By Leslie Macdonald, Jaime Warnock and Jaime Davis

The behavior, location, migration routes, and conservation of the Florida Manatee are aspects discussed in our presentation.

The first topic is the manatee’s behavior, which includes their daily activity, their social behavior, and their behavior when it comes to human interaction. During the day, they feed, rest, travel, and play. Manatees are herbivores who eat a wide variety of submerged, emergent, floating, and bank vegetation. When in salt water, they eat several species of sea grass including shoal, manatee, and turtle grasses. In fresh water they have more of a variety of plants to eat such as hydrilla, algae, and water hyacinth. They have also been known to haul themselves out of the water to eat bank vegetation and overhanging vegetation (Diet and Eating 1999).

Manatees have been observed participating in seemingly playful activities such as body surfing and follow the leader. Body surfing involves a group of manatees riding powerful currents generated by floodgates partially open. This is a very social time for them, and they do a lot of vocalizing and nuzzling. Follow the leader is when two or more manatees swim in a single file line while synchronizing their movements such as changing direction, breathing, and diving. They take turns being the leader so there does not seem to be a dominant leader (Manatee Behavior 1999).

Manatees are semi social, and their basic unit consists of the mother and calf. The calf depends on the mother for many things, including feeding, resting areas and travel routes. When the mother and calf travel together, they swim parallel to each other. For the calf, this may make swimming or communication with its mother easier (Reynolds and Odell 1991).

Manatees congregate during the coldest winter months, from December to February, at various power plants in Florida. This helps to keep them warm and is one of the few times they are seen in a big group (Reynolds 1992).

As far as manatee’s behavior with humans go, they do not attack when humans get close to their calves. Instead, they swim in between the calf and human to create space between them. They seem to like attention from people snorkeling with them. They will even turn on their backs to get their stomachs scratched. Crystal River is a well known spot for human interaction with manatees. Since people get attached to them quickly they have made certain rules to protect manatees. They can not be touched with both hands because it is considered riding. People are also not allowed to chase them, but must wait for the manatee to come to them (Motavalli 1997).

The West Indian manatee has many rivers where they live and migrate to. Crystal River on the gulf coast is the northern limit of their winter range. Manatees have also been seen in St. John’s River. They congregate in the natural warm water springs of Blue Spring State Park. Indian River lagoon is another place for manatees to inhabit because it is a major feeding area for them. They prefer areas that are rich in vegetation such as seagrass. The Florida manatee can inhabit rivers, bays, canals, and estuaries. They can also live in freshwater, saline, or brackish water and move freely within these extremes. The Florida manatee prefers water above 70 degrees F. These marine mammals stay in water over a meter deep and connected to the coast. They rarely venture into deep waters; however, there have been reports of some manatees seen in deep waters as far as the Dry Tortugas Islands which are 50 miles west of Key West, Florida (Manatees 1998).

The Florida manatees are tropical animals at the northern limit of their range which have adapted to the chill and even occasional frost of winter. The Florida manatee’s primary range extends from the St. Johns River in Northeast Florida, southward to the Miami area. Florida manatees have been seen as far north as Virginia and as far west as Mississippi (Reynolds and Odell 1991). To escape the colder water temperatures of winter, manatees migrate up rivers to springs where water stays a constant 72 degrees F (Wiley 1987). Important winter destinations are Crystal River, Sebastian River, Blue Spring State Park, Banana River at Cape Canaveral and various power plants along the coast of Florida (Ackerman 1995).

Crystal River’s manatee population has increased in winter, as well as all year round, from 38 in 1967-1968 to 292 manatees in 1992-1993. The reasons for this increase are probably due to reproduction and survival of resident manatees. Also, permanent immigration from areas further south and recruitment of their descendants have impacted Crystal River’s population. Crystal River is a very popular aggregation site because unlike other aggregation sites, it contains abundant food supplies. This is partly due to the introduction of exotic aquatic vegetation into Crystal River during the mid 1960’s (Ackerman 1995).

St. John’s River in Blue Spring State Park has also shown an upward trend in manatee population from 11 in 1970-1971 to 88 in 1993-1994. The reasons for increase are similar to the Crystal River area such as reproduction and survival of resident manatees and permanent immigration of adults (Ackerman 1995). In the Blue Spring area, there is a high rate of adult survival. This is probably due to increasing protection from direct injury and disturbance from boats, swimmers and divers (Langtimm et al. 1998).

High counts of manatees in the Banana River during the Spring reflect a temporary influx of manatees in transit during their Spring migration. No other area on the Eastern coast offers as much protected habitat as the northern Banana River. This area of the river is located inside the Kennedy Space Center and is closed to boating. In 1990, this part of the Banana River was completely closed for manatee protection, keeping human disturbance to a minimum in this area (Ackerman 1995).

