Entertainment Magazine: Science: Manatee and Sea Cows

The Florida Manatee

manateeBy Scott Sosssong

The Florida manatee, Florida’s state marine mammal, is a large aquatic relative of the elephant. They are grayish brown in color and have thick, wrinkled skin on which there is often a growth of algae. 

Their front flippers help them steer or sometimes crawl through shallow water. They also have powerful flat tails that help propel them through the water.

Despite their small eyes and lack of outer ears, manatees are thought to see and hear quite well.

Manatees are marine mammals of the order Sirenia, also known as "sea-cows". These beautiful animals can be found in shallow waters, bays, canals and coastal areas. The manatee has a streamlined body, with two flippers and one paddle-shaped tail. Their true color is gray, although it may appear brownish gray.

Adult manatees can grow up to 12 feet in length and weigh around 1,800 pounds. Females are generally larger than males. Although manatees have few natural predators, they are vulnerable to extinction and they are also called sea cows because the are a cousin from an elephant.





The Manatee: Trichechus manatus latirostrus

Length 10-12 feet
Weight 1,500-1,800 lbs
Lifespan 50-60 years in the wild

Diet

Herbivores: they eat marine and freshwater plants.

Population

The largest population of manatees is found in Florida, where there are over 3,000 individuals.

Range

Manatees take up residence primarily in Florida’s coastal waters during winter. Some individuals migrate as far north as the Carolinas or as far west as Louisiana in summer. In recent years, a manatee traveled to New York and another swam up the Mississippi River!

Behavior

Manatees can be found in the warm waters of shallow rivers, bays, estuaries and coastal waters. Rarely do individuals venture into waters that are below 68 degrees Fahrenheit.

Well known for their gentle, slow-moving nature, manatees have also been known to body surf or barrel roll when playing. They normally rest and feed often. Manatees communicate by squealing under water to demonstrate fear, stress or excitement.

Reproduction

Mating Season No specific period

Gestation About 1 year

Number of offspring 1 calf

Calves are born weighing between 60 and 70 pounds and measuring about 3-4 feet. They nurse underwater.


Watch video of the Mantee

Threats to the Manatee

Destruction and degradation of their coastal and freshwater habitat.  The leading known cause of death is by boat strikes; propellers and hulls inflict serious or mortal wounds. Most manatees have a pattern of scars on their backs or tails after surviving collisions with boats.

Scientists use these patterns to identify individuals. Manatees are also vulnerable to cold water.

They have been found crushed or drowned in flood-control gates and suffer harm from exposure to toxic red tide. In addition, a large number of manatees die from unknown causes each year.

Legal Status/Protection

save the manateeFederally listed as Endangered and state listed as Endangered. *Endangered Species Act; **Marine Mammal Protection Act; Florida Endangered and Threatened Species Act; Florida Administrative Code; Florida Marine Sanctuary Act; ***CITES Appendix 1.

* The Endangered Species Act requires the US federal government to identify species threatened with extinction, identify habitat they need to survive, and help protect both.  In doing so, the Act works to ensure the basic health of our natural ecosystems and protect the legacy of conservation we leave to our children and grandchildren.

** The Marine Mammal Protection Act prohibits, with certain exceptions, the take of marine mammals in U.S. waters and by U.S. citizens on the high seas, and the importation of marine mammals and marine mammal products into the U.S.

*** Convention on International Trade in Endangered Species of Wild Fauna and Flora, an international treaty with 172 member countries. Appendix I species cannot be traded commercially. Appendix II species can be traded commercially only if it does not harm their survival.

Manteea also called Sea Cows

Manatees (family Trichechidae, genus Trichechus) are large, fully aquatic marine mammals sometimes known as sea cows. The name manati comes from the Taino, a pre-Columbian people of the Caribbean, meaning 'breast'. They contain three of the four living species in the order Sirenia, the other being the dugong, which is native to the Eastern Hemisphere. The Sirenia is thought to have evolved from four-legged land mammals over 60 million years ago, with the closest living relatives being the Proboscidea (elephants) and Hyracoidea (hyraxes).

Manatees are mainly herbivores, spending most of their time grazing in shallow waters and at depths of 1-2 meters (3-7 ft). Much of the knowledge about manatees is based upon research done in Florida and cannot necessarily be attributed to all types of manatees. Generally, manatees have a mean mass of 400-550 kg (900-1200 lb), and mean length of 2.8-3.0 m (9-10 ft), with maximums of 3.6 meters and 1,775 kg seen (the females tend to be larger and heavier). When born, baby manatees have an average mass of 30 kg.

On average, most manatees swim at about 5 km/h to 8 km/h (1.4 m/s to 2.2 m/s; 3 to 5 miles per hour). However, they have been known to swim up to 30 km/h (8 m/s; 20 miles per hour) in short bursts. Manatees inhabit the shallow, marshy coastal areas and rivers of the Caribbean Sea and the Gulf of Mexico (T. manatus, West Indian Manatee), the Amazon Basin (T. inunguis, Amazonian Manatee), and West Africa (T. senegalensis, West African Manatee).

