Population demographics and overwintering ecology of southern California Pacific pond turtles, Actinemys (Clemmys) marmorata

The Pacific Pond Turtle (PPT), Actinemys (Clemmys) marmorata, is a small, highly aquatic turtle whose populations along its entire distribution range are in decline. As most of the published papers focus on the populations in the central and northern portions of the distribution range, the southern California PPT populations' demographics and overwintering ecology are not well-known or understood. A protected population of PTTs in Riverside County, California, was studied and the demographics of population size, survivorship and recapture probabilities, population structure, growth and sexual size dimorphism were analyzed. The overwintering ecology, including overwintering behaviors, timing and microhabitat characteristics of overwintering sites, of the same population were also studied using radiotelemetry. It was found that the southern California PPT population in 2008 contained approximately 120 individuals, had high adult female and juvenile survivorship rates, and lower than expected adult male survivorship rates. The population structure appeared to be that of a healthy, undisturbed population. The adult females were found to be significantly larger than the males. The PPTs exhibited terrestrial overwintering behavior as the seven turtles in the study all left the water to overwinter in upland locations. They utilized fewer locations than PPTs in northern populations and returned to the water earlier than northern PPTs. None of the study turtles were observed thermoregulating, as has been observed for all other PPT studies. The overwintering sites were located in a variety of habitat types. The knowledge gained from this study will help resource managers understand the population demographics and overwintering ecology of a robust southern California PPT population and utilize the knowledge to protect other PPT populations. Keywords: population size and structure, survivorship, sexual size dimorphism, overwintering, turtle, Pacific Pond Turtle