Temperature regulation in the platypus, Ornithorhynchus anatinus (shaw)

1. 1. The ability of the platypus ( Ornithorhynchus anaticus) to thermoregulate in air and in water was investigated. 2. 2. Normal body temperature (31·5 ± 2·0°C) was maintained over an ambient air temperature range of 0·5–25°C. 3. 3. Body temperatures increased and the platypuses suffered heat stress at ambient air temperatures > 25°C. 4. 4. A zone of thermal neutrality was found to exist between 15 and 25°C ambient; below this zone platypuses thermoregulated according to Newton's law of cooling. 5. 5. Thermoregulatory difficulties were found to exist with platypuses in water; it is suggested that the duration of feeding excursions in the wild may be limited by water temperatures.