Seasonal Habitat Use of the Western Pond Turtle, Emys Marmorata, in an Urban Environment

The western pond turtle, Emys (aka Clemmys, Actinemys) marmorata (Testudines, Emydidae), is the only native freshwater turtle along much of the West Coast of the United States, and is listed as a California Department of Fish and Game Species of Special Concern (CA DFG SSC). Populations of E. marmorata are in decline throughout their range, primarily as a result of habitat loss or alteration in developed areas. Despite these well-documented losses, few studies have examined aquatic and terrestrial habitat use patterns and the anthropogenically influenced landscape-level factors that are likely to be associated with these declines. Information on patterns of seasonal migration and periodic dormancy where these declines have occurred is fundamental to understanding E. marmorata's current situation and future status. Using radio telemetry, GPS, and GIS we have monitored the seasonal activity patterns of a 22 individuals from a population of E. marmorata in an approximately 5-mile portion of a Northern California urban waterway (Santa Rosa Creek, Sonoma County), to identify seasonal migration patterns as well as seasonal home range sizes. Turtles in this study lived almost exclusively within the stream channel. Turtles with a longer carapace length had larger home ranges. Turtles in this study had significantly larger home ranges than E. marmorata in studies that tracked turtles in less altered habitats. Average daily solar radiation significantly affected average daily movements, with larger amounts of solar radiation correlating to increased daily movements. Movements also varied significantly by month. Turtle length correlates with bromination start date, end date and overall length.