Fig. 5. Correlations between skin colour (grey intensity) and dorsal surface temperature in field and laboratory conditions. Filled black circles refer to values obtained during collection of frogs in the field (N=7; linear correlation: r²=0.95). Open circles with error bars refer to the average ± s.e.m. changes in skin greyscale intensity and temperature during Series II experiments when frogs were allowed to warm up in the sun. Numbers beside these values refer to the elapsed time in minutes (0–30). The two dotted lines, marked Light and Dark, refer to the minimum and maximum possible range of skin colour values defined by Series I experiments from frogs placed in complete dark or light at 20 and 30°C.