Overview

Brief Summary

Summary

Actinemys marmorata (Family Emydidae) occurs in the Pacific States of North America from Baja California Norte north through Washington and, possibly, into southernmost British Columbia, Canada. Recent genetic studies indicate the presence of four groups or clades within the species, although historically there were two recognized subspecies. The species appears to be declining in abundance in the northernmost and southernmost portion of its range, but not in the core of its range from central California to southern Oregon. The primary threats are loss and alteration of both aquatic and terrestrial habitats. These losses fragment remaining populations and, perhaps, magnify the effects of introduced species through predation, competition, and epidemic disease(s). Historically, A. marmorata were collected for the food and pet trades. Most states now protect the species and, in Washington, it is listed as Endangered. Research is ongoing on many aspects of the species' ecology, but not all of the studies are published. Greater effort is needed to protect and manage aquatic habitats as well as nesting and overwintering sites in adjacent uplands.
  • Bury, R.B. and Germano, D.J. 2008. Actinemys marmorata (Baird and Girard 1852) – western pond turtle, Pacific pond turtle. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., and Iverson, J.B. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 001.1-001.9, doi:10.3854/crm.5.001.marmorata.v1.2008, http://www.iucn-tftsg.org/cbftt
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Biology

Breeding occurs in late spring to mid-summer (4), with mating taking place under water (5). Most mature females nest every year, some laying two clutches per season (5). In early summer the eggs are deposited in the nest, which is generally dug in soil, close to a water source, but some females may dig their nests many metres away from the water's edge (9). The female lays an average of four to seven eggs (range 1 to 13) per clutch, which hatch after approximately 13 to 17 weeks (4); however, hatchlings from northern California northward over-winter in the nest (10). Western pond turtles develop slowly in areas with short or cool summers, taking up to eight years to reach sexual maturity. They can grow relatively fast in warmer regions and in some nutrient-rich habitats, where they can reach maturity in half that time (4). Turtles are thought to live up to 40 years (5). Adults face predation by a number of carnivores including racoons, otters, ospreys and coyotes. Hatchling turtles, being small with soft shells, are easily preyed upon by raptors, ravens, weasels, bullfrogs and large fish. The diet of the western pond turtle includes some plants, small fish, frogs, carrion and, most importantly, aquatic insects and larvae (4). Western pond turtles bask on mats of floating vegetation, floating logs or on mud banks just above the water's surface. In warmer climes they engage in aquatic basking by moving into the warm thermal environment in or on top of submerged mats of vegetation (4).
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Description

The Latin name 'marmorata' refers to the marbled pattern of both the soft parts and carapace of many western pond turtles (3). The low, broad, smooth carapace is usually light to dark brown or olive in colour, either with no pattern or with an attractive pattern of fine, dark radiating lines on the scutes (2) (3). The limbs and head are olive, yellow, orange or brown, often with darker flecks or spots (3). Males are usually identified from females by the position of the cloaca. In males, the cloaca is positioned beyond the edge of the plastron, whereas it does not reach the edge of the plastron in females. Males also have a yellow or whitish chin and throat (4), a flatter carapace, a more concave plastron (indented underside of shell), and a more pointed snout than females (5). The taxonomy of the western pond turtle is currently under debate; at present, the IUCN Red List recognises that the western pond turtle belongs in its own genus, Actinemys marmorata (1), however, there is deliberation that it may belong to the genus Emys (6). There were previously thought to be two subspecies of the western pond turtle: the southern western pond turtle (Actinemys marmorata pallida) and the northern western pond turtle (Actinemys marmorata marmorata) (5), but now there is evidence for four separate groups, which do not match the distribution of the earlier described subspecies (7).
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Distribution

occurs (regularly, as a native taxon) in multiple nations

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Absent

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) This turtle is discontinuously distributed and generally uncommon from western Washington (Puget Sound region, at least formerly) south to northwestern Baja California. Isolated populations occur in the Mojave River in California, the Carson River in Nevada (one population in the vicinity of Carson City), the lower Columbia River (two populations in Washington, one in Oregon), the Puget Sound Trough in northern Washington (rarely observed; no known extant populations), and in areas south of the Transverse Ranges in southern California and adjacent Baja California (Bury and Germano 2008). Western pond turtles still exist at probably numerous localities in the Central Valley of California (Germano and Bury 2001). Occurrences in the following locations may represent introductions and may or may not represent extant populations: Truckee, Carson, and Humboldt rivers in western Nevada; southern British Columbia; Snake River, Jerome County, Idaho (1894); and Canyon Creek area, Grant County, Oregon. Elevational range extends from sea level to around 6,000 feet. See Buskirk (1990) for some relatively new records from California, mainly from the Sierra Nevada foothills.

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Canada (?), Mexico, USA. Pacific States of North America from Baja California Norte, Mexico, north through Washington and, possibly, into southernmost British Columbia, Canada.
  • Bury, R.B. and Germano, D.J. 2008. Actinemys marmorata (Baird and Girard 1852) – western pond turtle, Pacific pond turtle. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., and Iverson, J.B. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 001.1-001.9, doi:10.3854/crm.5.001.marmorata.v1.2008, http://www.iucn-tftsg.org/cbftt
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Geographic Range

Western pond turtles (also known as Pacific pond turtles and Pacific mud turtles) are native to the west coast and are found from Baja California, Mexico north through Klickitat County, Washington. Within this region, there are two subspecies: northwestern pond turtles (E. m. marmorata) are found in areas north of the American River in California; southwestern pond turtles (E. m. pallida) are found in areas south of San Francisco. There are isolated inland populations in Washington, Oregon, California, Nevada and Idaho. It has been suggested that some of these isolated populations represent introductions through human transport, although there is no clear evidence for this.

