GIS Mapping of Raccoon (Procyon lotor) Trails and Associated Invertebrate and Vertebrate Traces in Storm-washover Fans, St. Catherines Island, Georgia Público

Abstract

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 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, I studied them on St. Catherines Island, Georgia, an undeveloped island with well-developed washover fans. I found that mapping trails with a handheld GPS unit and marking predation traces with waypoints was an effective method for documenting 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 multiple species of insect and bird traces 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 1-45 burrows/m² in density. Data from field surveys were imported into ESRI's ArcGIS to create maps of trails and other traces. Some of the raccoon trails are also visible on Google Earth images, thus GIS mapping provided a way to "groundtruth" these macroscopic traces. For paleoichnologists, such mapping may provide a model for interpreting bedding-plane exposures of ancient storm-washover fans.

Table of Contents

Table of Contents

INTRODUCTION 1

METHODS 5

RESULTS 8 DISCUSSION 19 CONCLUSIONS 22 REFERENCES 24 FIGURES AND TABLES

FIGURE 1. STUDY SITE LOCATION, ST. CATHERINES ISLAND 1

FIGURE 2. TRACES OF AN ALLIGATOR, RACCOON, AND SAND FIDDLER CRAB 2

FIGURE 3. DIFFERENCES IN RACCOON TRACK PRESERVATION 4

FIGURE 4. RACCOON TRAIL CUTTING THROUGH VEGETATION 7

TABLE 1. FREQUENCY OF SPECIES APPEARANCE IN SAMPLED QUADRATS 8

FIGURE 5. MAP OF RACCOON TRAILS ON LiDAR 10

FIGURE 6. MAP OF SAMPLED TRANSECTS ON LiDAR 10

FIGURE 7. MAP OF WAYPOINTS CONTAINING WRACK 11

FIGURE 8. MAP OF WAYPOINTS CONTAINING FIDDLER CRABS 11

TABLE 2. DESCRIPTIVE STATISTICS OF FIDDLER CRAB BURROW 12

TABLE 3. PEARSON'S CORRELATION CO-EFFICIENTS AND P-VALUES 13

FIGURE 9. MAP OF RACCOON AND FIDDLER CRAB OVERLAP 14

FIGURE 10. MAP OF HOG AND FIDDLER CRAB OVERLAP 14

FIGURE 11. MAP OF RACCOON AND GHOST CRAB OVERLAP 15

FIGURE 12. MAP OF HOG AND GHOST CRAB OVERLAP 15

FIGURE 13. MAP OF BIRD TRACKS 16

FIGURE 14. MAP OF ALLIGATOR TRACKS 17

FIGURE 15. TRAILS OVERLAIN ON SATELLITE IMAGE 18

FIGURE 16. TRAILS DRAWN ON SATELLITE IMAGE 18

FIGURE 17. TRAILS OVERLAIN ON 2010 SATELLITE IMAGE 22

About this Honors Thesis

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School	Emory College
Department	Environmental Studies
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Environmental Sciences Paleoecology
Palabra Clave	Ichnology Raccoons
Committee Chair / Thesis Advisor	Martin, Anthony, Emory University
Committee Members	Henderson, Stephen W, Emory University Page, Michael, Emory University

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