Wild salamanders living in some of North America's best salamander habitat are getting smaller as their surroundings get warmer and drier, forcing them to burn more energy in a changing climate.

That's the key finding of a new study co-authored by a Clemson University biologist and published Tuesday in the journal Global Change Biology that examined museum specimens caught in the Appalachian Mountains from 1957 to 2007 and wild salamanders measured at the same sites in 2011-2012.

The salamanders studied from 1980 onward were, on average, eight percent smaller than their counterparts from earlier decades. The changes were most marked in the Southern Appalachians and at low elevations, settings where detailed weather records showed the climate has warmed and dried out most.

"One of the stresses that warmer climates will impose on many organisms is warmer body temperatures," said Michael W. Sears of the biological sciences department. "These warmer body temperatures cause animals to burn more energy while performing their normal activities. All else being equal, this means that there is less energy for growth."

To find out how climate change affected the animals, Sears used a computer program to create an artificial salamander, which allowed him to estimate a typical salamander's daily activity and the number of calories it burned.

Using detailed weather records for the study sites, Sears was able to simulate the minute-by-minute behavior of individual salamanders based on weather conditions at their home sites during their lifetimes. The simulation showed that modern salamanders were just as active as their ancestors had been.

"Ectothermic organisms, such as salamanders, cannot produce their own body heat," Sears explained. "Their metabolism speeds up as temperatures rise, causing a salamander to burn seven to eight percent more energy in order to maintain the same activity as their forebears."

The changing body size of salamanders is one of the largest and fastest rates of change ever recorded in any animal and the data recorded in this study reveals that it is clearly correlated with climate change, according to Karen R. Lips, associate professor at the University of Maryland's (UMD) department of biology and co-author on the paper.

"We do not know if decreased body size is a genetic change or a sign that the animals are flexible enough to adjust to new conditions," said Lips. "If these animals are adjusting, it gives us hope that some species are going to be able to keep up with climate change."

The research team's next step will be to compare the salamander species that are getting smaller to the ones that are disappearing from parts of their range. If they match, the team will be one step closer to understanding why salamanders are declining in a part of the world that once was a haven for them.