Skip Navigation
Mysterious islanders Red-backed salamanders reveal a new pocket of biodiversity in Maine by Amanda Clark
Salamander illustration

Illustration by Carol Nichols

When evolutionary biologist Michael Kinnison saw a photograph of a red-backed salamander taken by an ornithologist working on Maine’s Petit Manan island — a 16-acre, rocky island with only one tree — his scientific mind began to question his eyes. Red-backed salamanders, he thought, weren’t on Maine islands.

They can’t swim.

“Salamanders are not animals you think of as inhabitants of marine islands in Maine,” says Kinnison, professor of evolution at the University of Maine. “As a rule, salamanders and seawater just don’t mix, and red-backed salamanders are the least aquatic of our Maine species.”

Nearly all amphibians are unable to tolerate the concentrations of salt in seawater, but the challenges of open water are even greater for this particular forest-dwelling species.

Red-backed salamanders lack lungs and absorb oxygen through their skin — a physiological trait that makes them, oddly enough for an amphibian, susceptible to suffocating, even in freshwater. And unlike many other salamanders, the red-back doesn’t have an aquatic larval stage.

So how did that salamander get there?

The salamanders could have floated to the islands in rotted logs or could have been stowaways on European ships during early settlement. One could have been dropped by a seabird. Or they might have walked there.

Kinnison discussed the peculiarity of the salamander sighting with his UMaine colleague Cynthia Loftin, unit leader for the U.S. Geological Survey Maine Cooperative Fish and Wildlife Research Unit, and an experienced herpetologist.

“I’m not sure if I said it out loud or not, but my response was along the lines of, ‘Are you crazy? Salamanders on rocky, treeless, ocean islands?’” says Loftin.

But she was intrigued.

The researchers wanted to know if the red-backed salamander on Petit Manan had been introduced recently by chance or if it had a more ancient history. They also wanted to know if red-backs inhabited other coastal islands in Maine.

“When we started this project, we were looking at the records of what amphibians were found on Maine islands. Though the Maine Department of Inland Fisheries and Wildlife had a very good reptile and amphibian database, islands were fairly underrepresented,” says Loftin.

The two researchers wrote a grant proposal to the Maine Outdoor Heritage Fund, found a graduate student interested in the project and set out to solve the mystery.

For three years, Nikko-Ideen Shaidani, a UMaine graduate student in biology, sampled red-backed salamanders on islands off the coast of Maine to conduct population genetic analyses that could shed light on when and where the salamanders originated.

red-backed salamander

Red-backed salamander

At the beginning of the project, the researchers considered a flood of explanations. The salamanders could have floated to islands in rotted logs. They could have been stowaways on European ships during early settlement.

One could have been dropped by a seabird. Or two or three or four.

Though many options seemed plausible, one hypothesis was especially intriguing: The salamanders might have walked there, before the islands were islands.

For this hypothesis, the investigators turned back the region’s geologic clock 12,000 years when, following glacial retreat and rebound of the land, sea levels were approximately 60 meters lower than they are today, roughly equivalent to a 20-story building.

Then, like the way a rising tide wraps around a sand castle, the sea level began to gradually rise and submerge the coast of Maine, shattering it into the many islands we see today.

“If the island salamanders had been isolated for thousands of years, then those populations may have adapted to their island ecosystems and thus become unique pockets of genetic diversity,” says Kinnison. “Identifying such unique components of diversity is especially valuable to resource managers and policymakers that prioritize populations and habitats for conservation.”

But before Shaidani could identify potentially noteworthy populations of red-backed salamanders, he had to catch them. Which is easier said than done.

Shaidani’s research sites were scattered across the coast of Maine — from the Isles of Shoals on the border of New Hampshire to Cross Island on the edge of New Brunswick, Canada.

Splitting the coast and islands into seven geographic domains, Shaidani surveyed as many as three island sites within each region, along with an adjacent mainland site.

His trips were planned on short notice and around nature’s schedule, often dictated by the weather or the swing of the tides. Once on an island, he usually had a few hours to collect and measure salamanders before making a hasty retreat.

Shaidani coordinated transportation to his research sites on ferries, research vessels and fishing boats with the help of the U.S. Fish and Wildlife Service National Refuge System, National Park Service, Maine Department of Inland Fisheries and Wildlife, and others.

Due to the rocky coastline of many of the islands, the larger boats could only take him so far. The last legs of his trips were often spent paddling in a raft to the island, where he would climb the slippery shoreline to his research sites. Then his search for salamanders began.

