U.S. Geological Survey scientists are working with other federal agencies, non-profit organizations, and private landowners to research the effectiveness of restoration projects for multiple species and aid in the recovery of the Oregon spotted frog.

“As landowners working to benefit wildlife, livestock, ecosystem health and water quality, partnering with scientists to research the Oregon spotted frog is a vital piece of our restoration ranching approach,” says Alex Froom, owner of a ranch on the Wood River in Oregon. Restoration work on their ranch includes removing invasive bullfrogs and improving habitat for Oregon spotted frogs.

The non-profit Trout Unlimited, whose work in the Klamath Basin is focused on restoring healthy ecosystems for fisheries, amphibians, and other aquatic species, is a key partner working closely with USGS. Several of the strategies being deployed on federally managed land and private ranches are aimed at improving the drought resilience of aquatic habitats, benefiting a wide range of species.

Historically, the range of the Oregon spotted frog overlapped with that of the North American beaver. Beaver numbers in the Pacific Northwest declined dramatically due to the fur trade in the late 1700s and early 1800’s, as did the ecosystem services they provide. Beaver dams and associated ponds retain water in landscapes that otherwise would not hold it. Warmer water along pond edges promotes development of frog eggs and tadpoles and provides adult frogs with feeding and basking areas. Radio telemetry studies suggest Oregon spotted frogs use other beaver-created features like channels and dams as shelter during the winter. Mimicking these features, or enhancing remnant channels and dams, are possible solutions for improving water retention, increasing shelter opportunities and providing additional habitat.

USGS monitoring of Oregon spotted frog populations is showing early signs of success with these types of projects.

In the longest running study of its kind in the Klamath, USGS researchers counted Oregon spotted frog egg masses and adults along Jack Creek on U.S. Forest Service and private land. Surveys were done at reference sites with no habitat modifications, sites where old beaver ponds were excavated and deepened, and sites that were excavated but had no remnant beaver ponds.

Thirteen years of annual sampling revealed that survival of adult Oregon spotted frogs was almost 20% higher at reaches with excavated remnant beaver ponds compared to reference sites. Satellite images revealed that vegetation at restored sites stayed green later into the summer- an indicator of improved water retention. One promising clue that restoration of this type can work was the fact that frog breeding was concentrated in two excavated beaver ponds relative to other sites.  

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At a site on Crane Creek, USGS scientists partnered with the U.S. Fish and Wildlife Service, Trout Unlimited, and the owner of the Sevenmile Ranch to collect Oregon spotted frogs prior to stream and riparian restoration. Restoration work included redirecting water from a canal back into historical creek meanders and creating a series of ponds. Once restoration was complete, researchers released the frogs and monitored where they went and where they chose to lay eggs. Numbers of egg masses and adults increased in restored areas, indicating modifications to the habitat were favorable for breeding success and survival.  

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“So far, we’ve seen a noticeable response from Oregon spotted frogs at one site, a smaller but still positive response at another site, and it’s still too early to tell how frogs will respond at two other sites,” says Christopher Pearl, wildlife biologist at the USGS Forest and Rangeland Ecosystem Science Center in Corvallis, Oregon. “The signs are encouraging, and we’re also learning a lot about habitat requirements and behavior of Oregon spotted frogs that will help our partners plan future restoration projects.”

That knowledge about how Oregon spotted frogs respond to habitat modifications is directly used for restoration and recovery planning. The U.S. Fish and Wildlife Service is responsible for assessing the recovery of threatened species and reevaluating listing under the Endangered Species Act.

“We’ve been working in partnership with the USGS for over two decades on all aspects of Oregon spotted frog conservation and recovery,” says Jennifer O’Reilly, biologist with the U.S. Fish and Wildlife Service and Oregon spotted frog species lead. “USGS has a strong understanding of the Service’s role in implementing the Endangered Species Act and has contributed research that’s crucial to our decision making.”

North American beaver populations are slowly recovering in the Pacific Northwest, and USGS is working with partners to study how Oregon spotted frogs respond to the arrival of beavers and newly constructed dams and ponds. Human-led wetland restoration is generating results now, but beaver may lead the way in the future. Either way, USGS scientists will be there to document the Oregon spotted frog’s recovery.