Thermoregulation in Neonate Brush Turkeys (Alectura lathami)

Abstract

Brush turkey neonates are able to thermoregulate between ambient temperatures of 10-38 C. They have a standard metabolic rate of 1.00 ± 0.04 ml O₂ • g⁻¹ • h⁻¹, within a thermoneutral zone extending from 29 to 38 C. Evaporative water loss is 2.57 ± 0.32 mg • g⁻¹ • h⁻¹ at temperatures below 38 C. Thermal conductance is 0.497 mW • g⁻¹ • C⁻¹ at temperatures below 29 C. Mean body temperature of homeothermic brush turkey hatchlings is 40.4 ± 0.2 C at ambient temperatures below 36 C. Chicks are unable to remain homeothermic at temperatures below 10 C when 5-16 h old but can cope with these temperatures after 24 h. Body temperature and evaporative water loss increase greatly at ambient temperatures greater than 39 C. Brush turkey and mallee fowl (Leipoa ocellata) neonates have similar body masses and thermal conductances, but brush turkeys have a higher standard metabolic rate, rate of evaporative water loss, and body temperature than do mallee fowl neonates and are less tolerant of thermal stress. These differences may reflect differences in the physical conditions of the posthatching environment. Brush turkeys inhabit jungle and thick scrub environments and hatch into a more mesic and cooler environment than do mallee fowl, which inhabit semiarid mallee areas.