“We’re above 48 degrees right now, and the pavement’s wet,” said St. Johns resident Philip Fensterer. “I think it could be a really good night.”
The late winter sky was darkening as the small group of damp but buoyant volunteers gathered around Fensterer in March, some scanning weather apps on their phones for the tell-tale radar blobs that promise a shower.
Fensterer is the self-described “frog taxi captain,” and these volunteers provide a unique taxi service for the resident frogs of Forest Park.
“So long as the temperature doesn’t drop in a hurry, we’ll see frogs,” Fensterer said as the volunteers began their patrol of the frontage road adjacent to a wetland a few yards above the Willamette River in Northwest Portland.
A semi rolls down U.S. Highway 30 near the northern boundary of Portland in March. The busy roadway poses a dangerous challenge to frogs who migrate between their spawning site at the Harborton wetland and their summer habitat in Forest Park.
Brooke Herbert, Brooke Herbert/OPB / OPB
Each winter, Northern red-legged frogs deposit their eggs in gelatinous masses in the Harborton wetland, where they incubate for several weeks. Once the egg-laying and fertilizing are finished, the frog parents are ready to head back uphill to their summer habitat in Forest Park. It’s that commute between the park and the wetland where things get tricky — even deadly.
That’s because the frogs’ migration runs straight through a high-speed section of U.S. Highway 30 between Portland and Scappoose. Ten years ago, a local resident came outside one rainy winter evening and saw the roadway covered with squished frogs. The sad news spread among local wildlife lovers, who then organized themselves to launch the Harborton Frog Shuttle.
To intercept as many frogs as possible, the volunteers constructed a makeshift fence of weed barrier fabric just high enough to block the frogs from hopping into the roadway. Once the frogs hit the cloth, the volunteers collect them and “taxi” them across the busy highway to the safety of Forest Park.
“Otherwise, it becomes real-life Frogger,” says Fensterer, recalling the 80s video game where frogs hop across a deadly roadway filled with moving cars and trucks.
The volunteers work when the frogs are moving. In practical terms, that means after sunset and usually from December to March. In the fall and early winter, the volunteers take the frogs downhill to the spawning grounds.
After spawning in early spring, they transport the frogs back uphill. Some nights are busy, with 100 or more frogs emerging from the forest or the wetland and heading toward the highway. Some days, not a single frog is seen. But the volunteers show up as long as the pavement is wet and temperatures are trending above 45 degrees.
“If it gets too cold or too dry, there’s not a whole lot of activity,” volunteer Garrett Wong explained.
A “frog taxi” arrives on Harborton Drive in Northwest Portland after transporting red-legged frogs safely across U.S. Highway 30 in March.
Brooke Herbert / OPB
The fight for frogs
Red-legged frog populations have declined over the years, and although they are not endangered, the native amphibians are federally listed as a “species of concern,” mainly due to lost habitat.
But 2024 looks like a good year for the frogs. By early March, the volunteer taxi had transported 1,400 males downhill to the pond for reproduction. The number of females was considerably less – under 200. This may be in part because females for some reason prefer to travel later, usually after the volunteers have returned home for the night, and when the traffic has died down.
The team also counted 739 egg masses during a survey of the Harborton wetlands in February – their second-highest number for the eight years they’ve been conducting the survey. By the end of March, the frogs are usually finished with their migration and are settled back into their Forest Park home. Only then do the teams relax and hang up their safety vests for the season.
“We put thousands of volunteer hours in every winter, and I don’t know how sustainable that is,” Fensterer admitted.
A better frog crossing?
The Oregon Wildlife Foundation is working closely with the Oregon Department of Transportation and Multnomah County on a more sustainable solution for these imperiled frogs, according to the group’s executive director, Tim Greseth.
One proposal Greseth’s group is working on is the installation of a specialized box culvert under the roadway to offer frogs and other small wildlife a safe way to cross. The proposed design allows the culvert to stay wet during rainy nights and to be illuminated with just enough ambient light so the migrating frogs feel comfortable enough to use it.
“We will use a short wildlife fence to funnel frogs during their downhill journey to the culvert,” Greseth said.
A similar fence will direct frogs toward the culvert during their uphill journey out of the wetlands, he said.
The novel solution is successfully facilitating the migration of larger animals, such as deer and elk, through traffic corridors in other parts of the state. One similar project between Linnton and Scappoose allows safe passage of small wildlife such as frogs by linking the Palensky Wildlife Area with the Tualatin Mountains north of Forest Park. The project was led by the Columbia River Estuary Study Taskforce, took more than a decade to complete and cost $3.4 million.
The eastside wall of the Palensky Wildlife Crossing near Scappoose. The structure allows frogs and other small wildlife to cross busy U.S. Highway 30. The crossing entrance and the adjacent water conveyance culvert are shown on the left. The photo on the right shows the interior surface of the crossing.
Courtesy of Columbia River Estuary Study Taskforce (CREST)
Greseth’s group has finished the first phase of the Harborton Frog Crossing project, which included a feasibility study and concept design. Phase II, which will focus on design and engineering, will cost more than a half-million dollars. Greseth estimates that construction of the final design, Phase III, could cost nearly $4 million. He doesn’t know yet how much it will cost to monitor the project, but that would come next in Phase IV.
“We’re taking this one step at a time, and so our first goal is to raise $544,000 for design and engineering,” Greseth said. “With plans mostly complete, we can then begin looking for the funding we need to build and install the culvert and associated crossing features.”
That step-by-step approach is by design, Greseth said. The conservation status of Northern red-legged frogs in Oregon is “sensitive,” rather than “threatened” or “endangered,” designations that would give the species a higher priority for protection. Additionally, red-legged frogs are, well, harmless.
“These frogs are a unique population, but do not pose a risk to the public,” Greseth said.
Unlike larger animals such as deer or elk, the frogs do not damage cars or endanger lives if they hop out into traffic on U.S. Highway 30. That makes it harder to fund the project, he said.
With the project wholly dependent on funding, Greseth said he expects to complete Phase II of the Harborton Crossing in spring 2027.
Till then, the Harborton “frog taxi” volunteers will be on the job.