Body temperature of the common grass-snake Natrix natrix (Linnaeus, 1758) in the natural habitat in the Volga basin and in the experiment

The common grass-snake in the Middle Volga basin and the Kama Urals are exposed to the change of the spring (autumn) and summer biotopes, which forms the change of temperature and other microclimatic conditions of the environment. The highest body temperature of a snake in the Urals is observed in September. The grass-snakes select the warmest substrate in April and May. Body temperature and external temperature vary from year to year. The common grass snake shows virtually no geographic variation in body temperature from the northern border of their habitat area to the Caspian Lowlands. The experiment with iBDL loggers implanted into the body of a snake showed that the minimum temperature of the body during daily activities lies in the interval from 13,6 to16,0°C. The maximum temperature lies in the interval of 32,6-36,6°C. Optimum air temperature is 21,2-26,0°C, optimum body temperature is 26,3-31,0°C. In general, the body temperature of a common grass-snake is highly dependent on the ambient temperature, but during the daily activity this dependence is greatly reduced.