Northwestern Pond Turtle - Actinemys marmorata

Males

Size: males are smaller than females
Throat: light in color with no markings
Chin: more pointed than on females
Head: larger than females
Carapace: a lower dome (flatter shell) than females
Plastron: concave
Tail: wider and thicker at the base than females

Females

Size: females are larger than males
Throat: dark speckled markings
Chin: more rounded than on males
Head: smaller than males
Carapace: a higher dome (taller shell) than males
Plastron: flat or convex
Tail: thinner at the base than males

Adults do not mate until they are aproximately eight to ten years old.
Mating occurs in April and May.

Sometime between late April and August, females climb onto land to dig a nest, usually along stream or pond margins in areas with full sunlight, where they lay a clutch of 2 - 11 eggs. Some females lay two clutches in a year while others lay eggs every other year.
Females in the Bay Area were found to prefer to lay their eggs in sunny areas with grass about a foot and a half high covering about 85 percent of the ground. (Carolyn Jones, SFGate.com, 7/31/13)

The length of incubation is not known. It may vary with altitude and latitude. Eggs incubated in a laboratory hatched in 73-81 days.
Hatchlings may emerge in late summer or fall, but some turtles may overwinter in the nest and emerge the following spring.
(Ernst, Barbour, & Lovich, 2009)

Spinks, Thomson and Shaffer "...propose using the name Emys marmorata for all populations north of the San Francisco Bay area plus populations from the Great Central Valley north.... Emys pallida is restricted to those populations inhabiting the central coast range south of the San Francisco Bay area to the species’ southern range boundary, including the Mojave River."

(Phillip Q. Spinks, Robert C. Thomson, and H. Bradley Shaffer.
The advantages of going large: genome wide SNPs clarify the complex population history and systematics of the threatened western pond turtle.
Molecular Ecology. 23(9): 2228-2241. June, 2014.)

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Janzen, Hoover, and Shaffer (1997 Chelonian Conservation Biology 2(4): 623-626) concluded that southern populations of A. marmorata, found in Baja California and adjacent southern California, are a different species from those to the north.

Spinks and Shaffer argued that subspecies should be abandoned because they are not supported on molecular grounds. (Spinks and Shaffer - 2005 Mol. Ecol. 14:2047-2064)

In 2010 Spinks (Spinks et al., 2010, Mol. Ecol. 19: 542-556) demonstrated deep phylogeographic divergence within the species, potentially warranting species recognition.


Alternate and Previous Names (Synonyms)

Actinemys marmorata marmorata - Northwestern Pond Turtle (Stebbins & McGinnis 2012)
Clemmys marmorata marmorata - Northwestern Pond Turtle (Stebbins 1966, 1985, 2003)
Clemmys marmorata - Pacific Pond Turtle (Stebbins 1954)
Clemmys marmorata - Pacific Mud Turtle (Emys marmorata; Emys nigra; Atinemys marmorata; Clemmys Wosnessenskyi; Chelopus marmoratus. Western Pond Turtle; Pacific Terrapin; California Terrapin; California Mud Turtle; Western Terrapin; Water Turtle) (Grinnell and Camp 1917)

Northwestern Pond Turtles may be nearly extinct in western Washington and British Columbia.


The Western Pond Turtle is in decline throughout 75 - 80% of its range. (Stebbins, 2003.) There a number of reasons for this decline.

Beginning in the 19th century, the commercial harvesting of Western Pond Turtles for food was a major threat to the species. That trade continued at least into the 1930s: Nussbaum, Brodie & Storm, 1983, remark that in the 1930s, Western Pond Turtles were trapped for food in California and sold to markets in San Francisco.

Another cause for the decline of the species was the massive wetland drainage projects in the Great Valley of the early 20th century which destroyed numerous wetlands and lakes and altered rivers, all of which destroyed or reduced suitable habitat for the Western Pond Turtle. Tulare lake, now gone, was once the home to an estimated 3.5 million pond turtles, almost all of which are now extinct in the area. (Stebbins & McGinnis, 2012.) The destruction or degredation of other wetlands throughout the state has certainly also added to the decline.

The introduction of non-native turtles into Western Pond Turtle habitat, especially the two most successful invasive turtle species, the Red-eared Slider and the Painted Turtle, has been another cause of the decline of the Western Pond Turtle. Both species are common in the pet trade and feral turtles now found in California were most likely released 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 for resources with other species of turtles, and both the Red-eared Slider and the Painted Turtle produce nearly twice as many offspring as the pond turtle which allows them to overwhelm and out-compete the pond turtle population.

Another threat to the pond turtle has been the American Bullfrog, an invasive species that has spread throughout the state. In 1994 report, Dan C. Holland writes that the invasive bullfrog (Rana catesbeiana) is a known predator of Western Pond Turtles, and the report includes a picture of a bullfrog preying on a juvenile pond turtle in San Diego County. Bullfrogs breed in such large numbers that adults can eventually eat so many hatchling turtles that fewturtles can survive to adulthood and after the existing adults die off there will be no more turtles at that location.  (Holland, Dan C. The Western Pond Turtle: Habitat and History. Final Report. Prepared for: U. S. Department of Engergy Bonneville Power Administration Environment, Fish and Wildlife... Portland OR.1994)

Photographic evidence also exists that shows that bullfrogs eat hatchling painted turtles.

St. John, Alan D. Reptiles of the Northwest: Alaska to California; Rockies to the Coast. Lone Pine Publishing, 2002.

Lemm, Jeffrey. Field Guide to Amphibians and Reptiles of the San Diego Region (California Natural History Guides). University of California Press, 2006.

Robert C. Thomson, Amber N. Wright, and H. Bradley Shaffer. California Amphibian and Reptile Species of Special Concern. University of California Press, 2016.

Watch more short movies of this turtle at Endangered Species International (www.endangeredspeciesinternational.org)