Oxygen consumption during pouch development of the macropod marsupial Setonix brachyurus

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Abstract
Measurements of Oo consumption at 9 or 10 temperatures in the 20-40[degree] C ambient temperature range were made on joeys with ages selected to cover the 180-day period of pouch occupancy. The rate of O2 consumption of joeys younger than 100 days increased directly with ambient temperature. After 100 days of age the O2 consumption rate at low temperatures rose and at about 140 days of age a constant rate was maintained over the full ambient temperature range. Heat transfer from joey to mother commenced after 100 days of age. At 150-180 days of age the rate of O2 consumption at 20[degree] C was approximately 12 times greater than at ages less than 100 days. A thermal neutral zone was established in the range 32-36[degree] C by joeys older than 150 days. At the usual pouch temperature of 36.5[degree] C, O2 consumption per unit wet body weight rose from 12 ml/kg/min. at birth to 17 ml/kg/min. at the end of pouch life. On a unit dry body weight basis it fell from 120 to 56 ml/kg/min. This decline parallels the decrease in growth rate.