Western pond turtle
|Western pond turtle|
|Genus:||Actinemys or Emys|
|Actinemys marmorata or Emys marmorata
(Baird and Girard, 1852)
Actinemys marmorata marmorata
|The range of the 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.
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 (4.5–8.5 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.
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 (1,001 ft) in Washington, and to about 915 m (3,002 ft) in Oregon. They also occur in Uvas Canyon area, Santa Cruz Mts, California.
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. 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.
In addition to their aquatic habitat, terrestrial habitat is also extremely important for Western pond turtles. Since many intermittent ponds can dry up during summer and fall months along the west coast, especially during times of drought, pond turtles can spend upwards of 200 days out of water. Many turtles overwinter outside of the water, during which time they often create their nest for the year.
Western pond turtles are omnivorous and most of their animal diet includes insects, crayfish and other aquatic invertebrates. Fish, tadpoles, and frogs are eaten occasionally, and carrion is eaten when available. Plant foods include filamentous algae, lily pads, tule and cattail roots.
Predation and Threats
Because of their hard shell, Western pond turtles are generally well protected. However, several predators do threaten this species, especially hatchlings, due to their small size and soft shell.
Raccoons, otters, ospreys and coyotes are the biggest natural threat to these turtles, and hatchlings have the additional threats of weasels, bullfrogs, and large fish.
Finally, this species has the threat of humankind. Due to habitat destruction, this species is currently listed as vulnerable on the IUCN Red List. With the removal of ponds, wetlands, and contamination of other water sources, this species is vulnerable and at risk of becoming extinct without the continuing efforts of reintroducing these turtles to their native range.
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 within 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.
The vast majority of hatchlings overwinter in the nest, and this phenomenon seems prevalent in most parts of the range, especially northern areas. This might explain the difficulty researchers have had in trying to locate hatchlings in the fall months. 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 50 years in the wild.
- Rhodin 2010, p. 000.105
- Tortoise & Freshwater Turtle Specialist Group (1996). "Actinemys marmorata". IUCN Red List of Threatened Species. Version 2008. International Union for Conservation of Nature. Retrieved 23 February 2009.
- Rhodin 2010, p. 000.139
- "Wildscreen Arkive". arkive.org. Retrieved 26 April 2016.
- Holland, Dan C., PhD. The Western Pond Turtle: Habitat and History, Final Report. U.S. Department of Energy, Bonneville Power Administration, Division of Fish and Wildlife; Wildlife Diversity Program, Oregon Department of Fish and Wildlife, August 1994.
- Rhodin, Anders G.J.; van Dijk, Peter Paul; Inverson, John B.; Shaffer, H. Bradley (2010-12-14). "Turtles of the World 2010 Update: Annotated Checklist of Taxonomy, Synonymy, Distribution and Conservation Status". Archived from the original (pdf) on 2010-12-15. Retrieved 2010-12-15.
- Wildscreen Arkive, “Western pond turtle”, Accessed April 25, 2016. http://www.arkive.org/western-pond-turtle/actinemys-marmorata/.