Summer came early this week for 15 western pond turtles reared at the Oregon Zoo.  The zoo returned the endangered reptiles to the wild at a number of different Columbia River Gorge locations on Tuesday.  The turtles have been in a simulated summer at the zoo’s conservation lab since last May, growing large enough to have a fighting chance in the wild.  Keepers prepare the turtles for life outdoors by helping them learn to hunt for food and giving them plenty of time outside to acclimate to changing temperatures.  Once the turtles reach about 50 grams in size, they’re taken to the Columbia River Gorge where a team of volunteers and conservationists return them to their natural habitat and monitor them for safety.  In one study, scientists estimated that 95 percent of the turtles released back to the Gorge survive annually.  The biggest threat to fragile baby turtles has been the bullfrog.