Tree shrews are nocturnally sleeping,primate-related animals that have been extensively studied in a well-developed model of social stress.Their sleep has received minimal attention.As a first step in assessing their utility as a model of the effects of social stress on sleep,we examined sleep,activity and core body temperature recorded via telemetry under baseline and chronic stress conditions.Six adult male tree shrews (weight 120-140 g) were intraperitoneally implanted with transmitters (DataSciences TL11M2-ETA-F20) for recording EEG,EMG,activity and core body temperature.The animals were maintained on a 12-12h light-dark cycle.Chronic stress was induced by placing two males in a single cage,but separated by wire mesh.The wire mesh was removed daily for 1.0 h immediately before lights offto allow physical contact.Behavioral states were visually scored based on EEG,EMG and activity.Over 24 h,the percentage of baseline time (Mean+SEM) spent sleeping was 51 +2% for total sleep,43+2% for NREM and 7.8±0.4% for REM.During the dark period,the percentage of time spent sleeping was 78± 1.2% for total sleep,75±+2% for NREM and 97± 1.3% for REM,whereas percentage of time with recorded activity was 9±3%.