Thermoadaptations of the reptiles of the Volga basin

The questions of the temperature adaptations of the reptiles, which dwell in the limits of Volga basin, are examined in the research. Such adaptations include the decrease of relative body surface in the direction from the south to the north, for example, that of Vipera renardi, the increase of the percentage of melanism among the reptiles in the same direction, their thermoadaptive behavior. The ratio of the reptiles' body temperature to the external temperature is described with the index of thermoadaptation (It), which makes it possible to estimate quantitatively the opportunities of the reptiles dwelling in both hot and relatively cold climate.