Biogeographic Regions: nearctic (Native )

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Continent: Middle-America North-America
Distribution: Canada (SW British Columbia) ?,  USA (west of the Cascade-Sierra crest, Washington, Oregon, California, W Nevada), Mexico (NW Baja California)  marmorata: N California, W Oregon, exterme S Washington, isolated colonies exist in the Truckee and Carson rivers in Nevada;
Type locality: “Puget Sound” [state of Washington].  pallida: S California, N Baja California
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Range

The range of the western pond turtle extends from Baja California Norte, north through the Pacific States of the USA, and barely into British Columbia, Canada. The handful of specimens found in British Columbia, Canada could represent introductions rather than native populations (8).
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Physical Description

Morphology

Physical Description

Western pond turtles are generally yellowish with dark blotches in the center of the plastron. There is marbled patterning throughout the body. The dorsal area is generally dark brown to olive. The shell tends to be low, wide, and smooth. Adult males have a larger head, pointier snout, thicker tail base, and a wider neck characterized by white and yellow on the chin and throat. Adult females tend to have a blunt snout, thinner tail base, and darker markings on the chin and throat. Western pond turtles have webbed feet. Hatchlings tend to have a longer tail, soft shell, and be a lighter brown; darkening as they age. They weigh approximately 5g at hatching and measure around 28 mm in shell length. The southern subspecies tends to grown only to 115 mm in shell length, northern subspecies reach 210 mm in shell length.

Range mass: 623.7 to 935.55 g.

Range length: 110 to 210 mm.

Average basal metabolic rate: Unknown cm^3 oxygen/hour.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger; sexes colored or patterned differently; sexes shaped differently

  • Office of Environmental Health Hazard Assesment. Exposure Factors for Western Pond Turtle (Clemmys marmorata). California: The California Wildlife Biology, Exposure Factor, and Toxicity Database (Cal/Ecotox). 1999. Accessed April 22, 2008 at http://www.oehha.ca.gov/cal_ecotox/report/clemmef.pdf.
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Size

Length: 18 cm

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Diagnostic Description

This species differs from the painted turtle (Chrysemys picta) and slider (Trachemys scripta) (the turtle species most likely to be introduced into the range of the western pond turtle) in lacking yellow lines on the head and limbs.

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Type Information

Syntype for Clemmys marmorata
Catalog Number: USNM 131830
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: ; Juvenile
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Syntype: Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6: 177.
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Syntype for Clemmys marmorata
Catalog Number: USNM 88
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: ; Juvenile
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Syntype: Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6: 177.
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Syntype for Clemmys marmorata
Catalog Number: USNM 7596
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: ; Juvenile
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Syntype: Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6: 177.
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Syntype for Clemmys marmorata
Catalog Number: USNM 7595
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: ; Juvenile
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Syntype: Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6: 177.
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Syntype for Clemmys marmorata
Catalog Number: USNM 7594
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: ; Juvenile
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Syntype: Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6: 177.
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Ecology

Habitat

Palouse Grasslands Habitat

This taxon is found in the Palouse grasslands, among other North American ecoregions. The Palouse ecoregion extends over eastern Washington, northwestern Idaho and northeastern Oregon. Grasslands and savannas once covered extensive areas of the inter-mountain west, from southwest Canada into western Montana in the USA. Today, areas like the great Palouse prairie of eastern  are virtually eliminated as natural areas due to conversion to rangeland. The Palouse, formerly a vast expanse of native wheatgrasses (Agropyron spp), Idaho Fescue (Festuca idahoensis), and other grasses, has been mostly plowed and converted to wheat fields or is covered by Drooping Brome (Bromus tectorum) and other alien plant species.

the Palouse historically resembled the mixed-grass vegetation of the Central grasslands, except for the absence of short grasses. Such species as Bluebunch Wheatgrass (Elymus spicatus), Idaho Fescue (Festuca idahoensis) and Giant Wildrye (Elymus condensatus) and the associated species Lassen County Bluegrass (Poa limosa), Crested Hairgrass (Koeleria pyramidata), Bottlebrush Squirrel-tail (Sitanion hystrix), Needle-and-thread (Stipa comata) and Western Wheatgrass (Agropyron smithii) historically dominated the Palouse prairie grassland.

Representative mammals found in the Palouse grasslands include the Yellow-bellied Marmot (Marmota flaviventris), found burrowing in grasslands or beneath rocky scree; American Black Bear (Ursus americanus); American Pika (Ochotona princeps); Coast Mole (Scapanus orarius), who consumes chiefly earthworms and insects; Golden-mantled Ground Squirrel (Spermophilus lateralis); Gray Wolf (Canis lupus); Great Basin Pocket Mouse (Perognathus parvus); Northern River Otter (Lontra canadensis); the Near Threatened Washington Ground Squirrel (Spermophilus washingtoni), a taxon who prefers habitat with dense grass cover and deep soils; and the Northern Flying Squirrel (Glaucomys sabrinus), a mammal that can be either arboreal or fossorial.

There are not a large number of amphibians in this ecoregion. The species present are the Great Basin Spadefoot Toad (Spea intermontana), a fossorial toad that sometimes filches the burrows of small mammals; Long-toed Salamander (Ambystoma macrodactylum); Northern Leopard Frog (Glaucomys sabrinus), typically found near permanent water bodies or marsh; Columbia Spotted Frog (Rana luteiventris), usually found near permanent lotic water; Pacific Treefrog (Pseudacris regilla), who deposits eggs on submerged plant stems or the bottom of water bodies; Tiger Salamander (Ambystoma tigrinum), fossorial species found in burrows or under rocks; Woodhouse's Toad (Anaxyrus woodhousii), found in arid grasslands with deep friable soils; Western Toad (Anaxyrus boreas), who uses woody debris or submerged vegetation to protect its egg-masses.

