Winter Microhabitat Selection and Growth of Jacky Dragons (Amphibolurus muricatus)

Most temperate-climate lizards become inactive during the winter months of each year. As temperatures drop, they must find appropriate overwintering microhabitats to avoid lethal surface temperatures and/or thermoregulate. The environmental variables that characterize such microhabitats and the cues that lizards utilize to assess them are a critical but understudied component of their natural history. While many studies of overwintering site selection focus on temperature, other factors constituting microhabitats (e.g., surface structures, substrate) may play a role in site selection. We used the Jacky Dragon (Amphibolurus muricatus), an Australian agamid lizard, to test for preference of using various cover types (leaf litter, open sand, sticks, rocks) for overwintering as well as the consequences of cover type selection. Jacky Dragons preferred overwintering beneath leaves compared to other structures, and this choice was associated with growth during winter, but not with survival. Our study highlights the potential importance of cover structures in overwintering site selection, suggests that midwinter activity may be common in Jacky Dragons, and calls for further study of the winter ecology of temperate-climate lizard species.