Field energetics of a large carnivorous lizard, Varanus rosenbergi

Abstract

Field metabolic rates (FMRs; CO2 production) and water influx rates of Varanus rosenbergi were measured seasonally by means of doubly-labelled water (3H218O). Metabolic rates and water influexes were highest in summer (0.18 ml CO2 g-1 h-1 and 17.9 ml H2O kg-1 day-1) and lowest in winter (0.04 ml CO2 g-1 h-1 and 6.5 ml H2O kg-1 day-1). FMRs and water fluxes were intermediate in spring. It is estimated that a 1-kg V. rosenbergi would need to consume 4.7 kg of prey each year to remain in energy balance and that the energy commitment to egg production requires a 40% increase in the food acquisition of a gravid female in late spring and early summer. It is calculated that water influxes in summer are totally provided from food but in other seasons, particularly winter, pulmocutaneous water exchange and/or drinking are significant avenues of water intake.