Grunts are abundant at Molasses Reef, Key Largo, Florida.
The Florida Manatee (Trichecus manatus latirostris, subspecies of the West African Manatee Trichecus manatus) is mammal that lives in the shallow waters off the Florida coast. The manatee has an interesting history, although the complete story, and quite possibly the most important part of the manatee’s chronicle, remains to be told. The manatee is commonly referred to as a sea cow, and has earned the name based on the fact that the majority of its life is spent grazing on sea grasses. Manatees, the gentle, semi-social creatures that they are seem to be the center of much lore and may be responsible for the stories of legendary mermaid sightings; they are even thought to be a possible explanation of the siren’s that tried to lure Ulysses and his crew into the jagged rocks in the Odyssey.
A manatee is a large, grayish, aquatic mammal that has a large body that tapers to a flat, paddle shaped tail. Manatees have two short flipper-like limbs with three to four nails on each (these nails help the manatee to gather food). The head and face of manatees are wrinkled with whiskers on the snout, while tiny eyes are located on the sides of a physically earless head. These swimming mammals have flexible lips that are used in conjunction with the flipper/arms to get food into the manatee’s mouth. Sea grass, the manatee’s favorite food is met in the mouth by two rows of top and bottom teeth. The teeth, take a lot of abuse from the manatee’s food of choice, so the teeth need often to be replaced, this is accomplished as the teeth re-establish themselves by moving from the back of the mouth forward. Manatees can grow to be as large as 13 feet and 3,500 pounds, but average around 10 feet and 1,200 pounds.
The manatees have a good sense of hearing. They have ear openings that are very small, but a large internal ear bone. To communicate they make chirping, whistling, and squeaking noises, like most other mammals, from the larynx. Scientists believe that manatees can see colors and can see objects as far away as 30 feet; and that they may too be able to taste and smell. Manatees are very contact oriented mammals that like to engage in a lot of body contact, using this as a tool to socialize with their herd. Manatees may also use the small hairs that are found sparingly over their bodies to detect contact.
A manatee’s life begins after a thirteen mont gestation, the new baby, called a calf, can be as large as 70 pounds and 4 feet in length. The babies are born a much darker color then the mother, and are able to see, swim, and hear right away. Manatee calves are also born with a full set of teeth, and have to teach themselves, with the help of their mother, to hold their breath for long periods of time. As the case with all other mammals, they drink mother’s milk for the first part of their lives. The calf will begin to consume sea grass after a few months, but will continue to feed off the mother for many more months.
A newborn will stay with its mother for approximately two years before setting off to be on its own. During this time the baby manatee is learning the locations of food, where they can find warm water, and how to migrate from one place to another. Once the calf leaves, the mother is able to have another baby, although the calves have been known to return for visits. (Twins have been known to have been born, but these cases are rare.) If perchance a new mother is killed or injured, another manatee will occasionally take care of the orphan. How many calves a mother manatee can have is unknown, although they can have babies for many years, the most known births by one manatee is six.
After four or five years, the manatee will be full grown, but like elephants will continue to grow throughout their lives (the largest recorded manatee was just over 13 feet and weighed over thirty-two hundred pounds). Manatees consume anywhere from one hundred to two hundred pounds of soggy grasses and weeds a day. They primarily feed off of sea grass (turtle grass and manatee grass), algae, mangrove leaves, and water hyacinths. The manatees get their protein from ingesting the many tiny animals that live in the grasses and algae on which they feed.
A female manatee reaches sexual maturity at approximately five years of age, while a male manatee has to wait until he is around nine years old. There is no noted breeding season for the animals, but the females go into estrous between spring and fall. When this happens, the males detect and pursue the female for up to three weeks. Manatees do not form permanent bonding pairs like some species of animal, but instead mate at random. When the mating herd if formed a female can mate with one or more males, making it very difficult for scientists to know who fathered the calf.