There are a limited number of reptiles found in the Palouse grasslands, namely only: the Northern Alligator Lizard (Elgaria coerulea), often found in screes, rock outcrops as well as riparian vicinity; the Painted Turtle (Chrysemys picta), who prefers lentic freshwater habitat with a thick mud layer; Yellow-bellied Racer (Chrysemys picta); Ringneck Snake (Diadophis punctatus), often found under loose stones in this ecoregion; Pygmy Short-horned Lizard (Phrynosoma douglasii), a fossorial taxon often found in bunchgrass habitats; Side-blotched Lizard (Uta stansburiana), frequently found in sandy washes with scattered rocks; Southern Alligator Lizard (Elgaria multicarinata), an essentially terrestrial species that prefers riparian areas and other moist habitats; Pacific Pond Turtle (Emys marmorata), a species that usually overwinters in upland habitat; Western Rattlesnake (Crotalus viridis), who, when inactive, may hide under rocks or in animal burrows; Night Snake (Hypsiglena torquata); Western Skink (Plestiodon skiltonianus), who prefers grasslands with rocky areas; Western Terrestrial Garter Snake (Thamnophis elegans), found in rocky grasslands, especially near water; Rubber Boa (Charina bottae).

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Central Pacific Coastal Forests Habitat

This taxon is found in the Central Pacific Coastal Forests ecoregion, as one of its North American ecoregions of occurrence. These mixed conifer rainforests stretch from stretch from southern Oregon in the USA to the northern tip of Vancouver Island, Canada. These forests are among the most productive in the world, characterized by large trees, substantial woody debris, luxuriant growths of mosses and lichens, and abundant ferns and herbs on the forest floor. The major forest complex consists of Douglas-fir (Pseudotsuga menziesii) and Western hemlock (Tsuga heterophylla), encompassing seral forests dominated by Douglas-fir and massive old-growth forests of Douglas-fir, Western hemlock, Western red cedar (Thuja plicata), and other species. These forests occur from sea level up to elevations of 700-1000 meters in the Coast Range and Olympic Mountains. Such forests occupy a gamut of environments with variable composition and structure and includes such other species as Grand fir (Abies grandis), Sitka spruce (Picea sitchensis), and Western white pine (Pinus monticola).

Characteristic mammalian fauna include Elk (Cervus elaphus), Black-tailed Deer (Odocoileus hemionus), Coyote (Canis latrans), Black Bear (Ursus americanus), Mink (Mustela vison), and Raccoon (Procyon lotor).

The following anuran species occur in the Central Pacific coastal forests: Coastal tailed frog (Ascaphus truei); Oregon spotted frog (Rana pretiosa VU); Northern red-legged frog (Rana pretiosa); Pacific chorus frog (Pseudacris regilla); Cascade frog (Rana cascadae NT), generally restricted to the Cascade Range from northern Washington to the California border; Foothill yellow-legged frog (Rana boylii) and the Western toad (Anaxyrus boreas NT).  A newt found in the ecoregion is the Rough skinned newt (Taricha granulosa).

Salamanders within the ecoregion are: Del Norte salamander (Plethodon elongatus NT);  Van Dyke's salamander (Plethodon vandykei); Western redback salamander (Plethodon vehiculum); Northwestern salamander (Ambystoma gracile);  Olympic torrent salamander (Rhyacotriton olympicus VU), whose preferred habitat is along richly leafed stream edges; Long-toed salamander (Ambystoma macrodactylum), whose adults are always subterranean except during the breeding season; Dunn's salamander (Plethodon dunni), usually found in seeps and stream splash zones; Clouded salamander (Aneides ferreus NT), an aggressive insectivore; Monterey ensatina (Ensatina eschscholtzii), usually found in thermally insulated micro-habitats such as under logs and rocks; Pacific giant salamander (Dicamptodon tenebrosus), found in damp, dense forests near streams; and Cope's giant salamander (Dicamptodon copei), usually found in rapidly flowing waters on the Olympic Peninsula and Cascade Range.

There are a small number of reptilian taxa that are observed within this forested ecoregion, including: Pacific pond turtle (Emys marmorata); Common garter snake (Thamnophis sirtalis), an adaptable snake most often found near water; Northern alligator lizard (Elgaria coerulea); and the Western fence lizard.

Numerous avian species are found in the ecoregion, both resident and migratory. Example taxa occurring here are the Belted kingfisher (Megaceryle alcyon); Wild turkey (Meleagris gallopavo); and the White-headed woodpecker (Picoides albolarvatus) and the Trumpeter swan (Cygnus buccinator), the largest of the North American waterfowl.

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Habitat Type: Freshwater

Comments: Habitat includes permanent and intermittent waters of rivers, creeks, small lakes and ponds (including human-made stock ponds and sewage-treatment ponds; Germano 2010), marshes, unlined irrigation canals, and reservoirs. Substantial populations can exist in water bodies in urban areas (Spinks et al. 2003). Sometimes this turtle is found in brackish water. It often basks on logs, vegetation mats, or rocks. In a northern California stream, deep large pools with logs, branches, or boulders were favored sites (Bury 1972). When disturbed, baskers seek cover underwater. In the northern and central part of the range, most overwinter in upland habitats (D. Holland; Reese and Welsh 1997). In San Luis Obispo County, California, radio-tracked turtles spent 34-191 (mean 111) days in terrestrial refuges, generally under leaf litter in woodland and coastal sage scrub habitats, mainly from October to February (n = 43 turtle-years) (Rathbun et al. 2002). However, some did not leave aquatic habitat, and this flexibility occurs throughout the range of the species (see Rathbun et al. 2002). Individuals commonly bask on land, near or way from water (Rathbun et al. 2002).

