Can behavior douse the fire of climate warming?

R ising air temperatures around the globe are affecting organismal abundance, distribution, and evolution (1, 2). Not surprisingly, biologists are endeavoring to assess and anticipate further impacts of warming. What is usually overlooked in these efforts is the fact that mobile organisms are not prisoners of climate warming: they can use behavioral adjustments (‘‘behavioral thermoregulation’’) either to buffer the impact of warming air temperatures or sometimes even to take advantage of them (3–5). However, an evaluation of behavior’s roles in modifying organismal responses to climate warming has never been attempted, at least on a large spatial scale. A new study in this issue of PNAS (6) develops a biophysically (heat transfer)based approach (7–9) that does just that. Kearny et al. (6) quantify whether a diurnal ectotherm’s use of behavioral adjustments (e.g., use of shade or burrows) alters the ecological impact of climate warming, and they do so on local, continental, and global scales. For us the key take-home lesson is that behavioral f lexibility is critical for organismal survival in a warming world; behavior can buffer the negative consequences of warming, or it can enhance the benefits of warming! The outcome depends on an organism’s physiology, availability of shade, and local microclimates, all of which vary with latitude. Many temperate-zone ectotherms live in environments that are considerably cooler than their optimum, and so becoming warmer is now their highest thermoregulatory priority. Warming will be beneficial to them, especially if they can use basking to take advantage of warming temperatures. In contrast, the priority for many tropical and continentaldesert ectotherms is staying cool. Climate warming will place them at risk, especially if shade is scant.