More than 500 Oregon spotted frogs reared at Woodland Park Zoo were released last week into marshy wetlands at a protected site in Pierce County.

The frogs were collected from wetlands as eggs and placed at the zoo for hatching and rearing for several months in a predator-free home as they transformed from tadpole to juvenile status, increasing their survival by giving them a head start until they were large enough to avoid predators.

Head starting and releasing the frogs is part of a cooperative program with Woodland Park Zoo, Northwest Trek Wildlife Park, Washington Department of Fish and Wildlife, the Sustainability in Prisons Project, and other zoos and state and federal agencies.

Washington declared the Oregon spotted frog an endangered species in 1997, and on August 28, 2014, the U.S. Fish & Wildlife Service listed the frog as a threatened species under the Endangered Species Act. It historically ranged from southwestern British Columbia to northeastern California. However, scientists have seen populations plummet, driving the frog toward extinction.

The native amphibian has lost ground to habitat loss from draining and development, disease and the introduction of invasive species such as the American bullfrog.

The Oregon spotted frog recovery project began in 2007. “This conservation recovery project gives hope for the precious frogs to recover,” said Dr. Jennifer Pramuk, a curator and reptile and amphibian expert at Woodland Park Zoo. “Helping to save species takes many, many hands on all levels.”

More than 5,000 frogs have been released since the program began. “It takes a great deal of effort to get a population growing,” said Lisa Hallock, a wildlife biologist for Washington Department of Fish and Wildlife. “We want to make sure that we do all we can to re-establish these frogs in the wild.”

In 2012, Northwest Trek Wildlife Park, Woodland Park Zoo and Oregon Zoo received the prestigious North American Conservation Award from the Association of Zoos & Aquariums for their participation in the Oregon spotted frog project.

Oregon Spotted Frog (Rana pretiosa)

Biologists estimate the Oregon spotted frog has disappeared from up to 90% of its former range. The current range of the Oregon spotted frog stretches from southwestern British Columbia, Canada, south through the Puget Sound/Willamette Valley trough and southern Cascade mountains, with its southernmost point in Oregon’s Klamath Basin.

Oregon spotted frogs are highly aquatic. They are found in or near permanent still water, such as lakes, ponds, springs, marshes, and the grassy margins of slow-moving streams.

The life expectancy of the species is five to eight years in the wild, though most do not live that long.

Both juvenile and adult frogs are carnivores, feeding primarily on insects, spiders, and earthworms. tadpoles eat a combination of commercial fish food pellets and a keeper-prepared mixture of boiled romaine, kale and spirulina. After they transform into juvenile frogs, they are fed live crickets and other insects.