Nineteen northwestern pond turtles reared at the Oregon Zoo were released in the Columbia River Gorge.  The species is listed as an endangered species in Washington and a sensitive species in Oregon.  The zoo says that 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 reach a weight of 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, is the largest frog species on the continent.  It can tip the scales at more than a pound and has been driving pond turtles and a host of other small, vulnerable aquatic species to the brink of extinction.