The Pine Woods Snake, Rhadinaea flavilata (Cope)

Abstract

Rhadinaea flavitata (Cope, 1871) is a small colubrid snake inhabiting a narrow coastal range in the southeastern United States. Its distribution closely approximates that of the low pine fiatwoods, which constitute its principal habitat. A few individuals have been found in other situations, especially in Florida hammocks and on coastal islands. The species is most commonly encountered in pine logs and stumps during March and April; with the approach of warmer weather and drier conditions in May and June, Rhadinaea and other small snakes become more difficult to find. R. flavilata feeds on small amphibians, lizards, and perhaps snakes; literature records referring to predation on insects are questioned. The pine woods snake kills or incapacitates some of its prey with a venom introduced into wounds made by enlarged rear maxillary teeth. Other snakes are likely its main predators and food competitors. R. flavilata lays two to four elongate eggs; the period of egg deposition is speculated to extend from May into August, although it probably is not so extensive in any given season; the natural nest is unknown. There is slight statistical evidence of unbalanced sex ratios in some populations. Structural variation was observed in many characters, and for discussion is classified as intrapopulational variation (including ontogenetic, sexual, and uncorrelated or "individuial" variation) and interpopulational (geographic) variation, the latter being compounded from the former. No geographic races are recognized in this species. Structurally the pine woods snake is a rather generalized Rhadinaea. Its closest living relative is R. laureata of the highlands of western Mexico. Fossils show that R. flavilata, or a genetic predecessor, had arrived in the southeastern United States at least by the third (Illinoian) glacial stage of the Pleistocene. The lack of marked geographic variation in this species can be explained by the relatively recent (postglacial) dispersal of a homogeneous Floridian stock throughout a relatively uniform pine-flatwoods habitat. Environment, nonselective genetic mechanisms, and natural selection are considered briefly in terms of the evolution of geographic variation. A seemingly primitive color pattern is retained at the northern limits of the range; the southern populations are characterized by loss of pattern and by increased variability (often anomalous) in scutellation. It is inferred that southern populations, being most influenced by a warming post-glacial climate, are evolving faster than northern populations.