Characterizing the population density of species is a central interest in ecology. Eastern North America is the global hotspot for biodiversity of plethodontid salamanders, an inconspicuous component of terrestrial vertebrate communities, and among the most widespread is the eastern red-backed salamander, Plethodon cinereus. Previous work suggests population densities are high with significant geographic variation, but comparisons among locations are challenged by lack of standardization and failure to accommodate imperfect detection. We present results from a range-wide monitoring network that accounts for detection uncertainty using systematic survey protocols and robust quantitative models. We analyzed mark-recapture data from 19 study areas across the range. Estimated salamander densities ranged from 1950 to 34300 salamanders/ha, with a median of 9965 salamanders/ha. We compare these results to previous estimates for P. cinereus and other abundant terrestrial vertebrates. We demonstrate that overall biomass of P. cinereus, a secondary consumer, is of similar or greater magnitude to widespread primary consumers such as white-tailed deer and Peromyscus mice, and 2-3 orders of magnitude greater than common high-biomass omnivorous species and other secondary consumer species. Our results add empirical evidence that P. cinereus specifically, and amphibians in general, are an outsized component of terrestrial vertebrate communities in temperate ecosystems.

Under the current amphibian biodiversity crisis, common species provide an opportunity to measure population dynamics across a wide range of environmental conditions while examining the processes that determine abundance and structure geographic ranges. Studying species at their range limits also provides a window for understanding the dynamics expected in future environments under increasing climate change and human modification. We quantified patterns of seasonal activity, density, and space use in the Eastern red-backed salamander (Plethodon cinereus) near its southern range edge and compare the spatial ecology of this population to previous findings from the core of their range. This southern population shows the expected phenology of surface activity based on temperature limitations in warmer climates, yet maintains unexpectedly high densities and large home ranges during the active season. Our study suggests that ecological factors known to strongly affect amphibian populations (e.g., warm temperature, forest fragmentation) do not necessarily constrain this southern population. Our study highlights the utility of studying a common amphibian as a model system for investigating population processes in environments under strong selective pressure.