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First published online December 3, 2004
Journal of Experimental Biology 207, 4551-4557 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01313

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Partitioning heat loss from mallard ducklings swimming on the air–water interface

Marilyn R. Banta^1,2, Aaron J. Lynott^1,3, Matthew J. VanSant¹ and George S. Bakken^1,*

¹ Department of Ecology and Organismal Biology, Indiana State University, Terre Haute, Indiana 47809 USA
² Department of Biological Sciences, University of Northern Colorado, Greeley, Colorado 80639 USA
³ South Vermillion High School, 770 West Wildcat Drive, Clinton, Indiana 47842, USA

View larger version (13K): [in a new window]   Fig. 1. Cloacal body temperature predicted by thermographic measurements of scalp temperature. (A) Cloacal temperature vs raw thermographic values. The effect of absorption and emission in the 80° lens attachment are evident. (B) Cloacal temperature thermographic temperature corrected for lens effects. True radiometric scalp temperature averages about 1°C lower than cloacal temperature. (C) Measured cloacal temperature vs cloacal temperature predicted by a regression to the data in Fig. 1B. In all cases, data points are from a single image, and overall precision can be improved by calculating the mean of data from several images.

View larger version (14K): [in a new window]   Fig. 2. Body temperature measured by calibrated thermography of a shaved spot on the scalp directly over the brain. This method agreed with cloacal temperature within <1°C and avoided the restraint and increased wetting of the down associated with the use of cloacal thermocouples. Body temperature decreased as water temperature decreased to 15°C, and then stabilized. The line is a LOWESS smoother (Cleveland, 1985) showing the trend.

View larger version (20K): [in a new window]   Fig. 3. Metabolic rate of 2–3-day-old ducklings vs water temperature, adjusted to the average mass of 48 g. The slope of the lines indicates the effect of water temperature on metabolic rate. The spacing of the lines indicates the additional effect of air temperatures. The lines are drawn using the heat transfer model in Equation 3. Even with 30°C water temperature and 45°C air temperature, there is no indication that the thermal neutral zone has been reached.

View larger version (16K): [in a new window]   Fig. 4. Plot of the thermal conductance to water (filled symbols) and corresponding conductance model (upper curve) and the thermal conductance to air (open symbols) and corresponding thermal conductance model (lower line). Both conductance models are taken from Equation 3. The horizontal axis is the temperature of the corresponding medium. The scatter in the conductance to air at 35°C results from uncertainties in the small difference between body and air temperature.