Interestingly the bottlenose dolphin was given the name truncatus by Montague in 1821 in that the animal observed in the River Dart, UK, had flattened or truncated teeth which we now know was likely due to tooth wear.1 Historically observations of abnormalities in the dentition of bottlenose dolphins has been limited to tooth wear due to occlusional friction, selective loss or breakage of teeth, and patterns of wear associated with feeding habits, such as strand feeding.2
Oral examination has been a component of dolphin health assessments conducted by NOAA for nearly a decade, as the mouth is routinely opened for several sampling techniques and overall patterns are noted. As part of the Natural Resource Damage Assessment (NRDA) for the Deepwater Horizon Oil Spill in the Northern Gulf of Mexico, health assessments were conducted in 2011 in Barataria Bay, LA and Sarasota Bay, FL. An unusual finding of extensive to total loss of dentition was noted in 6/32 bottlenose dolphins captured in 2011 in Barataria Bay.2 Alveolar bone changes and tooth loss have been noted previously in postmortem studies of grey seals in the Baltic Sea3 and in beluga whales in the St. Lawrence River,4 both populations having known exposures to chemical contaminants.
As further assessments under the NRDA, additional health assessments were conducted in 2013 comparing dolphins from two sites in the Northern Gulf (Barataria Bay, LA and Mississippi Sound off Alabama and Mississippi) and dolphins in Sarasota Bay, Florida. This study was undertaken to evaluate the unusual oral findings through intraoral radiography that is standard practice in both human and companion animal veterinary medicine. This is the first time that an extensive radiographic survey of dentition, wear and tooth loss in free-ranging bottlenose dolphins has been conducted.
There were 67 dolphins representing a wide range of age classes restrained and examined as part of this study. Dental radiographs of 57 dolphins were captured from the three locations: 16 dolphins in Sarasota Bay Florida, 31 in Barataria Bay, Louisiana, and 20 in the Mississippi Sound, Mississippi/Alabama. In the 2013 study only 1 of 31 dolphins captured in Barataria Bay presented with extensive tooth loss. The total number of dolphins in which extensive tooth loss was observed in Barataria Bay in the 2011 and 2013 was 7, but radiography was only performed on the one affected dolphin in 2013. Field radiography demonstrated that only a few tooth root remnants remained and retention of the unerupted teeth in the rostral maxilla and mandibles of the one animal with complete tooth loss. Qualitative boney changes were also noted in this animal representing a potential loss of bone density and expansion of alveolar bone that may be associated with the tooth loss process. Through radiography, this study also observed changes that may represent earlier stages of this tooth loss pathology. The entire study demonstrated the utilization of more complete dental examination for use in the field in wild dolphin evaluations.
The authors would like to thank the entire team of the 2013 NOAA Health Assessments, who without their coordination of effort and handling of the animals both in and out of the water this work would not have been possible. Jay Sweeney for his valuable lessons in oral handling, Erica Gebhard for technical assistance, data recording and radiologic film processing, Veronica Cendejas for veterinary technical assistance and Todd Speakman for photography.
* Presenting author
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