A manatee will spend most of its day lying around on the seabed, surfacing every couple of minutes to get some fresh air. A manatee can hold its breath for up to ten to fifteen minutes in a resting state, but may surface more frequently depending on their level of activity. When the manatee is not laying around it is either eating, which it does approximately 7 hours everyday, sleeping which it does as mush as 12 hours a day, socializing, or it is migrating, (manatees are usually found to be cruising at a speed of 2 miles per hour, but can reach speeds up to 15 mph.) to find warmer waters. (The manatee prefers water that is above 68 degrees Fahrenheit, if the water temperature gets below this temperature, then the manatee can die from cold stress.) The life span of these creatures is unknown, some studies have indicated that a manatee could live to be as old as 70, but the average life span is between 50 and 60 years old, if they are not eliminated sooner by unintentional human intervention.
The manatee, as stated earlier, prefers warm waters within the boundaries of the tropics. For this reason they are mainly found on the eastern seaboard of the United States, from Virginia to the tip of Florida, and then as far as Louisiana. There have been a few occasions that they have been seen near Texas, the Bahaman Islands, and even up around New York, but these are rare visits for the manatees. They can be found in: salt, fresh, or brackish waters. Manatees can be seen in shallow, slow-moving rivers, saltwater bays, estuaries, canals, and other costal areas. Manatees migrate to find warmer water temperatures in the northern part of Florida; in the southern section of Florida the manatees migrate to find fresh water or water with a lower amount of salt present. The Crystal River tributary, near the middle of the western coast of Florida, flows for roughly seven mile into the Gulf of Mexico, it is in this location that millions of gallons of clear 72 degree water flows year round. When the seasons change an winter rolls around, the waters of the Gulf turn much too cold for the manatees, it is during this time that large numbers of manatees migrate up the Crystal River to Kings Bay, where they can find a favorable mixture of warmer, fresh water. Staying in the temperature dropping waters of the winter time gulf would mean the manatees face getting a respiratory illness, which is the most common natural cause of death among the species. Recently the number of manatees that migrate up the river to Kings Bay have increased, due to environmental problems that other parts of the state are facing. Most of the Florida waters are facing problems with increased pollution, continuing construction and development (which leads to loss of wetland habitat), and the loss of a good portion of the manatees food supply in the form of costal grasses. Even the Crystal River area is beginning to see its water quality decrease, and this has manatee lovers alarmed. Manatees have found some refuge from the diminishing safe havens of warm water by finding some man made water heaters. Power plants, are typical producers of warm water for manatees. Without these warm water fields, like at the Indian River Lagoon, the manatees would parish during the winter. The problem is found when the manatees flood into these little warm havens that are not used to handling these large vegetation eaters. As manatees move in on the warm water areas, they must eat to stay alive, an as stated earlier they eat between 100 and 200 pounds of sea grass a day; sea grass that other animals natural to the area such as wild dolphin, small causations, bald eagles, and others must live on and in to survive as well. Animals who eat must obviously remove wastes as well, and with hundreds of manatee eating thousands of pounds of sea grass, and making thousands of pounds of waste, nutrient overloading is a foreseeable problem, leading to algal blooms, reducing the amount of needed oxygen in the aquatic environment.
Manatees have other problems besides finding enough food and suitable habitats for the changing seasons. Although theses mammals have no natural predators, they must deal with the dangers of sharing the water with humans. There are around 3,000 of these non-aggressive mammals left in the Florida waters. The most recent count that took place in March of 2002, said that there are 1,796 as of the count, but the survey does say that since it was a one day count, it can’t take into account all of the factors that may have contributed to the low numbers on that day. Factors such as weather conditions, winds, cloud cover, and air and water temperatures all can have immeasurable affects on the counts. Boat accidents are one of the leading causes of manatee mortality, resulting in 31 deaths through February of 2002, while only 15 were killed in the same time period in 2001. Manatee mortality is not only caused by the watercraft collisions, but also by being crushed to death or drowned in canal locks, and flood control structures, ingestion of fish hooks, and other types of litter, getting caught up in crab trap lines, and even vandalism. The reason that scientists believe that manatees are endangered is because their reproductive rate is so low, and the numbers are dwindling quickly. Scientist know that every species in the environment suffers losses from natural occurrences, and that the manatee species as a whole will adapt albeit very slowly to the constantly changing environment and unnatural stresses. Unfortunately, with the numbers decreasing the way that they are, it is possible that when the manatees travel in herds they may start to interbreed and cause degradation to the gene pool. Therefore, the loss of every manatee becomes critical.
