12/21/2020: It’s been relatively warm for a Texas winter, but I haven’t been seeing green anoles (Anolis carolinensis) out and about. In my backyard there are a few residents that can often be spotted from their favorite sunlit perches, and after briefly searching yesterday, I uncovered this male hiding underneath a log. Initially his body color was very dark, but he gradually assumed a lighter hue over the span of a few minutes. Not wanting to startle him away from his spot of dormancy, I slowly lowered the log and the anole promptly shuffled back into the refuge.
Being the most northern latitude species of the genus, A. carolinensis employs strategic activity patterns to survive cold spells. Throughout the winter, they bask opportunistically, only emerging on warm days. Usually, reptiles will seek out optimal basking spots in the environment; however, due to a strong affinity to their refuges, green anoles are instead more passive thermoregulators during the winter— showing very little perch changes to track sunlight patterns. Even though lizards are able to raise their metabolic rates on warm days, they tend to limit feeding and social interactions. One hypothesis for their inactivity is that digestion of prey will be halted when cold conditions resume, which can lead to rotting within the gut and potentially death. To deal with this problem, some lizards may increase the rate at which food passes at the expense of nutritional gain, though data are still needed to determine whether this response occurs broadly across lizards that inhabit cold environments. So why then come out to bask at all? Higher body temperatures during winter are sufficient in promoting gonad development and contributing to overall growth, both of which are advantageous for early breeding and competitive interactions in the spring.
Below are photos of two green anoles from springtime, also found around my house; photographed after pursuit [3]
