'Endless summer' is nearly over for zoo-reared western pond turtles
Portlanders may feel like summer's just reaching its peak. But for 10 western pond turtles reared at the Oregon Zoo, a nearly yearlong stretch of warm days and nights will soon be drawing to an end.
The turtles have spent the past 11 months at the zoo basking in the warmth and light of a simulated summer, and growing large enough to have a fighting chance in the wild. The zoo will return these endangered reptiles to the wild Aug. 1, with the help of its conservation partners and some teens from local youth programs. On June 21, the zoo released 27 of the largest turtles it had been rearing over the winter, and this batch of 10 will be the last ones for the year.
"Here at the zoo, the turtles experience summer year-round, so they don't go into hibernation," said Dr. David Shepherdson, Oregon Zoo conservation scientist. "In 11 months, they grow to about the size of a 3-year-old wild turtle and have a much greater chance of surviving to adulthood."
Once the turtles reach about 70 grams (a little more than 2 ounces), they are returned to their natural habitat and monitored for safety.
"At this size, the young turtles are able to avoid most of the predators that threaten them, such as non-native bullfrogs," Shepherdson said.
The turtle reintroduction is part of a collaborative effort by the Oregon Zoo, Woodland Park Zoo, Washington Department of Fish and Wildlife, U.S. Fish and Wildlife Service, Bonneville Power Administration and USDA Forest Service. As part of the Western Pond Turtle Recovery Project, conservation scientists "head-start" newly hatched turtles gathered from wild sites, nurturing them at both zoos for about 11 months. In one study, scientists estimated that 95 percent of the turtles released back to sites in the Columbia Gorge survive annually.
Local youths from Skamania County's Forest Youth Success program and the Oregon Zoo's Zoo Animal Presenters program will help biologists release the turtles in the Columbia River Gorge.
"We like to involve youth programs in these releases whenever possible," Shepherdson said. "When you actually see a zoo-reared turtle released back into the wilds of the Columbia Gorge, it makes a much bigger impact than if you're just learning about conservation efforts."
This year marks the 22nd anniversary of the Western Pond Turtle Recovery Project, begun by Woodland Park Zoo and WDFW in 1991. The Oregon Zoo has been a collaborator in the project since 1998.
Two decades ago, western pond turtles were on the verge of completely dying out in Washington, with fewer than 100 turtles left in the state. Today, researchers estimate there are more than 1,600. The biggest threat to fragile baby turtles has been the bullfrog. Native to areas east of the Rockies, this nonindigenous frog has thrived throughout the West, driving pond turtles and a host of other small, vulnerable aquatic species to the brink of extinction.
Other threats to the turtles' survival include habitat degradation and ulcerative shell disease, a condition that causes lesions in a turtle's shell and can lead to reduced fitness, paralysis and even death.
"We don't yet know what causes this disease, but we've been investigating," Shepherdson said. "Once we can identify the cause, we hope to develop an effective treatment."
Now listed as an endangered species in Washington and a sensitive species in Oregon, the western pond turtle was once common from Baja California to the Puget Sound. The Oregon Zoo's participation in the Western Pond Turtle Recovery Project is funded through the Oregon Zoo Foundation, the Bonneville Power Administration, the Foley Frischkorn Wildlife and Conservation Fund, GlobalGiving.org, and the Washington Department of Fish and Wildlife.
Both of Oregon's native turtles - the western pond turtle and the western painted turtle - are listed as "critical" on the state's sensitive species list. Find out how to help protect native turtles and report turtle sightings.