(Final) The Florida Manatee: Sea Cow of the Caribbean

This topic submitted by Rachel Whynott ( whynotrm@muohio.edu) at 3:44 PM on 6/4/07.

James returns from a wonderful SCUBA on Gaulin Reef in Grahams Harbor, San Salvador, Bahamas. See other beautiful phenomena from the Bahamas.

Tropical Field Courses -Interdisciplinary Studies-Miami University

The manatee of Florida and the West Indies is a truly unique creature, rich with history and riddled with present predicaments. It is one of four living species of Sirenians, and is closely related to elephants, aardvarks, and hyraxes. Like their close relatives, manatees lack a collar bone (Odell and Reynolds, 1991). Manatees are large, herbivorous marine mammals, generally weighing around 3,000 pounds. Females are typically larger than males. They have tough, gray, leathery skin with small heads and eyes. They have flexible upper lips covered in bristles called vibrissae to help them graze aquatic vegetation (Clapham et al., 2002).

During the summer months, Florida manatees can be found as far north as Virginia. During the winter months, manatees are generally found around Florida and southern Georgia, in rivers, estuaries, and along the coastline. They can easily travel between saltwater and freshwater environments, but they are extremely sensitive to temperature changes (Odell and Reynolds, 1991). The Florida manatee cannot withstand water temperatures lower than 68 degrees Fahrenheit. When subjected to low temperatures, the manateesÕ flesh freezes and they develop bumps on their faces. If exposed for too long, they die (Walker, 2003).

Manatees become sexually mature between six to ten years of age, and they can live up to 60 years of age (Save the Manatee Club). Their gestation period is between 12 and 14 months. Females generally give birth to a single calf that nurses for about 18 months. The bond between mother and calf is the strongest social connection in manatees, and communication between the two is achieved through Òhigh-pitched squeaks and squealsÓ (Clapham et al., 2002).

Manatees are not nocturnal or diurnal. They participate in the same activities during both the day and the night, including traveling, play, resting, exploring, and six to eight hours of feeding. They may perform these activities alone or with others (Odell and Reynolds, 1991).

Manatees have long been of interest to humans, although little was researched on the animal until 25 years ago. Christopher Columbus recorded seeing ÒmermaidsÓ on January 9, 1493, which were really three manatees (Ò01/09/1493Ó). There have been many tales of mermaids seen by sailors, which are believed to have been manatees. Manatees have had other uses to sailors besides providing them with thoughts of beautiful half-fish, half-woman forms. Manatee flesh was highly prized by European sailors and natives alike as an important and nutritious food source. It was so important to the European explorers that the Catholic Church deemed the manatee a fish so that it could be eaten at all times. Manatee meat is also pleasing to the taste and slow to spoil, which made it all the more valuable to the people who consumed it (Ripple, 1999).

Manatees have also provided uses beyond food. When butchered, all parts of the manatee would have a use. Manatee oil was used in lamps and in cooking. Other parts were used for medicinal purposes, such as the tears for an aphrodisiac and the skin for asthma remedy (Ripple, 1999). The skin was also used to make whips and shields. Bones were carved into figurines and arrowheads. The natives of Florida would often trade what they did not use to the Europeans who were coming to settle in the area. Years later, people would trap and drown manatees in nets to sell to museums for around 100 U.S. dollars (Odell and Reynolds, 1991).

However, the ever-decreasing manatee population was a cause to outlaw hunting and place restrictions to protect the manatees. With no natural predators, the manateeÕs slow reproduction rate was never a problem until human hunting and habitat destruction began (Save the Manatee Club). Humans were responsible for at least 35 percent of the Florida manatee deaths in 1998 (Ripple, 1999). Human involvement to protect manatees became vital to their continued survival, and laws have been put into effect to do just that.

Humans kill manatees in many ways. Some are outright slaughtered illegally by poachers for their ivory-like bones. Others become tangled in fishing nets and drown. Still others die from eating trash thrown in the water or from pollution caused by factories and sewage plants. The leading cause of death of manatees in Florida is collisions with watercraft (Save the Manatee Club). 1,164 recorded deaths out of 4,672 from 1974 to 2002 in Florida are due to preventable collisions with watercraft. In 2002 alone, a record 95 manatees died due to collisions with watercraft (Walker, 2003). The majority of these accidents kill older manatees that are fertile or have calves, which further hinders the growth of the population as a whole. Watercraft generally kills manatees in two ways. Most manatees that come into conflict with watercraft die as a result of a direct collision. Fast-moving boats may directly hit the manatee, and the impact could cause death or serious injury that leads to death. The second leading cause of death due to watercraft is a result of propeller injury. Manatees are curious creatures, and they are frequently sliced by propeller blades when they venture too close (Ripple, 1999). If the cuts are bad enough, a manatee could die from blood loss or other complications. As the number of watercraft increases, so do the number of injuries and deaths that occur due to them. This is not surprising, given that between 1996 and 1997 there were about 400 boats for every manatee in Florida (Ripple, 1999). The number has risen since then.

