Experiments on Toleration of High Temperature in Lizards with Reference to Adaptive Coloration

In 1939 the writer accumulated data bearing upon the relations of desert lizards to environmental conditions of radiant energy and high temperature.1 These data were analyzed with respect to what the writer considered a well-established and fairly obvious principle of animal ecology, namely: that animals might, through natural selection, become adapted in their coloration to the physical conditions of the environment. Recently, stimulated largely by the publication of Cott's Adaptive Coloration in Animals (Cott. '39). there has been a revival of interest in animal in which the relationship of coloration to climatic conditions has been largely overlooked. Despite the fact that Punnett ('15), Dobzhansky ('37), Shull ('36, '37), Hovanitz ('40) and others have called attention to the overemphasis f requently placed upon protective coloration, the effect of Cott's book, whether intentional or not, has been to deny that the colors observed in animals may be adjusted to the physico-chemical environment. The current tendency seems to be to accept as habitat-adaptations only those cases where the coloration of the individual is directly induced by environmental conditions. In this category might be included those mammals which adopt a white winter coat as a direct response to reduced temperature. Other cases of environmentally induced coloration such as the classical cases described by Poulton ('87) of the effects of colored light on Lepidopterous larvae and pupae are generally described as adaptations entirely to predation factors.