A useful way to differentiate Western Pond Turtles from Red-eared Sliders, according to wildlife biologist Brandon Stidum, "...is to look at the marginal scutes 8-12 (...the scutes above the tail, or back scutes). Sliders have bifid or slightly forked scutes, where Western Pond Turtles do not; theirs are all smooth and do not split (except for traumatic injuries, but it’s usually only one or a few, not all scutes). The forking in the tail gives red-eared sliders the appearance that the tail is serrated or split in appearance. While looking for the presence and size of inguinal and axillary scutes is the best way to differentiate between the 2 once you have them in hand, a good way to do it from a distance is to look at the back scutes of the turtles."
Introduced melanistic sliders and old sliders whose red "ears" have faded, are often difficult to distinguish from the California native Western Pond Turtle, especially at a distance in the field, and even in hand. According to Bob Packard, with the Western Riverside County MSHCP Biological Monitoring Program, his organization confirms the identification of these turtles based on the presence of large inguinal and axillary scutes on the sliders, which are absent on the pond turtles, and by an interesting behavioral clue: the majority of sliders tend to be aggressive, biting readily, while pond turtles are far more reluctant to bite.
You can also use the information illustrated above about differentiating the two species from a distance by observing the rear marginal scutes, or back scutes, (scutes above the tail).
Short Videos of the Similar Southwestern Pond Turtle Species
Southwestern Pond Turtles compete for limited basking space on a small pond.
Southwestern Pond Turtles
basking in the sun.
Southwestern Pond Turtles
in an Alameda County pond.
3.5 - 8.5 inches in shell length (8.9 - 21.6 cm). (Stebbins 2003)
Hatchlings are aproximately 1 inch (2.5 cm) in shell length.
The tail of a young turtle is almost as long as its shell.
A small to medium-sized drab dark brown, olive brown, or blackish turtle with a low unkeeled carapace.
Color and Pattern
Usually with a pattern of lines or spots radiating from the centers of the scutes.
The plastron lacks hinges, and has 6 pairs of shelds which can be cream or yellowish in color with large dark brown markings, or unmarked.
The legs have black speckling and may show cream to yellowish coloring.
The head usually has a black network or spots may show cream to yellowish coloring.
Turtles south of the Transverse Ranges tend to be lighter, from yellowish brown to light brown.
Male / Female Differences
Males usually have a light throat with no markings, a more pointed chin than females, a low-domed carapace (a flatter shell), and a concave plastron.
Females usually have a throat with dark speckled markings, a more rounded chin than males, a high-domed carapace (a taller shell), and a flat or convex plastron which tends to be more heavily patterned than a male's plastron.
Life History and Behavior
Diurnal and aquatic.
Typically active from February through November, with the length of the active season depending on the temperature of the habitat.
May be active during warm periods in winter in warmer climates.
Pond turtles are often seen on a log or rock basking above the water, but they will quickly slide into the water when they feel threatened.
Pond turtles seldom bask by floating at the surface of the water.
Hibernation and Estivation
Some Western Pond Turtles slow down their metabolic processes and hibernate underwater during several months in the Winter. They often cluster in the shallow end of the pond. They survive so much time underwater by using cloacal respiration - pumping water through the cloaca through pouches that function similar to gills - extracting oxygen from the water and releasing carbon monoxide.
Other pond turtles pass the Winter by moving to woodlands above the creek or pond they inhabit and burying themselves in loose soil or entering California ground squirrel burrows, where they down their metabolic processes. They remain underground through the Winter until temperatures warm up enough for them to become active. If they leave a creek due to heavy winter flows, they will return to the creek in Spring when the flow of the water subsides.
During hot dry Summer droughts, some pond turtles will estivate by burying themselves in the soft bottom mud of a pond or creek, again relying on cloacal respiration.
When creeks and ponds dry up in Summer, some pond turtles that inhabit creeks will travel along the creek until they find an isolated deep pool, others stay within moist mats of algae in shallow pools.
Turtles Walking on Land Do Not Always Need to be Picked Up and Rescued
Turtles sometimes leave the water to search for food, a better place to live, a mate, or to lay their eggs in the spring - typically from March to June. 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. Some people want to help a turtle they think is in danger by picking it up and bringing it home or to a wildlife rehabilitation center, but most of the time this harms the turtle by removing it from the wild without reason. Sometimes turtles do get lost or stranded in yards or on busy roads or somewhere where they may be in danger. 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.