Another threat to manatees is canal locks and flood gates. These structures are located in rivers where manatees reside, and many manatees die each year from getting crushed in them, or they drown by getting stuck in the structure or the currents caused by the structures (Save the Manatee Club). Between 1974 and 1999, more than 130 manatees perished in this way (Ripple, 1999).
Habitat loss and destruction also affects the future of manatee survival. As humans continue to industrialize and develop, manatees lose more and more of the area they require to live. Also, the more humans that move into the area, the more boats and other manatee dangers there will be for them to contend with (Ripple, 1999).

Manatees are also at risk due to factors not related to humans. There are only about 3,000 manatees left in Florida (Save the Manatee Club). Scientists testing FloridaÕs population of West Indian manatees found that they have Òdangerously low genetic diversityÓ (ÒGenetic Uniqueness,Ó 1998). The individuals in the Florida population are more genetically alike to each other than other populations of West Indian manatees are to each other in other places in the Caribbean. The Florida manatee population does not interact and interbreed with other populations of manatees because of the distance between them across large expanses of deep waters. The lack of genetic variation could be a serious threat to the manatee, as the population will be less able to survive disease and environmental threats. If something were to wipe out the population of manatees in Florida, they would probably not be replaced naturally from other populations (ÒGenetic Uniqueness,Ó 1998). Therefore, it is important for humans to step in to help assist their continued survival.
The first step to save the manatee is to remedy our own exploitations and abuses of the manatee. Since a large number of their deaths are directly attributable to humans, a good place to start helping them recover would be to prevent those deaths that we cause. To do this, many laws have been put into effect to protect manatees and their surroundings.

The first law to protect manatees from hunting was put into effect in 1893 in Florida (Walker, 2003). However, poaching still occurred, and a more stringent policy was needed. The federal government stepped in during 1972 with the Marine Mammal Protection Act of 1972 and then the Endangered Species Act of 1973 (Save the Manatee Club). These acts made it unlawful Òto harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or attempt to engage in any such conductÓ manatees (Ripple, 1999). Then Florida created the Florida Manatee Sanctuary Act of 1978. It prohibits Òany person, at any time, intentionally or negligently, to annoy, molest, harass, or disturb any manateeÓ (Save the Manatee Club). Florida has also put in no-entry zones for boaters, swimmers, and divers, as well as places where there are speed limits for boats.
Humans are also helping manatees in other ways. The rescue, treatment, and release of injured manatees helps save lives every year. SeaWorld, the Lowry Park Zoo, and many others assist in treating manatees and raising public awareness about manatee conservation (Ripple, 1999). Necropsies are performed on dead manatees to determine the cause of death, so those that are preventable can be looked into and so the program to protect manatees can be updated and modified according to current needs. Also, much research is done on manatees, as understanding them will help to save them.

The Florida Manatee Recovery Plan was created by the U.S. Fish and Wildlife Service to work on increasing the numbers of manatees in Florida. Its goals include preserving manatee habitat, keeping tabs on the population numbers and their whereabouts, and to find out the causes of death of manatees and reduce them (Ripple, 1999). There are 13 ÒkeyÓ counties in Florida that are the main focus of the recovery plan, as 80% of manatee deaths occur there. Most have begun putting measures into place to protect the manatees that reside in their waters (Save the Manatee Club).

The past, present, and future of manatees has been and is intertwined with ours. Without humans, it is highly possible that the manatee population would not have reached such low levels. Now, manatees need the help of concerned people to continue their existence here on earth. If we do not continue to make laws protecting manatees, and if we quit making the public aware of manatees and their needs, there is a real possibility that manatees may not be around for future generations to enjoy.

Works Cited
Ò01/09/1493: Columbus mistakes manatees for mermaids.Ó The History Channel.
.
Clapham, Phillip J., James A. Powell, Randall R. Reeves, and Brent S. Stewart. (2002).
ÒWest Indian Manatee.Ó Guide to Marine Mammals of the World. Chanticleer
Press, Inc. 482-485.
ÒGenetic Uniqueness Threatens Florida ManateeÕs Future.Ó (1998). University of
Florida. November 18, 1998. /11/981118081606.htm>.
Odell, Daniel K. and John E. Reynolds III. (1991). Manatees and Dugongs. Facts on
File, New York, NY. 16-21, 49-54.
Ripple, Jeff. (1999). Manatees and Dugongs of the World. Voyageur Press, Inc.,
Vancouver, B.C. 88-100, 110-118.
Save the Manatee Club. ÒManatee Facts.Ó .htm>.
Walker, Cameron. (2003). ÒManatee May Lose Endangered Status in Florida.Ó National
Geographic News. February 26, 2003. News/2003/02/0226_030226_manatees.html>.