Fig. 2. Body temperature measured by calibrated thermography of a shaved spot on the scalp directly over the brain. This method agreed with cloacal temperature within <1°C and avoided the restraint and increased wetting of the down associated with the use of cloacal thermocouples. Body temperature decreased as water temperature decreased to 15°C, and then stabilized. The line is a LOWESS smoother (Cleveland, 1985) showing the trend.