Introduction
The Western Pond Turtle ( Actinemys marmorata ) is California's only native aquatic freshwater turtle. This species, ranging from the Puget Sound lowlands in Washington through western Oregon and California, south to Baja California, occupies a variety of aquatic habitats, including streams, ponds, lakes, and both permanent and ephemeral wetlands. While these turtles spend much of their lives in the water, they also require terrestrial habitats, particularly for nesting. Western Pond Turtles are known for their adaptability, which extends to their diet.
Physical Characteristics and Habitat
Adult Western Pond Turtles typically range from 15-20 cm (6-8 inches) in length and weigh between 448-1100 g (1-2.4 pounds). Their coloration varies from brown to black on the carapace (upper shell), often exhibiting lighter marbling when viewed closely. The plastron (lower shell) is characterized by black and yellow hues. The head and legs are dark, sometimes with yellow markings, but lack the distinctive stripes seen on painted turtles.
These turtles inhabit permanent and temporary waters, including rivers, creeks, small lakes, ponds, marshes, irrigation ditches, and reservoirs. They frequently use basking sites like logs and rocks, often basking on land. When disturbed, they seek cover underwater.
Omnivorous Diet: A Varied Menu
Western Pond turtles are omnivorous. Their diet consists of water plants, algae crustaceans, midges, dragonflies, beetles, stoneflies and caddisflies. The Western Pond Turtle is a scavenger and opportunistic predator with a preference for live prey. Their diet often includes adult and larval insects, worms, crustaceans, carrion, and algae. They eat a variety of insects, tadpoles, frog eggs, snails, leeches, aquatic beetles, dragonfly larvae and fish. Plant foods include filamentous algae, lily pods, tule and cattail roots. Some sources suggest that males tend to consume more insects and vertebrates, while females lean towards algae and other plant material.
Feeding Behavior and Activity
Western Pond Turtles are most active when water temperatures are above 60°F. They are diurnal for the major part of the year. However, during the hot summer months, they can choose to avoid the day and move about at night. Normally, these turtles like to sit on sandy areas, rocks or logs and bask in the sun for the major part of the day, getting their body temperatures up. They are also often found basking in shallow waters. These turtles are very shy and timid, and will quickly dive into the water at the first sign of danger.
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Reproduction and Growth
Female pond turtles usually reach sexual maturity around 10-15 years of age. Males mature quicker at 8-12 years. Mating in the wild takes place in the spring and sometimes in the fall.
Nesting occurs from late May until the middle of July. Females find a suitable site, usually with dry soil, sparse vegetation and a southern exposure. The female digs a hole for the nest - first by softening the soil with urine and then scooping out the soil using her hind feet, one after the other. Once the site is prepared, she deposits a clutch of 3 to 13 eggs. After laying the eggs, the hole is filled with a mixture of vegetation and dirt to provide an air space, then covered with wet soil to keep the eggs in a humid environment. This slow process can take anywhere from two to four hours. The eggs incubate naturally underground for 90-130 days, depending on summer temperatures.
Hatchling pond turtles are very small - averaging 2.5-3.1 cm (1-1.2 inch) in length and weigh 3-7 g (.011-.025 ounces). They may emerge from the nest in the fall or spend winter in the nest and come out in the spring. Hatchlings are independent at birth.
Growth rate largely depends on external environmental factors, such as water, temperature and food abundance. Colder water and less food slows the growth rate.
Threats and Conservation Status
Populations of western pond turtles are in decline due to: disease, upland and aquatic habitat alterations and destruction, in addtion to the introduction of predators. The biggest threat to the species is the bullfrog and introduced warm fresh water fish, such as bass. Both prey on small juvenile turtles. The western pond turtle ( Clemmys marmorata ) is listed by Washington State as an endangered species. Currently listed as Vulnerable by the IUCN. US Fish and Wildlife consider the Western Pond Turtle a species of special concern, and California state law protects them. The northern populations have virtually disappeared in some ranges!
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Conservation Efforts
The Oakland Zoo is raising hatchlings right here at the Zoo in our Biodiversity Center! With our zookeepers taking care of these baby turtles with plenty of nutrient-rich foods and veterinary care, they grow in just one year to the size it would take them three or four years to reach in the wild. Then, when we release them into the wild. They are big enough to protect themselves and have a much better chance of survival! Each summer our zookeepers team up with biologists and students from Sonoma State University to study the Western Pond Turtle. Out in the field the Zoo is involved in opportunities including incubating nests and using telemetry equipment to track nesting females. Predator protection netting is put over nest sites or eggs are brought back to the lab for incubation and hatching.
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