Western Pond Turtle
Western Pond Turtle (Actinemys marmorata) lives in rivers and is the West Coast’s only native freshwater turtle. Adult turtle shells are between 7 and 9 inches in length, have a yellowish stomach, black spots and lines on their head, and have a low unkeeled carapace.
The Western Pond Turtle’s geographical distribution has shrunk considerably over the years. Their range used to extend from British Columbia, Canada down to Baja, California. Now they’re only found in southern Washington, Oregon, California, and Nevada (where they’ve been introduced). On Stanford lands, native western pond turtles live in the San Francisquito Creek watershed.
Western Pond Turtles can be found in a variety of fresh water sources, including lakes, ponds, rivers, streams, creeks, reservoirs, marshes, and irrigation ditches. The species also relies on suitable terrestrial habitat to search for food, a better place to live, a mate, or to lay their eggs in the spring - typically from March to June. Western Pond Turtles have been found to migrate over half a mile in a yearly cycle. If you see a turtle walking on the land, it is probably not sick or lost, so the best thing you can do for the turtle is to leave it alone. Sometimes turtles do travel into unsuitable habitats, like roads, that present a clear and immediate danger to the turtle’s survival. If you find one in such a situation, it's ok to move it out of danger, but it's best to leave it in a safe place as close to where you found it as possible..
Community relationships and behavior
Western Pond Turtles are generalists. They eat aquatic plants, invertebrates, worms, frog and salamander eggs and larvae, crayfish, carrion, and sometimes frogs and fish.
Western Pond Turtles generally mate in the spring. Females will travel to an upland terrestrial location to nest their clutch of eggs, typically between 1 and 13 in number. The young remain in the nest until the next spring after hatching. When the time comes to leave they’ll migrate to aquatic habitat.
Western Pond Turtles are designated as a state “species of special concern” in California. Populations have declined by as much as 80% in some regions. Habitat alteration and destruction is the primary threat to Western Pond Turtle conservation. At the beginning of the 20th century extensive wetland drainage projects in the Great Valley further reduced suitable habitat, destroying the home of at least 3 million turtles. Dam construction and wetland management also disturbs their natural life cycle by altering their aquatic habitats. In addition to habitat destruction, a number of other factors impact individual survival and population viability. Nonnative species also pose a threat to the Western Pond Turtle. The Red-eared Slider and the Painted Turtle are common pets and their presence within California is most likely due to release by their owners. Since the Western Pond Turtle is the only native freshwater turtle in its historic range, it did not develop the ability to successfully compete with other species of turtles and both the Red-eared Slider and the Painted Turtle produce nearly twice as many offspring. Another threat to the pond turtle is the American Bullfrog, which preys on the western pond turtle.
Global warming is also threatening the sex ratios of recently hatched Western Pond Turtles. The hatchling sex is regulated by the incubation temperature of the nest, with an equal ratio of male to females attained at a temperature of around 84.9°F.
Western Pond Turtle at Stanford
Western Pond Turtles are monitored annually at Stanford and while population numbers are low, they have remained stable over the past several decades. The greatest threats to local population persistence at Stanford are small population size and isolation, non-native species, road mortality, and climate change.
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