For more than two decades the Oregon Zoo has been working to restore a quiet, shy Northwestern species to its historic range. As a result, Western pond turtle numbers are on the rise.
The Western pond turtle (Actinemys marmorata) was once common from Baja California to Puget Sound.
- are 6 to 8 inches long and weigh 1 to 2.4 pounds
- reach sexual maturity at approximately 10 years
- live up to 70 years
They live in and around streams, ponds, lakes and permanent wetlands. Turtles nest on land and feed, breed and bask in water.
Turtle populations have declined due to:
- water diversion
- draining or filling of wetlands
- invasive plants: reed canary grass and Himalayan blackberry
- introduced predators: bullfrogs and largemouth bass
- a slow development rate – hatchlings are extremely vulnerable to predation
Western pond turtle populations are much reduced and concentrated in a few locations. They are listed as endangered in Washington and threatened in Oregon.
Western pond turtle recovery
In 1990, the Western pond turtle recovery plan began to bring the turtles back. A “head-starting” project was initiated, which accelerates turtles’ natural growth rates, and thus their ability to withstand predation. The Oregon Zoo collaborates with Woodland Park Zoo in Seattle, Wash. and the Washington Department of Fish and Wildlife. Other partners include Bonneville Power Administration and the U.S. Forest Service.
What the recovery project looks like:
- Spring: Conservation scientists head into the field to count, trap, mark and fit transmitters on adult females.
- Summer: Females are monitored via transmitter every two hours during the nesting season, June to July, in order to identify nest sites. A female digs a vase-shaped nest in dry, densely packed soil, urinating on the soil to soften it. She deposits two to 11 eggs and covers the nest with mud and vegetation. Then she leaves the area. Conservation workers protect the nest with a wire enclosure – a cage to keep predators out. The eggs incubate naturally all summer.
- Fall: Scientists and volunteers collect the quarter-sized hatchlings and bring them to the zoo, where they can grow safe from predators, with ample light, warmth and food.
- Winter: In the wild, hatchlings become dormant in the cold. But the enhanced light and warmth at the zoo stimulates them to continue to eat and grow.
- Spring: About 10 months after their summertime hatch, juvenile turtles are larger than if they had remained in the wild and survived. Now large enough to avoid being eaten by most predators, they are returned to the wild in areas designated by the recovery plan.
Some juvenile turtles when released are equipped with radio transmitters so biologists can learn about post-release dispersal, habitat use during active and hibernation periods, and ultimately, survival rates.
Successes and ongoing recovery work
The Western pond turtle recovery plan requires:
- at least five turtle populations be established in both the Puget Sound and Columbia River Gorge areas
- each population to consist of at least 200 turtles, of which no more than 70 percent are adults
- turtle release areas to be protected from development and free of major disturbances. Areas must allow for natural recruitment of juveniles, creating a self-sustaining population
The first turtles released in 1991 in the Columbia River Gorge are reproducing and laying eggs in the wild. Over the past two decades, approximately 1,500 turtles have been released, and with good results: the gorge turtle population ranged from a low of 150 in 1990 to approximately 1,500 in 2011. Scientists tracking them estimate that 95 percent of the turtles released to sites in the Columbia River Gorge have survived.