do Gila Monsters simply function within broad, undefended physiologic boundaries?

Publications

1. Davis, J. R. and T. C. Theimer. 2003. Increased Lesser Earless Lizard (Holbrookia maculata) abundance on Gunnison's Prairie Dog colonies and short-term responses to artificial prairie dog burrows. Am. Midl. Nat. 150:282-290.

Email: j.davis @asu.edu