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An Analysis of Background Color‐Matching in Amphibians and Reptiles

Norris, Kenneth S., Lowe, Charles H.
Ecology 1964 v.45 no.3 pp. 565-580
absorption, color, habitats, lighting, predators, reflectance, reptiles, salamanders and newts, temperature, texture, wavelengths
The colors of living amphibians and reptiles have been studied, using a General Electric recording reflectance spectrophotometer. The animals were brought to activity temperature levels and the appropriate surface pressed over the reflectance port of the machine while a color record was taken. Background samples from the localities at which the animals were taken were also recorded. Reptiles and amphibians living on backgrounds of relatively uniform color tend to match that background through superposition with considerable fidelity. The animal's color curve is superimposed over that of the background. Ventral color in most forms tested was lighter than the dorsal surfaces of the same animal. It was darker only in some forest—dwelling salamanders and in desert lava—dwelling species. The difference results primarily from the highly reflective ventral surfaces of these forms. The ventral surfaces of white—bellied amphibia show clear oxyhaemoglobin absorption peaks, as do the dorsal surfaces of some amphibia. These effects are entirely absent in curves recorded from reptiles. It is concluded that the degree of background color—matching is related to: (a) the degree of color uniformity of the animal's background, (b) the degree of exposure of the color—matched species to predator, (c) the illumination level prevalent in the habitat, (d) the size range of the color—matched species, (e) the ecological restriction of the species, (f) the qualities of the visual apparatus of predators upon the species, and (g) the adaptive compromise struck by the species. The size of a color—matched animal, or the size of the part of its body that is normally exposed, is related to the point at which such color—matching breaks down. This point of just noticeable difference between animal and background is also determined by the wave—length discrimination curves of the predators, the closeness of the match involved, the uniformity of the background color and its texture, and the presence of absence of concealing patterns. Background color—matching varies greatly in its degree of perfection. This variation is the result of adaptive compromise and balance between this adaptive characteristic and many others that in one way or another affect its complete expression.