By: Selena Kupfner, Lisa Edge, and Alicia Holmes

Manatees migrate both seasonally and non-seasonally. They migrate seasonally because of the air temperature and non-seasonally due to their exploratory drive. When the temperature starts to drop to about 68 degrees the manatees start to move because they can not survive in temperatures less than 68 degrees because of their low metabolic rate (Stewart 1999). In the winter months (November-March), manatees travel to warmer waters mainly in Citrus County, Florida. The temperature around Crystal River, Florida in Citrus County remains a constant 72 degrees Fahrenheit year round. Approximately 300 of the estimated 2500 manatees in the US live around the warm spring fed Crystal River in the winter (Hockman 1997). In the summer months, manatees wander aimlessly up and down the coast exploring and feeding along the way. There is no real pattern to their migration, it is very unpredictable (Hartman 1979). Most never travel above the Carolinas; however, every year there are a few exceptions. Chessie is a manatee that traveled all the way to Chesapeake Bay and had to be airlifted home to Florida. If Chessie tried to go back on his own he would have surely died from pneumonia (Stewart 1999).

Most manatees migrate up and down the Florida West Coast, but some do travel along the East Coast in the summer. Trichechus manatus has also been seen around selected power plants in the winter. They have been seen around five Florida Power and Light Company plants. The artificial warm waters are drawing some manatees further north in the winter, which does pose a problem if they decide to travel back down after temperatures have dropped (Reynolds 1994).

Manatees navigate by means of submarine landmarks, currents, salinity, and thermal gradients. They move at about 2-6 miles per hour cruising (Stewart 1999). They prefer low turbidity waters of temperatures above 68 degrees, and they prefer mostly freshwater. Off of shallow, low energy coastlines, manatees remain well away from the shore. Off of high-energy coastlines, they remain right outside the breakers (50-100 m). In waterways they migrate via channels dredged for boats, which leads to many deaths. They also tend to circumnavigate around the jetties. Low tides keep them from going into certain channels, so they prefer high tide where they can get closer to shore for better vegetation. When migrating manatees stay mostly in saltwater but visit freshwater areas for feeding and resting. They seem to move from one river to the next, much like cows moving from one field to the next. Some of the main residential areas of the manatees in Florida are the mouth of the Suwannee River, the spring fed rivers of Citrus County, and the Little Manatee and Manatee Rivers. (Hartman 1979)

Manatees are found inn tropical or subtropical regions. Within the United States they are confined to peninsular Florida and the coast of Georgia (1993). Manatees inhabit both freshwater and saltwater between 1.5 m and 1.6 m deep (1993). The depth at which they are found is determined by vegetation growth (Hartman 1979). Event though manatees can live in saltwater habitats they prefer salinity levels of <25 ppt (Hartman 1979). Manatees inhabit bays, estuaries, rivers, and coastal areas. The following are critical habitats in Florida: King’s Bay at Crystal River, St. Johns River, and Homosassa River (1993). The Indian River Lagoon is an important feeding area. Manatees are also found in waters of the Everglades National Park up to the Suwannee River along the Gulf Coast (Reynolds 1952). In the past the winter range of the manatees was thought to be south of the Sebastian River, but recently they have been found in Cape Canaveral, Fort Lauderdale, Port Everglades, Riviera and Fort Myers, and Tampa Electric Company’s Apolla Beach plant in Tampa Bay ( Hartman 1979).

Manatees can mate at the surface or underwater in a variety of positions (Reynolds 1952). Estrous females are often found in water <1 m deep. It is believed that the females seek shallow water to escape from the males (Hartman 1979). Pregnant females seek quiet sheltered backwater in which to give birth (Reynolds 1952).

Manatees are herbivores; however, their protein intake is supplemented by the invertebrates that live in the grasses and algae they feed on (http://www.xtalwind.net/). Manatees feed on the bottom, at the surface, in the middle of the water column, and on overhanging and bank vegetation (Hartman 1979). Manatees are actually known to haul themselves out of the water to get vegetation. Manatees feed in any accessible area depending on plant growth. Shallow grass beds with access to deep channels are preferred feeding areas (1996). They are generally selective on what they feed on. It is not unusual for an individual to return to the same location repeatedly until the food source is depleted (Hartman 1979). There is evidence that manatees time their movements to coincide with the availability of food For example, during the rainy season in southern Florida, manatees move up the canals to the flood control dams to feed on water hyacinth and the other vegetation pouring through the gates (Hartman 1979). Manatees use their bilobed lips and flippers to manipulate food (http://www.manateeworld.net/). Their right and left lips can operate somewhat independently of each other, which help in the manipulation process. Manatees also use their front pads to break apart vegetation into smaller pieces (Hartman 1979). During these sessions the animal concentrates on one particular species of plant; however, manatees are known to feed on up to sixty different species. Manatees consume approximately 4-9% of their body weight a day depending on the season (http://bluegoose.arw.r9.fws.gov/). Consumption is at its greatest rate right before winter. Manatees eat a variety of freshwater and saltwater grasses. Some freshwater grasses commonly consumed are Hydrilla verticillata, water hyacinth, alligator weed, and some species of algae (Hartman 1979). Saltwater grasses include, turtle grass (Thalassia testudinum), manatee grass (Syringodiium filiform), and shoal grass (Halodule wrightrii). Manatees do however, avoid blue-green algae because of its natural toxins (Hartman 1979).

