The frogs have turned up in Wisconsin, South Dakota, California, Missouri, Quebec, Denmark, China, and Japan. There was also a large breakout in Lake Champlain on October 9 of last year. Researchers collected 230 Leopard Frogs and 16.5 percent were deformed. So far, the species affected have included Leopard Frogs, Mink Frogs, Green Frogs, Grey Tree Frogs, American Toads, and Spring Peepers. The explanations for this sudden outbreak are varied.
Some biologists believe that the deformities are a result of parasitic infestation.
Others suspect chemical pollutant, such as a pesticide. One possibility is the chemical used for mosquito control called methporene which had been shown to cause leg deformities in laboratory situations. Other possibilities include a viral or bacterial disease, heavy metal, and acidification. Some experts even suggest the depletion of the ozone layer is causing the defects. Since eggs float on top of the water, they can absorb extra sunlight with ultraviolet radiation.