Oregon Zoo to return western pond turtles to wild with help of local agencies, youths
After one of the rainiest Junes on record and a relatively cool July, Portlanders may feel like summer's just getting under way. But for seven 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 July 25, with the help of its conservation partners and some teens from local youth programs. On June 6, the zoo released 20 of the largest turtles it had been rearing over the winter; 31 more turtles will be released this month including this batch of seven that 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 eleven months, they grow to about the size of a three-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 and large-mouth bass," Shepherdson said.
Local youths from the U.S. Fish and Wildlife Service's Youth Conservation Corps 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 21st anniversary of the Western Pond Turtle Recovery Plan, begun by the 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 Columbia River Gorge. Today, researchers estimate that there are more than 1,600. Habitat degradation and disease were, and still are, problems, but the biggest threat to fragile baby turtles is 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.
To help restore these rare pond turtles to their natural habitat, recovery workers take to the field each year. Under the supervision of western pond turtle experts Kate and Frank Slavens, Jerry Novak and WDFW employee Eric Holman they count, trap and fit transmitters on adult female western pond turtles. The female turtles are monitored every two hours during the nesting season to determine where they nest. The nests, which the females dig in the ground and then cover after depositing their eggs, are protected with wire "exclosure" cages that help prevent predators from eating the eggs. The eggs are then allowed to incubate naturally, and the hatchlings are collected in the fall. Some turtles are also captured when they are observed leaving unmarked nests. The hatchlings are about the size of a quarter when they are removed and taken to the zoo facilities, where they can grow in safety. Unlike wild turtles, zoo turtles are fed throughout the winter, so by their summer release, the 11-month-olds are about as big as 3-year-old turtles that grew up in the wild.
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 Plan 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.