Study finds salamanders surprisingly abundant in Northeast forests

Scientists knew that red-backed salamanders were abundant in eastern North America, but a recent study found that the density and biomass of red-backed salamanders in the region were much higher than expected. The study authors estimated that there were an average of 5,300 salamanders in each football field-sized patch of forest in the Northeast. Although each salamander is only 3 inches long, the sheer number of salamanders means that their biomass is the highest of any animal in the Northeast other than insects, similar to or larger than white-tailed deer.

Research, “Salamander density across its range reveals key components of terrestrial vertebrate biomass in eastern North American forests” Conducted jointly by the U.S. Geological Survey and many partner institutions, it provides the first calculations of the density and biomass of this common but rarely seen species throughout its range.

This study captured a surprising number of red-backed salamanders in the Northeast, suggesting that red-backed salamanders, and possibly amphibians, play a more pervasive role in terrestrial temperate ecosystems than previously thought.

“The red-backed salamander’s biomass is very large, which suggests that they play a ‘small but mighty’ role in the ecological health of Northeastern forests.” Evan Grant, lead author and U.S. Geological Survey research wildlife biologist“If the red-backed salamander disappeared, it could have quite a big impact on the ecosystem.”

Many salamanders, like the red-backed salamander, are so small and spend most of their lives underground that it’s easy for most people to overlook them. In fact, Grant often refers to salamanders and other amphibians as “hidden biodiversity” because, despite their abundance, they’re so well hidden. But that doesn’t mean people should ignore their ecological roles. Salamanders eat things that larger animals can’t, and they themselves are prey for other animals, which means salamanders play an outsized role in an ecosystem’s food web.

“Salamanders play a vital role in forest ecosystems,” David Miller, professor of wildlife ecology at Penn State and co-author of the study“They’re at the top of the food chain on the forest floor, where all the organisms break down into the soil and sustain the entire web of life. In fact, salamanders are so important to this life cycle that we can use them as a barometer of forest health.”

Unfortunately, just as scientists are beginning to realize the true importance and ecological significance of salamanders’ “hidden biodiversity,” a new wildlife disease that is particularly severe for salamanders is becoming a looming threat and causing serious concern among scientists and wildlife managers.

BatrachochytriumBsalamander disease, or Bsal for short, is a fungal disease closely related to the chytrid fungus that has had a devastating impact on amphibian populations around the world. The disease was first discovered in the Netherlands in 2013. Unfortunately, since Bsal emerged, it has devastated Central European salamander populations and continues to spread across Europe.

Bsal has not yet been found in the United States, so scientists and wildlife managers are preparing for its arrival. North America has a Bsal Task Force whose mission is to limit the invasion and reduce the impact of Bsal in North America. However, natural resource managers have run into problems trying to develop proactive management guidance for a disease that has not yet appeared on U.S. shores.

They needed evidence that proactive management was more effective than waiting until the disease was detected in the wild, so Grant recently co-authored another paper that tested a range of proactive and reactive management measures to predict their effects on salamander populations.

This studyProactive management is better than reactive action when it comes to wildlife disease control” used computer modeling to confirm what is intuitively obvious: namely, that initiating management of wild populations before Bsal arrives is actually more successful in achieving the management goal of preventing salamander disappearances than waiting until Bsal is detected or doing nothing.

“If we do nothing to control Bsal, models predict that this disease will be catastrophic to North American salamander species,” Lead author Molly Bletz, assistant professor of disease ecology at Penn State The second study concluded: “This study provides strong quantitative support for proactive management actions. Essentially, proactive action is our best option if we want these endangered salamander species to continue to exist in the future.”

Types of proactive management actions considered include:

• Make it harder for amphibians to spread diseases among themselves by creating barriers or increasing habitat complexity;
• Reducing Bsal fungal spores in aquatic habitats by temporarily increasing water temperature, salinity, or abundance of zooplankton that feed on the fungus;
• Improving the health of amphibians through methods such as supplemental feeding, increasing the abundance of local beneficial antifungal microorganisms, or through vaccination can help amphibians resist disease.

While the second study did not assess how active management of Bsal would affect other parts of the ecosystem, visitor satisfaction or financial costs, Bletz, Grant and others have begun evaluating those results so managers can gain a comprehensive understanding of the relative benefits of active versus passive management.

“With new understandings of how common salamanders are in ecosystems, and empirical evidence of the benefits of proactive management of salamander populations threatened by Bsal, protecting the ‘hidden biodiversity’ of amphibians is more important than ever,” he said Blitz.