“The feeling of arriving to a scenic island, exploring its unique landscape, and digging through the substrate in search of elusive salamanders is unlike any other,” says Shaidani.

Red-backed salamanders thrive in forest ecosystems, swiftly moving among rocks, fallen logs and leaf litter, eluding their many predators — mainly mammals, snakes and birds. They are an integral part of an ecosystem, providing food for their predators and consuming a smorgasbord of invertebrates.

Photo courtesy of Nikko Shaidani Researchers complete the last leg of their trip to Great Duck Island in a raft.

True to their name, most red-backed salamanders have a dark red stripe that streaks down the middle of their tiny black backs. Though the stripe makes them relatively easy to identify, it is effective camouflage for an animal that lives among debris of the forest floor.

This particular species is said to be the most abundant in the forest, says Loftin about red-backs on the mainland. And Shaidani’s study found that island red-backs live up to that reputation.

Red-backed salamanders didn’t just turn up on one island, or even a few islands. They turned up on almost every island Shaidani surveyed, and often in surprising numbers.

“It’s mind-blowing to think that these salamanders could actually be the most abundant vertebrate on many of Maine’s islands, and yet they were overlooked for all this time. Not to mention, unlike seabirds and other common inhabitants, red-backs live there year-round,” says Kinnison.

Once Shaidani captured a salamander, he anesthetized it to take measurements, a tissue sample and photographs. For genetic analysis, he removed a few millimeters off the tip of each salamander’s tail before releasing the animal back into the environment. This species of salamander can lose and regrow its tails to evade predators, making the location ideal for tissue sampling.

Over the three years, Shaidani sampled 604 salamanders and spent hundreds of hours in the field.

He used the tissue samples to conduct microsatellite DNA and trait-based assessments of divergence, comparing island populations to mainland populations and each other, to better understand their possible relationships, isolation, ecology and adaptations to island ecosystems.

His analyses are ongoing, but have yielded interesting initial results. Overall, his findings support general genetic differentiation occurring among island and mainland populations, as well as an interesting pattern among island populations.

“Salamanders from distant islands were found to have the greatest genetic divergence values,” Shaidani says. “These island salamanders likely have been isolated for an extended period of time and may even represent glacial relics.”

It’s mind-blowing to think that these salamanders could actually be the most abundant vertebrate on many of Maine’s islands, and yet they were overlooked for all this time. Not to mention, unlike seabirds and other common inhabitants, red-backs live there year-round.”
Michael Kinnison

Glacial relics are species estimated to have originated from the time after the last glacial period, approximately 12,000 years ago.

Though further genetic analysis is needed, this pattern of divergence is consistent with distant islands being isolated earlier than near-shore islands when sea levels rose.

Thus, there is the possibility that salamanders might have been there already — or arrived soon thereafter.

“If what this analysis is showing is that there is a uniqueness between the islands, then that is important information for our natural resource managers to have because they can decide whether conserving these unique populations is important for the biodiversity of the state,” says Loftin.

Photo courtesy of Nikko Shaidani Petite Manan Island, Maine.

Amphibians face some of the greatest rates of local and global extinctions due to habitat loss, disease, pollution and invasive species interactions.

“Locations that support isolated and unique populations of one species have greater odds of supporting isolated and unique populations of other species, and so our work on red-backs might be indicative of broader repositories of biodiversity,” says Kinnison.

At the same time, island systems often are more susceptible to species losses due to their isolation, small populations, limited gene pools and common enemies — diseases, predators and competitors.

According to the World Conservation Monitoring Centre, 75 percent of all documented animal extinctions since 1600 A.D. have been of island taxa, making island systems a priority for conservation and resource management. The researchers note that thwarting this trend may require that conservation efforts include more than threatened and rare species.

“Often people don’t keep track of common species, and don’t necessarily notice when populations are declining,” says Loftin. “For this particular species, because it’s so widely distributed, it’s a good species to look at to address the particular question of isolation on islands.”

Widely distributed and abundant animals like red-backed salamanders are often more effectively studied than sparsely distributed and rare species when it comes to identifying the role of landscapes — or seascapes — in producing pockets of biodiversity or detecting changes in abundance or geographic range.

However, these inferences often depend on having good baseline data on where such species exist today.

The researchers submitted their findings to the Maine Amphibian and Reptile Atlas Project (MARAP) to expand amphibian species records to encompass understudied island systems. MARAP, maintained by Inland Fisheries and Wildlife in cooperation with UMaine and the Maine Audubon Society, is a database of the state’s 34 amphibian and reptile species.

Back to top

Fall/Winter 2015

Back to the Fall/Winter 2015 Issue