Final: cows of the sea

This discussion topic submitted by Sean Edwards ( edwardsm@miamioh.edu) at 11:48 am on 6/9/01. Additions were last made on Wednesday, May 7, 2014.

Sean Edwards

Cows of the Sea

The life of one of the laziest mammals on the earth is found in the shallow waters just off the Florida coast. This mammoth animal is known as the sea cow or the Florida manatee (Trichechus manatus latirostrus). The Florida manatee is a subspecies of the West Indian manatee. There are 2,600 manatees living off the coast of Florida. Despite many efforts this number is dwindling each year. Their lazy life style is what has cause their numbers decrease, being killed by the rapidly growing boat population of the Florida waters.
Florida manatee is from the Trichechidae family, along with the other two species of manatees: the West African manatee, Amazonian manatee. Florida manatee is in a subspecies with the Antillean manatee due to its cranial differences and the territories they cover. Despite many efforts to track the background of the manatee there has been little success. Early in the twentieth century it was thought that manatees were related to walruses and seals. Because of the fingernails found at the end of the pectoral flippers and other characteristics scientists believe the closest relatives to the manatee are elephants and aardvarks.
A Florida manatee is a large mammal that is found in the waters off the Florida coastline. They can grow to be about ten feet long and weight up to twelve hundred pounds. In most cases the female is larger than the males. The enormous animal is brown in color, and due to its slow movement algae may grow in patches on their thick, wrinkly skin. Protruding from the upper body is two pectoral flippers that assist in steering. The flippers are also used to entice food toward their mouth, and for guidance along the sea floor. At the rear of the animal is a fin that is used for propulsion. The manatee can use its fin to reach speeds up to fifteen miles per hour. Often they are moving at much slower speeds, usually less than six miles per hour.
Manatees, in the Florida area, are mostly found in the warmer waters of south Florida. In some odd cases the mammal has been sited in waters off the north coast of Virginia, and in the Mississippi river delta. The life of a manatee is spent in costal regions, rivers, and canals, where vegetation and sea grass is plentiful. Most of the time the manatees are found in brackish waters over 1 meter deep, and they prefer water temperatures above 70 degrees Fahrenheit. If water temperatures decrease below 68 degrees the manatees stop eating, have to cope with cold stress, and often times die. During the colder months of winter, manatees travel to the warmer waters of the Gulf Coast springs, or to waters south of the Sebastian River on the Atlantic side. In some regions of Florida the manatees have found many artificial resources for warm water including the discharge from power plants. Hundreds of manatees have been found to congregate around the Florida Power and Light Company's plants at Cape Canaveral, Fort Lauderdale, and the many other electrical plants along the Florida coast.
In the areas where food is plentiful manatees have adapted to feeding themselves on a regular basis. Most of the time they are devouring a variety of shoreline, floating, or submerged vegetation. Their diet normally includes manatee grass, turtle grass and shoal grass. In one day a manatee can eat up to fifteen percent of their body weight, that could add up to be as little as thirty two or as much at one hundred and eight pounds of vegetation. They have been known to partially crawl up on a bank and eat vegetation on the shore, or hanging off of nearby tree branches. Along with food, manatees have to drink fresh water. They have been witnessed drinking from sewage deposits, hoses and any other fresh water source that they find.
Manatees have very good eyesight. In clear water they can notice objects from ten yards away. Their eyes have developed both cone and rod cells. The rod cells are used for sight in low light situations. This means that the manatee can see in both dim and high light. Hearing in the manatees is formed for lower frequencies between 3 and 5 kHz. They hear through a large ear bone found in the upper part of their head. It is thought by some scientists that the manatee really hears through their large cheekbone. Smell and touch are not as potent as their eyesight, but they both play an important roll in the survival of the manatee. The taste buds of the manatee are found on the backs of their tongue. It is thought that the taste buds of the manatee have helped it determine what plants are editable and what plants are poisonous. The manatee has two openings for smell, but little is known of how well the manatee can smell.
Manatees are very agile and move well under water. Despite this they normally are found in shallow water, but manatees have been known to dive as deep as thirty-three feet. When they dive, they only drop about ten feet below the surface. While in a relaxed state the manatee can spend up to twenty minutes under water. During a period of activity the manatee normally breathes every two to three minutes. As manatees become more active, they breathe more often.
