METABOLIC DEPRESSION IN ESTIVATING LONG-NECK TURTLES (CHELODINA-RUGOSA)

Long-neck turtles, Chelodina rugosa, inhabit seasonally ephemeral wate r holes on the coastal floodplains of the wet-dry tropics of Australia . Late in the annual dry season, the turtles bury themselves in the dr ying mud and estivate for as long as 4-5 mo until the wet season rains begin. We measured the oxygen consumption of five turtles that were i nduced to estivate in containers of mud at 30 degrees C. This was typi cal of soil temperatures measured in natural estivation sites. The met abolic measurements of estivating turtles were compared to the standar d metabolic rates (SMRs) at 30 degrees C of these five postestivation turtles after they had spent 36 h in water and to the SMRs of 10 prees tivation turtles. There was no difference between the pre- and postest ivation SMRs, but the metabolic rates of estivating turtles decreased over about 2 wk to 28% of the SMR. This was not a response to starvati on, because postestivation turtles were not fed This metabolic depress ion conserves energy and, presumably water during estivation, which le ngthens the time the turtles can survive the dry conditions and allows them to emerge from estivation with more resources for growth and rep roduction.