Activity rhythms in the Mongolian gerbil under natural light conditions

Male and female Mongolian gerbils (Meriones unguiculatus) were maintained from birth under natural light conditions. They were observed in adulthood over 24-hour periods for the occurrence of locomotion, digging, scrabbling, sleeping, grooming, eating and drinking. The animals exhibited a crepuscular activity rhythm in all behaviors except drinking. Peak activity levels occurred at approximately 6-8 a.m. and 6-8 p.m., the hours of day which encompassed dawn and dusk. There were no sex differences in the rhythmic cycling of activity. Results are discussed in relation to basal metabolic rate of the animals, nutritional requirements and ambient temperature conditions.