By Erik Derr ( | First Posted: May 23, 2013 05:52 PM EDT

(Photo : Reuters)

(Photo : Reuters)

The world's frog population apparently isn't hopping as much as it once did. The same goes for toads and salamanders.

In fact, new research from the United States Geological Survey shows amphibians have been in trouble for decades, with an average 3.7 percent rate of decline throughout the country.

The findings were published in the online journal PLOS One.

Biologists said they first recognized something was wrong with amphibians back in 1989, when they compared reports of vanishing species across the planet.

A global assessment in 2004 concluded about one-third of the amphibian species in the world, particularly in the United States, were declining.

"Amphibians have been a constant presence in our planet's ponds, streams, lakes and rivers for 350 million years or so, surviving countless changes that caused many other groups of animals to go extinct," said USGS Director Suzette Kimball. "This is why the findings of this study are so noteworthy; they demonstrate that the pressures amphibians now face exceed the ability of many of these survivors to cope."

The new USGS study, which included the analysis of 48 species at 34 locations over nine years, is the first to present detailed monitoring data on the overall condition of U.S. frogs, toads and salamanders.

The research found even species that appeared the healthiest saw an average population decline of 2.7 percent annually.

The populations of higher-risk species fell by 11.6 percent annually, putting them on track to vanish in six years from half the ponds, stretches of a streams or rivers they now occupy.

The study explained that because amphibians develop in water and on land and because they generally sit at the middle of their respective food chains, eating small things like insects while bigger predators including fish eat them, they represent an integral  part of their ecosystems.

"It may well be that amphibians are getting the worst of a number of global patterns," Mike Adams, a USGS ecologist and the study's lead author, told Reuters. "We're seeing things like climate change and disease and invasive species that are affecting amphibians."

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