Boily P, Kvadsheim P H, Folkow L P
Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA.
J Theor Biol. 2000 Dec 7;207(3):317-23. doi: 10.1006/jtbi.2000.2176.
Heat flux models have been used to predict metabolic rates of marine mammals, generally by estimating conductive heat transfer through their blubber layer. Recently, Kvadsheim et al. (1997) found that such models tend to overestimate metabolic rates, and that such errors probably result from the asymmetrical distribution of blubber. This problem may be avoided if reliable estimates of heat flux through the skin of the animals are obtained by using models that combine calculations of conductive heat flux through the skin and fur, and convective heat flux from the surface of the animal to the environment. We evaluated this approach based on simultaneous measurements of metabolic rates and of input parameters necessary for heat flux calculations, as obtained from four harp seals (Phoca groenlandica) resting in cold water. Heat flux estimates were made using two free convection models (double-flat-plate and cylindrical geometry) and one forced convection model (single-flat-plate geometry). We found that heat flux estimates generally underestimated metabolic rates, on average by 26-58%, and that small variations in input parameters caused large variations in these estimates. We conclude that cutaneous heat flux models are too inaccurate and sensitive to small errors in input parameters to provide reliable estimates of metabolic rates of marine mammals.
热通量模型已被用于预测海洋哺乳动物的代谢率，通常是通过估计通过其鲸脂层的传导热传递来实现的。最近，克瓦德海姆等人（1997年）发现，此类模型往往会高估代谢率，而且这种误差可能是由于鲸脂的不对称分布造成的。如果通过使用结合了通过皮肤和毛发的传导热通量计算以及从动物体表到环境的对流热通量计算的模型，获得动物皮肤热通量的可靠估计值，那么这个问题或许可以避免。我们基于对四只在冷水中休息的格陵兰海豹（Phoca groenlandica）的代谢率以及热通量计算所需输入参数的同步测量，对这种方法进行了评估。使用两种自然对流模型（双平板和圆柱几何模型）和一种强制对流模型（单平板几何模型）进行了热通量估计。我们发现，热通量估计值通常会低估代谢率，平均低估26% - 58%，并且输入参数的微小变化会导致这些估计值出现很大变化。我们得出结论，皮肤热通量模型不够准确，且对输入参数的小误差过于敏感，无法为海洋哺乳动物的代谢率提供可靠估计。
