Summer came early last week for 11 northwestern pond turtles reared at the Oregon Zoo.  With the help of volunteers and wildlife officials, care staff returned the endangered reptiles to the Columbia River Gorge.  Since last spring, the turtles have basked in the warmth and light of a simulated summer at the zoo’s conservation lab, growing large enough to have a fighting chance in the wild.  Once the turtles weigh about 50 grams, they’re taken to ponds along the Columbia River Gorge, where a team of conservationists returns them to their natural habitat and monitors them for safety.  In one study, scientists estimated that 95% of the turtles released back to sites in the Gorge survive annually.  The American bullfrog, native to the eastern United States but considered invasive here, and has been driving pond turtles and a host of other small, vulnerable aquatic species to the brink of extinction.  The northwestern pond turtle, also known as the western pond turtle, is listed as an endangered species in Washington and a sensitive species in Oregon.  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, U.S. Forest Service and other partners.