Hoping to find clues in the case of the deformed frogs, the U.S. Fish and Wildlife Service this summer used a Bay watershed site to launch a nationwide amphibian study in wildlife refuges.

In the past five years, an increasing number of frogs, toads and other amphibians with severe malformations — such as missing, or extra, limbs — have been observed throughout the United States and around the world.

This summer, biologists from the U.S. Fish and Wildlife Service worked with volunteers to collect amphibians at 43 wildlife refuges in 31 states from Maryland to Alaska for studies aimed at learning the impact of pollutants on amphibian malformations.

“Frog populations around the world are in a state of dramatic decline,” said USF&WS Director Jamie Rappaport Clark in kicking off the survey at the Patuxent Research Refuge in Maryland. “When frogs and toads are either not found at all, or are found with malformations on our national wildlife refuges, there is something wrong.”

What that something is, no one knows. Possible causes include fungal infections, diseases, habitat loss, thinning ozone and increased ultraviolet radiation, pollution and other contaminant factors. Declines have taken place in seemingly unlikely spots, such as wildlife refuges and wilderness areas.

In 1997, the USF&WS found malformation rates as high as 18 percent at refuges in the Northeast and Midwest. Among refuges with high rates were three in the Bay watershed: The Patuxent Research Refuge and the Eastern Neck National Wildlife Refuge in Maryland, and the Eastern Shore National Wildlife Refuge in Virginia. Some of those were being resampled in this year’s work.

Information from the wildlife refuge studies will be combined with data being gathered by other agencies within the Department of Interior to help determine causes of malformations and amphibian decline, as well as possible actions needed to halt the problem.

Amphibians are considered bellwethers of environmental change. Frogs and toads are highly sensitive to their environment because they breathe partly through their skin.

Fourteen species of amphibians have disappeared from Australia in recent years. Eighteen species of frogs, toads and salamanders are listed as either threatened or endangered in the United States and Puerto Rico.

Clark urged people to help by using fewer pesticides and fertilizers. “If we all take these actions, we will not only be helping amphibians, but we will be taking care of our watersheds and other species like birds and fish.”

The survey was launched at the Patuxent refuge because it was the site of research in the 1960s that helped to link DDT to reproductive problems in bald eagles and other birds.