This project focuses on habitat use and life history characteristics of the giant garter snake(Thamnophis gigas), a species endemic to Central Valley wetlands and federally listed as threatened. Trapping and searching methods are being evaluated for appropriate use to meet study objectives. Passively induce transponder (PIT) tags are being used in the study to permanently mark and establish a data base for giant garter snakes sampled during the study. Morphological measurements and tissue samples for genetic determinations are being taken to improve the taxonomic description of this species, which is inadequately treated in the current literature. Surgical techniques and design of radio transmitters have been modified to successfully use radio telemetry for this species. Radio telemetry is showing aspects of habitat use and movements that were previously poorly understood for this species. For example, we have found these snakes remain motionless to avoid detection rather than readily fleeing from disturbance, a trait previously thought to be characteristic of this species. Because of their motionless behavior and cryptic coloration, we determined visual surveys to be of little use in detecting this species. The Fish and Wildlife Service had earlier proposed visual surveys as a method of population censusing in the Habitat Conservation Plan for the Giant Garter Snake; we suggested seasonal searching and trapping methodology. We also found snakes to be active far later into the fall than was previously believed, an observation which will change suggested timing of road, ditch, and levee maintenance in the rice fields these snakes inhabit. This study is ongoing, and new proposals are being written to extend and expand the study to make it a true ecosystem study of agricultural and natural wetlands in the Central Valley. For more information, contact Glenn Wylie.
