Protecting Manatee Habitats

Surveying Secondary Springs in North-Central Florida:
Identifying and Protecting the Thermal Network

Limitations on the range of the endangered Florida manatee, Trichechus manatus latirostris, are largely determined by water temperature. Manatees can die of cold stress if they are exposed to moderately cold water temperatures for an extended period of time or from short-term exposure to extremely cold temperatures. They have learned to utilize man-made warm water sources, such as power plant outfalls, where the abundance of warm water sustains them throughout the winter. This use of possibly unreliable man-made warm water sources has the potential to cause problems for the manatee population in the future. As power plants get older and new technologies are established, the availability of warm water sites will most likely be reduced. This could have a substantial effect on the manatee population.

The other warm water sources available to manatees in Florida are the unique natural springs that maintain water temperatures averaging 70°F in north Florida and 75° F in central Florida. Manatee reliance on springs for warm water will likely increase over time as man-made refugia become less prevalent. Springs throughout Florida are threatened by the ever-increasing human population. Increased water usage and extensive land use changes negatively impact springs by reducing flow discharge and negatively impacting water quality. Protection of springs is necessary to maintain water quality and to protect species that rely on spring systems, including the Florida manatee. Monitoring of manatee use of springs throughout Florida is a high priority within the U.S. Fish and Wildlife Service manatee recovery plan. Understanding current and future habitat needs of the Florida manatee population is critical to survival. Wildlife Trust has been conducting monitoring of manatee use of Crystal River and Homosassa Springs, FL since 2004, in collaboration with and through funding by the U.S. Geological Survey - Sirenia Project. This year, we will also be monitoring manatee use of secondary springs in central Florida as they slowly become more important habitat for manatees.  These secondary springs have never been monitored on a regular basis due to a lack of funding, but based on public sightings from citizens it is suspected that increased numbers of manatees are utilizing these increasingly important habitats. Until scientific documentation of this increase in use is obtained, it will be difficult to enact adequate protection for these invaluable habitats. We plan to expand our coverage to secondary springs throughout the region including springs in the St. Johns River system, Weeki Wachee Springs (Hernando County), and Sulphur Springs (Hillsborough County). Systematic documentation of manatee use of these critical winter habitats will provide ecosystem managers with the information they need to provide further protection for these unique spring habitats.

Funder: Jane's Trust; Partner: U.S. Geological Survey, Sea to Shore Alliance

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