Temperature, habitat selection, and egg incubation times in the green snake, Opheodrys vernalis.

Abstract

The presence of the smooth green snake, Opheodrys vernalis in Cheboygan County, Michigan was first noted by Ruthven in 1912. Ruthven's original and Wright's (1957) updated description of the range of O. vernalis show that Douglas Lake in Cheboygan County, Michigan is near the northern limit of this snake's distribution. Various aspects of the life history of Opheodrys vernalis have been described by several authors. Langlois (1924) was among the first to describe the oviparous reproductive process of this snake. Blanchard (1928, 1922) gave detailed descriptions of the oviposition process, eggs, incubation times, and young of O. vernalis. Lueth (1941), and Cowles and Bogert (1944) were among the first to show that environmental temperatures do affect snakes and reptiles. It was Cowles and Bogert (1944) who were the first to demonstrate that certain reptiles do maintain and regulate their body temperatures by thermal exchange with the environment. Brattstrom (1965) summarizes the work of several researchers and identifies the several thermoregulatory categories, and the physiological and behavioral mechanisms employed by a wide variety of reptiles. The question has been raised by Packard, Tracy, and Roth (1977): and by Sexton, and Claypool (1978); of how an ectothermal oviparious reptile, such as Opheodrys vernalis, can exist in cool northern climates when much of their life history depends upon suitable temperature. In their paper, Sexton and Claypool concluded that part of the answer lies in the selection of nest sites, having maximum and minimum temperatures consistently above shaded air temperature, the mean maximum being 28 C and mean minimum 18 C. The purpose of this project was to add further information to the partial answer provided by Sexton and Claypool. The questions that I have attempted to answer are: does the green snake, Opheodrys vernalis, have a preference of habitat based upon temperature; is there any relationship between habitat and body temperature; and, is there any relationship between these and reproductive success?