USGS Western Ecological Research Center

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Scientists at the USGS Western Ecological Research Center study the many ecosystems of the Pacific Southwest. Follow our expeditions and projects through this outreach page, and learn more about your local landscape with our library of Outreach Factsheets and photos. Thanks for joining us!

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Western Pond Turtle (Emys marmorata) --Photographer: Ken Bohn/San Diego Zoo
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Zoo, City and USGS Study San Diego's Native Pond Turtles
MONDAY AUG 22 2011
Editor's Note: An earlier version of this post listed the San Diego Zoo partnering department as the Institute of Conservation Research. This is incorrect. 

Quick -- name all the native species of turtles found in California.

The answer is one: the western pond turtle (Emys marmorata). In fact, many of the red eared sliders and other turtles found in California's parks and wilderness are nonnative species from other countries or regions, and are adding pressure to our lone native freshwater turtle. In addition to invasive species, other stressors like land use change and loss of connected habitats may have contributed to isolated and reduced populations of this shelled swimmer.

Western pond turtles are listed as a Species of Special Concern by the state of California.

In the last few years, USGS Western Ecological Research Center has worked closely with partners like the San Diego Association of Governments (SANDAG), the San Diego Zoo Department of Herpetology and the zoo's Department of Veterinary Services to help track this dwindling native species. This research was featured in the Los Angeles Times yesterday:

Pond turtle research is led by ecologists Robert FisherChris Brown and colleagues at the WERC San Diego Field Station. Their work on field tracking, invasive species monitoring and turtle population genetics helps local partners understand the habitat changes taking place in the San Diego region. Zoo partners work on captive breeding of the pond turtles, while SANDAG partners consider land planning options.

Western Pond Turtle (Emys marmorata) --Photographer: Ken Bohn/San Diego Zoo

The work began in 2003 when WERC began monitoring the once-abundant populations within the Multiple Species Conservation Program (MSCP) region of San Diego. During these surveys, WERC detected just over 120 southwestern pond turtles, including only 18 females in five locations. The population and genetics data suggested that without active management, the species could eventually be lost from the region, especially as two-thirds of the females were detected at only one location.

“Like many other native species in southern California, we needed to understand how pond turtles were coping with habitat loss and invasive species pressure,” says lead scientist Robert Fisher.

Check out the WERC western pond turtle project page at

Check out the WERC Field Guide to Reptiles and Amphibians of Coastal Southern California here:

-- Ben Young Landis

Pond turtle photograph courtesy of Ken Bohn/San Diego Zoo.

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