Distribution and Social Structure of an Estuarine Bottlenose Dolphin (Tursiops truncatus) Population in Northern South Carolina
Date of Award
Master of Science in Coastal Marine and Wetland Studies
Coastal and Marine Systems Science
Robert F. Young
Christopher E. Hill
Jenna C. Hill
Information regarding habitat preference of apex predators may pinpoint areas dense in resources such as prey species. Knowledge of how animals use their habitat can enable the classification and targeted management of important habitat features. This study was conducted to determine the distribution and social structure of an inshore population of bottlenose dolphins within the North Inlet-Winyah Bay estuary in northern South Carolina. Photo-identification surveys were conducted along defined transect routes. Home ranges of individual dolphins were calculated using the minimum convex polygon method and the fixed kernel density method using Geographic Information System (GIS) software. Mean group sizes and coefficients of association were compared between warm and cold seasons. Coefficients of association were calculated using the half weight index. Additionally, these same social parameters were compared between dolphins using only North Inlet, those using only Winyah Bay, and those using both systems. Surveys were performed during the warm months (221 hours of survey time from May through October) and during the cold season (52 hours of survey time from December through February). The 2011-2012 population estimate for the North Inlet-Wnyah Bay population was 84, and fewer dolphins were present in the North Inlet-Winyah Bay estuary during the cold months than during the warm months. The majority of the dolphins in this study used both North Inlet and Winyah Bay. However, three individuals were sighted only in North Inlet, and 38 individuals were sighted only in Winyah Bay. Group sizes were larger in the warm season than the cold season. Dolphins that had at least 10 independent sightings associated non-randomly, and individuals in the population formed distinct communities with overlapping ranges. The mean coefficient of association was 0.24 for all dolphins with at least 10 sightings, and the associations were weaker than in most other studied populations. However, when determining mean coefficients of association within North Inlet transects (0.48) and Winyah Bay transects (0.34), the associations were similar those observed in other studies. The mean home range was 32.79 km². Home ranges were larger in the warm season than the cold season. While the kernel density method, compared to the Minimum Convex Polygon method, seems to more accurately estimate the home range of dolphins in open water systems, the small creeks in North Inlet coupled with the clipping feature in ArcGIS make the minimum convex polygon method just as accurate because dolphins had limited travel routes within the creeks.
Brusa, Jamie L., "Distribution and Social Structure of an Estuarine Bottlenose Dolphin (Tursiops truncatus) Population in Northern South Carolina" (2012). Electronic Theses and Dissertations. 4.