Eight adult and eight infant degus were continuously observed over two 24-h sessions in order to determine the effects of large vs. small enclosure size on the stability of activity and sleep cycles. Behaviors were categorized into one of five mutually exclusive categories. Although the proportion of time spent engaging in sleep and other activities was not found to vary significantly, the circadian placement of activities by age and sex class was found to be altered as a function of enclosure size. These results are examined with reference to prevailing theories concerning the functions of sleep.