Nesting sites are on sandy banks and bars or in fields or sunny spots up to a few hundred meters from water (Nussbaum et al. 1983, Storer 1930, Lovich and Meyer 2002). Females may remain overnight at a nest site before returning to water (Rathbun et al. 1992). In San Luis Obispo County, California, females nested in open areas with little vegetative cover that were 6-80 meters (mean 28.2 meters) (possibly up to 170 meters) from water (Rathbun et al. 2002).

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Habitat and Ecology

Habitat and Ecology
Terrestrial nest sites

Systems
  • Terrestrial
  • Freshwater
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Western pond turtles use both aquatic and terrestrial habitats. They are found in rivers, lakes, streams, ponds, wetlands, vernal pools, ephemeral creeks, reservoirs, agricultural ditches, estuaries, and brackish waters. Western pond turtles prefer areas that provide cover from predators, such as vegetation and algae, as well as basking sites for thermoregulation. Such cover also provides shelter when wintering. Western pond turtles are observed in aquatic habitats ranging from 1 to 40 degrees Celsius. Juveniles are found primarily in areas between 12 and 33 degrees Celsius, whereas adults are found between 10 and 17 degrees Celsius. Adults tend to favor deeper, slow moving water, whereas hatchlings search for slow and shallow water that is slightly warmer. Terrestrial habitats are used for wintering and consist usually of burrows in leaves and soil. Western pond turtles also lay their eggs in terrestrial habitats.They are rarely found at altitudes above 1500m.

Range elevation: 0 to 1980 m.

Range depth: 1 to 5 m.

Habitat Regions: temperate ; terrestrial ; freshwater

Aquatic Biomes: lakes and ponds; rivers and streams; brackish water

Wetlands: marsh ; swamp

Other Habitat Features: suburban ; agricultural ; riparian ; estuarine

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The western pond turtle species occurs from sea level to around 1,500 metres in mountains (2) (3). It is found in ponds, lakes, streams, large rivers, slow-moving sloughs, and quiet waters. The turtles prefer aquatic habitats with exposed areas for basking, with aquatic vegetation, such as algae and other water plants, but they also live in clear waters, especially where there is cover such as boulders or fallen trees in the water (4). The western pond turtle also spends significant amounts of time in upland terrestrial habitats and has been found more than one kilometre from water (5).
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Reproductive females may migrate up to a kilometer or more between the usual home range and the nesting site; most of the migration may occur along a stream course (Rathbun et al. 1992). In the northern and central parts of the range, some move up to 480 meters between summer habitat and upland wintering habitat (D. Holland). In San Luis Obispo County, California, turtles moved horizontally 8-280 meters (mean 50 meters) from the edge of creek beds to terrestrial flood-season refuges; refuges were up to 38 meters in elevation above the creek bed; some turtles moved among multiple terrestrial refuges; in some creeks some turtles did not leave aquatic habitat (Rathbun et al. 2002). In the Trinity River, northern California, turtles refuged an average of 203 meters from water (Reese and Welsh 1997).

In a northern California stream, Bury (1972) reported a home range length of 275-2425 meters (average 976 meters for males, 0-750 meters (average 248 meters) for females, and 0-1150 meters (average 363 meters) for juveniles. Some individuals move 2-2.5 kilometers between the lower courses of coastal streams (D. Holland). At two sites in southern California, linear aquatic home ranges of adult females were 658-4,263 meters (mean 1,273 m)eters and 32-966 meters (mean 335 meters) (Goodman and Stewart 2000).

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Trophic Strategy

Comments: This turtle is a scavenger and opportunistic predator with a preference for live prey; adults are partially herbivorous; food items are mostly aquatic (Bury 1986). Diet often includes adult and larval insects, worms, crustaceans, carrion, and algae. Apparently this turtle does not forage on land (Rathbun et al. 2002).

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Food Habits

Western pond turtles are omnivores. Animal prey includes crustaceans, midges, fish, dragonflies, beetles, stoneflies, grasshoppers, and caddisflies. They will eat carrion as well. The plant portion of their diet consists primarily of willow (Salix) and alder catkins (Alnus), tule grass (Scripus), ditch grasses (Ruppiaceae), pond lily inflorescences, and green filamentous algae. They have been observed using a "gape-and-suck" form of taking in small invertebrates in the water column. Males tend to eat more insects and vertebrates and females eat more algae and other plant material.

Animal Foods: amphibians; fish; carrion ; insects; aquatic crustaceans; other marine invertebrates

Plant Foods: flowers; algae

Primary Diet: omnivore

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Associations

Ecosystem Roles

Western pond turtles are prey for numerous species and predators of other, smaller species. These turtles act as hosts for several parasitic organisms.

Commensal/Parasitic Species:

  • Ingles, L. 1930. A New Species of Telorchis from the Intestine of Clemmys marmorata. The Journal of Parasitology, Vol. 17, No. 2: 101-103.
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Predation

Their primary anti-predator adaptation is their thick carapace and wariness. At hatching, young turtles are both small enough and soft enough to make easy prey, so achieving adult size best protects these turtles from predation.

Known Predators:

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 - 300

Comments: In Oregon, this species was observed in 83 of 313 sites surveyed in 1991 (Holland 1993). In California, there are probably more than 100 extant occurrences (see map in Jennings and Hayes 1996), but the viability of many may be low.

Southern California: In 1960 this turtle was known from 87 localities from Ventura County, California, to the Mexican border; by 1970, the number of localities was reduced to 57 (Brattstrom 1988, Brattstrom and Messer 1988). In 1987, 53 of 255 surveyed sites in southern California had turtles; 25 of these were in Ventura County. Of the 53 sites, only 10 were thought to contain reproductively viable populations (Brattstrom 1988, Brattstrom and Messer 1988). These surveys determined that the species was increasingly rare south of the Santa Clara River: Los Angeles County (10 sites); San Diego County (8 sites); Orange County (4 sites); western Riverside County (3 sites); and southwestern San Bernardino County (3 sites). Only five of the populations south of the Santa Clara River were thought to be reproductively viable (Brattstrom 1988, Brattstrom and Messer 1988).

