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.
Average percentage of individuals that chose each overwintering cover type per enclosure (n = 14). Bars represent standard error. Letters above bars denote groups that were statistically different from each other.
Percent change in mass across cover materials. Sample sizes for each cover are given in parentheses beneath the x-axis. Boxes and whiskers show quartiles, solid horizontal lines show the median, dashed horizontal lines show the mean, and open circles show raw data points that are above, below the upper, lower quartiles. For tile, only raw data points are shown. Letters denote groups that were statistically different from each other.
Percent change in snout–vent length (SVL) across cover materials. Sample sizes for each cover are given in parentheses beneath the x-axis. Boxes and whiskers show quartiles, solid horizontal lines show the median, dashed horizontal lines show the mean, and open circles show raw data points that are above, below the upper, lower quartiles. For tile, only raw data points are shown. Letters above bars denote groups that were statistically different from each other.
Regression between change in snout–vent length (SVL) and change in mass. Dark, solid line shows the trendline for x and y values. Dashed lines provide a reference of zero.
Contributor Notes
Associate Editor: J. D. Litzgus.