The Effect of Body Temperature and Postirradiation Cold Exposure on the Radiation Response of the Hibernator Citellus tridecemlineatus

The effects of exposing ground squirrels, Citellus tridecemlineatus, to⁶⁰ Co radiation while at body temperatures of 5°C, 13°C, 23°C, or 37°C and of maintaining groups of these squirrels in environments with temperatures 5°C, 13°C, and 23°C for up to 90 days have been studied. These studies were conducted in the form of three separate experiments. Results of experiment I indicated that squirrels irradiated while hibernating at 5°C and immediately placed in an environment of 23°C had higher percentages of survival than squirrels irradiated while active or while hibernating and maintained in a cold room at 5°C for 30 days. The percentage of survival was higher among squirrels in the latter groups than among squirrels irradiated while active. Results of experiment II showed that squirrels with body temperatures of 5°C, 13°C, 23°C, or 37°C at the time of irradiation exhibited marked differences in survival percentages at 180 days postirradiation. For example squirrels receiving 1250 rads had survival percentages of 33%, 75%, 50%, and 0%, respectively. Experiment III indicated that a complicated relationship existed between the effects of a postirradiation exposure to environments of 5°C, 13°C, or 23°C for 90 days and the effects of irradiating squirrels while at body temperatures of 5°C, 13°C, 23°C, or 37°C. Paramount in this relationship was a marked deleterious effect on survival among squirrels maintained in the 13°C environment.