Variation in body temperature in free-ranging western grey kangaroos Macropus fuliginosus.

Using implanted temperature loggers we measured temperature in the carotid artery in five (4 male, 1 female) western grey kangaroos (Macropus fuliginosus) every 5 min for between 39 and 74 days. Dry bulb temperature during the study ranged from an average minimum of (mean � SD) 11 � 3�C to maximum of 24 � 5�C. Black globe temperature measured in the southern shade of a grass tree, the habitat chosen by kangaroos during the day, ranged from an average minimum of 10 � 4�C to an average maximum of 30 � 6�C. There were nine days where maximum shade globe temperature exceeded 40�C. Carotid blood temperature averaged 36.5 � 0.1�C (n = 5), ranging from an average minimum of 35.5 � 0.3�C to a maximum of 37.3 � 0.1�C The resultant average daily range was 1.8 � 0.3�C. Body temperature was highest during the night and dropped rapidly early in the morning, reaching a nadir at 1000 hours, after ambient temperature and solar radiation had begun increasing. Body temperature then rose gradually during the day to reach a peak in the early evening. The nychthemeral variation in carotid blood temperature was largely independent of ambient conditions. There was a weak but significant association between early morning radiation levels and the minimum body temperature reached, suggesting that peripheral warming influences the morning decrease in core temperature.