Many power plants have also been important winter aggregation sites for Florida manatees. These artificial heated sources have allowed manatees to remain north of their historic wintering sites. More than 200 manatees congregate at some of these power plant outfalls. The most important of the power plants are located at Cape Canaveral, Riviera Beach, Fort Lauderdale, Port Everglades, Fort Myers, and Tampa Bay (Manatees 1998). The Tampa Bay area has become increasingly more populated since 1986 when a small no entry zone was created at Tampa Electric Company’s Big Bend plant. Then in 1989, the zone was expanded through the entire canal. Due to this expansion, disturbance from boats has been greatly reduced, and the documented number of deaths in the Tampa Bay area is low compared to other aggregation sites (Ackerman 1995).

Some of these aggregation sites are in higher risk areas for manatees than others. The Northeast area of Florida has the highest death percentage at 40 % from 1974-1992. The majority of the deaths are caused by human disturbance and direct injuries from boats. The lowest death percentage, at 9% from 1974 to 1992, occurred in the Northwest area of Florida, which indicates that the Crystal River area is one of the safest places for manatees to live. There is a very low number of deaths due to boating injuries and other human disturbances (Ackerman et al. 1995).

There are between 2,600 to 3,000 West Indian manatees left in the U.S. Florida manatees can live about 50 to 60 years. Human related mortalities are some of the main reasons manatees die at an early age. There was a study done on manatees between 1976 and 1992. They found that the largest number of natural deaths was in the Southwest. About 90 manatees died of natural causes in the Southwest between 1976 and 1992. Manatees also have problems surviving in the cold weather. In the Northeast, between 1976 and 1992, 68 manatees died of cold-related reasons. The most compelling evidence of human related mortalities are boat related accidents. Between 1976 and 1992, 203 Florida manatees were killed in boat related accidents. They are usually killed by the propellers or the hulls of speed boats. Manatees can also be killed by partially opened floodgates. In the Southeast, 59 manatees were killed this way between 1976 and 1992. They can drown in the water current from the upstream flow or they are simply crushed by the flood gates. They can also be crushed by navigation locks. Manatees are also victims of poaching and vandalism. This can be for food or just harassment. Accidental entanglement is another cause of death for the Florida manatee. They can get tangled in fishing lines which cuts off their circulation and causes infection. Habitat destruction is one of the largest causes of death for manatees. Because the population of Florida has grown so dramatically for the past 50 years, much of the seagrass beds and salt marshes have been destroyed (Manatees 1998).

The Marine Mammal Protection Act of 1972 protects the West Indian manatee. It states that it is illegal to kill, injure, or capture any marine mammal. Considering that the Florida manatee is an endangered species, they are protected under the Endangered Species Act of 1973. This states that it is unlawful to harass, hunt, capture, or kill a marine mammal. The Florida Manatee Sanctuary Act of 1978 states that it is illegal to annoy, molest, harass, or disturb a marine mammal. The Manatee Recovery Plan sets a list of goals geared toward recovering manatees from their current endangered status (The Manatee 1996-97).

Ackerman, Bruce B. 1995. Aerial surveys of manatees: A summary and progress report. In: O’Shea, T.J., B.B. Ackerman, F.H. Percival, editors. Population biology of the Florida manatee. Washington D.C.: U.S. Department of the Interior: National Biological Service. p 13-27.

Ackerman, B.B., S.D. Wright, R.K. Bonde, D.K. Odell, and D.J. Banowetz. 1995. Trends and patterns in mortality of manatees in Florida, 1974-1992. In: O’Shea, T.J., B.B. Ackerman, F.H. Percival, editors. Population biology of the Florida manatee. Washington D.C.: U.S. Department of the Interior: National Biological Service. p 223-241.

Langtimm, C.A., T.J. O’Shea, R. Pradel, and C.A. Beck. 1998. Estimates of annual survival probabilities for adult Florida manatees (Trichecus manatus latirostris). Ecology 79: (3) 981-998.

"Manatees" 1998. http://www.seaworld.org/manatee/manatees.html

"Manatees: diet and eating habits" and "Manatees: Behavior." http://www.seaworld.org/manatee/dietman.html

Motavalli, Jim. "Manatee mania: is Florida loving its endangered animals to death?" Earth Action Network March-April 1997: 46-48.

Reynolds, JE. Manatees and Powerplants March 1992: 163-177.

Reynolds, J.E., and D.K. Odell. 1991. Manatees and Dugongs. N.Y.: Facts on File. 56 p.

"The Manatee" 1996-97. http://www.geocities.com/Heartland/5960/manatee.html

Wiley, J.P. 1987. Manatees, like their siren namesakes, lure us to the deep. Smithsonian 18: 92-98.

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