Lizards paid a greater opportunity cost to thermoregulate in a less heterogeneous environment

Abstract

Summary The theory of thermoregulation has developed slowly, hampering efforts to predict how individuals can buffer climate change through behaviour. Mixed results of field and laboratory experiments underscore the need to test hypotheses about thermoregulation explicitly, while measuring costs and benefits in different thermal landscapes. We simulated body temperature and energy expenditure of a virtual lizard that either thermoregulates optimally or thermoconforms in a landscape of either low or high quality (one or four basking sites, respectively). We then compare the predicted values in each landscape with the observed values for real lizards in experimental arenas. Lizards thermoregulated more accurately in the high‐quality landscape than they did on the low‐quality landscape, albeit only slightly so, but spent similar amounts of energy in these landscapes. Basking, rather than shuttling between heat sources, accounted for the majority of the energy consumed in both landscapes. These results did not support the predictions of our model. In the low‐quality landscape, real lizards thermoregulated intensely despite the potential to save energy by thermoconforming. In the high‐quality landscape, lizards moved more than expected, suggesting that lizards explored their surroundings despite being able to thermoregulate without doing so. Our results suggest that non‐energetic benefits drive thermoregulatory behaviour in costly environments, despite the missed opportunities arising from thermoregulation. We propose that energetic costs associated with thermoregulatory movement will become substantial in homogeneous environments such as flat plains and dense forests. The theory of thermoregulation should incorporate these aspects if biologists wish to predict responses of ectotherms to changing climates and habitats. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12795/suppinfo is available for this article.

Miami heat: Urban heat islands influence the thermal suitability of habitats for ectotherms

“…Therefore, urban habitats are more favorable for A. sagrei , which may have trouble persisting in more close‐canopied sites, such as forested habitats, that restrict their ability to achieve higher body temperatures. It is important to note that while costs of thermoregulation may be lower in urban sites, Basson, Levy, Angilletta, and Clusella‐Trullas () showed that even in a low‐quality thermal habitat with high thermoregulatory costs in the laboratory, Cordylus lizards prioritized maintaining T b within T pref . It may be necessary to maintain warmer body temperatures that confer higher activity in urban habitats in the Miami area, even if costly, to successfully compete with multiple other introduced and native anoles (Kolbe et al, ), or manage urban predation pressure (Chejanovski, Avilés‐Rodríguez, Lapiedra, Preisser, & Kolbe, ).…”

Costs of thermoregulation in variable thermal environments in the jacky dragon (Amphibolurus muricatus)

“…Such results were found in bearded dragons, where animals were examined in several types of thermal arenas and found to lose thermoregulatory precision only in the arena with very high variability (Cadena & Tattersall, ). Similarly, for lizard species in more‐complex arenas, patch dispersion that requires greater locomotion leads to reduced accuracy in thermoregulation (Sears et al ., ; Basson et al ., ).…”

Competition during thermoregulation altered the body temperatures and hormone levels of lizards

“…Thus, the structure and complexity of the thermal landscape likely plays a role in thermoregulatory performance (Basson et al . ; Sears et al . ), with more complex environments potentially ameliorating the negative thermoregulatory effects of competition.…”