Friday, August 02, 2013

Florida Manatee Conservation Status: Endangered

A recent headline in the Tampa Tribune reports that Florida manatee mortality has increased in recent years due to red tide and cold weather events. Manatee advocates interviewed in the article argue that these events should stall any movement to down-list manatees from endangered to threatened. Others, including property rights advocates and recreational boaters, argue that manatees should be upgraded from endangered to threatened.  Yes, these two (often polarized) stakeholder groups actually use a different word to describe reclassification.  What do you think?

Save the Manatee Club's Webcam captures manatees aggregated at Blue Springs...note the mother-calf pairs!

As a scientist, I believe it is important to consider all the available data before voicing an opinion to decision makers.  No matter what your perspective, it is imperative that you have the facts (data) before lobbying for your case with lawmakers.  In most cases, the legislators have little or no understanding of biology, ecology, conservation, or behavior.  So, it's important to be able to develop of logical argument for your perspective, supported by data and established biological concepts.  Here are some resources that may help you develop your argument:

Background and Legal Status
West Indian manatees were listed as endangered by the US Fish & Wildlife Service (FWS) in 1967. When the Marine Mammal Protection Act (MMPA) was passed in 1972, West Indian manatees gained federal protection. The following year (1973) the new US Endangered Species Act (ESA, which celebrates its 40th Anniversary this year) listed manatees as endangered.

At the state level, manatees were added to Florida's imperiled species list as threatened in 1974. In 1979, the status was changed to endangered (2007 Florida Manatee Management Plan). During these early years, manatee status was based on qualitative, rather than quantitative data. In fact, very little data were available at that time.

In 1999, the Florida Fish and Wildlife Conservation Commission (FWC) adopted new rules to standardize how species are evaluated for inclusion on the state's imperiled species list. In 2001, the FWC received a petition to reclassify the manatee. Final action on that petition was delayed until April 2005, when a biological review committee recommended upgrading manatees from endangered to threatened.  The FWC Commissioners accepted this recommendation in 2007.  However, before official action was taken, the 2007 IUCN Red List assessment was published, categorizing the Florida manatee as endangered (C1 ver 3.1).  Additionally, Florida Governor Charlie Crist sent a letter to the FWC, asking Commissioners to postpone a decision until the state could come up with a better method to estimate manatee population numbers.

In 2010, new threatened species rules approved by the Florida FWC Commission went into effect. The 2013 revised list of Florida's Threatened and Endangered Species reflected the changes to the rules. Basically, all federally listed species that occur in Florida were included on Florida’s list as Federally-designated Endangered or Federally-designated Threatened species. Since manatees are Federally-designated Endangered, they remain listed as endangered in Florida.

This moves the battle between manatee and property-rights/recreational boater advocates in Florida to the federal level. In December 2012, the Pacific Legal Foundation, representing Save Crystal River, a property rights organization, filed a petition with the USFWS to down-list manatees.  According to the petition, FWS has 90 days to respond. As of this writing, nothing official has been published regarding the petition. Save the Manatee Club and other manatee advocates continue to argue that the status should remain endangered.

Population Monitoring and Aerial Surveys
Several types of aerial surveys are used to count manatees in Florida.  The numbers mentioned in the Tribune article (1000 in 1973; 5000 in 2013) reflect the number of manatees counted during synoptic aerial surveys.  These counts are NOT statistically valid population estimates.

Synoptic surveys are simultaneous aerial surveys conducted each winter, which cover known manatee habitat where manatees aggregate on warm water effluents during cold spells. The Florida Fish and Wildlife Conservation Commission (FWC) uses these surveys to obtain a minimum count of manatees statewide.  Synoptic surveys are flown by an interagency team, usually one to three times each year, during the coldest days. The survey meets Florida's statute 370.12 (4), which requires an annual, impartial, scientific benchmark census of the manatee population. From 1991 through 2011, the counts have been conducted 27 times and these data are available online.  However, variables other than actual population size significantly affect the probability of counting a manatee, given a manatee is present in Florida's waters.  Therefore scientists have been reluctant to give actual population estimates, or even trends from year to year.

Rescue and Mortality Response
Florida Fish & Wildlife Conservation Commission (FWC) staff located throughout Florida are responsible for investigating every report of a dead or injured manatee.  FWC researchers work closely with law enforcement, volunteers, agencies, and organizations to verify injured or dead manatees. Once confirmed, a rescue or carcass salvage is initiated.  Injured manatees are transported to manatee rehabilitation facilities; manatee carcasses are transported to the St. Petersburg pathology lab, where a necropsy is performed to determine cause of death and collect other life history and pathology data. Mortality data are posted at on FWC's website.  Scientist have a lot more confidence in manatee mortality estimates than they do in manatee population estimates.

