Arboreal Perch Properties and the Operative Temperature Experienced by Small Animals

Abstract

The effects of perch properties on the thermal environment of small animals were explored by placing hollow electroformed copper lizard models on simulated tree trunks of varying properties. The operative temperatures (Te) of models on perches were compared to reference models suspended away from the perch. Operative temperature increased with increasing perch diameter, decreasing heat storage capacity, and increasing absorption of solar radiation by the perch. Models on log perches measured Te values up to 12°C higher than the reference models. These results indicated that perch surface temperature and the heated thermal boundary layer of the perch were the primary factors increasing Te. Simulated thermoregulatory posture adjustments could affect Te by up to 6.5°. Movement from the sun to the shade side of 16+ cm diameter perches could change average Te by up to 18°. The thermal effects of sunlit aboveground perches should be explicitly considered in thermal energy budget models or thermal maps.