The Oregon spotted frog was once common in the Pacific Northwest. The Oregon Zoo and its conservation partners are working to repopulate the historic range of this small amphibian.
The Oregon spotted frog (Rana pretiosa) is the most aquatic native frog in the Northwest, and lives in or near perennial bodies of water. It needs shallow water and abundant aquatic plants for basking and cover. Ideal conditions are marshes that can support a large enough population to withstand predation. Its historic range: British Columbia to northern California.
Named for black spots that cover its body and legs, this frog is 1.74 to 4 inches long at maturity. After metamorphosis, frogs eat live animals, primarily insects, and begin to breed at 3 years of age.
Why frog populations have declined
With more humans and changes to the environment, frogs have lost almost 90 percent of their previous habitat from:
- loss of wetlands, due to draining, damming or filling
- invasive species such as the Eastern bullfrog and bass that prey on tadpoles and frogs
- livestock overgrazing of streamside vegetation
- introduced plants like reed canarygrass that displace native vegetation
- the chytrid fungus, native to Africa, which threatens amphibian populations
The Oregon spotted frog is the most threatened frog in the Pacific Northwest. It is considered endangered in Canada and Washington, threatened in Oregon and is a candidate for listing under the federal Endangered Species Act.
Oregon spotted frog recovery
The key to reestablishing spotted frogs populations in the wild is to nurture them in a safe environment until they metamorphose beyond the tadpole stage, when they’re most vulnerable to predation. Since 2007, zoo staff and volunteers work with the frogs at every life stage:
- Early spring – Staff and volunteers monitor frog populations in the wild by conducting frog egg mass surveys. In March they collect egg masses at wild sites and transport them to the zoo. Eggs hatch in about three weeks.
- Spring and summer – Staff and volunteers nurture tadpoles at the zoo and other sites. Tadpoles eat algae, detritus and carrion. During summer, they metamorphose into frogs.
- Late summer and early fall – Frogs are released into natural areas such as Dailman Lake at Joint Base Lewis-McChord – a protected site with one of the largest, relatively intact wetlands in the Puget Lowland.
After release of the frogs, scientists continue to monitors release sites for egg masses and frog populations.
Success and ongoing work
In 2011, 1,200 frogs were released and conservationists found 11 gelatinous egg clusters at Dailman Lake. These clusters indicate that some frogs released in previous years are thriving and breeding. Conservationists are hopeful that progress will continue, allowing the program to expand to other wetlands. In addition to the Oregon Zoo, the Woodland Park Zoo, Northwest Trek and Cedar Creek Corrections Center in Washington also raise frogs for release. In 2012, the Oregon Zoo, Woodland Park Zoo and Northwest Trek were awarded with "top honors" in the AZA's North American Conservation Awards category for the collaborative Oregon spotted frog reintroduction project. The award recognizes "exceptional efforts toward regional habitat preservation, species restoration and support of biodiversity."
The zoo works with these partners on frog recovery efforts:
- Joint Base Lewis-McChord
- Mountain View Conservation & Breeding Centre
- Northwest Trek Wildlife Park
- NW Zoo & Aquarium Alliance
- Point Defiance Zoo & Aquarium
- Port Blakely Tree Farms
- The Nature Conservancy
- U.S. Geological Survey
- U.S. Fish & Wildlife Service
- Washington Department of Fish & Wildlife
- Washington State Department of Natural Resources
- Washington State Department of Transportation
- Woodland Park Zoo