Northwest Trek Wildlife Park releases nearly 400 endangered frogs back into the wild

Nearly 400 endangered northern leopard frogs raised at Northwest Trek Wildlife Park are now back in the wild at the Columbia National Wildlife Refuge in Grant County.

For four years, Northwest Trek has received northern leopard frog egg masses in the spring from the one remaining wild population at the Potholes Reservoir, collected by Washington Department of Fish and Wildlife (WDFW) biologists. Keepers at Northwest Trek then raise the frogs in a controlled environment, monitoring the overall condition of their tanks, including water temperature, pH levels, good bacteria, nitrogen cycle, and oxygen levels. They also protect the frogs from predators and feed them.

“All this work is happening behind the scenes from the public and is part of the wildlife conservation efforts that are fundamental to Northwest Trek’s mission,” explained Conservation Manager Marc Heinzman.

Keepers and WDFW staff release the frogs back into the wild each summer, with the goal to establish a new population.

“It's exciting for everyone involved, but especially for the keepers who personally cared for these frogs, to see them return to their natural habitat,” said Heinzman. “Being part of this crucial effort to save an endangered species in Washington is incredibly rewarding.”

Once abundant throughout North America, northern leopard frogs are rapidly disappearing from their native ranges in Washington, Oregon, and western Canada. The species has been listed as endangered in Washington since 1999. The likely causes of frog decline in the Pacific Northwest include habitat loss and degradation, diseases, non-native species, and climate change. According to WDFW officials, northern leopard frogs are an essential indicator of water quality due to their permeable skin. Improving and conserving wetland habitat will help frogs and other species, ranging from amphibians to waterfowl and deer.

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Nearly 400 endangered northern leopard frogs raised at Northwest Trek Wildlife Park are now back in the wild at the Columbia National Wildlife Refuge in Grant County.

Successful conservation efforts often involve adapting strategies to identify the best outcomes for recovering a particular species. This year, the nearly 400 frogs raised at Northwest Trek were released back into the wild in two stages.

In May, half were transferred as tadpoles into rearing pens at the release site in Eastern Washington, where they foraged for algae and then mosquitoes from the environment around them. The other half continued to be raised at Northwest Trek until they metamorphosized into adult frogs and were hand-fed crickets. The two sets were released into the wild together at the same location in August.

All the frogs were tagged as tadpoles with a small injection of non-toxic reflective dye just underneath their skin. The frogs returned to the wild as tadpoles were marked with blue dye. The remaining frogs were marked with orange dye. Now, when biologists shine a light on the frogs in the wild, the dye glows, helping identify which frogs survived and offering more information about their movement.

The project’s partners — WDFW, U.S. Fish & Wildlife Service (USFWS), Oregon Zoo, and Washington State University — will investigate whether transferring the frogs as tadpoles rather than as adult frogs will improve their survival rate.

Funding for the northern leopard frog reintroduction is provided through a competitive state wildlife grant awarded to WDFW from USFWS’s Office of Conservation Impact program and Potholes Supplemental Feed Route mitigation funds provided by the Washington Department of Ecology.