Wild salamanders that live in the Appalachian Mountains are shrinking because they must burn more energy as the local climate gets hotter and drier, according to a new study.
Researchers found that the salamanders they collected between 1980 and 2012 were 8 percent smaller than those collected in earlier decades, starting in 1957. The findings confirm predictions that some species will shrink in response to climate change. The climate where the salamanders live has gotten warmer and drier, researchers said.
"We compared the size of the museum specimens to the current animals and we were surprised to see that, in fact, many species has become smaller over just a 50- to 60-year period," said study author Karen Lips, a biologist at the University of Maryland. [8 Ways Global Warming Is Already Changing the World]
The researchers' interest in salamander size was sparked by a decline in salamander populations in the Appalachians since the 1980s. Lips had noticed a similar decrease in frogs she studied in Central America, which turned out to have been caused by a lethal fungal disease. So she wondered if the decline in size of Appalachian salamanders might also be linked to a disease.
Between summer 2011 and spring 2012 Lips and her students collected and measured salamanders in Maryland, Virginia, West Virginia, North Carolina and Tennessee, and also took DNA samples. The wild salamanders were compared to specimens previously collected by Richard Highton, a University of Maryland biologist, who began collecting in 1957.
The team found no evidence of fungal disease in the 16 salamander species they examined. However, they did find that six salamander species grew notably smaller and just one species got a bit larger since 1957. The animals shrank 1 percent per generation on average.
In order to examine the changing climate's effect on the salamanders' activity, the researchers created a computer model of an artificial salamander and combined it with weather data. They found that modern salamanders were as active as their ancestors, but, as cold-blooded animals, they had to burn 7 to 8 percent more energy to maintain the same level of activity.
"It is a general principle that, as the temperature increases, the rate of your cellular processes goes up, and so your metabolism will go up under these conditions," Lips told Live Science.
But extra energy typically comes with a higher price tag, as bigger salamanders may have to spend more time resting in cool ponds or searching for food. And there are other consequences of smaller size that may ultimately impact the abundance of salamander populations.
"As they get smaller, that means they can't quite reproduce as much," Lips said, adding that, when it comes to amphibians, the bigger they are, the more they can reproduce.
"Larger males get more mates, larger females produce more offspring, have fewer predators, eat larger prey, males tend to occupy bigger or better territories, and larger animals of both sexes generally come out on top in most interactions with other salamanders of their own species or other species," she said.
The findings were published March 25 in the journal Global Change Biology.