The estrous herd is the only other close association of manatees except the family unit, which consists of the cow and the calf. The courting bulls will remain with the cow for a week to more than a month. There can be seventeen courting bulls around a female at one time. The bull only follows the female while she is moving. The courting bulls mouth and embrace the back of the cow, ride her when she surfaces, and roll upside down in an effort to approach her abdomen (Hartman 1979). In turn, the cows seek out the shallow waters where it is difficult for the bull to approach her abdomen.

The main cause of male aggression between manatees is to get close to a cow. As the bulls are turning to embrace a cow, they collide with one another, which is followed by squeaks and groans. The frequency of collisions increased when the sexual peak heightened. The clashes between the manatee bulls are short and don't occur very often.

The social interactions outside the estrous herd are casual and brief. Cows that are trying to get away from bulls would tear through the vegetation and plunge into the mud. The bulls appear to have very strong sexual appetites and spend a lot of their time courting cows.

It is said that manatees exhibit homosexuality. They do this in response of being pushed away by the females. They embrace one another from side to side or head to tail. The bulls were also seen to mouth and kiss one another at the surface. This is seen in the wild as well in captivity.

Manatees are considered mildly social mammals. The manatee is considered fully independent and generally spends its time alone. Manatee sightings of individuals alone was 53% of the time, 17% in groups of two, 13% in groups of three, and 6% were in groups of four (Hartman 1979). Recent data suggests that manatees are now more often seen in groups of two or more than single manatees. The cow and calf is what comprises the family unit. The bulls show to be more actively social than cows. Manatees while traveling from place to place do not even swim with one another. Researchers believe that manatees do not assist distressed or wounded individuals. In groups at Crystal River, there was no evidence of communal defense or mutual aid (Hartman 1979). The aggression between manatees was confined to collisions between bulls chasing females. Manatees enjoy going to rubbing stations where they rub their bodies against the rocks. At these stations, the juveniles usually move for the adults. There appears to be no territoriality between the manatees.

Manatees have comfort activities such as stretching, scratching, mouth cleaning, rooting, and sneezing. The stretching sessions usually interrupt the manatee's resting. They usually arch their backs convexly then concavely (Hartman 1979). They bring their flippers and chin down into their chest. The stretching is accompanied by the manatee groaning.

Manatees use their flippers to scratch. They are confined to the chest, ventral neck and head regions (Hartman 1979). To scratch other areas, the manatees go to rubbing stations. They slam into and roll around on the rocks. The manatees will also rub up against anchors and anchor ropes. They also rub on logs in the water.

Manatees also use their flippers to clean their mouths. The manatee opens its mouth, wrinkles back its nose, and inverts the lobes of its upper lip to free particles of vegetation stuck in its mouth. Manatees root in which they take in water and sand and appear to chew it and then spit it back out. Researchers are not sure why they do this. They think it may be either for cleaning their mouths or just for pleasure. They also believe that the sand ingested may give them needed minerals.

It is also believed that manatees do sneeze. It has been seen that the manatee opens its mouth and lets out a mass of bubbles from its nostrils. They surface at once after doing this.

The manatees have two resting positions. They hang suspended near the surface or lie on the bottom of the river. Their eyes are normally closed while they are resting. They sometimes roll with their chest and flippers out of the water. They have to move their tail and flippers to keep their balance. They usually rest in waters 1 to 3 meters but sometimes deeper.

Play is seen in manatees when they slide along the bottom on their bellies, then roll on their backs skimming the sand and plunging, tumbling and barrel rolling through the water. The play normally occurs when the animals were fully fed and rested.

The mother-young interaction is one that is seen a lot. The cow seeks the safety and shelter of backwater to give birth and nurses her calf for a couple of days. Once the calf is born, she pushes it to the surface to start its rhythm of breathing. The cow and calf remain together for one to two years. While the mother rests, the calf leaves her side to explore, feed or rest alone. The calves would also play with others. The cow would answer right away if her calf screamed.

The manatees do not really react when they encounter other animals. They pass dolphins and otters while they are swimming and do nothing to interact. They would only react when they picked on by large fish, but not small ones.

Manatees do have interest in things such as bottles and plastics on the bottom. They take rocks and such and grind it with their teeth. They transport glass, plastic, rubber and other foreign objects from one place to another.

Hartman, DS. 1979. Ecology and behavior of the manatee (Trichechus manatus). cornell University, New York.

Hockman, F. 1997. Manatee madness (swimming with manatees is a tourist attraction in Citrus County, Florida). Insight on the News, 13: 45.

Manatee recovery plan: trophic relationships and reproduction. 1996. http://bluegoose.arw.r9.fws.gov/NWRFiles…als/FLManateePopDemgraphy.html

Reynolds, JE. 1994. Observations of Florida manatees (Trichechus manatus latirostris) around selected power plants in winter. Marine Mammal Science, 10: 163-177.

Reynolds, JE and Odell, DK. 1952. Manatees and dugongs. Library in Congress, New York: 35-38.

Stewart, D. 1999. Making sense of manatees. National Wildlife, p 1-5.

The trouble with manatees. http://www.xtalwind.net/~cfa/2anatomy.htm

The trouble with manatees. http://www.xtalwind.net/~cfa/3habitat.htm

West Indian manatee (Trichechus manatus). 1993. Endangered and Threatened Species of the Southeastern United States (The Red Book) FWS. http://www.fws.gov/r9endspp/i/a/saa0c.html

The wonderful world of the manatee. http://www.manateeworld.net/descrip1.htm