The Rough Earth Snake (Virginia striatula): Ecology of a Texas Population

Abstract

A 35 month mark-recapture study of an earth snake population was conducted in Brazos County, Texas. Monthly trapping success was positively correlated with cumulative rainfall for that month plus the two preceding months. Earth snakes fed entirely on earthworms. Home range area measured via implantation of radioactive tantalum tags was positively correlated with rainfall during the month prior to trailing. Estimates of mean home range size (up to 100 m2 for adult females) obtained with tantalum tags resembled other estimates based on markrecapture data. At an age of about one year, minimum mature snout-vent length of females was 197 mm. Females probably first gave birth at age two years. Minimum mature snout-vent length of males was 140 mm (age 7-9 months); males may mate during their first spring. Estimates of population density ranged from 348 snakes/ ha in 1969 to 229 snakes/ha in 1971. There was a correspondence between population size and total rainfall during the preceding November-February. Reproduction resulted in estimated annual population increases of 2.6, 3.3, and 2.0 times (19691971). An earlier population study of Virginia striatula (Clark 1964) was based entirely on preserved specimens captured in Bryan-College Station, Brazos County, Texas. Those aspects of this species' ecology best studied by mark-recapture procedures remain poorly known. Our data on trapping success, food habits, growth, maturity, movements, and populations expand earlier findings. Results for V. striatula are compared with findings for the western ribbon snake (Thamnophis proximus) which were obtained concurrently on the same area (Clark 1974). STUDY AREA. The study area (a rectangular plot 89.6 X 189.6 m; 1.70 ha) located at the Texas A&M University Research Annex 6 km WSW of Bryan, Brazos County, east-central Texas had been a one-block portion of the housing area of a 1 Present address: Patuxent Wildlife Research Center, Laurel, Maryland 20810. 2 Present address: School of Forestry Stephen F. Austin State University, Nacogdoches, Texas 75961