Once thought to be a mermaid, the mythical half-fish, half-woman creature of the ocean, the manatee is one of the most entrancing mammals of the seas. In ancient times, as sailors traveled around the world, they would mistake the manatee for mermaids swimming through the waters. The manatee, or Trichechus manatus, is classified in the Phylum: Chordata, Class: Mammalia, Order: Sirenia, and Family: Trichechidae. Common names of the four different species are Amazonian, African, West Indian, and Florida manatee. The manatee has only one related species, the dugong, and can only be traced through evolution with the elephant and hyrax, which eventually adapted to land.
To begin, let one visualize a picture of this great creature. Physical characteristics of the manatee include a greyish-brown large, rounded body that narrows down to a flat, paddle-shaped tail, two flippers with 3-4 fingernails on each, thick wrinkled skin, and a whiskered upper lip. They can grow up to 9-13 feet long and weigh between 800-3500 pounds! Playing, tumbling, kissing, and nuzzling characterize their day-to-day interaction. They are gentle, non-territorial animals that may have independent, overlapping, or often identical ranges of living. Covering up to 125 miles of coastline in a summer, they occupy no apparent "home".
Out at sea, reproduction occurs in mating herds of one female and several males, birthing generally one calf every 2-3 years. The newborn calf weighs approximately 77 pounds and stays with the mother for the first two years of life. Aside from this closely-knit bond of mother and calf, manatee do not form stable social groups or herds.
Though usually residing in small groups or pairs, manatees face no real natural endangerments. Predators are rare; so relative to the little demand for defense, manatee have none. Along with the concerns of predation, the manatee must be aware of their environment. The manatee tends to roam in shallow, slow moving, freshwater and saltwater areas with plentiful water plants. On average, the manatee spends 7-8 hours a day munching on sea grasses and aquatic plants, consuming 80-100 pounds of vegetation. In addition, seeing as they can allow only a few degrees of variation in water temperature, it is critical that the manatees move about to favorable waters.
One current issue of concern along the Florida coasts are the effluents of warm water supplied by power plants along the sea shore. Factories pump in the cool water to their machinery and dispose warm water back into the ocean. These areas of artificial warming tease the manatee into exploring new habitat. At 20 degrees Celsius, the manatee can function normally. However, if a power plant ceases operation or has even a brief failure, and breaks the warming of water effluents, the water temperatures may drop below 20 C. At 18-19 degrees C feeding becomes irregular and below 16 degrees C feeding and other activity ceases. This poses the threat of disease and death. "Power-plant overhauls and shutdowns, alterations of industrial and power-plant cooling streams, water withdrawals from the aquifer, alteration of recharge areas, vessel traffic within warm-water discharge areas, restriction of physical access to refugia, and capping of natural springs are some threats which would seriously impact manatees"(USFWS, 15). Water quality and vegetation are also affected by water contaminants associated with industrial and sewage treatment discharges.(USFWS, 14) In conjunction with these discharges, manatees may be susceptible to a number of viruses and bacteria present in human and animal wastes, and to parasites transmitted through fecal material. At or near these power plants, animals are exposed to oil or chemical spills. "All industrial warm water sites in Florida where manatee aggregate are near to power plants"(O'Shea et al., 254). Is there cause for concern with many plants still practicing these techniques? According to the U.S. Geological Survey: Biological Resources Report, an interagency research team is studying the Florida manatee's response to the loss of an industrial warm-water discharge near Jacksonville, FL. Another company "recently modified its discharge system on the Amelia River, in compliance with water quality standards regulated by the Florida Department of Environmental ProtectionÍ(and) as a result, heated water will no longer be available to manatees, as it has been in past winters"(USGS 1997, 1). Elimination of these artificial warm-water sources north of the manatee's natural range is viewed as a positive step in protecting this endangered mammal. Understanding the effects of the warm water effluents is beneficial for planning future changes in industrial drainage. According to Carol Knox, Florida Department of Environmental Protection, "We are concerned that the manatee's natural migratory patterns have been changed by the industrial warm-water effluents, and hope to work with the industries involved to ensure that manatees can adjust to the modification or elimination of these effluents."(USGS 1997, 1) Exposure to colder temperatures in the north may affect manatee metabolism, reproductive success, and general health. It is essential that the effects of the warm water refuges are found, for in the future they may be eliminated as health and ecological standards continue to tighten.
Industry is not the only opposing threat to the manatee. In fact there are many reasons that this mammal is in danger. Historically, "manatees were hunted for the flesh, bones, and hide by Native Americans and later by the early colonists"(USGS 1995, 2). Their fat was used for lamp oil, bones, were used for medicinal purposes, and the hide, for leather. "This hunting is thought to be largely responsible for the manatee's initial decline"(USGS 1995, 2). Natural events also imperil the lives of manatees. In 1977, 1981, 1984, and 1989 uncommonly cold winters lowered water temperatures throughout Florida, killing manatees that can not survive such conditions. Another reason for decline in population is attributed to periodic red tide blooms. "Red tide toxins accumulate in sea squirts which adhere to sea grassesÍ(and) this poison is ingested incidentally by manatees feeding on sea grasses"(USGS 1995, 2). Other causes of death are illegal hunting, high levels of toxicants in coastal waters contributed by runoff, ingestion of litter, increased motor traffic, habitat loss, motor boats and watercraft collision(very devastating!), factories, flood gate/canal lock, various perinatal incidents, and other natural events. The single largest problem facing the manatee, however, is human interference.
