Amphibian populations concern scientists

Almost one-third of the world's 6,000 amphibian species are on the brink of extinction. But just 12 percent of all bird species and 23 percent of all mammal species are threatened.

Harsh winters and hot summers limit the fungus in the Midwest. While many frogs and salamanders safely rest in burrows below ponds in the winter, freezing temperatures kill the fungus.