PORTLAND, Ore. (KOIN) — After months spent growing bigger and stronger in a lab, 23 endangered turtles native to the Pacific Northwest are swimming wild and free. 

The turtles were released Thursday into the Columbia River Gorge. They had been living at the Oregon Zoo since October.

Conservation scientists at the Oregon Zoo gather newly-hatched western pond turtles from sites in the wild and bring them to a special lab at the zoo where they’re protected and nurtured until they have a fighting chance of survival. 

The turtles live in the warmth and light of a simulated summer in the Western Pond Turtle Recovery Project lab. In less than a year, they grow to a size that would take a wild turtle two or three years to achieve. 

Western pond turtles are native to areas west of the Rockies but their top predator — the bullfrog — is not, according to the Oregon Zoo. 

Bullfrogs thrive in places like Oregon and Washington, where they have driven pond turtles and other small aquatic species to the brink of extinction. Twenty years ago, scientists estimated there were fewer than 100 turtles left in Washington. 

The Oregon Zoo’s Western Pond Turtle Recovery Project has released more than 1,500 turtles since that time. Researchers have found that 95% of the turtles released back to sites in the Columbia Gorge survive annually. 

Learn more about Turtle Haven in the Columbia River Gorge

The Oregon Zoo also works to save endangered California condors, Oregon silverspot butterflies and northern leopard frogs.