Circadian Activity in Yellow Ground Squirrels Spermophilus fulvus Licht. (Sciuridae): the Pilot Instrumental Study

Animal circadian activity was mostly studied in captivity with artificial environment. We performed pioneer study of daily activity using telemetry for yellow ground squirrels (Spermophilus fulvus), burrowing hibernating rodents. Eight individuals were fitted with glued-on radio transmitters contained accelerometers and light sensors in the wild colony in 2021. Our data showed that S. fulvus was strictly diurnal and active aboveground only during daytime. The squirrels ceased locomotor activity and rested when they entered their burrows. As the season progressed, the duration of aboveground activity decreased. In contrast to similar species with peaks of aboveground activity in the morning and in the evening, yellow ground squirrels didn’t break the activity in midday. Probably, prolonged hibernation and, therefore, time deficiency induced S. fulvus to use day hours as effective as possible.