The relationship between premortem sighting distribution and potential toxin exposure of manatees salvaged during the Brevard County, 2012-2013 Unusual Morality Event.

Brevard County is considered an important habitat for manatees ( Trichechus manatus latirostris) along the East Coast of the United States due to the presence of two power plants where many individuals congregate during the winter and as a travel corridor to winter aggregation sites during the spring and fall. July 25, 2012 marked the beginning of a sudden and unexplained increase in manatee deaths in Brevard County, which ultimately led to the classification of an Unusual Mortality Event (UME). The working hypothesis indicates that mortality is caused by the ingestion of an unknown toxin or pathogen. Identifying the source of the toxin or pathogen is critical to both understanding the impact of the UME as well as the management and response efforts. Since 1978, the U.S. Geological Survey has been using unique scar patterns to identify individual manatees and record their life histories in the Manatee Individual Photo-Identification System (MIPS) database. The goal of this study was to examine the sighting histories of carcasses previously identified in MIPS to determine if there were any associations between premortem sighting history, specifically overwintering location, and the likelihood of an animal being part of the UME. The association between overwintering location and the likelihood of being a UME animal was not significant, but the association between reproductive status and the likelihood of being a UME animal was significant. Manatees residing in Brevard County year-round may have developed a tolerance to the agent while animals that only spend part of the year in Brevard County have not, and are more at risk. This UME may also be the result of abrupt diet changes that disrupted individuals’ gut microbiota resulting in increased susceptibility to an opportunistic pathogen in Brevard County. Although the relationship between premortem sighting history and the likelihood of being a UME animal was not statistically significant, this serves as an important baseline study for continued efforts to locate and identify the source of this UME.