Newly constructed wetlands welcome California red-legged frogs back to the Tahoe

By Sophia Hamann
Tahoe National Forest
July 17, 2023

On a warm spring day in 2024, a cool breeze filtered through burned vegetation while birds and Sierran tree frogs created a chorus of sound. Dragonflies hovered above the water’s surface as a group of Forest Service employees led by American River Ranger District’s Fisheries Biologist, Dan Teater, observed the wetland habitat that had been burned by the Mosquito Fire in 2022.  

Hidden within the wetlands were a set of eyes poking above the water that stood out from the sea of tree frogs. “Don’t move,” Teater said to his colleagues as he grabbed for his binoculars. The eyes belonged to a California red-legged frog (Rana draytonii); a threatened species who haven’t been found in the Tahoe National Forest for decades. “It was one of the top ten moments of my career,” said Teater as he recalled the moment that he realized California red-legged frogs were occupying the newly constructed wetlands and returning to the Tahoe National Forest once again. 

A career highlight indeed, considering that these wetlands only exist today because Teater and a team of dedicated people spent years planning and tracking down funds to create wetland habitat for this listed species. “These projects are the things we biologists do that keep us inspired,” continued Teater.  

Leaping into action to help a threatened species 

Left: A California red-legged frog occupying the newly constructed wetlands. Photo by Dan Teater, USFS. 

In 1997, California red-legged frogs were listed as threatened under the Endangered Species Act.  This designation prompted frog surveys across the Tahoe National Forest, which showed no evidence of California red-legged frogs within the forest boundaries. 

Once common along California’s coastal communities and inland through the Sierra Nevada range, California red-legged frogs have suffered major declines largely due to habitat loss. These frogs are especially scarce within the Sierra Nevada where only a few known populations exist.  

In 2006, a population of California red-legged frogs were discovered on private property in the Michigan Bluff area, near the Tahoe National Forest. The landscape of this area had been heavily altered by hydraulic mining during the gold-rush era, where high pressure water jets washed gravel and nutrients away from the mountainsides.   

“It was a big deal in our environmental community to discover that these frogs had persisted through the gold rush,” said Teater, explaining that the site the frogs were found in was a scar left over from hydraulic mining. Not only had California red-legged frogs survived the gold rush, but this small population continues to persist through human development, a changing climate, invasive species and even wildfire. 

“We have a job to protect aquatic habitat and federally listed species,” Teater responded when asked why conserving California red-legged frogs is important. Under the Endangered Species Act and the Tahoe National Forest Plan, the Forest Service is legally directed to improve habitat of threatened or endangered species like the California red-legged frog.  

Plus, we do it for the frogs and the ecological benefits they provide. “This species is an indicator to overall ecological health,” continued Teater. As the California red-legged frog population dwindles, the gap in the food web grows larger—species that eat California red-legged frogs must find food elsewhere while species that are eaten by the California red-legged frog increase in numbers, resulting in the loss of balance and diversity within the ecosystem.  

Determined to help the listed species, the Tahoe National Forest began planning to build California red-legged frog wetland habitat on National Forest lands surrounding their breeding site.  

If you build it, they will come 

The project came to fruition in 2021, when representatives from the Forest Service, U.S. Fish and Wildlife Service and the Sheltowee Environmental Education Coalition arrived in Foresthill, Calif. to help construct 18 low-maintenance ponds near where the frogs had been discovered.  

The agencies were joined by over 100 volunteers from across the country who represented organizations such as the American Conservation Experience, Great Basin Institute, South Yuba River Citizens Legue, Trout Unlimited, Save the Frogs, Rio Grand Return, Bat Conservation International, Barceloux-Tibessart Foundation, Sequoia Ecological and AmeriCorps. 

After securing funding from the U.S. Fish and Wildlife Service and grants from the Resource Advisory Committee from both Nevada County and Placer County, volunteers and employees wasted no time getting to work.  

The wetlands were modeled after a similar project done on the Eldorado National Forest for California red-legged frogs, which had begun to see some success. It was through this project that the Tahoe National Forest was introduced to Wildlife Biologist and Wetland Ecologist Tom Biebighauser, who helped visualize the construction.  

After a 34-year career with the Forest Service along with positive results on similar projects, Biebighauser was able to provide essential knowledge and guidance through every step of the project. 

"There aren't that many places where you can find the California red-legged frog,” said Biebighauser, in reference to his work building frog breeding habitat across the west coast. “We want to try to increase their numbers and give them a good place to live.” 

Giving the frogs a good place to live on the Tahoe National Forest came with its own set of challenges. Through tracking their movements, it is understood that California red-legged frogs travel approximately one-mile from their breeding grounds, meaning that the new wetlands had to be constructed on National Forest lands within one-mile of where they were discovered near Michigan Bluff.  

