The western pond turtle (Actinemys marmorata or Emys marmorata), or Pacific pond turtle is a small to medium-sized turtle

Turtle

Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

 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

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, 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

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

.

Taxonomy

Its genus classification is mixed. Emys

Emys

Emys is a small genus of turtles. Its members are:* Emys orbicularis - European pond turtle* Emys trinacris - Sicilian pond turtle * Emys blandingii - Blanding's turtle * Emys marmorata - Western pond turtle- Sub-species :...

and Actinemys were used among published sources in 2010.

Physical description

The dorsal

Dorsum (biology)

In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...

 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

Sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

; that is, males have a light or pale yellow throat and a concave plastron, and the cloacal vent is at or posterior to the edge of the carapace.

Distribution

Western pond turtles originally ranged from northern Baja California

Baja California

Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...

, Mexico, north to the Puget Sound

Puget Sound

Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...

 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

Willamette Valley

The Willamette Valley is the most populated region in the state of Oregon of the United States. Located in the state's northwest, the region is surrounded by tall mountain ranges to the east, west and south and the valley's floor is broad, flat and fertile because of Ice Age conditions...

 north of Eugene, Oregon

Eugene, Oregon

Eugene is the second largest city in the U.S. state of Oregon and the seat of Lane County. It is located at the south end of the Willamette Valley, at the confluence of the McKenzie and Willamette rivers, about east of the Oregon Coast.As of the 2010 U.S...

, 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.

Ecology and behavior

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 themselves just below the surface where water temperatures are elevated. Individuals display aggressive behavior toward one another while sunning. Western pond turtles will rapidly dive off basking sites when approached by humans, even at distances of over 50 m. 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.

Western pond turtles seek refuge in deep water, under submerged logs and rocks, in beaver burrows and lodges, and by "swimming" into deep silt. They are extremely difficult to detect under these conditions. Turtles can be encouraged to use artificial basking substrate, or rafts, which allows for easy detection of the species in complex habitats.

Diet

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

Reproduction

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

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.