GIS MAPPING OF RACCOON (PROCYON LOTOR) TRAILS AND ASSOCIATED INVERTEBRATE AND VERTEBRATE TRACES IN STORM-WASHOVER FANS, ST. CATHERINES ISLAND, GEORGIA

In coastal environments, storm-washover fans represent transitional zones between marginal-marine and terrestrial environments that can undergo rapid ecological change. Because of their location and dynamism, trace assemblages of washover fans are quite varied and often reflect mixes of flora and fauna that ordinarily would not overlap. For example, on Georgia-coast washover fans, insects, fiddler crabs, mud snails, wading birds, shorebirds, deer, raccoons, feral hogs, and alligators regularly share these spaces. Additionally, on the Georgia barrier islands, habitual movements of raccoons (Procyon lotor) form trails, which are the most visually prominent traces crossing fans. These trails, which are 25-30 cm wide and tens of meters long, often branch and otherwise connect with one another, forming clear pathways that originate in the maritime forest and often trend north-south, following the shoreline. To better define these traces, we conducted a study of them on St. Catherines Island, Georgia, an undeveloped island with well-developed washover fans. We found that mapping trails with a handheld GPS unit and marking predation traces with waypoints effectively documented raccoon presence and behaviors on washover fans. Berm to marsh transects with quadrat sampling were used to document traces of raccoons and other animals. Deer, hog, alligator, fiddler crab, ghost crab, and traces of multiple species of insect and birds were identified in the transects. Multiple trackways across washover fans frequently joined at one or two primary trails through dense regions of Spartina alterniflora and Juncus roemerianus. Trails crossing washover fans are often associated with food acquisition, especially predation on fiddler crabs (Uca pugnax and U. pugilator), which range from 2-30 burrows/m². Data from field surveys were imported into ArcGIS to create digital maps of trails and other traces. Amazingly, some of the raccoon trails are also visible on Google Earth images, thus GIS mapping provided a way to “groundtruth” these landscape-altering traces. For paleoichnologists, we expect that such mapping may provide a model for better interpreting bedding-plane exposures of ancient storm-washover fans.