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Malformed frogs found on Kenai

Posted: Monday, August 21, 2000

A number of wood frogs near the Swanson River oil fields were found to have severe malformations of limbs and eyes after a summer-long study by the U.S. Fish and Wildlife Service. It is not known if these deformities are naturally caused or the result of pollution. No link has been made to oil field operations.

Jordan Stout, an environmental contaminants specialist with Fish and Wildlife, said frogs on the Kenai Peninsula only were collected from the Swanson River area, so comparisons to other parts of the Kenai National Wildlife Refuge cannot be made.

"Because of certain funding and field limitations, and this being the first time we've done this project, we tended to look at ponds near the road system," Stout said.

Researchers from the refuge surveyed 20 ponds along Swanson River and Swan Lake roads, looking for frog egg masses and doing water quality studies.

Twenty-six deformed frogs were found, comprising 6 percent of the samples taken. In a normal frog population, 1 percent can be expected to have natural deformities. In one pond, researchers report nearly 17 percent were deformed.

"They started the studies in May and continued tracking the tadpoles through the summer," Stout said.

He said it was important to collect the amphibians as they were turning from tadpoles to frogs just as they were about to leave the ponds.

"Before that, you won't see any deformity because they haven't developed limbs yet, and after that, good luck, as they disperse out into the woods," Stout said.

The wood frog is the only amphibian on the peninsula.

Researchers don't know yet if the deformities are caused by pollution in the environment, increased ultraviolet radiation from the sun because of a thinning ozone layer in the atmosphere, disease, parasitic infection or through natural predation from other animals such as fish or insects during the tadpole stage.

"Nationally, frogs are an indicator," said refuge manager Robin West. "They are sensitive to contamination and solar radiation that can affect their genetics."

Since the deformed frogs found on the peninsula were missing limbs, the cause could be something other than genetic problems.

"If they're missing limbs, like here, it could be either-or," West said. "It could have been a tern swooping down taking a leg from tadpoles."

Extra limbs on frogs are a sign of genetic damage, he said.

If the malformations are the result of predation, there should have been evidence of deformed frogs in the past, however, Stout said there is very little historical data on the wood frog on the peninsula.

"It's a natural system, so there is some variability," he said.

Ted Bailey, the supervisory wildlife biologist at the refuge, said he will hold off on saying what caused the frog deformities until lab results come back.

Frogs and data collected on the peninsula will be sent to a U.S. Geological Survey laboratory in the Lower 48 to be examined. Test results are not expected until January.

The deformed frog discovery on the peninsula was made as part of a nationwide study of frog deformities. There will be more studies of frogs in the refuge next summer.



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