The development of endothermy during pouch life in the Eastern Barred bandicoot (Perameles gunnii), a marsupial

Marsupials are born ectothermic and gradually become endothermic during pouch occupancy. In order to study the timing of this transition, we measured the metabolic rates of eight pouch-young eastern barred bandicoots (Perameles gunnii) at 25°C (the thermoneutral zone of adults), at 35°C (pouch temperature), and after injection with norepinephrine. From 5 to 7 wk of age, oxygen consumption (V̇O2) was higher at 35°C than at 25°C. At 8 wk, V̇O2 was significantly higher at 25°C than at 35°C. Norepinephrine administration at 5 and 6 wk had no effect on metabolic rate, but at 8 wk, near pouch vacation, it resulted in a significant increase in metabolic rate. Our results indicate that signs of thermoregulation for P. gunnii begin at 7 wk, and at 8 wk the species is endothermic, that is, able to increase heat production in response to both cold and norepinephrine. The appearance of fur, first seen at the age of 6 wk and fully developed at 8 wk, coincides with the onset of endothermy. © 2006 by The University of Chicago. All rights reserved.