Having multiple plastic responses to a change in the environment, such as increased temperature, can be adaptive for two major reasons: synergy (the plastic responses perform better when expressed simultaneously) or complementarity (each plastic response provides a greater net benefit in a different environmental context). We investigated these hypotheses for two forms of temperature-induced plasticity of Battus philenor caterpillars in southern Arizona populations: color change (from black to red at high temperatures) and heat avoidance behavior (movement from host to elevated refuges at high host temperatures). Field assays using aluminum models showed that the cooling effect of the red color is greatly reduced in a refuge position relative to that on a host. Field assays with live caterpillars demonstrated that refuge seeking is much more important for survival under hot conditions than coloration; however, in those assays, red coloration reduced the need to seek refuges. Our results support the complementarity hypothesis: refuge seeking facilitates survival during daily temperature peaks, while color change reduces the need to leave the host over longer warm periods. We propose that combinations of rapid but costly short-term behavioral responses and slow but efficient long-term morphological responses may be common when coping with temperature change.

Caterpillar ModelsData from experiment using aluminum operative temperature models of caterpillarscaterpillarModels.csvSpectra of models and caterpillarsReflectance spectra of painted aluminum models and live caterpillarsmodelCaterpillarSpectra.csvEffect of behavior and color on survivalData from experiment on the effects of behavior and color on survival using live caterpillarsbehaviorColorSurvival.csvCalibration of models with caterpillarsData for comparison of temperatures of different colored caterpillars with the corresponding aluminum models.modelCalibration.csvEffect of color on behaviorData from field experiment on the effect of color on refuge-seeking behavior using live caterpillarsbehaviorColor.csv