The Western Pond Turtle (Actinemys marmorata), the only native freshwater turtle in California, occurs in a variety of habitats from sea level to about 2040 m elevation, from mesic forests to deserts. The San Joaquin Desert in California once supported large populations of this species in lakes, sloughs, and marshes fed by water from the mountains of the Sierra Nevada. Because of damming in the mountains and agriculture on the desert floor, much of the aquatic habitat is gone. Although some biologists proffered that only non-viable populations of Western Pond Turtles occurred in the San Joaquin Valley south of the delta, I found a surprisingly robust population of this species at Goose Lake, an ephemeral freshwater lake on the desert floor in northwestern Kern County. From 1995 to 2006, I marked 737 individuals. Growth rates and reproduction were fairly high compared to other populations of Western Pond Turtles in ponded waters. The average yearly population estimate was 597.4 turtles with annual survivorship estimates of 0.81 for adult males, 0.73 for adult females, 0.84 for juveniles 80–119 mm carapace length (CL), and 0.73 for juveniles <80 mm CL. The estimate of λ denoted a stable population. Although the population occurs in a habitat controlled by an agricultural water district, permanent water is always available and the site is secure from poaching. Despite severe decreases in numbers of turtles in the San Joaquin Desert over the past 100 y, based on this study and other recent studies, there are several populations of Western Pond Turtles in the area that appear to be large and stable.
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Vol. 104 • No. 3