Amphibian-monitoring team makes shocking discovery in photo
Oregon Zoo conservationists working in Washington's Conboy Lake National Wildlife Refuge may have unintentionally documented a record-breaking bullfrog, which experts believe could weigh upward of 50 pounds.
The American bullfrog — an invasive species known to prey on local amphibians — can be seen lurking behind volunteers as they pose for a group photo following an egg-mass survey at the Conboy wetland.
"Clearly the problem is bigger than we imagined."
—Karen Lewis, conservation research associate
Oregon Zoo conservation research associate Karen Lewis didn't notice the well-camouflaged leviathan until a full week after the survey, while reviewing photos with the volunteers.
"We just stood around the computer screen with mouths agape," Lewis said. "Judging by the frog's distance from the volunteers and the size of the adjacent vegetation, we believe this individual could weigh in the neighborhood of 50 pounds."
Bullfrogs typically can grow up to 8 inches in length and seldom exceed 1.5 pounds. The photo is currently being analyzed by wildlife officials.
"This discovery has raised more questions than answers," Lewis said. "Invasive species are a huge problem for the recovery of a wide range of native wildlife, but clearly the problem is bigger than we imagined."
The volunteers in the photo had been conducting an egg-mass survey to document populations of the Oregon spotted frog, one of the Northwest species most threatened by non-native American bullfrogs.
With the notable exception of Conboy Lake, Oregon spotted frogs have disappeared from almost every wetland where bullfrogs have invaded. The seemingly "bullfrog-proof" nature of Conboy Lake spotted frogs makes them particularly important to the recovery of the species.
Researchers wouldn't speculate about whether the Conboy spotted frogs' skill at evading predators might be an adaptation to sharing their habitat with the freak of nature seen in the photo, which Lewis described as "capable of devouring a cat."
Since 1998, zoo staff and volunteers have worked closely with biologists at the Washington Department of Fish and Wildlife to document and protect the Oregon spotted frog, which is considered threatened in Oregon, endangered in Washington and Canada, and is a candidate for listing under the federal Endangered Species Act.