Daniel H. Slone, Bradley M. Stith and James P. Reid
USGS Florida Integrated Science Center, Gainesville, FL, USA

Everglades National Park (ENP) provides habitat for a substantial population of manatees. We compiled and standardized into GIS existing datasets on manatees within and around Everglades National Park, including aerial surveys, remote telemetry data, and carcass recovery data. We analyzed and summarized these datasets to describe how manatees make use of the waters of ENP, and to assist park managers with the ENP General Management Plan. The relative importance of different areas to manatees was highlighted, and qualitative evaluations were made on how these areas might be affected by ecosystem management, park operations and management, and park visitor use.

Aerial survey and telemetry data show that throughout the year, manatees are present within most accessible waters in ENP. During the winter and spring, manatee distribution is shifted inland, likely for thermal refuge in winter and to access freshwater in the dry spring. During the summer and fall, temperatures are warmer and freshwater is more available, and their distribution is shifted more towards offshore areas for feeding in shallow seagrass beds offshore.

Manatees in this region of Florida may be very vulnerable to cold stress, especially during severe winters, due to the absence of significant springs or warm water effluent. Large numbers of manatees overwinter in ENP, but they are scattered across the landscape in smaller aggregations. The potential exists for boaters or even canoeists to disturb manatees that are thermo regulating in these small winter aggregation sites, so temporary seasonal sanctuaries where entry by any vessel is prohibited during the winter may be appropriate.

Special areas of concern were identified where manatees may be more vulnerable to boat strikes. These areas include offshore seagrass beds, where the water is shallow and boat speeds may be high, such as the Chokoloskee region, where boat density is high, and the watercraft mortality rate is also high. Also of concern are shallow inshore rivers, where manatees make frequent movements to access freshwater. These channels are narrow, and the animals have little space to escape approaching watercraft.

There are several areas where improved data collection would enhance our understanding on manatee habitat use and potential conflict areas within the Everglades region, including remote tracking, especially with GPS satellite-linked technology, locations and characteristics of warm water sites and manatee use patterns of these sites, new aerial survey methodologies to compensate for availability and observation biases, photo-identification data needed to estimate vital rates for this region, current information on boat usage, and how restoration efforts in ENP may impact manatees.

Contact Information: Daniel H. Slone, USGS Florida Integrated Science Center, 2201 NW 40th Terrace, Gainesville, FL 32605 USA, Phone: 352-264-3551, Fax: 352-374-8080, Email: dslone@usgs.gov

(This abstract is from the 2006 Greater Everglades Ecosystem Restoration Conference.)

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