More than 100 western pond turtles –a species on the verge of extinction in Washington a decade ago– will be released in the Columbia Gorge and a south Puget Sound wildlife area Thursday (July 18) as part of an on-going cooperative recovery project by the Washington Department of Fish and Wildlife (WDFW), Seattle's Woodland Park Zoo and the Oregon Zoo in Portland.
The recovery effort centers on collecting newly-hatched turtles from the wild and giving them a head-start in the safety of zoo quarters until they grow large enough to survive pond predators such as bullfrogs and large-mouth bass.
The recovery project is detailed in a new article in WDFW's "Fish and Wildlife Science" electronic magazine on the Internet. The article includes photos and video clips of the turtle recovery project, as well as links to WDFW's recovery plan for the western pond turtle.
Listed as a state endangered species in 1993, the western pond turtle had declined to about 150 animals statewide when the recovery project was launched in 1990. Although once common in the Puget Sound region and the Columbia Gorge, nearly all the remaining turtles were concentrated in two populations in Klickitat and Skamania counties in the Columbia Gorge. Habitat loss, predation by non-native species such as bullfrogs, and disease decimated their numbers.
The WDFW recovery plan goals include establishing four self-sustaining populations of western pond turtles in the Columbia Gorge and three in the Puget Sound area. Besides head-starting juvenile turtles from the Gorge, recovery workers are using captive breeding to re-introduce pond turtles in suitable Puget Sound habitat. Other goals of the recovery plan are predator control and habitat protection.
The newest releases bring the total number of head-started turtles to 494. Some 456 juvenile turtles have been returned to the Columbia Gorge. In addition 38 captive-bred turtles have been introduced to a wildlife area near Steilacoom in Pierce County.
Scientists tracking the released turtles estimate that 90 percent of the turtles released back into the Columbia Gorge, and 88 percent of the turtles re-introduced near Steilacoom have survived.
Two years ago, one of the first turtles released in 1990 in the Columbia Gorge laid eggs of her own. The pond turtle, which can live up to 50 years in the wild, takes about 10 years to reach sexual maturity.
"The high survival rate of head-started turtles and the fact some of those animals are going on to reproduce on their own, both give us strong reasons to be optimistic about the long-term success of the recovery effort," said Harriet Allen, WDFW endangered species manager.
Each year since the head-starting project was launched, recovery workers take to the field under the supervision of pond turtle expert Kate Slavens to count, trap and fit transmitters on adult female western pond turtles. Female turtles are monitored closely during the nesting season to determine when they leave the water to nest. The nests, which the female digs in the ground and then covers after depositing her eggs, are protected with wire "exclosure" cages to keep predators from eating the eggs. When the eggs hatch in the early fall, volunteers return to the nest sites and collect the small hatchlings– each about the size of a quarter and take them to zoo facilities, where they can grow in safety. After about 10 months, when the juvenile turtles have grown large enough to avoid being consumed by pond predators such as bullfrogs or large-mouth bass, they are returned to their birthplace in the wild.
Some of the juvenile turtles are equipped with radio transmitters before release so biologists can learn more about post-release dispersal, habitat use during active and hibernation periods and survival.