OCEAN LECTURE SERIES

"The Mystery of Marine Mammal Strandings: Why do Whales, Dolphins, and Arctic Seals Turn up on Florida's Beaches?"
• Gregory D. Bossart, Ph.D.

About the Lecture

The mystery of stranded marine mammals has intrigued humans since the ancient Greeks first recorded these events. Strandings may be small-scale events involving single animals, or larger-scale events involving dozens of animals, which are termed mass strandings. Strandings may be routine, caused by commonly seen injuries or diseases, or they may be extraordinary, caused by complex or unknown factors sometimes termed unusual mortality events. We are learning more about strandings and can explain the cause of many of these events. However, the cause of some strandings continues to remain elusive.

Over the last decade in the United States, approximately 40,000 stranded marine mammals have been reported by regional stranding networks with an average of 3,600 strandings per year. Marine mammal strandings are common along the Florida coast and typically involve various dolphin and whale species. Singular strandings are the most common in Florida with a few notable mass strandings. Research has shown that marine mammals may strand for a variety of reasons including human-related factors such as entanglement in fishing gear or marine debris, ingestion of plastics, or boat strikes; injuries caused by sharks or other natural predators; illness or disease; natural or anthropogenic toxins in the environment; premature separation of neonates from their mothers; and environmental and oceanographic events which cause changes in distribution and abundance of marine mammal prey, thereby leading to starvation. It's been more challenging, however, to determine the causes of many recent Florida mass strandings, which sometimes involved dozens of seemingly healthy animals. One theory is that the strong social bonds forged by some species result in healthy animals following a sick leader or parent into shore. Other theories involve animals that may be disabled by a growing burden of chemical pollutants found in their tissues. Most scientists are skeptical, however, about another theory, which describes beached marine mammals as suicidal.

Marine mammals have a great deal to tell us about the health of our oceans and are probably one of the best sentinel organisms for ocean health. Additionally, marine mammals are conspicuous and charismatic megafauna that elicit strong human emotions and are thus more likely to be observed. As such, health maladies that impact these species may make humans more likely to pay attention to deteriorating ocean health issues. Therefore, it is in our own best interest to determine what marine mammals may be telling us about their own health that could potentially impact our own well being. Stranded marine mammals may be the ultimate messengers of this vital information. This presentation discusses unique case histories and possible causes of stranded marine mammals along the central Atlantic Florida coastline that have been handled by the marine mammal staff at Harbor Branch.

About the Speaker

Dr. Gregory D. Bossart has spent the past 28 years working in marine mammal and avian medicine and wildlife pathology. He has over 70 publications focused primarily on the pathological basis of disease in wild animals. Dr. Bossart received his doctorate in veterinary medicine from the University of Pennsylvania in 1978 and completed an NIH fellowship in comparative pathology from the University of Miami School of Medicine in 1986. He completed a Ph.D. in comparative immunology from Florida International University in 1995. He has worked at Harbor Branch since 2000 and is currently Senior Science in the Marine Mammal Research and Conservation program. Dr. Bossart has been in private veterinary practice and presently is a clinical veterinary consultant and conducts conservation outreach programs in Brazil, Mexico, Columbia, Belize, and Guyana.