Rates of turnover of water, energy and sodium were measured for free-ranging thorny devils (Moloch horridus), which are myrmecophagous agamid lizards, in a semi-arid Western Australian habitat. There were significant differences in body water content and water turnover rate (WTR) measurements for cool, wet, average and hot periods, although the field metabolic rate (FMR) and sodium turnover (NaTR) rate did not differ significantly between weather conditions. The thorny devil had a substantially lower field WTR during dry periods (10-15 ml kg-1 d-1) than expected for semi-arid and arid lizards, although the WTR was higher in wet conditions (30-35 ml kg-1 d-1). The field metabolic rate of thorny devils (0.134 ml CO2 g-1 h-1) was only slightly less than that expected for a semi-arid/lizard (0.178 ml CO2 g-1 h-1), despite the apparently slothful nature of the thorny devil. The sodium turnover rate of the thorny devil (1.5-2.5 mmol kg-1 d-1) was within the range reported for other semi-arid/arid lizards. The field metabolic rate of the thorny devils suggests that they consume about 750 ants per day. The ratio of water to energy turnover measured for thorny devils in the field (0.11 ml H2O kj-1) was the same as that predicted from the composition of ants and their digestibility by thorny devils (0.11 ml H2O kj-1). However, the ratios of sodium-to-energy turnover (30 μmol Na+ kj-1) and sodium-to-water turnover (277 μmol ml H2O-1) were substantially higher than expected ratios (10 and 89 respectively). © 1995, Brill. All rights reserved.
|Number of pages||8|
|Publication status||Published - 1995|