Correlation between Counts and Deaths?
By plotting trend lines for manatee synoptic survey counts and manatee mortality by year, we see that the two are positively correlated in some years and negatively correlated in other years.  Notice where the two lines touch (2002).  The minimum count for 2002 (1,758) was significantly lower than the year before (3,300) and the year after (3,127).  Scientists are confident (based on what we know about manatee biology, reproduction, and life history) that the population could not have possibly declined 50% one year and then increased 100% the next year.  More likely, the low synoptic survey count was due to a mild winter and poor visibility, making it difficult for observers to see manatees during the flights (Journey North). The high mortality was due to a significant red tide event.

So, if we cannot estimate manatee population numbers with statistical confidence, how did the IUCN assess the population as endangered in 2007 Here's the explanation:  
Trichechus manatus latirostris (EN C1):
The Florida manatee subspecies is listed as Endangered on the basis of a population size of less than 2,500 mature individuals and the population is estimated to decline by at least 20% over the next two generations (estimated at ~40 years) due to anticipated future changes in warm-water habitat and threats from increasing watercraft traffic over the next several decades.  In an attempt at full disclosure, you should know that I worked on the IUCN Assessment for the Antillean subspecies that year and am a co-author on this assessment.  Multiple lines of evidence, including modeling, probability of sighting data, proportion of calves/juveniles to adults data, and other life history data to make estimates.  However, some scientists call them guesstimates rather the estimates because they are derived, in part, from data that cannot be statistically analyzed.

What do I think?  Should the Florida manatee be down-listed?  Using the Precautionary Principle, I am not aware of statistically valid data that would support downlisting.  However, if the legal status for manatees is changed from endangered to threatened, the species is still at risk of extinction.  Existing protection must remain in full force.  To reduce protection would likely produce a significant and deleterious effect on the manatee population in Florida.

Read the Tribune Story here:

Wednesday, January 09, 2013

2012: A Good Year for Manatees?

Milder winter temperatures lead to lower annual manatee mortality count in 2012

Florida Fish & Wildlife Conservation Commission
Press Release January 8, 2013
Contact: Kevin Baxter, 727-896-8626
Additional Photos available:

Researchers with the Florida Fish and Wildlife Conservation Commission (FWC) documented fewer manatee deaths in 2012 than in the previous three years, as milder winter temperatures led to significantly less cold-related mortality. The FWC recorded 392 manatee carcasses in state waters last year, of which a quarter were determined to be from human-related causes.
FWC researchers, managers and law enforcement staff work closely together to evaluate mortality data and identify necessary actions. Actions may include steps to protect vital habitat or special patrols to ensure compliance with manatee speed zones.

The FWC is committed to conservation actions that reduce human-caused manatee deaths, including those related to watercraft. The FWC’s Division of Law Enforcement, in cooperation with partner agencies, uses knowledge of local boating conditions and habits, well-posted speed regulatory zones and up-to-date manatee information as part of its on-the-water enforcement operations.
Researchers documented 81 watercraft-related deaths in 2012, slightly below the yearly average of the past five years.

“Protecting manatees is a priority,” said Maj. Jack Daugherty, FWC’s Boating and Waterways section leader. “Our officers take time to patrol manatee zones, identify areas that have presented problems, and generally work with the public to educate them on how to boat safely and in a way that doesn’t harm the environment.”

To help prevent cold-related deaths, the FWC continues to work with partners to enhance availability of warm-water sites important to manatee survival. Among recent efforts was the restoration of Fanning Springs by the FWC and partners, which improves manatee access to a natural warm-water habitat off the Suwannee River.

To view preliminary 2012 manatee mortality data, visit and click on “Manatee Mortality Statistics.”  To learn more about manatee conservation, go to

As part of its conservation efforts, the FWC rescues distressed manatees throughout the state. The FWC and partners rescued 81 manatees in 2012, in many cases as a result of citizens contacting the agency. To report a dead or distressed manatee, call the FWC’s Wildlife Alert Hotline at 888-404-FWCC (3922).

Florida residents can also help manatees by purchasing the manatee specialty license plate, available at county tax collectors’ offices. The funds collected for these plates go directly to manatee research and conservation.

Friday, November 16, 2012

Florida manatees on the Move!

