Amphibians like the red-legged frog are Earth's ultimate tough guy. For millions of years they have endured, even surviving previous mass extinctions.
But now scientists say their numbers are declining at a rate that sends a deafening warning about human impact on climate change and the environment.
"These guys are survivors, yet here they are in our time, when more than 40 percent of amphibians around the world are threatened," says Associate Professor Vance Vrendenburg from the San Francisco State University.
Climate change and disease are seen as the most serious threats to amphibians, including a fungus known as chytridiomycosis.
Professor Vrendenburg says small increases in water temperature has allowed the fungus to spread more effectively, while rising air temperatures and pollution can damage their natural habitat.
"The perfect storm is happening," Professor Vrendenburg warns. "All these different factors are leading to Their decline, and it's really serious. We've been finding dead frogs by the hundreds and thousands."
The new report comes as the Department of the Interior is proposing changes to the Endangered Species Act. The changes would eliminate the need for an independent scientific review in certain cases when it comes to assessing how federal projects, such as dams or highways, might affect protected species.
CBS