Human activities "directly or indirectly affect mortality, reproduction and recruitment, distribution and behavior, abundance and distributions of vegetation, the condition and availability of warm-water refugia, levels of contaminants and pathogens, and other vital physical, chemical, and biological processes of manatees and their habitatÍ"(USFWS, 13). A large concern is the population boom along the shores of the Florida coast causing land erosion, contamination of resources and water, noise pollution, crowding of the shoreline waters where the manatee swim, and increased number of motor boats and collisions with the animals. The list goes on. As humans come closer to the manatee, the further it is pushed into extinction.
The question is then asked, "What can be done?" Beginning in 1893 a Florida law was passed to protect the manatee. Since 1907, there has been a $500 fine for any person who kills or harms a manatee. In 1967, they were named on the Endangered Species list and then in 1978 the entire state of Florida was named a "refuge and sanctuary for manatees" through the Florida Manatee Sanctuary Act. This law allows the "State of Florida to designate the manatee sanctuaries and establish speed zones for boats"(USGS 1995, 3). Finally in 1972 the manatee were recognized on the federal level under the Marine Mammal Protection Act. In addition to these legal mandates, education and awareness are important aspects of recovery of the manatee population. This includes enforcing the existing laws as well as teaching mutual respect of humans with their environment. Rehabilitation facilities are being developed to aid injured animals, as well as teach the public the significance of saving these wonderful creatures. There is a 24-hour "Manatee Hotline" for reporting injured, sick, distressed, or dead manatees. According to the U.S. Fish and Wildlife Service, 1989, these are a few other things being done on behalf of the manatee:
Research programs and studies by local and national groups, habitat protection, that as with research, involves a number of agencies and institutions including the State of Florida, the Federal government and private organizations, growth management activities which included "possibly one of the most important pieces of legislation enacted by the State of Florida", the Local Government Comprehensive Planning and Land Development Regulation Act(LPDA) of 1985.(15-18) This "mandated that planners consider water quality; conservation, use, and protection of wildlife and marine habitats; protections of native vegetation; and restrictions of activities adverse to threatened or endangered wildlife when developing county and local comprehensive development plans"(18). The enactment of the LPDA made it mandatory for growth management plans to address impacts to manatees and their needs. Regulatory, permitting, and enforcement activities are being addressed about "problems of manatee protection and conservation by reviewing proposed dredge-and-fill activities and construction projects in waters of the United States where projects may jeopardize manatees of their habitats"(18). Education and public awareness has been very essential. Numerous private organizations and groups have undertaken a wide range of public awareness and educational activities including: distributing bumper stickers and brochures, publicizing upcoming events and providing information on particular hazards to manatees, producing TV documentaries and public service announcements, and developing workshops to educate teachers and the general public.
With that in mind, one must then refer to the objectives of it all. The long term recovery goal for the Florida manatee, as stated by the Marine Mammal Protection Act of 1972, will be "to maintain 'the health and stability of the marine ecosystem' and to determine and maintain their numbers at 'optimum sustainable population' levels in the southeastern United States"(USFWS, 21). In the interim, this plan seeks to down-list the manatees from "endangered" to "threatened" under the Endangered Species Act of 1973. To achieve this objective, "it will be necessary to establish and maintain a viable, self-sustaining population of manateesÍ(and) the most effective way to reach this goal is to reduce mortality and injury; ensure the continued existence of suitable habitat, upgrading where possible; minimize harassment; and monitor the status of manatee populations and their habitats"(USFWS, 21). Only until populations indicate that they are growing or are stable and when mortality rates and security of habitats are controlled at acceptable levels, will the manatee be considered for down-listing. What can you and I do? Take a hint from the famous author Paul Hawken, leave the world better than you found it, take no more than you need, try not to harm life or the environment, make amends if you do.
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Reynolds, John E., III, Mario A. Leon, William A. Szelistowski, Biological Conservation "Status and conservation of manatees Trichechus manatus manatus in Costa Rica." v. 71 no2 ('95) p. 193-6.
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Unterbrink, Mary, Manatees: Gentle Giants in Peril, Great Outdoors Publishing Co., St. Petersburg, Florida, 1984.
O'Shea, Thomas, Bruce B. Ackerman, and H. Franklin Percival et al., "Population Biology of the Florida Manatee", U.S. Department of the Interior National Biological Service, Washington D.C., August 1995.
U.S. Fish and Wildlife Service. 1989. "Florida Manatee (Trichechus manatus latirostris) Recovery Plan." Prepared by the Florida Manatee Recovery Team for the U.S. Fish and Wildlife Service, Atlanta, Georgia. 98pp.
U.S. Geological Survey. 1997. "Interagency Partners Work with Industry to Protect Endangered Florida Manatees." Released by Hannah Hamilton, www.nbs.gov/pr/newsrelease/1997/12-10.html. Gainesville, Florida, p. 1-3.
U.S. Geological Survey. 1995. "Endangered Species: West Indian Manatees" Prepared by U.S. Department of the Interior and U.S. Fish and Wildlife Service, www.nbs.gov/features/kidscorner/manatee.html. p. 1-3.
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