Seasonal activity and thermoregulation in Meriones unguiculatus: A gerbil's choice

Summary Mongolian gerbils were observed over seasonal changes in day length and temperature in an outdoor enclosure containing an extensive burrow system. Animals could choose between the stable environment of their burrow and the daily and seasonal flunctuations aboveground. Surgically implanted radio transmitters provided body temperature and location of animals.Gerbils avoided temperature extremes by emerging from their burrow when ambient temperature fell below burrow temperature in hot weather and rose above burrow temperature in cold weather. They delayed emergence in the winter until several hours after sunrise and emerged before or after sunset in summer (Fig. 1).Circadian changes in core-body temperature corresponded to increases and decreases in behavioral activity. Emergence from the burrow was predictable by an increase in body temperature, as a warm-up period preceded emergence (Fig. 3).We conclude that gerbils, when subjected to extreme temperatures in the wild, probably time their activity to correspond to preferred ambient temperatures and thus shift from diurnal activity in the winter to nocrurnal activity in the summer (Fig. 2). This desert rodent's exceptional thermoregulatory capacity adapts it for synchronizing its daily activity to temperature.