Radiotelemetric Study of Thermoregulation in a Lace Monitor

A temperature-signalling radio transmitter was implanted into the abdominal cavity of a 4200 g lace monitor (Varanus varius). The animal was then released at its place of capture in eastern Australia and its body temperature and movements were recorded for five days as it moved about freely in its natural habitat. Observations were made from places of concealment, at distances of 60-100 yards, to avoid influencing the lizard's behavior. During the five-day period the animal travelled over 1-3/4 miles, and at night took refuge in hollow trees with which it seemed to be thoroughly familiar. There was regularity in morning emergence from the tree hollows. All emergences occurred over a 25-min time span. Warming during the basking period was rapid (0.14' C/min), and normal activity temperatures were reached in less than one hr. The fall in body temperature, after the lizard became ensconced for the night, was considerably slower (0.02/min), which can be explained by physiological mechanisms and the gradual decline in ambient temperatures after sundown. The mean body temperature throughout the active period, which averaged about 11 hr a day, varied from day to day only 1.2' C and averaged for the total five-day period, 35.5? C (range 35.0?-36.2? C). There was an afternoon rise in temperature of 1?-2' C prior to retreat for the night.