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Global Abundance

100,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but quite large (presumably greater than 100,000). This species occurs in many areas and often is abundant in hill and mountain habitats (Bury and Germano 2008). In Oregon, this turtle occurs widely in low to very low densities (Holland 1993). In Washington, the total population in the early 1990s was fewer than 100 individuals in the wild (Andelman and Gray 1992). In California, there are probably a couple hundred extant occurrences statewide (Jennings and Hayes 1996), and some populations include 100s of individuals per hectare of river surface (see Reese and Welsh 1998); however, many populations are small and declining (Jennings and Hayes 1996).

In southern California, populations along the Mojave River were regarded as "small" by Brattstrom and Messer (1988). Holland (1991) estimated that no more than 100 individuals occurred along the Mojave River. Research by Lovich (unpublished) through the late 1990s indicated that at least 34 western pond turtles survived at Camp Cady and Afton Canyon (combined).

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General Ecology

In a northern California stream, density was estimated at 214 turtles/hectare, based on captures of 578 individuals (35% juveniles) in a 3.5-kilometer stretch of stream (Bury 1972, cited by Ernst et al. 1994). Turtles generally were congregated in separated pools along the stream. Reese and Welsh (1998) stated that Bury (1972) recorded densities as high as 445/hectare. Bury (1979) reported that density of this population was 170 turtles per acre (420/hectare). In California, some populations include 500-1000 individuals per hectare (Holland and Bury manuscript, cited by Reese and Welsh 1998), others only 13-19/hectare (e.g., 1,210 turtles over 63 stream kilometers) (Reese and Welsh 1998). In western Oregon, Nussbaum et al. (1983) stated that one oxbow lake of 1.5-2.0 hectares contained an estimated 75 individuals. Another oxbow lake of about the same size contained an estimated 180 individuals.

These turtles are subject to predation by various Carnivora and introduced bullfrogs and fishes.

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Life History and Behavior

Behavior

Communication and Perception

Western pond turtles find food using both sight and smell. Moreover, based on the mating ritual it is clear that touch is important in communication among sexes.

Communication Channels: tactile

Perception Channels: visual ; tactile ; chemical

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Cyclicity

Comments: Pond turtles are most active when water temperatures are above 15 C (Bury and Holland). Activity occurs from February to mid-November in the northern part of the range; year-round in the south (Stebbins 1985). Most activity occurs from April to October in northern California (Bury 1972, G. Hammerson). Activity occurs diurnally and on warm nights. In a northern California stream, turtles began foraging at around sunrise (0600); most left the water to bask when the sun first fell on basking sites; individuals basked periodically between 0800 and dusk, with a peak from 0900 to 1000; at other times, turtles foraged or were inactive (Bury 1972).

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Life Cycle

Development

Females deposit eggs in a nest they dig on land at night. After incubation, hatchlings leave the egg only if the temperature is below 81 degrees Fahrenheit. Hatchlings tends to be male if the incubation temperature was below 86 degrees Fahrenheit or female if the incubation temperature was above 86 degrees Fahrenheit). Hatchlings immediately return to the water and grow at a rate of 3.29 mm/month, .08 mm/month, .05 mm/month, and .04 mm/month during successive growth seasons. Growth is accompanied by darkening of the body and hardening of the shell. After about 8 years of growth, the rate slows as the turtles mature into adults. Growth rate depends on environmental factors such as water, temperature, and food abundance. Colder water and less food slows growth.

Development - Life Cycle: temperature sex determination

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Life Expectancy

Lifespan/Longevity

As hatchlings, western pond turtles are easy prey and have a survival rate of 8 to 12%. Adults can live 40 to 70 years or even longer. As adults the average survival rate increases to around 45%. In adults there is a 4:1 male to female ratio, which is probably a reflection of the prolonged amount of time females are exposed to terrestrial predators while laying eggs.

Range lifespan

Status: wild:
80 (high) years.

Typical lifespan

Status: wild:
40 to 70 years.

Average lifespan

Status: wild:
50 years.

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Lifespan, longevity, and ageing

Maximum longevity: 27.3 years (captivity)
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Reproduction

Mating occurs in April-May in central coastal California (see Rathbun et al. 1992). Reproductive females lay one or two clutches of 3-11 eggs, April-August (varies with location); June-August in central coastal California. Incidence of double clutching appears to be very low in the northern part of the range. Egg laying probably peaks in June-July throughout most of the range. In San Bernardino County, California, females that double clutched deposited eggs in May and June (Goodman 1997). Eggs hatch in about 10-12 weeks. Young probably overwinter in nests and emerge in March-April (central coastal California; see Rathbun et al. 1992). Age of first reproduction in females reportedly is about 7-9 years in the south and 10-14 years in the north (Bury 1979, D. Holland), but individuals in some populations exhibit much faster growth (Bury et al. 2010, Germano 2010) and earlier maturation. For example, females in a population in central coastal California reached reproductive maturity as early as 4 years of age (Germano and Rathbun 2008), and females at various sites in southern Oregon took 5-9 years to reach maturity (Germano and Bury 2009). Some live at least 4 decades (R. B. Bury and D. Holland).

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Western pond turtle males court females using their forelimbs to scratch the anterior edge the female’s carapace. This is followed by the female raising her posterior end, after which mating occurs. Due to the seclusive nature of these animals there is not much known about the mating process.

Mating System: polygynandrous (promiscuous)

Western pond turtles mate from May through August, with most females laying eggs in alternating years. Although the average age of maturity is between 8 and 14 years of age, females in the southern subspecies occasionally reach maturity at an earlier age. Nests are built up to 402 m from the water with an average distance of 28 m and require at least 10 cm of soil. Hatching success rates are approximately 70%, as there is a high rate of nest predation and complete nest failure. Nests are generally found in flat areas with low vegetation and dry, hard soil. Incubation takes approximately 3 months, with most hatchlings staying in the nest chamber until the following spring. Some hatchlings in southern and central California emerge in the fall.

