Florida Manatees: On the Brink of Extinction

Author:  Feng Charles
Institution:  Human biology
Date:  September 2005

Just off the Florida coastline, you'll find manatees grazing on bright green tufts of sea grass and floating peacefully on the ocean's surface. Their massive body size , they weigh as much as cars , allows them to avoid worrying about predators. With their firm position atop the food chain, manatees have not significantly evolved for at least 40 million years. Indeed, manatees seem to lead an idyllic life.

Florida manatee (Trichechus manatus). Source: U.S. Fish and Wildlife Service/Galen Rathbun.

Florida manatee (Trichechus manatus). Source: U.S. Fish and Wildlife Service/Galen Rathbun.

Yet, census data currently estimate that there are only about 3,000 of these creatures left in the United States. In the last hundred years, human urbanization has been the greatest threat to manatee populations. Manatees can drown in flood control structures (such as levees), ingest fishhooks and other litter, or become entangled in fishing nets. Collisions with watercraft, however, result in the largest proportion of manatee deaths.

Unfortunately for the manatee, boating is an integral part of Florida's tourism and culture. Florida welcomes more than 40 million visitors a year to bask on its splendid beaches and enjoy its water. With nearly 8,000 miles of coastline, it is not surprising that Florida issued licenses to 1.6 million boaters in the year 2000 alone. Floridians and tourists alike spend the majority of their boating time in shallow water , the same area where manatees rest and search for food. As a result, the number of manatees killed by boats increased at an average rate of 9% per year between 1975 and 1989. While a manatee swims at a leisurely three or four miles per hour, boats speed along at 20 miles per hour. Much like a deer hit by a car, a manatee receives the brunt of the impact when it collides with a boat , if the whirling propellers make contact first, the gruesome result is far worse.

Cheryl Buckingham of the University of Florida has shown that manatees ignore the number of boats present in a particular location if it offers a thermal refuge , a warm area in otherwise cold waters. Manatees place certain priorities , such as a heat source , above the dangers associated with boats, thus placing themselves at greater risk for injury or death.

In addition, the manatees' reproductive ability , at a rate of one calf every two to five years , matches their laidback lifestyle. Due to boat collisions, their reproduction rate does not keep up with the increasing rate at which they die. Like many mammals, their reproductive cycles are cyclical , unfortunately, the onset of the boating season correlates with the period of time the manatees are most active in mating rituals.

If boat collisions don't kill the manatees, the injuries that result could still impair reproductive or auditory abilities. Indirect consequences of boating include decreased habitat quality and behavioral disturbance, resulting in the disruption of normal feeding and breeding patterns.

Despite the documented effect of boats, fisherman say recreational boaters are only partly to blame. Stowell Robertson, executive director of the Indian River Guides Association, a group of sport-fishing guides, doesn't believe that boats are the main source of manatee death. He told the Christian Science Monitor, "We know what kills most of the manatees in this area: the fuel barges." Fuel barges, large vessels that carry gasoline, sometimes travel through manatee habitats, disrupting manatee foraging and behavior.

Whether barges or recreational boaters are to blame, the result is the same: public outcry. After public pressure mounted in 1989 over the increasing number of manatee deaths due to boating accidents, then-Florida governor Bob Martinez instituted a number of recommendations: statewide nighttime speed limits for all waters and daytime speed limits for channels, increased law enforcement, and mandatory operator licenses.

Unfortunately, more than a dozen years later, many of these recommendations still remain well-intentioned thoughts that have not been carried out sufficiently.

"In the late 1980s, the state of Florida embarked on the strategy of county-by-county protection plans instead of proposed state-wide boating safety and manatee protection measures," said James Reid, a manatee researcher at the U.S. Geological Survey. "This has resulted in the current situation of delayed plans, bitter hostility among parties, and conflicts in interests."

Politicians have since set up slow-speed zones in the 13 Florida counties that account for 80 percent of all boat collision-related manatee deaths. The goal is to give boaters and manatees more time to avoid each other. In this way, during a possible collision, at least the impact may be considerably reduced. The usefulness of this legislation, however, is quite limited: the speed-zones are only in effect in the winter, even though mortalities aren't season-specific. Moreover, the laws themselves are difficult to enforce, since a small number of officers have to cover large areas of ocean.

