The Circannual Cycle of Richardson's Ground Squirrels in Southern Alberta

Abstract

Times of spring emergence and autumn immergence were determined for Richardson's ground squirrels ( Spermophilus richardsonii ) in southern Alberta from 1975 to 1978. Spring emergence of females was synchronous and was not affected by their age, reproductive success in the previous year, or time of autumn immergence. Time of spring emergence correlated with climatic conditions, in particular with warming of the shallow layers of soil. Time of autumn immergence was asynchronous, even within the same age and sex class, and was affected by the condition of the animal. Factors affecting fattening, and hence immergence, included age and sex of the squirrel, its reproductive success that year, and the availability of food. Synchrony was reestablished in the following spring, suggesting that emergence is the point in the annual cycle at which entrainment occurs.