Body temperature depends on air and microhabitat temperatures.

Results of generalized additive models (GAM) testing the dependence of body-to-air temperature excess Tb − Ta on air temperature Ta and body-to-microhabitat temperature excess Tb − Tm on microhabitat temperature Tm for individual species of Erebia butterflies. The fitted relationships are visualised in Figs 1 and 2. Estimated d.f. describes the complexity of the fitted relationship; e.d.f. = 1 for a linear relationship, e.d.f.>1 for a non-linear relationship.