Summer's barely getting started in Portland, but for 14 western pond turtles reared at the Oregon Zoo, a yearlong stretch of warm days and nights has just drawn to an end.
Since last May, 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 at the Columbia River Gorge.
"Here at the zoo, the turtles don't go into hibernation," said senior keeper Shelly Pettit. "They experience summer year-round, and in less than a year grow to about the size of a 2- to 3-year-old wild turtle. This gives them a much greater chance of surviving to adulthood."
Once the turtles reach about 50 grams (a little less than 2 ounces), they are returned to their natural habitat and monitored for safety.
"When the young turtles are this big, they're able to avoid predators that threaten them, like non-native bullfrogs," Pettit said.
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.
As part of the Western Pond Turtle Recovery Project, conservationists "head-start" newly hatched turtles gathered from wild sites, nurturing them at the zoo for up to a year. In one study, scientists estimated that 95 percent of the turtles released back to the Gorge survive annually.
"We've been doing this for more than 20 years now, and we feel we've been successful in preventing extinction," said Dr. David Shepherdson, Oregon Zoo conservation scientist. "We've made the first step toward recovery — but we're not there yet."
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. 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 Western Pond Turtle Recovery Project is 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.