The Florida manatee (Trichechus manatus latirostris) is a subspecies of the West Indian manatee, a marine mammal adapted to tropical and subtropical regions. Monitoring manatee health is required under the Endangered Species Act and the Marine Mammal Act because of the animal's endangered status. Much of the northwest Florida coast is ideal manatee habitat during most of the year, but during the winter, water temperatures often go below optimal conditions for manatee survival. The constant flow of ground water discharging from the numerous springs in this coastal region provides important warm-water refuge for manatees during the winter months.Many manatees depend on this spring flow and return to Crystal River regularly. When the same individual is caught repeatedly, scientists can track its health over time, much like giving it annual physical checkups. Repeat catches provide data on vital signs and yield samples of tears, DNA, blood, urine, and feces for laboratory analysis. They also provide an opportunity to collect visual data on manatees, using such unique marks as boat scars to identify individuals. These data are incorporated into a large photo ID database used to research manatee life histories, migration patterns, and population dynamics.
Pulling an aquatic mammal that weighs more than half a ton out of the water is a carefully choreographed operation requiring teamwork and experience. Generally, manatees are captured by using rescue boats designed specifically for hauling the large animals out of the water. The annual assessments, however, are large group efforts designed to examine as many manatees as possible over a short timeframe, and so small beaches are used as examining tables. The beaches are cleared of rocks and hard objects, and commonly a rug is placed over the sand to minimize any injury and make the manatee as comfortable as possible. The beaches are exposed only at low tide, creating a short window of time for the health assessments.
"This year, we're transporting the manatees to a second beach so that we can begin netting the next manatee while the first one is being assessed," said USGS Sirenia Project biologist Bob Bonde, who leads the manatee captures. "This allows us to increase the number of manatees that we can examine."
The team sets up along a stretch of river near Three Sisters Springs within a fairly restricted area, making it easy to spot and capture manatees as they pass. A point person watches for an approaching manatee. With the help of a circling boat, the experienced capture crew nets the manatee, hauls it close to shore, transfers it onto a stretcher, and carefully transports the manatee onto the nearby beach. The highly skilled health-assessment team then conducts a detailed physical examination.
Watching the team at work, an observer can see that Bonde has built partnerships with a wide variety of veterinarians and marine-mammal medical experts. This season, Bonde created separate capture and assessment teams, with at least one veterinarian leading each manatee assessment. Capture teams included partners experienced in manatee-rescue procedures, such as the U.S. Fish and Wildlife Service (USFWS), the Florida Fish and Wildlife Conservation Commission (FWCC), and the Volusia County Manatee Watch Program. Other participants included university students involved in related research projects and staff from zoos and aquariums nationwide who provided help while learning more about assessing manatee health. DOI Assistant Secretary Lynn Scarlett and then-USGS Director Mark Myers observed some of this year's health-assessment activities.
The USFWS manages the Chassahowitzka National Wildlife Refuge, which includes various smaller refuges within Kings Bay, creating a series of protected springs and keys that stretch as far south as Tampa Bay. The Friends of Chassahowitzka National Wildlife Refuge Complex is a support organization that works with USFWS staff to keep the general public informed about ecosystem resources and policies needed to protect them.
Many residents of Florida's Nature Coast, aware that manatees give a special status to their springs, do much throughout the year to increase awareness and protect the springs for the manatees. Additionally, much of the area is part of a national wildlife refuge system encompassing the Chassahowitzka National Wildlife Refuge, the Crystal River National Wildlife Refuge, and three refuges in Tampa Bay. Within this system, specific areas designated as "manatee-only" sanctuaries create a refuge from boats and snorkelers. Unfortunately, these areas are not interconnected, and so manatees risk injury from motorboat traffic when moving from one protected area to another.
Adjacent to Three Sisters Springs is a 57-acre plot that has been filled and leveled but remains largely undeveloped. The current owners are considering selling the land, and a joint effort by State, Federal, and regional agencies and private organizations is underway to purchase the land and have it managed by the USFWS as part of the Crystal River National Wildlife Refuge. Purchase of the area would preserve the springs as an additional sanctuary as well as a public resource; plans include an educational information center and an observation area that would enable visitors to see manatees without going out into the water by boat.
DOI Assistant Secretary Lynn Scarlett visited Three Sisters Springs to recognize Felburn Foundation Executive Director Ellie Schiller on behalf of the USFWS—which, like the USGS, is a DOI agency—and the Friends of Chassahowitzka National Wildlife Refuge Complex ("Friends"). Her visit included a swim with the manatees and a chance to observe the health-assessment teams at work. Scarlett recognized Schiller for her tireless work in assisting State, Federal, and regional efforts to acquire lands for the protection of manatee habitat. Scarlett presented Schiller with a framed photograph and brief life history of "Ellie," a 30-year old manatee who had a long history of recorded sightings and was named to honor Schiller. Scarlett announced that if the land purchase is successful, the proposed interpretive center will be named in Schiller's honor. Several USGS and USFWS personnel attended the ceremony, along with many community leaders. Among the attendees were Crystal River Mayor Ron Kitchen, Jr., then-USGS Director Myers, and Friends President Lacy Blue-McLean. USGS Eastern Region Communications Chief AB Wade and Public Affairs Specialist Hannah Hamilton also participated in the event, gathering information and video footage.
Despite stormy conditions, the USGS manatee-health-assessment season was an overall success, resulting in the capture and assessment of 13 manatees. The annual assessment, now in its fourth year at Crystal River, is building on a historic USGS database that contains data from the examination of more than 300 manatees throughout the State. The assessment is a valuable tool in determining the fitness of manatees and has been used to improve the handling of wild manatees and to determine clinical standards for captive manatees. The data have overall implications for monitoring ecosystem health because many marine mammals are commonly used as sentinels for identifying emerging threats to the ocean environment and human health.
Manatee-assessment data can be used in conjunction with other USGS research to model spring and coastal ecosystem change and its effects on manatees. For example, a recent USGS threat analysis, "A Quantitative Threats Analysis for the Florida Manatee (Trichechus manatus latirostris)" modeled the potential risks that various scenarios pose to manatee populations and generated data that USFWS could use in management decisions (see "Manatee Five-Year Review"). The survival and reproduction estimates were made possible by the USGS photo ID database that tracks individual manatees.
The assessment season came to a fitting end when the research crew spotted "Ellie" again on January 12 as they were finishing up their fieldwork. The team succeeded in radiotagging her and will continue documenting the next chapter of her life history.
For additional information about USGS manatee research, see Manatee - Sirenia Project.
in this issue:
Manatee Health Assessment