The Development and Assessment of Standardized Methodologies for Monitoring the Forest Ecosystem Indicator Species Plethodon Cinereus

The red-backed salamander P. cinereus is an important component of forest ecosystems and, because they are widely distributed, occur at high densities, and are sensitive to environmental change and habitat disturbance/alteration, they are an ideal indicator species for assessing forest ecosystem health. However, the behavioral ecology of P. cinereus, specifically the fact that they spend much of the time below the surface, means that individuals are difficult to detect, making indices and estimates of population size both challenging to interpret and difficult to compare across space and time. The use of P. cinereus as a bioindicator therefore requires the development of standardized sampling protocols and analytical methods. Sampling using artificial cover objects (ACO's) is a widely accepted and applied field sampling method for monitoring P. cinereus, and typically, counts from cover board arrays are simply compared among locations, seasons and years, although more recent application of mark-recapture models allow inference to be made about true population size. Despite ACOs being a standard technique, the spacing and extent of ACO arrays varies widely, and little effort has been made to understand whether estimates from different designs are comparable. Recently developed spatial capture-recapture (SCR) models are the canonical analytical framework for analyzing spatially indexed capture data such as that collected from mark-recapture data collected using ACO's. SCR provides estimates of true density (individuals per unit space), a measure of a population that is explicit repeatable and thus comparable, rather than abundance for an unknown area (as is estimated under traditional mark recapture models). What is unclear, however, is whether ACO's influence densities by altering the availability of suitable habitat refugia which may attract individuals into the study area, artificially inflating the number of salamanders encountered and the resulting estimates of density. Here we propose experimentally manipulating cover board designs (configuration and density) over time to assess whether estimates of salamander density are influenced by the amount and arrangement of available cover, or whether they remain constant regardless of ACO design, and thus reflect true salamander density. Specifically, we will estimate initial P. cinereus using spatial capture-recapture and quantify how local densities change in response to changes in ACO array density.