Oregon Zoo returns western pond turtles to wild with help of local conservationists
Summer hasn't even started in Portland, but for 19 western pond turtles reared at the Oregon Zoo, an eight-month stretch of warm days and nights has just drawn to an end.
Since last September, the turtles basked in the warmth and light of a simulated summer in the zoo's conservation lab, growing large enough to have a fighting chance in the wild. Today, with the help of its conservation partners and local wildlife agencies, the zoo returned these endangered reptiles to the wild in the Columbia River Gorge.
"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 eight 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, USDA Forest Service and other partners. 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 up to 11 months. In one study, scientists estimated that 95 percent of the turtles released back to sites in the Columbia Gorge survive annually.
This year marks the 24th 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. Since then, more than 1,500 zoo-headstarted turtles have been released. 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 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 cure."
The western pond turtle, once common from Baja California to the Puget Sound, is listed as an endangered species in Washington and a sensitive species in Oregon. The species is currently under USFW review to determine whether it will be given federal protection under the Endangered Species Act.
A recent survey in Clackamas County failed to document any trace of the imperiled western pond turtle during its first year of searching. During the survey, funded in part by an Oregon Zoo Future for Wildlife grant, a biologist-led team of volunteers searched 15 sites, from remnant natural wetlands to stormwater ponds found behind big-box stores. ODFW conservation biologist Susan Barnes called the failure to spot a single western pond turtle "moderately alarming."
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.