Walsberg G E, Wolf B O
Department of Zoology, Arizona State University, Tempe 85287-1501, USA.
J Exp Biol. 1995 Jul;198(Pt 7):1499-507. doi: 10.1242/jeb.198.7.1499.
We report the first empirical data describing the interactive effects of simultaneous changes in irradiance and convection on energy expenditure by live mammals. Whole-animal rates of solar heat gain and convective heat loss were measured for representatives of two ground squirrel species, Spermophilus lateralis and Spermophilus saturatus, that contrast in coloration. Radiative heat gain was quantified as the decrease in metabolic heat production caused by the animal's exposure to simulated solar radiation. Changes in convective heat loss were quantified as the variation in metabolic heat production caused by changes in wind speed. For both species, exposure to 780 W m-2 of simulated solar radiation significantly reduced metabolic heat production at all wind speeds measured. Reductions were greatest at lower wind speeds, reaching 42% in S. lateralis and 29% in S. saturatus. Solar heat gain, expressed per unit body surface area, did not differ significantly between the two species. This heat gain equalled 14-21% of the radiant energy intercepted by S. lateralis and 18-22% of that intercepted by S. saturatus. Body resistance, an index of animal insulation, declined by only 10% in S. saturatus and 13% in S. lateralis as wind speed increased from 0.5 to 4.0 ms-1. These data demonstrate that solar heat gain can be essentially constant, despite marked differences in animal coloration, and that variable exposure to wind and sunlight can have important consequences for both thermoregulatory stress experienced by animals and their patterns of energy allocation.
我们报告了首份实证数据，描述了辐照度和对流同时变化对活体哺乳动物能量消耗的交互影响。对两种毛色不同的地松鼠物种——侧纹黄鼠（Spermophilus lateralis）和饱和黄鼠（Spermophilus saturatus）的代表动物，测量了其整体的太阳热增益速率和对流热损失速率。辐射热增益被量化为动物暴露于模拟太阳辐射下导致的代谢产热减少量。对流热损失的变化被量化为风速变化引起的代谢产热变化量。对于这两个物种，在所有测量的风速下，暴露于780 W m-2的模拟太阳辐射都显著降低了代谢产热。在较低风速下降低幅度最大，侧纹黄鼠达到42%，饱和黄鼠达到29%。以单位体表面积表示的太阳热增益在两个物种之间没有显著差异。这种热增益相当于侧纹黄鼠截获的辐射能量的14 - 21%，饱和黄鼠截获的辐射能量的18 - 22%。随着风速从0.5增加到4.0 m s-1，动物隔热指标——体表阻力，在饱和黄鼠中仅下降了10%，在侧纹黄鼠中下降了13%。这些数据表明，尽管动物毛色存在显著差异，但太阳热增益基本可以保持恒定，并且不同程度地暴露于风和阳光下，对于动物所经历的体温调节压力及其能量分配模式都可能产生重要影响。