Breeding interval: Western pond turtle females breed in alternating years.

Breeding season: The breeding season takes place from May through August.

Range number of offspring: 1 to 13.

Average number of offspring: 6.

Range gestation period: 80 to 100 days.

Range birth mass: 3 to 7 g.

Range age at sexual or reproductive maturity (female): 8 to 14 years.

Range age at sexual or reproductive maturity (male): 8 to 14 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

After the eggs are laid, there is no evidence of parental care.

Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female)

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Emys marmorata

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Statistics of barcoding coverage: Actinemys marmorata

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NX - Presumed Extirpated

United States

Rounded National Status Rank: N3 - Vulnerable

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NatureServe Conservation Status

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Range extends from Washington or British Columbia to northern Baja California; many populations still exist, and the species is locally numerous, but distribution and abundance in the northern and southern parts of the range and in the Central Valley of California have declined as a result commercial exploitation for the pet trade, habitat loss and degradation, introduced species, and (locally) disease.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Other Considerations: Surveys in Oregon in 1991 found populations that were heavily adult biased.

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IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A1cd

Version
2.3

Year Assessed
1996
  • Needs updating

Assessor/s
Tortoise & Freshwater Turtle Specialist Group

Reviewer/s

Contributor/s
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Status

  • Bury, R.B. and Germano, D.J. 2008. Actinemys marmorata (Baird and Girard 1852) – western pond turtle, Pacific pond turtle. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., and Iverson, J.B. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 001.1-001.9, doi:10.3854/crm.5.001.marmorata.v1.2008, http://www.iucn-tftsg.org/cbftt
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Current threats to western pond turtles are numerous and include fire, flooding, drought, upper respiratory disease, habitat destruction, and lack of genetic variation. The lack of variation is due to the isolation of individual populations over ranges to large to be covered by migration. Habitat destruction is the result of intense urbanization. Additionally humans pose a great threat via off-road vehicles, chemical spills, and incidental catch by fishermen. Lack of research has prevented western pond turtles from being added to the federal endangered species list.

Although recommended for the federal endangered species list, western pond turtles are currently only recognized as state species of special concern by the California Department of Fish and Game (CDFG). Western pond turtles have been extirpated for nearly 20 years in British Columbia, are listed as endangered in Washington, and as sensitive with critical standing in Oregon.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: vulnerable

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Status

Classified as Vulnerable (VU) on the IUCN Red list 2007 (1).
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Global Short Term Trend: Decline of 10-30%

Comments: Abundance apparently is declining in the northernmost part and southern one-third of the range but not in the core of the range from central California to southern Oregon (Bury and Germano 2008).

Global Long Term Trend: Decline of 30-50%

Comments: This species appears to have experienced at least a moderate decline in abundance and area of occupancy and a small reduction in the extent of occurrence (Bury and Germano 2008). On the other hand, this species has colonized and is locally common in many human-made habitats that were created over the past century (Bury and Germano 2008).

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Threats

Degree of Threat: Medium

Comments: The major threat is habitat destruction and fragmentation. Over 90 percent of the wetland habitats within the historical range in California has been eliminated due to agricultural development, flood control, water diversion projects, groundwater depletion, and urbanization (Rathbun et al. 1992, USFWS 1992, Lovich and Meyer 2002), though robust populations still occur in some areas of the Central Valley (Germano and Bury 2001). In northern California, damming of the mainstem Trinity River may have negatively impacted juveniles (Reese and Welsh 1998). Other localized threats include habitat degradation caused by contaminant spills, grazing, and off-road vehicle use (USFWS 1993), as well as turtle mortality on roads (Holland 1994). Habitat fragmentation perhaps magnifies the effects of introduced species through predation, competition, and epidemic disease (Bury and Germano 2008).

In Washington, the decline was exacerbated in 1990 by an upper respiratory disease epidemic that left a total population of fewer than 100 individuals in the wild; the disease was responsible for the death of 35-40 percent of the individuals in one of only two known populations in the state.(Andelman and Gray 1992). A large die-off of 42 western pond turtles in northern California in 1993 also may have been due to disease (Holland 1994).

Invasion of exotic pest species is another threat. Saltcedar or tamarisk (Tamarix) is an invasive pest plant species that is firmly established in southern California. Changes in channel morphology and hydrology associated with saltcedar invasion along the Mojave River have degraded the remaining limited turtle habitat (Lovich and de Gouvenain 1998, Lovich and Meyer 2002).

Introduction of non-native turtles [red-eared sliders (Trachemys scripta), painted turtles (Chrysemys picta)] into California may threaten western pond turtles Dudley and Collins (1995), but no data are available to substantiate this claim. Disease might spread from introduced turtles to western pond turtle populations (Holland 1994).

Bullfrogs are widely established in the range of the western pond turtle and may consume hatchling and young turtles (Holland 1994). Bullfrog predation may eliminate recruitment in some western pond turtle populations in southern California (Overtree and Collings 1997).

Humans widely utilized western pond turtles for food at least until the 1930s, and exploitation continues on a smaller scale in some areas. Turtles are also collected for sale in the pet trade. Bury (1989) reported that one pet wholesaler obtained about 500 western pond turtles from a southern California lake and shipped them to Europe.

Lack of genetic variability may be a significant threat to the continued survival of populations in Oregon and Washington and possibly elsewhere.

Size structure of populations (biased toward larger individuals) sometimes has been used to conclude that little or no recruitment has occurred, but in fact many populations include a substantial proportion of young individuals that have grown rapidly to large size (Bury et al. 2010).

