Status of the Western Pond Turtle (Clemmys marmorata) in Washington (1993)

The western pond turtle (Clemmys marmorata) is state-listed as a threatened species by the Washington Wildlife Commission. A proposal to list the species as threatened or endangered under the Endangered Species Act is under review by the U. S. Fish and Wildlife Service.

This species is a highly aquatic turtle that occurs in streams, ponds, lakes, and permanent and ephemeral wetlands. Western pond turtles spend much of their lives in water, but require terrestrial habitats for nesting, overwintering, and dispersal. Although generally wary they may be seen basking on emergent or floating vegetation, logs, rocks, and occasionally mud or sand banks. The diet of this species consists primarily of small invertebrates, carrion, and plant material. In Washington, the species overwinters in upland habitats adjacent to water bodies or in mud bottoms of lakes or ponds. Nesting occurs from May to August in hard soils with scant vegetative cover up to 200 m from the watercourse. These turtles are long-lived, with an estimated lifespan of 50 to 70 years. They require more than 10 years to attain sexual maturity.

The western pond turtle range extends from Washington south through Oregon to Baja California. The historic range in Washington included disjunct populations in the Columbia River Gorge and the Puget Sound region. Western pond turtles have essentially been extirpated in Puget Sound and have undergone significant declines from historic levels in the rest of their Washington range. Presently, viable populations are restricted to two isolated sites in Skamania and Klickitat counties. Intensive 1992 surveys found 69 western pond turtles in the state (3 in Puget Sound and 66 in the Columbia Gorge).

Habitat loss and alteration are the primary causes of the decline in western pond turtle numbers. Wetlands have been filled for residential and industrial development, particularly in the Puget Sound region. Water diversion projects and construction of dams have reduced available habitat and have isolated populations. Exotic predators such as bullfrogs and some large fish, which have been introduced to lakes and ponds, exact a toll on hatchling and young turtles. Human disturbance can keep females from crossing over land to lay eggs, or can cause turtles to reduce the amount of time spent in maintenance behaviors such as basking. Loss of lakeside vegetation to grazing and trampling can make habitat less suitable for hatchlings and juveniles.

An unknown disease killed at least 36 turtles in Klickitat County in 1990, highlighting the precarious condition of the state's population. A captive breeding program has been established to build a population of turtles for future release into suitable Washington habitat. A headstart program was used to enhance the survival of hatchling turtles from wild nests. Predator control and habitat enhancement has occurred at some occupied sites. The Department of Wildlife has acquired land supporting one of the two most important populations in the state, and is in the process of acquiring the other.

The western pond turtle has been extirpated from a significant portion of its range in Washington. Viable populations remain only in a few restricted areas in the Columbia Gorge. The population is estimated to number fewer than 100 individuals and has recently declined from already low numbers. The species is highly vulnerable to extirpation in Washington in the foreseeable future by natural or human-caused factors.

It is recommended that the western pond turtle be reclassified from threatened to endangered in Washington.