Despite the slow-speed zones, boating accidents remain the number one cause of manatee deaths. In order to prevent boats from further harming these creatures, policymakers suggest that boaters add speedometers to measure their boat's velocity, as well as the mandatory usage of small, audible motors, so boats traveling at reasonable speeds can easily be heard. Policymakers also believe that signs defining a 5 mile per hour speed limit would help if placed in easily noticeable areas where large numbers of boats and manatees encounter each other.

Implementation of these regulations would be relatively straightforward, since only 10% of boaters polled in a Florida State University study indicated that the slow-speed zones reduced their ability to enjoy boating. A few inexpensive add-ons should not affect their boating experiences. Reid's sentiments echo this research. "Most boaters are for manatee protection; the industry and those that want no government regulation are the vocal faction," he said.

Consequently, conservationists suggest that the government carefully focus on the whole infrastructure of waterfront development as it pertains to water recreation, particularly in areas where manatees have a high population density. Counties could produce comprehensive development plans, including the specific locations for navigational channels, marinas, docks, and floodgate controls. There could be specified zones for water-skiing and fishing, as well as mandatory manatee-sensitivity seminars for boaters akin to driver's training.

Policy makers should still be mindful of implementing new laws at the expense of old ones. "I am not convinced that more rules and regulations are needed," said Quinton White, a marine scientist at Jacksonville University. "Improved enforcement of current laws and increased education about manatee protection will continue to allow the number of manatees to increase."

Boaters are willing to compromise as well. A University of Florida study indicates that the average resident is willing to pay four times the amount for manatee protection as the average boater is willing to pay for unlimited speeds in the waterways.

In March 2002, the first law that gave some weight to manatee protection in county development proposals was finally passed. Jim Kalvin, president of Standing Watch, a boater advocacy group based in Naples, Fla., said in response, "We're satisfied with this law [because] we got our rights written into the statute." This suggests that perhaps out of moral obligation, or maybe out of pity for these gentle creatures, Florida residents are willing to do their share to ensure the manatees' continued survival. It is now up to the government to carry out the legislation.

Ideally, sanctuaries would be created in areas of high manatee population density , even if those areas are popular destinations for boaters. In Crystal River and Blue Spring, where the shores are totally set aside for marine conservation, manatee populations have increased at a faster rate relative to other cities along the Florida shoreline. At the same time, human-related manatee deaths have significantly decreased. Thus, Crystal River and Blue Spring are the physical manifestations of tireless efforts on the part of environmentalists to protect the manatees. Now more reserves are necessary in order to ensure that manatees will be around for future generations to enjoy.



Suggested Websites

Save the Manatee Club: http://www.savethemanatee.org

Manatee Information: http://www.geocities.com/manateecondo/about.htm

Earthwatch Manatee Research Mission: http://www.earthwatch.org/expeditions/reynolds.html

Suggested Reading

Bossart, G.D. The Florida manatee: On the verge of extinction? Journal of the American Veterinary Medical Association. 214: 1178-1183 (1999).

Buckingham C., et al. Manatee response to boating activity in a thermal refuge. Wildlife Society Bulletin. 27: 514-522 (1999).

Griebel U. and A Schmid. Brightness discrimination ability in the West Indian manatee (Trichechus manatus). Journal of Experimental Biology. 200: 1587-1592 (1997).

Lefebvre, L., et. al. A characterizing manatee habitat use and seagrass grazing in Florida and Puerto Rico: Implications for conservation and management. Pacific Conservation Biology. 5: 289-198 (2000).

Richey, W. Water rights: Florida boaters vs. manatees. Christian Science Monitor. 5 February 2001.

Shackley, M. Manatees and tourism in southern Florida: Opportunity or threat? Journal of Environmental Management. 34: 257-265 (1992).

Wright, I., et al. Trends in manatee (Trichechus manatus latirostris) counts and habitat use in Tampa Bay, 1987-1994: Implications for conservation. Marine Mammal Science. 18: 259-274 (2002).