Meeting Abstract

P2.3  Jan. 5  Alternate overwintering strategies in the Gila Monster, Heloderma suspectum: Implications of refuge location on timing and duration of inactivity, thermal biology, and energetics. DAVIS, J.R.**; DENARDO, D.F.; Arizona State University, Tempe j.davis@asu.edu

Low temperatures can reduce performance of many physiologic processes including digestion, immune function, and metabolic rate. Thus, in temperate environments, many ectotherms often seek out relatively innocuous microclimates within refugia and become inactive for long periods during the winter. In extremely cold environments, adequate overwintering microhabitats may be limited, thus individuals must migrate, often significant distances, to high-density den sites. However, in regions having milder winter temperatures, adequate winter refugia are plentiful and individuals in a population may chose alternate overwintering strategies. While each leads to survival, alternate overwintering strategies may differentially influence overwintering duration and body temperature during inactivity, both of which can impact energy balance. Here, we present preliminary results of a field study describing the overwintering behavior of a large, long-lived ectotherm, the Gila Monster, Heloderma suspectum. We studied a Sonoran Desert population of Gila Monsters, in which all individuals spend the vast majority of time during the active season foraging or mate-searching in the bajada surrounding rocky hills and buttes. Some Gila Monsters then overwinter within their active season home range, while others move back to refugia on the slopes of hills or buttes. We used surgically implanted miniature temperature dataloggers to determine the effects that overwinter site selection has on body temperature and the timing and duration of overwintering. We then estimate the implications of overwintering behavior on energetics and suggest explanations for alternate overwintering strategies in this species.