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Effect of Wind Speed, Air Temperature, Body Size and Vapor Density Difference on Evaporative Water Loss from the Turtle Chrysemys scripta
Journal article

Effect of Wind Speed, Air Temperature, Body Size and Vapor Density Difference on Evaporative Water Loss from the Turtle Chrysemys scripta

Robert E. Foley and James R. Spotila
Copeia, v 1978(4), pp 627-634
28 Dec 1978
DOI: https://doi.org/10.2307/1443689

Abstract

Animals Body size Body temperature Evaporation Reptiles Turtles Vapors Water loss Water temperature Wind velocity
Evaporative water loss (EWL) was determined for a range of sizes of Chrysemys scripta tested at three air temperatures (15, 25 and 35 C) and three wind speeds (10, 100 and 400 cm s-1). Rates of water loss ( mg g-1 hr-1) increased as wind speed and air temperature increased but were inversely proportional to body size. An increase in wind speed from 10 to 100 cm s-1 caused a large initial decrease in boundary layer thickness and a large increase in EWL. A further increase in wind speed to 400 cm s-1 had a relatively smaller effect on EWL because much of the boundary layer had already been removed at the 100 cm s-1 wind speed. Schlieren photographs show the effect of wind speed on boundary layer thickness. Maximum rates of water loss were recorded for the smallest turtles exposed to a wind speed of 400 cm s-1 at 35 C. Minimum rates of EWL were obtained for the largest turtles in still air (10 cm s-1) at 15 C. EWL was similar for large turtles (2000 g) in still air (10 cm s-1) at all three temperatures. Rates of EWL from small turtles (200 g) in moving air increased sharply as temperature increased to 25 and 35 C. The interaction of wind speed (V), air temperature ( T a) body size (W) and vapor density differences (VDD) are described by multivariate regression equations. Predictions of basking behavior are given based on laboratory data and operative environmental temperatures computed for field conditions. Evaporative water loss plays a minor role in controlling basking behavior.

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