Manatee FAQ: Population

Q. What is a synoptic survey?
A. A synoptic survey is a statewide aerial survey designed to get a head count of individual manatees. The success of surveys is very dependent on weather conditions. If the weather is cold and clear, then manatees are gathered around warm water sites, making it easier to get a count.

The synoptic surveys, which are required by Florida law, are often mistakenly used as a gauge of how the manatee population is faring, but most population scientists agree that the surveys alone cannot be used to evaluate the manatee population. No information on manatee population health and trends can be inferred from the survey count. They are simply a snapshot of the number of manatees seen on those days.

Get more information on the current status of the manatee population and to see synoptic survey results from previous years.



Q. What's a better way to assess the manatee population?
A. A more accurate picture of the manatee population could be obtained by looking at factors such as past and projected population trends, area of geographic range and critical habitat, the number of mature individuals, and the probability of extinction. In addition, there is ongoing research that utilizes annual adult survivability and other long term research that is better suited to assessing the health and stability of the manatee population.

Q. How many manatees are left in the world?
A. Outside of Florida, little is known about the population of West Indian manatees or other sirenians in the world. By far, the largest population of West Indian manatees is found in the U.S. (Florida). Elsewhere, they are found in small population pockets throughout their range. All sirenian species in the world are considered endangered.

Q. Is the manatee population increasing?
A. Many researchers agree that in two areas in the state Florida the manatee population is growing, through both reproduction and migration of manatees from other areas of the state. These two areas, Blue Spring in Volusia County (known by researchers as the Upper St. Johns River) and Crystal River/Kings Bay in Citrus County (known as the northwest region), have been protected areas for over 30 years and are relatively rural areas with less boat traffic. Blue Spring is a no-entry zone (refuge) and several no-entry zones (sanctuaries) have been established in Kings Bay. Both sites also have substantial slow speed zones in surrounding waterways. It is believed that, because of these factors, these two sub-populations have increased. It is important to note, however, that these two groups combined comprise only about 16% of Florida’s total manatee population.

No one yet knows the status of the two remaining manatee regional sub-populations. The data available from these regions is not sufficient to make a statistically reliable estimate of the population trend. The East Coast and Southwest manatee populations may be stable at best or may be declining. This is important because these two regional sub-populations make up the remaining 84% (the vast majority) of the manatee population in Florida.

In 2003, a population model was released by the U.S. Geological Survey that predicted an extremely grave situation confronting the manatee in both the Southwest and Atlantic regions where the vast majority of manatees are found. It states, “In the absence of any new management action, that is, if boat mortality rates continue to increase at the rates observed since 1992, the situation in the Atlantic and Southwest regions is dire, with no chance of meeting recovery criteria within 100 years.”

See a copy of the USGS manatee population model in PDF format


Q. Has the manatee population grown since the 1950s and 1960s?
A. No one knows how many manatees there were in the 50s and 60s because there was little or no research being done. There could have been 10,000 manatees in Florida at that time or 500. Scientific, methodical research to determine the minimum population statewide began in earnest in the early 1990s when the first synoptic aerial surveys were conducted. Each synoptic survey results in a minimum population number. However, because of extreme variability between surveys due largely to weather conditions, this does not yield a statistical estimate of the population and cannot be used for population trend analysis.


Q. In terms of evolution, how long have manatees been around?
A. Actual manatee fossils found all over the world go back as far as 60 million years. Modern manatees evolved from four-footed land mammals. Manatee fossils found in Florida’s springs date back about 45 million years.





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