MAJOR PATHOLOGIC FINDINGS AND PROBABLE CAUSES OF MORTALITY IN BOTTLENOSE DOLPHINS STRANDED IN SOUTH CAROLINA FROM 1993 TO 2006

Abstract

Although cause-of-death information on bottlenose dolphins (Tursiops truncatus) can be located in the literature, few citations include mortality data over a long period of time covering a broad geographic region. This study describes major pathologic findings and probable causes of death of bottlenose dolphins over a 14-yr period (1993-2006) for the coastal region of South Carolina. Probable causes of death for 97 cases were determined based on gross pathology and histopathology. In an additional 30 cases, probable cause of death was apparent from gross pathology alone, and carcass condition precluded histopathology. Of the 97 dolphins examined grossly and histologically, 30 (31%) likely died of infectious disease and 46 (47%) of noninfectious disease; the cause of death was unknown in 21 (22%). Bacterial infections accounted for the large majority of fatal infections and emaciation was the leading cause of noninfectious mortality. Twelve dolphins were killed by human interactions. Of the 30 dolphins diagnosed from gross examination alone, 23 likely died from human interaction and seven were killed by stingray-spine inflictions. Although the absence of consistent use of microbiology, biotoxin analysis and contaminant testing decreases the conclusiveness of the findings, this study has broad implications in establishing baseline data on causes of death of bottlenose dolphins for future studies and for the detection of emerging diseases.