Telemetric field studies of body temperature and activity rhythms of Acomys russatus and A-cahirinus in the Judean Desert of Israel

Two species of the genus Acomys coexist in arid zones of southern Israel. A comys,russatus is distributed in extremely arid areas, while A. cahirinus c ommon in both Mediterranean and arid regions. Individuals of both species f rom a rodent community in the fin Gedi Nature Reserve were implanted with t emperature-sensitive transmitters. Body temperature (Tb) rhythms were recor ded in free-ranging mice at four different seasons of the year. A. cahirinu s(30-45 g) showed a nocturnal rhythm of Tb throughout the year. In the acti vity phase during the night Tb increased to 38.2 degrees C. During the day Tb decreased to 34 degrees C. This species displayed this pattern in summer also when ambient temperatures rose above Tb The Tb Of A. russatus (45-65 g) varied between 34.8 and 41 degrees C during the hot season, showing a bi modal temperature rhythm with maximal values in the morning and in the even ing. Measurements of activity in this species showed inactivity during the hottest period of a summer day. In winter A. russatus showed no clearly det ectable diurnal or ultradian rhythm in Tb, which remained constant between narrow limits of 35.2 and 36.8 degrees C.