Manatee

Organisms / Vertebrates / Mammals

Trichechus manatus

Tampa Electric, Apollo Beach (Manatee Viewing Area)

March 14, 2008

Photograph Needed

Descriptive Information

Field Marks: Manatees are splotchy grayish black in color, and they are known for floating face down with their backs barely skimming the surface of the water. Their backs are often covered in deep scars from boat propellers whose drivers do not see them. At capture Manatees come to be identified by their unique scar patterns that appear white against their dark skin. They have rounded blunt snouts with two circular little nostrils. Their tale is flat and appears to be a flat fan configuration.
Size: The average is over 13 feet in length, and they generally weigh between 1500-3500 or more.
General Habitat: They live in Fresh, Brackish, and shallow salt water.
Range: All Fl coasts; rivers lakes with outledts to sea. Winter: warm springs and other warm-water outfalls mainly along c and s FL coasts. Major wintering sites include Crystal River, Homosassa River, Tampa Bay, Fort Meyers, Boca Grande, Port Everglades, Riveria Beach (near Titusville) and St. John’s River especially near Blue Spring.

Field Observations
We first observed a family of three manatees. The mother was large and was slowly drifting a little ways away from her baby who was not at first visible. Instead, the mother was interacting with a smaller manatee that appeared to be about three to four years old. The back was indented with several large distinctive propeller scars. The mother and younger manatee touched their noses together and swam very close together. Then a baby calf surfaced from what appeared to be underneath the mother. The calf then swam onto the mothers back before rolling off. This behavior was repeated several times before the mother rolled to her side. All three of the manatees swam together away from the main canal and ambled slowly along for the length of the observation. The calf never let the mother get far away from it before it would swim to catch up with her.

Later we observed a group of about 15 manatees in the main canal of the power plant. The manatees were breeding with one female in the centers and five or six males surrounding her and mating with her. The female appeared to have little choice in who her mates were, instead each of the males took turns with her. There were several different groups each with a female in the center. These manatees appeared to move faster and more often than the family we had previously observed. They would often use their tales and fins to make small ripples in the water.

Manatees, also referred to as sea cows, are a group of large marine mammals. They have thick dense bones, so they keep their buoyancy in the water through extra large lungs. Manatees can remain submerged for up to 15 minutes. They lack an outer ear, but they do have internal ones. Their sense of hearing is excellent and the mother and calf have actually been observed using sound to communicate. Their tails are used both for propulsion and as a rudder. Manatees are herbivores and prefer to eat submerged grasses, but they will also eat floating vegetation; they will eat over 60 species of plants in all. They have also been observed eating snails as a source for calcium and phosphorous. They will usually feed for about 6-8 hours each day. Typically they live in shallow slow moving rivers. Manatees can be found in estuaries and costal water ecosystems and are dependant upon a steadily available food supply and warm water. They usually migrate to different habitats in the winter and summer because without warm water they will freeze. Female Manatees, referred to as cows, become sexually mature around 5-9 years of age and males, known as bulls, become sexually mature around 9-10 years of age. They do not mate for life. The average gestation period for manatees is 13 months. They usually have one calf every 2-5 years, and the chance for twins is extremely low, only about one percent. Calves stay with their mothers for about 2 years. Manatees are mildly social and like to cluster in small communal groups and engage in pastimes like playing tag, body surfing, and barrel rolling. They are at the highest level of endangerment.

References
Gingerich, Jerry Lee. Florida’s Fabulous Mammals. Tampa: World Publications, 2003.

Alden, Peter, Richard B. Cech, Amy Leventer, Gil Nelson, and Wendy B. Zomlefer. National Audubon Society Field Guide to Florida. New York: Alfred A. Knopf, 1998.

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