Occurrence of the Garter Snake, Thamnophis Sirtalis, in the Great Plains and Rocky Mountains

This 1961 monograph documents one of the most ambitious attempts to map the distribution of a North American reptile. Henry S. Fitch, the era's most prolific herpetologist, turns his attention to Thamnophis sirtalis, the common garter snake, whose range stretches from Atlantic to Pacific, making it the most widespread reptile on the continent. The work focuses specifically on populations across the Great Plains and Rocky Mountains, where subspecies boundaries blur and identification becomes treacherous. Fitch meticulously examines Thamnophis sirtalis parietalis and Thamnophis sirtalis fitchi, tracing their ranges, describing their distinguishing characteristics, and documenting how these snakes adapt to environments as varied as prairie grasslands and montane coniferous forests. Perhaps most valuably, Fitch discusses the methodological challenges that bedevil any attempt to map snake occurrences: specimen misidentification, the difficulty of accessing remote habitats, and the simple fact that snakes resist easy observation. This is field biology at its most painstaking, a work that reminds readers that understanding even 'common' species requires extraordinary effort.