The Role of Thermal Radiation in Animal Ecology

Abstract

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Thermodynamic Equilibria of Animals with Environment

“…The absorptivity of the pig was measured with the spectrophotometer to be 0.59 for a white pig and 0.79 for a black pig. Kelly, Bond, & Heitman (1954) measured the spectral reflectance of white, red, and black pigs. They found the white pig to absorb 49% of incident solar radiation, the red about 75%, and the black about 93%.…”

“…A pig could endure partial shade at air temperatures of 35°C, full shade up to 40°C, and air temperatures as high as 45° to 50°C only if he is fully shaded from the sun but radiating to the cold sky as well. Kelly, Bond, & Heitman (1954) clearly recognized the advantage of constructing animal shelters which would shade the animals from the sun but let them also exchange radiation with the cold north sky. These investigators state that "beef cattle of European breeds cannot usually live without shade in the summers of the Imperial Valley of California."…”

Effect of Paloverde (Cercidium) Trees on the Radiation Flux at Ground Level in the Sonoran Desert in Winter

“…A by-product of the analysis provides some estimates of the sizes of errors that can be encountered with the assumption that the animal's effective body-surface temperature is that of the surrounding air. Recent discussions of animal energy budgets are given by Hardy 1949;Kelly, Bond, and Heitman 1954;Kleiber 1961;Gates 1962;Birkebak 1966;Bartlett and Gates 1967;Norris 1967;Porter and Gates 1969;and others. As the heat loss of a homoiotherm equals heat gain when body core temperature is stable, during a cool or cold night the balanced budget is Heat in = Heat out metabolism + radiation absorbed = radiation emitted…”

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“…Since both these depend on the sun, indirect radiation will be minimal close to dawn and dusk, and be greatest when the sun is near its zenith. Even at maximum, indirect energy is less important than direct; Kelly et al (1954) estimated that at most onethird of the absorbable energy available at high noon might be indirect. Infrared from all these sources may cause some heating of both Colias color extremes.…”