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The western pond turtle is rare from mid-Oregon north and from the Los Angeles basin south, but is relatively abundant in the centre of its range in southern Oregon and northern California (2). In specific parts of its range, the greatest current threat for the western pond turtle is loss of habitat and fragmenting populations, through conversion of wetlands to farmlands, water diversions and urbanisation (5). In the past the western pond turtle, like other turtles, was intensively collected for the pet trade, but this has declined dramatically in recent years (4). Occasional losses occur through the illegal collection of turtles for food by immigrant populations from Asia, mortality from motor vehicles and predation from introduced species such as the bullfrog (5).
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Management

Preserve Selection and Design Considerations: For adequate protection, preserves should include aquatic habitat and adjacent upland habitat for nesting, hibernation, and estivation..

Biological Research Needs: Better information is needed on demography and on management and monitoring methods.

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Global Protection: Many (13-40) occurrences appropriately protected and managed

Comments: Probably more than a dozen occurrences are adequately protected.

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Conservation

Commercial harvest or take of western pond turtles has been prohibited in all U.S. states where it is found since the 1980s (5). It is listed as Endangered in Washington State, and protected in Oregon and California (4). The recent increase in stock ponds and other man-made water sources appears to have a positive impact on population numbers and a few “head-start” programmes claim to have had excellent survivorship rates after being released into the wild (3). “Head-start” programmes are where the young are raised in captivity until their shells begin to harden and they are less susceptible to predation. However, re-introduction is limited if the habitat of the species is not protected.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

There are no adverse effects of western pond turtles on humans.

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Economic Importance for Humans: Positive

There is no current documented economic benefit of western pond turtles. From the 1800s to the 1930s these turtles were sold for human consumption and collected for pet trade. This kind of trade is largely illegal today, although poaching may still occur.

Positive Impacts: pet trade ; food

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Risks

Stewardship Overview: Effective protection of habitat includes not only the aquatic habitat but also adjacent terrestrial habitat used for nesting, hibernation, estivation, and dispersal (Holland 1994, Spinks et al. 2003, Bury and Germano 2008). This may require protection of riparian corridors 500 meters or more from the wetland boundary (Holland 1994). Road construction, grazing and off-road vehicle use should be reduced or eliminated from riparian corridors utilized by this species for feeding, nesting, and overwintering/estivation. This species would benefit from habitat restoration, including elimination of saltcedar (Tamarix) and revegetation of habitat with native plants. In some areas, bullfrog control may be necessary to prevent or eliminate excessive predation on hatchlings and juveniles. In arid regions of southern California, construction of small ponds may provide valuable refugia during times of drought or in areas where the stream channel has been severely degraded by saltcedar. [Source: J. Lovich]

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Wikipedia

Western pond turtle

The western pond turtle (Actinemys marmorata or Emys marmorata), or Pacific pond turtle is a small to medium-sized turtle growing to approximately 20 cm (8 in) in carapace length. It is limited to the west coast of the United States of America and Mexico, ranging from western Washington state to northern Baja California. In May 2002, the Canadian Species at Risk Act listed the Pacific pond turtle as being extirpated in Canada.

Taxonomy[edit]

Its genus classification is mixed. Emys and Actinemys were used among published sources in 2010.[3]

Physical description[edit]

The dorsal color is usually dark brown or dull olive, with or without darker reticulations or streaking. The plastron is yellowish, sometimes with dark blotches in the centers of the scutes. The shell is 11–21 cm (4.5 to 8.25 in) in length. The dorsal shell (carapace) is low and broad, usually widest behind the middle, and in adults is smooth, lacking a keel or serrations. Adult Western Pond Turtles are sexually dimorphic; that is, males have a light or pale yellow throat.

Distribution[edit]

Western pond turtles originally ranged from northern Baja California, Mexico, north to the Puget Sound region of Washington. As of 2007, they have become rare or absent in the Puget Sound area. They have a disjunct distribution in most of the Northwest, and some isolated populations exist in southern Washington. Pond Turtles are now rare in the Willamette Valley north of Eugene, Oregon, but abundance increases south of that city where temperatures are higher. They may be locally common in some streams, rivers and ponds in southern Oregon. A few records are reported east of the Cascade Mountains, but these may have been based on introduced individuals. They range up to 305 m (1,000 ft) in Washington, and to about 915 m (3.000 ft) in Oregon. They also occur in Uvas Canyon area, Santa Cruz Mts, California.

Ecology and behavior[edit]

Western pond turtles occur in both permanent and intermittent waters, including marshes, streams, rivers, ponds, and lakes. They favor habitats with large numbers of emergent logs or boulders, where they aggregate to bask. They also bask on top of aquatic vegetation or position. Consequently, this species is often overlooked in the wild. However, it is possible to observe resident turtles by moving slowly and hiding behind shrubs and trees.

Turtles can be encouraged to use artificial basking substrate, or rafts, which allows for easy detection of the species in complex habitats.

Diet[edit]

Western pond turtles are omnivorous and most of their animal diet includes insects, crayfish and other aquatic invertebrates. Fish, puss, tadpoles, and frogs are eaten occasionally, and carrion is eaten when available. Plant foods include filamentous algae, lily pads, tule and cattail roots.

Reproduction[edit]

Clemmys marmorata01.jpg

Females produce 5-13 eggs per clutch. They deposit eggs either once or twice a year. They may travel some distance from water for egg-laying, moving as much as 0.8 km (1/2 mile) away from and up to 90 m (300 ft) above the nearest source of water, but most nests are with 90 m (300 ft) of water. The female usually leaves the water in the evening and may wander far before selecting a nest site, often in an open area of sand or hardpan that is facing southwards. The nest is flask-shaped with an opening of about 5 cm (2 in). Females spend considerable time covering up the nest with soil and adjacent low vegetation, making it difficult for a person to find unless it has been disturbed by a predator.