As weather cools, Florida manatees move to warmer waters

Florida Fish & Wildlife Conservation Commission (FWC) 
Press Release: November 15, 2012
Contact: Diane Hirth, 850-410-5291

Additional photos available on FWC’s Flickr site: Go to

Now that the weather outside is chilly, Florida manatees are migrating to warmer waters. They swim in search of a warm winter refuge such as freshwater springs or canals adjacent to power plant outflows.  An adult manatee may weigh 1,000 pounds or more but is susceptible to cold. Water temperatures dipping to 68 degrees or below can produce cold stress in these aquatic mammals, and even cause death.

With many of the seasonal manatee protection zones going into effect on Nov. 15, the Florida Fish and Wildlife Conservation Commission (FWC) cautions boaters to be vigilant about slowing down and watching out for manatees. In Broward County, some slow speed zones formerly active only on weekends are now in effect every day during the cold season. November is designated as Manatee Awareness Month because of this seasonal migration.

“Many manatees in Florida have scars from run-ins with boats. We can do our part to help by complying with slow-speed and no-entry zones that indicate manatees may be in the area,” said Kipp Frohlich, who leads the FWC’s imperiled species management section. “Boaters should slow down where manatees like to congregate, such as seagrass beds and warm-water sites.”

How to spot Florida’s official marine mammal?
Boaters and personal watercraft operators should scan the water near or in front of their vessels and look for signs that manatees are close by, including repetitive swirl patterns called a manatee footprint, a mud trail, or a snout or fluke (tail) breaking the water’s surface.

For a complete list of boating rules and regulations and other information, please visit FWC's Manatee page here:

Wednesday, October 31, 2012

Sirenews (Number 58 October 2012)

The latest issue of Sirenews is now available online at  Older issues are archived here:

In this Issue:

  • Sirenia Specialist Group Update
  • Tribute to Dr. Edward "Ed" Keith
  • Book Announcement:  Sirenian Conservation: Issues and Strategies in Developing Countries
  • News from the Secretariat to the UNEP/CMS Dugong MOU
  • English Language Writing Assistance
  • Third International Conference on Marine Mammals of Southeast Asia (SEAMAM III)
  • Local News from Australia, Brazil, Cuba, Iran, Suriname, and the United States of America
  • Recent Literature

Sirenews is the official newsletter of the IUCN/SSC Sirenia Specialist Group.  As such, please remember that Sirenews is an informal forum, not to be considered citable, formally-published literature; it is NOT "peer-reviewed", and contributions to it should not be quoted nor cited without the written permission of the author.  The opinions expressed are those of the writers and not necessarily those of IUCN or other organizations.

Sirenews (ISSN 1017-3439) appears twice a year in April and October and is edited by Cynthia R. Taylor and James A. Powell, Sea to Shore Alliance. Sirenews is supported by the U.S. Marine Mammal Commission and archived by Sirenian International.  Submission deadlines are April 1 and October 1.  Material may be submitted by e-mail to: Cynthia Taylor (ctaylor at sea2shore dot org).

Sunday, December 04, 2011

Her name was Griselda...

Photo by Matthew Beck
Her name was Griselda.  First documented as an adult in Crystal River in 1977, Griselda had given birth to at least 12 calves.  Unfortunately, I only saw her laying on the cold stainless steel necropsy table.   I had taken 3 international colleagues to witness a necropsy at the pathology lab on the campus of Eckerd College.  We were all in Tampa for 19th Biennial Meetings of the Society for Marine Mammalogy.

Griselda, an extremely successful mother manatee is gone forever from the Florida manatee population due to a boat strike that broke her shoulder blade and dislocated her 4th rib on the left side--rupturing her aorta.  She died of internal bleeding, probably within an hour of being hit.  Griselda was lactating, which means there is an orphan calf out there somewhere...hopefully old enough to survive on its own.

Unfortunately, this is the not the first time I've witnessed this cause of death.  One of the known manatees in Belize died in exactly the same way a few years ago, also leaving an orphaned calf.   This type of injury often leaves no external marks, no propeller cuts, and no bruising -- only a necropsy can determine the cause of death in such a case.  It occurs when the foot of an engine strikes the manatee on the back resulting in acute force at the point where the ribs attach to the spine.  In both cases that I've witnessed, the 4th left rib was subluxed (dislocated downward) piercing a large vein or artery near the heart.  As the heart continues to beat, blood is pumped out of the circulatory system into the muscles or body cavity.  Death generally comes within minutes.

Manatees have evolved over millions of years to be extremely successful in shallow aquatic environments.  But, they are not well designed for competition with motorized boats, which have only been around a few years.  We humans, as operators of these powerful machines, must take responsibility for preventing such deadly encounters.  Download this brochure and learn how to prevent tragic mortality events in Florida:

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