When seeking or protecting a basking spot, Western Pond Turtles may show aggressive behavior by opening the mouth and exposing the yellow and pinkish mouth lining to scare off another turtle. Occasionally they will also bite or ram.
Diet and Feeding
Eats aquatic plants, invertebrates, worms, frog and salamander eggs and larvae, crayfish, carrion, and occasionally frogs and fish.
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)
Found in ponds, lakes, rivers, streams, creeks, marshes, and irrigation ditches, with abundant vegetation, and either rocky or muddy bottoms, in woodland, forest, and grassland. In streams, prefers pools to shallower areas. Logs, rocks, cattail mats, and exposed banks are required for basking. May enter brackish water and even seawater.
A. marmorata ranges north of California into Oregon, Washington and British Columbia (west of the crest of the Cascades and Sierras) (It may now be extinct in western Washington and British Columbia.) An isolated population occurs at Susanville. Another isolated population occurs in Nevada in the Truckee, Carson, and East Walker Rivers (Stebbins 2003).
Range in California
According to the paper that split the former species into two species **, all populations of pond turtles in California "... north of the San Francisco Bay area plus populations from the Great Central Valley north including the apparently introduced Nevada population..." are the [Northwestern] Pond Turtle. The [Southwestern] Pond Turtle "... 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 ... Although we tentatively include populations from Baja California in E. pallida, we also recognize that these animals may represent a distinct species pending results from additional analyses."
** 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.
It is not clear from the Spinks, Thomson, and Shaffer paper referenced above what species of Western Pond turtle occurs immediately south, east, and west of the San Francisco Bay, since no specimens from that area were used in the study which described the two species. Nor is there any mention of hybrids occurring in this area, only this: "Emys marmorata and E. pallida show very limited intergradation in a few populations in the northern central coast range and adjacent Sierra Nevada foothills, although at all intergrade sites we also found pure individuals of the locally prevalent species.")
On my range maps I previously showed the area south, east, and west of the San Francisco Bay as an "area of uncertainty." In 2017
I changed my range maps to follow the only source I can find that shows the two species range in that part of the bay area: Robert C. Thomson, Amber N. Wright, and H. Bradley Shaffer. California Amphibian and Reptile Species of Special Concern. University of California Press, 2016. Their range map (which is now online at the CDFW website) shows A. pallida ranging throughout area south, east, and west of the San Francisco Bay. I am doing that now, to be consistent with the state Species of Special Concern information, though I am not convinced that it is accurate. The eastern boundary and contact area between the two species is apparently the edge of the South Coast Ranges where they meet the floor of the great valley.
Stebbins (2003) describes the elevation range of the Western Pond Turtle - Clemmys marmorata, which has now been split into two species, as "Sea level to around 6,696 ft. (2,041 m) but mostly below 4,980 ft. (1,371 m)."
Notes on Taxonomy
Previously, the Western Pond Turtle, Actinemys marmorata, was split into two subspecies: A. m. marmorata and A. m. pallida.
The single species has been split into two full species, corresponding to the previous two subspecies - Actinemys marmorata, and Actinemys pallida.
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.)
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.
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)
The following conservation status listings for this animal are taken from the October 2021 California "Special Animals List" and the October 2021 "State and Federally Listed Endangered and Threatened Animals of California" list, both of which are produced by multiple agencies and available here: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. You can check the link to see if there are more recent lists.
If no status is listed here, the animal is not included on either list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status you can go to the NatureServe and IUCN websites to check their rankings.
The Special Animals List shows this turtle as Emys marmorata - Western Pond Turtle. It does not track the species by the two formerly recognized subspecies nor does it recognize the 2014 description of two species of pond turtles (as this site does.)
Special Animals List Notes:
1) The paper: Spinks, Phillip Q. & H. Bradley Shaffer. 2005. Range-wide molecular analysis of the western pond turtle (Emys marmorata): cryptic variation, isolation by distance, and their conservation implications. Molecular Ecology (2005) 14, 2047-2064. determined that the current subspecies split was not warranted. Therefore, we are now tracking the western pond turtle only at the full species level.
2) The paper: Spinks, Phillip Q., & H. Bradley Shaffer. 2009. Conflicting Mitochondrial and Nuclear Phylogenies for the Widely Disjunct Emys (Testudines: Emydidae) Species Complex, and What They Tell Us about Biogeography and Hybridization. Systematic Biology. 58(1): pp. 1-20 determined that the correct genus name is Emys.
NatureServe Global Ranking
Vulnerable - Apparently Secure
NatureServe State Ranking
Vulnerable in the state due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation from the state.