A fourth species, the Dwarf Manatee (T. bernhardi) was recently proposed for a population found in the Brazilian Amazon, although some have questioned its validity, instead believing it is an immature Amazonian Manatee. Florida is usually the northernmost range of the West Indian Manatee as their low metabolic rate makes cold weather endurance difficult. They may on occasion stray up the mid-Atlantic coast in summer. Half a manatee's day is spent sleeping in the water, surfacing for air regularly at intervals no greater than 20 minutes.

Florida Manatees (T. m. latirostris) have been known to live up to 60 years, and they can move freely between different salinity extremes; however, Amazonian Manatees (T. inunguis) never venture out into salt water. They have a large flexible prehensile upper lip that acts in many ways like a shortened trunk, somewhat similar to an elephant's. They use the lip to gather food and eat, as well as using it for social interactions and communications. Their small, widely spaced eyes have eyelids that close in a circular manner. Manatees are also believed to have the ability to see in color.

They emit a wide range of sounds used in communication, especially between cows and their calves, yet also between adults to maintain contact and during sexual and play behaviors. They may use taste and smell, in addition to sight, sound, and touch, to communicate. Manatees are capable of understanding discrimination tasks, and show signs of complex associated learning and advanced long term memory. They demonstrate complex discrimination and task-learning similar to dolphins and pinnipeds in acoustic and visual studies. Manatees typically breed only once every other year, since gestation lasts about 12 months, and it takes a further 12 to 18 months to wean the calf. Only a single calf is born at a time and aside from mothers with their young or males following a receptive female, manatees are generally solitary creatures.

Quick Guide to Manatees

DESCRIPTION: Large, seal-like body that tapers to a powerful flat tail. Two agile forelimbs with three to four toenails on each, which act like arms to help the manatee maneuver in shallow water, grasp and move food toward their mouths, and act like flippers during swimming. Thick and wrinkled skin with a rough texture - a bit jiggly under the neck and arms. Their skin reacts to touch, as their bodies are very muscular - contracting and changing shape slightly when scratched or tickled. Powerful upper lips which articulate to help maneuver food or dig through sediment.

SIZE : Average 9 to 10 feet long, weighing around 1,000 lbs. Can grow as large as 13 feet and weigh more than 3,000 lbs. Calves are born weighing about 40 lbs, gaining about 700 lbs. during their first year.

BEHAVIOR : Gentle and generally slow-moving. Most of the time is spent eating vegetation (100-150 lbs. per day), resting and traveling. On average manatees can travel about 40 to 50 miles a day, sometimes farther. Chessie, the famed manatee rescued from the cold waters of the Chesapeake Bay and returned to Florida, was tagged with a locating device which showed he traveled as far as Rhode Island during hot summer months.

SIGHT : Some people believe Manatees are near sighted, or may have limited depth perception. It is believed that they can differentiate between colors. It is unclear how manatees navigate in pitch black or murky waters - when their eyesight would be of no use. They do have sparse bodyhair over their bodies, and thick whiskers on their faces. It is not clear if this aids in navigation. One expert is convinced, however, that they know exactly where swimmers are, even in blackout conditions.

HEARING : Manatees can hear very well despite the absence of external ear lobes. They are not believed to have the capabilities of echolocation.

COMMUNICATIONS : Emit sounds that are within human auditory range. They make sounds such as squeaks and squeals when frightened, playing, or communicating; particularly between cow and calf. No air is released from the manatee when these sounds are made, and it is not clear where the sounds are being produced or if they serve any other purpose.

BREATHING : Manatees are mammals and breath air through their noses at the surface - with nostrils which close tightly when submerged. They breath every few minutes when active or swimming, and every 10 to 15 minutes when resting. They are capable of exchanging 98% of their lungs capacity in one breath. Their lungs are very large, and are also used for buoyancy control. The rushing sound of a deep exhale and breath sound much like a snorkeler. This sound, and the associated "footprint" left by the manatees tail and body at the surface are clues which reveal the presence of manatees in the area.

HABITAT AND FOOD : Manatees are found in coastal waterways, estuaries, salt water bays, rivers and canals, particularly where seagrass beds are located. Manatees are completely herbivorous and can eat 10-15% of their bodyweight daily. In captivity they are fed lettuce and other greens, and given elephant vitamins.

REPRODUCTION : Females mature around 5 to 9 years of age, and males not until 6 to 9 years of age. It is believed that one calf is born every 2 to 5 years. Twins are rare in the wild. Gestation period is around 13 months. Newborns weigh approximately 40 pounds at birth and stay with them other for several years.

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