A majority of the manatee's day is spent eating plants found around and in the water. They may spend up to ten hours a day eating. The rest of their day is spent sleeping, traveling or playfully investigating things in the water. At times the manatees gather in groups. The groups might be formed to obtain food, finding a mate, or for a little fun. These groups vary in number, age, and sex.
Reproduction occurs year round in the Florida manatee, but a majority of the births occur in the spring or summer time. Normally the cow (female) will give birth once every two to five years. Once the manatee reaches sexual maturity, nine to ten years for the bulls, and seven to eight years for the cows, it begins to look for a mate. When the females are ready to reproduce, they form groups with males specifically for mating. In any one group there can be up to fifteen males attempting to mate with one cow. The males often follow the estrous female for several weeks. During these few weeks the cows attempt to elude the males, but they remain at her side showing their willingness to mate with her. Mating is the only relationship between the male and female, the male does not stay to help raise the young.
Once the calves are born they do not leave their mother's side for up to two years. On rare occasions the mother might have twins. When born, the calves weigh between seventy and one hundred pounds, and range between two and three feet long. Immediately after birth the mother attempts to teach the young calf how to breath. Many times the mother will nudge her calf to the surface to help it breath. A few days after birth the calf "talks" to its mother, this is a very important part of the relationship with the mother and her calf. Their "talking" normally consists of squeaks, chirps, squeals, and chirps underwater. For the first few days the calves are kept near the surface. In a few months the calf normally will double its weight from suckling milk from it's mothers breasts, which are located behind her fins. At six months the calf will begin to eat submerged plants for example: hydrilla, turtle grass, and manatee grass. Within a year the manatee might have gained over five hundred pounds. To survive beyond their mother's care the manatees must learn the locations of food, warm waters, and also the migratory patterns. In five years the manatee is normally fully grown.
The Florida manatee is on the endangered species list. The manatee encounters a large of deaths each year. The causes for death come from human intervention, and natural deaths. Humans have killed many manatees. The manatees have died from boats, floodgates, navigation locks, and other sources. Boats are the number one reason for death of the manatee. On many occasions the manatees are killed when they come up for air after bring on the bottom sleeping. Their death is normally from the impact of the hull or the propeller damaging a vital organ. Floodgates have also played a role in the deaths of the manatee. The manatees have been caught in the closing of the doors or have been caught in the water current and drown. In other areas manatees become tangled in the fishing lines and crab lines. These lines can wrap tight around a flipper and cut off the circulation. The end result might be an infected flipper or the limb is severed. Since 1987 the manatee death rate per year has increased by one hundred and forty nine.
Natural causes have also taunted the extinction of the manatee. About 61% of the reported dead manatees are due to natural causes. Manatees have died from a few natural reasons the number one killer being the exposure to cold waters. If the water temperature drops below 68 degrees for a prolonged time the manatees cannot survive. An array of diseases and parasites have taken their toll on the sea cow.
As humans we have felt a need to take actions to save the remaining 2,600 manatees. The Florida manatee is one of the most endangered marine animals in the United States. Many acts and laws have been implemented to assist in the prolonged life of the manatees. Federal laws are in place in the United States that do not allow the killing, capturing, hunting, or harassing these animals. These laws are the Mammal Protection Act of 1972 and the Endangered Spices act of 1973. In Florida, the Florida Manatee Sanctuary Act of 1978 has established Florida as a sanctuary for the manatees. A violation of this law carries a hefty fine and or jail time. At any rate, we need to enforce these laws and implement more to keep these beautiful animals on the surface of the earth.


Bibliography

U.S. Fish and Wildlife Service. 1989 "Florida Manatee (Trichechus manatus latirostris) Recovery Plan." Atlanta, Georgia. 98pp.

"Sirenian." The Columbia Encyclopedia, 6th ed. New York: Columbia
University Press, 2001. www.bartleby.com/65/. [6-03-2001].
Zeiller, Warren. Introducing the Manatee. University Press of Florida. 1992

Hartman, Daniel. Ecology and Behavior of the Manatee (Tricheschus manatus) in Florida. Special publication #5 The American Society of the Mammologists. 1979

"Manatee." Encyclopedia Britannica. http://www.britannica.com/eb/print?eu=51681.

Manatee: A Sea world Educational Department Resource. http://www.seaworld.org/manatee/manatees.html

Manatee: The Wonderful world of the manatee. http://www.manateeworld.net/

"The Trouble With Manatees and the Florida Water Story." http://www.xtalwind.net/~cfa/

The Florida Manatee: http://www.ecofloridamag.com/archived/manatees.htm


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