The people in Florida are divided on what should be done with the manatee problem. There are many who want to save this endangered animal, and others who want to have their water freedom (boaters), and a few who think that the manatees are doing more harm then good. Those that argue that the manatees are hurting the environment are saying that they are becoming an invasive species and destroying the habitats of the native species that are found there. They say that the manatees are endangering hundreds of native species including the sea grasses they eat. They say that the sea grass takes 1 to 5 years to re-grow, and the loss of the sea grass will cause the downfall of all the other species that also depend on it to survive. Manatee supporters will tell you that they help increase the amount of water plant biodiversity, by limiting invasives like the Hydrilla which cause trouble once they get too big. Boaters on the other hand, are afraid that since the manatee has become the “poster child” for curbing development and growth, that the “average” person is going to lose access to the water and only the rich will be able to use the water ways for recreation. They argue that over the past 30 years the number of manatees has increased, and manatee protection enthusiasts use the term extinction as a scare tactic. The boaters will tell you that the number of manatees has increased 400% while the number of boats has increased by the same percentage (estimates suggest that there are over one million watercraft operators annually), and protection agencies don’t want to view these numbers as a successful collaboration of mammal and boat. A recent report from the U.S. Fish and Wildlife Service (FWS) said that the manatees could be taken off the endangered species list in less then two years if current population trends continue, this news greatly upset some environmentalists saying that the FWS is driven solely by politics.
Today manatees are protected under the Endangered Species Act of 1973, and the Marine Mammal Protection Act of 1972. Manatee protection agents say that increased manatee speed zone enforcement is the most important effort to aid in conservation that can be taken. Other measures that are being taken are: to reduce harassment of the manatees and to prevent people from feeding wild manatees. Researchers are constantly working on ways to track and record the manatees, and find ways to keep them safe from flood gates and navigation locks, and other problems that they may come across.
While doing research on the subject it is possible to find numerous sites and sources on manatees and what can be done to help these “gentle giants,” it is more difficult to find those who appose the manatees, although it is possible. In any case the manatee debate will become more and more of a foreseeable problem in the coming years as boaters and conservationist try to find an agreeable compromise.
Boat/US Magazine: “Will Manatee Lawsuits Endanger Boating?” Lydecker, Ryck. May 2000.
Boat/US Magazine: “Manatees Show signs of Recovery” Sept. 2001.
CNN-Experts race to find why manatees are dying. Correspondent: Zarrella, John. April 3, 1996.
Coral Reefs: Reefs since Columbus, Abstract Volume 16 Issue 5 (1997) pp S23-S32
Dolphin Research Center “Manatee Conservation.” http://www.dolphins.org/learn/lmm-mcon.htm#Current
Ecologist Society of America: Ecology: Estimates of annual survival probabilities for adult Florida manatees (Trichecus manatus latirostris).: Langstrom, C.A., Issue: April, 1998
Florida Marine Research Institute: http://www.floridamarine.org/features/view_article.asp?id=6780
National Wildlife: Making Sense of MANATEES, Stewart, Doug. April-May 1999.
Manatee Brain: http://www.manateebrain.org/07evolution/index.html
Manatee Coast: http://www.colzoo.org/animalarea/shores/manatee_coast/index.html
Mother Earth News: “One small step for Man-atee Kind.” 2001 Ogden Publications, by Manahan, Kristen. June 2001.
Save the Manatee Club: http:www.savethemanatee.org/
The Silver Think Tank: http://www.manateestudy.com/
“The Trouble with Manatees and the Florida Water Story”: http://www.xtalwind.net/~cfa/
Wild Times copyright 2001.: http://www.ecofloridamag.com/archived/news_manatee_conservation.htm
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