Salamanders surprisingly abundant in eastern North American forests

Scientists knew that red-backed salamanders were abundant in eastern North America, but a recent study found their densities and biomass, or their total quantity across the region, were much higher than expected. 

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

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 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 red-backed salamander, plethodon cinereus, is a relatively common and small salamander,” said Louise Mead, a professor in the College of Natural Science and the Ecology, Evolution, and Behavior Program at MSU. “Given estimates of its density in forests across its range and the extensive research already done on physiology, behavior, territoriality, and evolutionary history, the red-backed salamander provides a unique opportunity to study a small but mighty species, further examining local adaptation and possible impacts of landscape and climate changes.” 

The incredible magnitude of red-backed salamander presence in the eastern North American 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 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, a research wildlife biologist at the USGS and lead author on the paper. “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 mean people should overlook their ecological roles. 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. 

“Salamanders serve a vital function in forest ecosystems,” explained David Miller, associate professor of wildlife population 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.” 

Unfortunately, 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 is a looming threat and a serious concern for scientists and wildlife managers. 

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. Sadly, since its introduction, Bsal 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. There is a North American Bsal Task Force, which Warwick and Grant serve on, whose mission is to limit the invasion and reduce the impact of Bsal in North America.  

MSU’s contribution to the study also provided an opportunity for students.  

“MSU joined the Salamander Population Adaptation Research Collaboration Network, or SPARCnet, in 2016 and, since 2017, students, postdocs and community members have been collecting and contributing data from six plots located at Rose Lake State Wildlife Research Area,” said Alexa Warwick, an assistant professor in the College of Agriculture and Natural Resources. “We have integrated sampling, data collection and analysis into the ecology labs taught by Mead in both the fall and spring engaging upwards of 200 students each year.”

Warwick also engages students in another amphibian project looking at ways to mitigate disease spread through the pet amphibian trade.

“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,” said Bletz. 

This research was recently published in the journal Biology Letters.

Read the full story in MSU Today.