UNIVERSITY PARK, Pa. — Two recent studies involving Penn State researchers shed light on the ecological importance of red-backed salamanders and confirmed that proactive measures could prevent costly impacts from a wildlife disease spreading across Europe that has not yet reached North America.

Scientists were aware that red-backed salamanders were abundant in eastern North America, but a recent study found their densities and biomass across the region were much higher than expected. The study authors estimated an average of 5,300 salamanders in every patch of forest the size of a football field in the Northeast. Even though each individual salamander is a mere 3 inches long, the sheer number of red-backed salamanders means that they also have some of the highest biomass estimated for animals other than insects in the Northeast, similar to or greater than white-tailed deer.

The study, conducted by Penn State, the U.S. Geological Survey (USGS) and many partner institutions and published by the USGS, was the first time that the densities and biomass for this common, but rarely seen, species were calculated across the extent of its range.

“Salamanders serve a vital function in forest ecosystems,” explained David Miller, professor of wildlife ecology at Penn State and co-author of the study. “They are at the top of the food chain on the forest floor, where everything is breaking down into the soil that sustains this entire network of life. In fact, salamanders are so important to this life cycle that we can use them as a barometer for forest health.”

The incredible magnitude of red-backed salamander presence in the Northeast captured in this study suggests that red-backed salamanders, and likely amphibians in general, play a more prevalent role in terrestrial temperate ecosystems than previously suspected, the researchers said.

“The very large biomass of red-backed salamanders tells us that they are likely ‘small but mighty’ in terms of their role in the ecological health of northeastern forests,” said Evan Grant, lead author and USGS research wildlife biologist. “If red-backed salamanders disappeared, there would probably be some pretty large ecosystem-level consequences.”

Many salamanders, like the red-backed salamander, are tiny and spend the majority of their time underground, so it’s easy for most people to overlook them. In fact, Grant commonly refers to salamanders and other amphibians as “hidden biodiversity” because, though they are often abundant, they hide well — but that doesn’t diminish their ecological role. Salamanders eat things that bigger consumers can’t eat and are themselves prey for other animals, meaning salamanders punch above their weight in an ecosystem’s food web.

Unfortunately, the researchers said, just as scientists are beginning to understand the true magnitude of salamanders’ “hidden biodiversity” and ecological importance, a new wildlife disease that is particularly hard on salamanders looms.  

Batrachochytrium salamandrivorans, or Bsal for short, is a fungal disease closely related to the chytrid fungus that is already devastating amphibian populations around the world. It was first found in the Netherlands in 2013 and, since then, has decimated the salamander populations in central Europe and continues to spread across Europe.

Bsal hasn’t been detected in the U.S. yet, so scientists and wildlife managers are preparing for its arrival with the North American Bsal Task Force. However, they needed to determine if proactive management guidance for a disease that isn’t even on U.S. shores yet would be more or less effective than waiting to respond until the disease is detected in the wild. So, Grant co-authored another recent paper that tested a series of proactive and reactive management actions to forecast the impact on salamander populations over time.

This study, “Proactive management outperforms reactive actions for wildlife disease control,” used computer modeling to assess the best salamander management approach in the face of Bsal.

“If we do nothing to manage Bsal, the model forecasted that the disease would be catastrophic to North American salamander species,” said Molly Bletz, assistant professor of disease ecology at Penn State and lead author of the second study. “This study gives strong quantitative support to proactive management actions. Basically, if we want these at-risk salamander species to be around in the future, doing something proactively is our best bet.”

The types of proactive management actions considered included:

• making it harder for amphibians to spread the disease amongst themselves through installing barriers or increasing habitat complexity
• reducing Bsal fungal spores in aquatic habitats by temporarily raising the water temperatures, increasing the salinity or increasing the abundance of zooplankton that consume funguses
• helping amphibians fight off the disease by improving their health through supplemental feeding, etc., increasing the abundance of local, beneficial anti-fungal microbes or through vaccination

While this second study did not estimate how proactive management for Bsal may affect other parts of the ecosystem, visitor satisfaction or financial cost, Bletz, Grant and others said they are working on estimating these outcomes to provide a full account of proactive versus reactive management.

“With a new understanding of how incredibly prevalent salamanders are in an ecosystem, and with the empirical justification for the benefits of proactive management for salamander populations threatened by Bsal, it is more critical than ever to protect the ‘hidden biodiversity’ of amphibians,” Bletz said.

Editor’s note: This story was adapted from a USGS release.