Effect of Temperature on Development of Scutellation in the Garter Snake, Thamnophis elegans atratus

Abstract

ALTHOUGH there seems to have been some feeling in herpetological circles that certain geographic variation in scale characters of reptiles might be due to temperature rather than to genetic differences, no successful experiments have been reported that test this hypothesis. The Pacific coast garter snake, Thamnophis elegans atratus (see Fox, 1948; Fitch, 1940: 89), displays an average reduction in certain scale counts northward and coastward from warmer to cooler regions. This race of garter snake occupies a narrow strip of the coast of California from about the Oregon state line to Santa Barbara (Fitch, loc. cit.). Because of the trend of scale variation in this form a set of experiments was designed to test the effect of temperature on the scale characters of developing embryos from a carefully studied, homogeneous, local population. Technical difficulties in breeding and raising reptiles made a genetic approach impractical.