Giant Garter Snake Trapline - Gray Lodge Wildlife Area [ds1001]

Trap line sites were selected by identifying each potential habitat type available during the trapping season and sites were assigned a number. A random number was then generated selecting the sites to be used for each trap period. Canal sites were selected based on water availability during each trapping session. Trap lines were equally allocated among the three habitat types. Seven trap lines during 2013 were selected for resurvey (four in different years and three in same year). This type of surveying provides better results for a mark and recapture study, however, lower than anticipated snake abundance and recapture rates prevented quantitative estimation of GGS population size. Our preliminary study phase occurred August through September of 2012. This consisted of twenty-one day, 50-trap lines being deployed, in each distinct aquatic habitat types at GLWA. A total of ten trap lines were surveyed. All traps were checked daily for the presence of GGS and to record by-catch and habitat characteristics from every 5thtrap. During this period we had nine confirmed GGS and had seven recaptures, and four sightings over 8,907 trap days. Our full-season-protocol study phase (April 2013 to September 2013) began on April 1, 2013. This phase consisted of six twenty-one day, 50-trap lines (300 traps total) being deployed in three distinct habitat types at GLWA. All traps were checked daily during the six month trapping period for the presence of GGS and to record the by-catch and habitat characteristics from every 5thtrap. During this period we had 29 confirmed GGS captured, four recaptures, and one sighting over 38,864 trap days. 29 new traplines were surveyed and seven traplines were resurveyed. To capture the effects of seasons, the project data were split into three distinct periods: early (April and May), middle (June and July), and late (August and September). Prey species caught abundantly in our traps included bullfrogs, tree frogs, crayfish, insects (most often dragonfly larva), mosquito fish, and several species in the sunfish and bass families. Besides GGS, T. elegans (mountain garter snake, 17 individuals) and T. sirtalis (valley/common garter snake, 120 captures) were commonly found in traps. All snakes were measured, weighed, marked using PIT tags and scale cauterization, photographed for identification and then geo-referenced to a trap and habitat of capture. Weight was measured in grams using an appropriate scale. In a few instances the proper scale was unavailable and snakes were classified as 300g. Length was quantified in millimeters in two separate measurements: Snout-vent length (SVL) and tail-vent length (TVL). Scales measurements were taken and recorded for pre/post ocular, 6th and 7th supralabials. Counts of supr and infra labials taken. All data were entered into a Microsoft Access database for analysis and double checked for data quality.

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