The lack of available flat land and suitable soil in areas that had been mined within the checkerboard landscape of public and private land ownership posed additional challenges. Despite the setbacks, suitable locations were found and construction of the wetlands proceeded. 

 

Photo 1 and 2: Wetlands during construction. Photos by USFS. 

Ranging anywhere from 30x30 feet to 60x60 feet and 4-7 feet deep, the wetlands were lined with geotextile fabric and aquatic-safe liners and covered with a thick layer of soil, resembling natural looking depressions on the landscape.  

Many hands made quick work, and after about two weeks the wetlands were completed. Rain filled them with water, and shortly after, a loud chorus of Sierran tree frogs could be heard echoing across the landscape. 

“I want our target species, the California red-legged frog, to find these newly constructed wetlands on their own volition,” said Teater, who hypothesizes that the Sierran tree frogs act as a vocal attraction for the California red-legged frog. Teater explained that once the Sierran tree frogs move in and start singing their recognizable chorus, they may as well be singing water, water, water, food, food, food, over a loudspeaker to California red-legged frogs, who eat the unsuspecting tree frogs.  

Sierran tree frog basking in one of the newly constructed wetlands. Photo by Elizabeth McDonnel, USFS.

Though not yet the target species, other wildlife moving in proved the wetlands to be beneficial to the ecosystem. A deer or bear may stop by for a refreshing drink of water, bats could snack on the bugs, or a passing migratory bird may land in the water to rest on its long journey.  

“The wetlands were holding water, benthic macroinvertebrates were coming in, dragonflies and bats were utilizing the wetlands...and then, unfortunately, the Mosquito Fire happened,” said Teater.  

Resilience after the Mosquito Fire 

In 2022, a wildfire blazed through the Tahoe National Forest and surrounding communities, burning nearly 77,000 acres across El Dorado and Placer Counties. The Mosquito Fire consumed the forest surrounding the wetlands and breached the Michigan Bluff area, where the population of California red-legged frogs had been discovered years prior. 

Only skeletal husks of oak and pine remained of the forest surrounding the wetlands. But beyond all expectations, a small population of frogs survived in Michigan Bluff, and so too did the newly constructed wetlands. 

“The wetlands remained,” said Biebighauser. “They survived and filled with water the next spring, but that fire was so hot, it even consumed the trees that we had placed in the water to provide the habitat for the frogs.” Much like furniture inside a house, frogs need logs and vegetation to rest on and to lay their eggs. Though the shell of the ponds remained, much of what made them appealing to wildlife had burned.  

Efforts towards rehabilitating burned areas is a Forest Service priority, important for forest health and to prevent future wildfires from devastating the same areas again. As a result, the Tahoe National Forest initiated the process of restoring the wetlands using Burned Area Rehabilitation (BAR) funds and Burned Area Emergency Response Funds (BAER) to stabilize soil, improve drainage and revegetate the fire impacted areas.  

Volunteers and Tahoe National Forest employees revegetate one of the wetlands that had been burned in the Mosquito Fire. Container plants and native seed were deployed to stabilize sediment and provide emergent vegetation for amphibians to attach their egg massess to. Photo by Dan Teater, USFS.

In late 2023, volunteers and employees rolled up their sleeves once again to remove hazard trees and plant native vegetation around all 18 of the wetlands. Once revegetation was completed, it was only a matter of time to see if the wetlands would welcome frogs and other wildlife back to the Tahoe National Forest.  

By the following spring, Sierran tree frogs could be heard once again singing their chorus from the wetlands, unknowingly advertising their location to the nearby California red-legged frogs and other wildlife. Shortly after, Teater spotted a California red-legged frog occupying one of the burned wetlands.  

 

Photo 1: Constructed wetland showing habitat conditions before the Mosquito Fire in 2022. Notice all of the woody material in place to provide cover and basking habitat for amphibians. Photo by USFS. Photo 2: Rehabilitated wetlands, post-Mosquito Fire. Photo by USFS.  

California red-legged frogs hop home to the Tahoe National Forest 

Since Teater first saw a pair of eyes belonging to the California red-legged frog in the spring of 2024, more have joined the ranks. “If you build it, they will come,” said Teater. “It’s a really great thing to see these frogs using what we installed and that it’s working.”  

As of May 2024, four more red-legged frogs have been spotted within the wetlands, along with bats, deer and of course, Sierran tree frogs. As the wetlands heal from the scars of the Mosquito Fire, biologists will continue to monitor the site for evidence of California red-legged frogs returning to the Tahoe National Forest.