The effect of roads on the movement and landscape structure of the northern pine snake, Pituophis melanoleucus, in the Pinelands of New Jersey
New Jersey, the most densely populated state in the nation, has a dense complex of roads. Both paved and unpaved roads fragment the globally rare Pine Barrens occupied by the Northern Pine Snake (Pituophis melanoleucus), a state threatened species. These roads can act as barriers to ecosystem connectivity and wildlife mortality, loss of genetic corridors, and decreased reproductive success. Roads represent a major threat to slow moving herpetofauna that are extremely vulnerable to vehicular road injuries and death. The Northern Pine Snake is a large bodied vagile species that is particularly impacted by roads in New Jersey. Of 536 reported occurrences for Northern Pine Snakes (Pituophis melanoleucus) in the New Jersey biotics database 120, or 23%, were dead on road (NJDEP, 2009). We examined the mean rate of movement of the Northern Pine Snake across three different substrates: sand, asphalt, and concrete. We tested twelve snakes (n=12) seasonally 2012 at the Warren Grove Gunnery Range (WGR), Burlington County, New Jersey. We analyzed the New Jersey Pinelands landscape (FRAGSTATS 4.2) to identify suitable habitat patches utilizing road type and land use/land cover (LULC) data as delimiting factors of patches. Road type was scored throughout the Pinelands landscape utilizing substrate type, width, and vehicular density.
Snakes had the fastest rate of movement across sand (mean = 0.11m/s) compared to paved substrates: asphalt (0.09m/s) and concrete (0.06m/s). These data suggest that coarser substrates facilitate increased mobility of snakes. Using the snake’s mean rate of movement of asphalt, we estimated that it would take an adult Northern Pine Snake a minimum 2.07 minutes to cross an asphalt road, from shoulder to shoulder, at a 90 degree angle. Pairing this information with the New Jersey traffic report data for three roads intersecting the study site, we calculated the number of cars a snake would likely encounter during a single traverse. We identified 3,872 total habitat patches with 156 patches greater than 200ha. We describe the connectedness of habitat patches within this landscape. Identified patches can be sampled in the future to examine differences in population genetic among identified habitat patches for this state threatened species.