FREE-RUNNING PERIODS OF ENDOGENOUS CIRCANNIAN RHYTHMS IN GOLDEN MANTLED GROUND SQUIRREL CITELLUS LATERALIS

1. 1. Endogenous circannian rhythms in the hibernator, Citellus lateralis, have been studied for four consecutive years under constant environmental conditions. 2. 2. The interrelationships of the homothermy-heterothermy rhythm and the body-weight rhythm are discussed relative to the Bünning hypothesis for circadian rhythms. 3. 3. The circannian free-running period has been examined in relation to sex, castration and wild caught juveniles. Evidence is presented in favor of the genetic origin of the behavior pattern. 4. 4. After two successive circannian rhythms there is an increasing discrepancy in their relationship to the presumptive seasons, which indicates that a Zeitgeber is required to entrain the rhythms. 5. 5. It was found that the life span of these animals is about 5 years. © 1969.