Patterns of gas exchange and extended non-ventilatory periods in small goannas (Squamata: Varanidae)

Standard metabolic rate and evaporative water loss were measured for three species of small goanna (Varanus caudolineatus, V. brevicauda and V. eremius). Four general patterns of gas exchange are associated with often extended periods of no gas exchange, which presumably are non-ventilatory periods. Extended periods of no gas exchange continued for as long as 137 min at 14°C, 37 min at 20°C and 28 min at 25°C. These extended non-ventilatory periods have two important implications. First, when measuring Vo_2std, it is important to recognize these non-ventilatory periods and not include them in the period for determining standard metabolic rate or else ensure that any non-ventilatory periods are accompanied by an “oxygen deficit payback” period. Second, the extended non-ventilatory period enables the partitioning of cutaneous and respiratory standard evaporative water loss. Pulmonary evaporative water loss, expressed as a percentage of total evaporative water loss, was found to be very low: 4.7%, 2.4% and 5.9% at 14, 20 and 25°C, respectively.