Researchers study impact of warming on salamanders
University Park, Pa. —Researchers in Penn State’s College of Agricultural Sciences are spearheading a four-year-old collaborative effort to assess the impact of a warming climate on the Eastern red-backed salamander, a creature that lives on or under the forest floor.
Because these salamanders do not have lungs, breathe through their skin and must live in damp places, they are extremely sensitive to changes in temperature and moisture, according to David Munoz, doctoral degree candidate in ecology who helped create the Salamander Population Adaptation Research Collaboration Network, or SPARCnet (http://psu.ag/2sGSBw4).
Woodland salamanders, which are found throughout most areas of North America, are the most abundant vertebrate group in Eastern temperate forests, and they are imperiled by forestry practices, land use, pollution and warming. “Although they are often overlooked organisms, we view these salamanders as the canary in the coal mine related to climate change in the Northeast,” Munoz said.
“They are particularly sensitive to thermal changes, so we’re using them as a model species to understand how warming conditions will affect organisms in the future. Scientists are becoming increasingly confident about how the climate will change, but we don’t know how wildlife will respond.”
With 30 salamander-monitoring sites in 12 states, SPARCnet is a partnership between Penn State, Cornell, Michigan State and Ohio State universities, the University of Massachusetts at Amherst, the U.S. Geological Survey’s Patuxent Wildlife Research Center and its Northeast Amphibian Research and Monitoring Initiative, and a number of smaller educational institutions, including Susquehanna and Lock Haven universities in Pennsylvania.
The network also includes dozens of citizen scientists who help survey salamanders and who present the research to high school classes.
Salamander-monitoring sites stretch from New Hampshire in the north to Virginia in the south and as far west as Michigan. To attract red-backed salamanders, each site consists of dozens of untreated, rough-hewn, wooden squares in forested plots that create spaces cooler than the surrounding forest floor litter.
Researchers are employing the traditional wildlife science mark-and-recapture method to determine salamander abundance across SPARCnet, marking the amphibians with a permanent visual implant. A technique originally devised to study fish, it involves injecting a fluorescent dye or elastomer under the skin of salamanders.
“It’s like a tattoo, and once it is injected, it hardens into a tiny plastic bead,” said Munoz, who is advised by one of SPARCnet’s founders, David Miller, assistant professor of wildlife population ecology in the Department of Ecosystem Science and Management. “We have a system with each salamander getting a different color in different places on its body, so using the color-location combination, each individual is unique in our data. That allows us, over time, to accurately estimate salamander survival and abundance.”
Researchers also are collecting soil temperature and moisture readings at salamander- monitoring sites and cataloging soil and vegetation types. Some of the collaborators are investigating other aspects of salamander population dynamics, such as physiology (how heat affects metabolism) at Penn State and genetics at Ohio State.
Through SPARCnet, researchers can piece together the big picture when it comes to the red-backed salamander’s fate. Scientists have access to large data sets to help them understand not only what is happening to local populations, such as the one in Moshannon State Forest being studied by Penn State, but also range-wide developments.
Early findings from the research suggest that salamander growth decreases under really hot summer conditions, noted Munoz, who earned his master’s degree in wildlife and fisheries science at Penn State. Adult red backs can reach about 3.5 inches in length.
“From analysis that we have done so far with just looking at the population in Maryland, we found that when we have really hot summers, the growth rates of salamanders are reduced by 60 to 70 percent,” he said. “However, ongoing research suggests that woodland salamanders may be more threatened in the Northeast by warmer winters than hot summers.”
Scientists are concerned, Munoz explained, because if salamanders are growing more slowly they have two options: The females either have to survive longer to reach the size at which they can reproduce or they have to start reproducing at smaller sizes. But, he said, female salamanders that are much smaller can’t support as many eggs.
“Right now we’re trying to figure out if there is any evidence across the species’ range that they can do these things — that they can reproduce at smaller sizes and still have healthy populations, or are there any longer survival rates at different locations.”
This wide perspective on the salamander’s range is what makes SPARCnet innovative, Munoz believes. Traditional approaches to understanding how wildlife adapt to climate change take a static species approach, he said, assuming all animals of a species have the same response to warming – whether it’s the southern, middle or northern part of the range.
“We don’t assume that all populations of red-backed salamanders will have the same response to climate change. Some populations may not be much affected, some may do better, and others will surely be harmed.”