PORTLAND, Ore. -- Some Oregon Zoo animals are headed back to the wild.

The zoo is releasing about 55 endangered Western pond turtles that have spent the past 11 months under lights to simulate perpetual summer.

Zoo officials say the lights trick the turtles into avoiding hibernation, so they experience about three years of growth in less than a year.

The extra growth gives them a better chance against larger predators such as nonnative bullfrogs and largemouth bass.

 Video: Zoo explains turtle program

The turtle conservation program is part of a collaborative effort by the Oregon Zoo and the Woodland Park Zoo in Seattle, along with state and federal agencies.