Oecologia

, Volume 136, Issue 4, pp 515–523 | Cite as

Energetics of bluetongue lizards (Tiliqua scincoides) in a seasonal tropical environment

  • Keith A. Christian
  • Jonathan K. Webb
  • Timothy J. Schultz
Ecophysiology

Abstract

We studied the physiological ecology of bluetongue lizards (Tiliqua scincoides) on the Adelaide River floodplain in tropical Australia to determine the seasonal patterns of energy expenditure and to determine the mechanisms by which seasonal differences were achieved. Field metabolic rates (FMR) were significantly lower in the dry season (37.6 kJ kg−1 day−1; n=9) than in the wet (127.3 kJ kg−1 day−1; n=7). Water flux was also lower in the dry season (6.8 ml kg−1 day−1; n=9) than in the wet (39.4 ml kg−1 day−1; n=7). Measurements of body temperatures (Tb) and movements of free-ranging animals, and standard metabolic rate (SMR) of recently caught animals, allowed a detailed analysis of energy budgets for wet and dry seasons. In the dry, bluetongue lizards expended 90 kJ kg−1 day−1 less energy than in the wet season. Unlike some other lizards of the wet-dry tropics, SMR did not differ between seasons. About 5% of the seasonal difference in FMR was due to lower night time Tb during the dry season, and about 7% was due to lower diurnal Tb. The remaining 88% of the decrease in energy expended in the dry season was due to a substantial decrease in other costs that may include reproduction, growth, digestion and activity. If we assume the animals fed daily and the costs of digestion are taken into account, the estimates are: 14% of the savings result from lower Tb at night, 20% from lower Tb in the day, and 66% result from decreased activity. It is therefore apparent that, unlike some agamid and varanid lizards that use a combination of behavioural and physiological mechanisms to conserve energy when food and water are limited, bluetongue lizards primarily use behavioural mechanisms to achieve a dramatic reduction in energy expenditure in the dry season.

Keywords

Field metabolic rate Energy budgets Wet-dry tropics Thermal ecology Seasonality 

Notes

Acknowledgements

We thank the Northern Territory University and the Australian Research Council for financial support. Work was done under permits from the Northern Territory University Animal Ethics Committee and the Parks and Wildlife Commission of the Northern Territory. Access to the study site was made possible by the Parks and Wildlife Commission of the Northern Territory and the Department of Primary Industries and Fisheries of the Northern Territory. We thank Jennifer Koenig and Greg Brown for their help in the field, and Keith Newgrain for carrying out the isotopic analyses and providing valuable input throughout the project.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Keith A. Christian
    • 1
  • Jonathan K. Webb
    • 1
  • Timothy J. Schultz
    • 1
  1. 1.School of Environmental SciencesNorthern Territory UniversityDarwinAustralia

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