U.S. Fish & Wildlife Service
Southeast Region News Release

FOR IMMEDIATE RELEASE                        Diana M. Hawkins

April 30, 1996                                    or Vicki M.




The cause of the killer disease that since March 1996 has claimed the lives of more than 150 of Florida's endangered manatees has so far eluded a special national team of experts of wildlife biologists and other marine mammal experts.

In search of a diagnosis, many collaborators from federal, state and private organizations have been assisting Florida Marine Research Institute scientists with the ongoing investigation by testing the hypotheses most likely to explain the record-breaking number of manatee deaths over the past 6 weeks.

Since January 1, 1996, more than 255 manatees have been found dead in Florida's waters. Some 155 of these deaths, however, have inexplicably occurred in Southwest Florida since March 5, 1996, and recent analyses of blood and tissues are providing clues, but have so far failed to determine conclusively the actual cause of death. The February 1996 U.S. manatee population count turned up at least 2,639. This shows that approximately 9.6 percent of U.S. manatees have perished in the first 4 months of this year, a significant loss.

Experts are testing three different hypotheses in their search for a cause of death: 1) death caused by a biological toxin, such as that produced by a red tide; 2) death resulting from a disease caused by a virus or bacterium; and 3) death caused by a contaminant, such as a pesticide. It is also possible that a combination of factors is involved. Tissue samples collected from dead manatees have been sent to laboratories across the country with expertise in identifying biotoxins, infectious agents, and contaminants. None of the results received so far have been conclusive.

The Florida manatee -- whose gentleness and approachability has endeared it to millions of Floridians and visitors to the State -- is a large herbivorous marine mammal that was listed as an endangered species in 1967. Its recent high death rate was the main topic of discussion at an April 19, 1996, meeting held at the Florida Marine Research Institute in St. Petersburg, Fla. Biologists from the Florida Department of Environmental Protection, the U.S. Fish and Wildlife Service, the National Biological Service, the University of Miami, Mote Marine Laboratory, and Sea World of Florida presented findings and discussed strategies to coordinate and enhance their fact-finding mission and to determine the cause of these fatalities.

The Florida Marine Research Institute has organized an effective team approach to document this highly unusual manatee loss of life. Information has been collected on dates and locations of dead manatees, and environmental data has been gathered, including water temperature, salinity, and counts of the phytoplankton (toxic microscopic marine organisms) that cause red tide blooms, patches of red discoloration in the water caused by trillions of these tiny organisms. This information has been entered into a geographic information database so that clues to the manatee deaths can be identified and analyzed. A preliminary review of existing data has shown that there is a striking correlation between the distribution of dead manatees and sites with high phytoplankton counts; however, a definitive causal relationship between the red tide and the manatee deaths has yet to be firmly established.

A review of the Florida Marine Research Institute's red tide data for the last 20 years indicates that in only two years, 1982 and 1996, have the phytoplankton levels been high and persisted into March and April. A favorite spot for Southwest Florida manatees to spend the cold winter months is in the vicinity of the Florida Power and Light plant on the Caloosahatchee River near Fort Myers. In February 1996, more than 400 manatees were sighted congregating at this location. Typically, as the weather begins to warm in late February and early March, these manatees start to make their way back towards the Gulf of Mexico. During the first weeks of the recent die-off, this river proved to be a key area for fatalities. In 1982, however, only 37 manatee deaths were attributed to ingestion of the red tide phytoplankton, which they encountered as they migrated downriver towards the ocean.

Some live manatees, exhibiting apparent neuromuscular problems have been rescued in Southwest Florida and taken to a rehabilitation facility at Lowry Park Zoo in Tampa. The recovery of three females took several days, during which they required assistance to stay afloat to breathe. Caretakers used flotation vests to help keep the disabled manatees from drowning. A male manatee was recently rescued by State biologists and is expected to recover.

The U.S. Fish and Wildlife Service and the National Biological Service will continue to assist Florida Marine Research Institute researchers in its efforts to document and understand this tragic manatee die-off, and will identify research and management needs to prevent or reduce such events in the future.

X X X Release #96-24

1996 News Releases

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