Hatchlings[edit]

Some hatchings overwinter in the nest, and this phenomenon seems more prevalent in northern areas. Winter rains may be necessary to loosen the hardpan soil where some nests are deposited. It may be that the nest is the safest place for hatchlings to shelter while they await the return of warm weather. Whether it is hatchlings or eggs that overwinter, young first appear in the spring following the year of egg deposition. Individuals grow slowly in the wild, and their age at their first reproduction may be 10 to 12 years in the northern part of the range. Western pond turtles may survive more than 30 years in the wild.

References[edit]

  1. ^ a b Rhodin 2010, p. 000.105
  2. ^ Tortoise & Freshwater Turtle Specialist Group (1996). Actinemys marmorata. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 23 February 2009.
  3. ^ Rhodin 2010, p. 000.139


Bibliography[edit]

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Names and Taxonomy

Taxonomy

Comments: Molecular data and morphological evidence indicate that the genus Clemmys (sensu McDowell 1964) is paraphyletic (see Bickham et al. 1996, Holman and Fritz 2001, Feldman and Parham 2002). Based on morphological data, Holman and Fritz (2001) split Clemmys as follows: Clemmys guttata was retained as the only member of the genus; Clemmys insculpta and C. muhlenbergii were placed in the genus Glyptemys (as first reviser, Holman and Fritz gave Glyptemys Agassiz, 1857, precedence over the simultaneously published genus Calemys Agassiz, 1857); and Clemmys marmorata was transferred to the monotypic genus Actinemys.

Genetic data support the basic features of this arrangement. An analysis of emydid relationships based on molecular data (Feldman and Parham 2002) identified four well-supported clades: Terrapene; Clemmys guttata; C. insculpta and C. muhlenbergii; and Clemmys marmorata, Emys orbicularis, and Emydoidea blandingii. Feldman and Parham retained Clemmys guttata as the only member of that genus; regarded Clemmys marmorata, Emys orbicularis, and Emydoidea blandingii as congeneric (in the genus Emys, which has priority); and placed C. insculpta and C. muhlenbergii in the genus Calemys. However, Feldman and Parham were unaware that Holman and Fritz (2001) had given Glyptemys precedence over Calemys, so the correct generic name for these turtles under the arrangement of Feldman and Parham is Glyptemys. In contrast to Holman and Fritz (2001), Feldman and Parham (2002) argued that placing Clemmys marmorata in the monotypic genus Actinemys would unnecessarily obscure its phylogenetic relationships, and they recommended that marmorata be included in the genus Emys. Nevertheless, Crother et al. (2003) preferred the arrangement of Holman and Fritz (2001) and retained Emys and Emydoidea as distinct genera as well as Actinemys marmorata as the preferred name for the western (or Pacific) pond turtle.

Iverson, Meylan, and Seidel (in Crother 2008) reviewed the foregoing studies as well as additional research and reasoned that monotypic genera do provide phylogenetic information and accepted Actinemys marmorata and Emydoidea blandingii as the scientific names for the western pond turtle and Blanding's turtle, respectively.

See also McDowell (1964), Merkle (1975), Lovich et al. (1991), and Bickham et al. (1996) for information on relationships among turtles of the genus Clemmys (sensu lato).

See Seeliger (1945) for information on variation and descriptions of the two subspecies (marmorata and pallida), which intergrade over a large area in central California. Buskirk (1991) reviewed the characters used by Seeliger to distinguish the subspecies; he concluded that the subspecies were of questionable validity.

Bury (1970) noted that (1) specimens from Baja California apparently differ from both of the described subspecies and (2) further studies are needed to define better the variation of the species throughout its range.

Based on morphological data, Holland (1992) determined that there are three evolutionary groups in C. marmorata: a Columbia River form, a northern form ranging from the Willamette Valley of northern Oregon to central California, and a southern form extending from the central California coast and San Joaquin Valley south to northern Baja California.

Janzen et al. (1997) examined range-wide DNA variation and found little genetic variation overall. Data generally were consistent with the current taxonomy of two morphologically based subspecies, though southern populations, particularly those in Baja California, included some unique genetic variants possibly indicative of status as a distinct species; at the least these were thought to merit special conservation attention.

Spinks and Shaffer (2005) used rapidly evolving mitochondrial and nuclear DNA sequence data to analyze phylogeography and population genetic variation across the range of the species. Nuclear DNA sequences displayed extremely low levels of variation, but phylogenetic analyses based on mtDNA recovered four well-supported and geographically coherent clades: a large Northern clade composed of populations from Washington south to San Luis Obispo County, California, west of the Coast Ranges; a San Joaquin Valley clade from the southern Great Central Valley; a geographically restricted Santa Barbara clade from a limited region in Santa Barbara and Ventura counties; and a Southern clade that occurs south of the Tehachapi Mountains and west of the Transverse Range south to Baja California, Mexico. The Northern clade is congruent with the distribution of the subspecies marmorata (Washington-central California), but no clade is congruent with the distribution of the southern subspecies pallida from central California to Baja California. The authors concluded that "recognition of the current subspecies split is not warranted, based on the available genetic evidence." Crother (2008) acknowledged this finding and did not list any subspecies for Actinemys marmorata.

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Subspecies

None currently recognized, previously two: Actinemys marmorata marmorata (Northern Pacific Pond Turtle) and Actinemys marmorata pallida (Southern Pacific Pond Turtle). Genetic data suggest four phylogenetic clades.
  • Bury, R.B. and Germano, D.J. 2008. Actinemys marmorata (Baird and Girard 1852) – western pond turtle, Pacific pond turtle. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., and Iverson, J.B. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 001.1-001.9, doi:10.3854/crm.5.001.marmorata.v1.2008, http://www.iucn-tftsg.org/cbftt
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