Text and photos (c) 2013 Erkki “Eric” Siirila, copyright & all rights reserved. (The article below is a short version of a more complete magazine article published elsewhere.)
There were about 2,500 manatees in Florida 30 years ago. In 2013 the number is approximately 5,000. “We have learned to live together with these animals”, says Visitor Services Specialist Ivan Vicente from the Crystal River office of the U.S. Fish and Wildlife Service. The conservation measures have lead to visible results in spite of the fact that boat propellers, fishings gear and toxic algal blooms (red tides) still threaten the population of the West Indian manatee, Trichechus manatus, in the U.S.
As manatees do not have any thick layer of blubber (unlike whales) under their skin, in autumn the U.S. manatee population migrates to the warm water areas of Florida. All the animals spend in the State the months between November and March. In spring and summer, some manatees migrate to other states while others stay in Florida most or all of the year.
Of the 2,800 manatees on the West Coast of Florida during wintertime, about 550 stay in the Crystal River wetlands. The reason is the underwater springs, the water temperature of which is higher than that of the sea and rivers in winter. Another 2200 manatees stay on the East Coast of Florida during the coldest months. The Atlantic and Gulf of Mexico populations never mix in spite of the fact that together they are considered the Florida manatee, a subspecies (Trichechus manatus latirostris) of the West Indian manatee.
Even in winter, the manatees sometimes leave their favorite warm-water spots. They do this in order to feed on sea grass, which does not grow in fresh water. Processing sea grass results in a lot of gas in the digestive system. This is one reason why the manatees look so fat.
On the West Coast of Florida, manatees have become an important attraction for nature tourism. In the Crystal River area, 34 companies have a license to arrange paddling or snorkeling tours to the protected areas. The number of customers per year is around 150,000. Numerous boats of the tour companies can be observed in the most popular destination Three Sisters’ Springs from early morning to late afternoon. Most of the time there are 20-50 snorkelers in the water. An approaching manatee may be touched, but disturbing a sleeping manatee may result in a fine. Boaters are fined when they do not respect the manatee-related speed restrictions while navigating the rivers and canals. Still, accidents do happen and it is common to see propeller cuts on the backs of manatees.
Outside the Crystal River wetland parks, many of the Florida manatees spend the winter months in the warm-water discharge spots of power plants. As some of the State´s power plants will be shut down in the near future, there are plans to continue discharging warm water into the wetland areas where the manatees are used to spending the coldest months. If this is not done, manatee deaths from exposure to cold water could be expected. There is a problem even in the natural wintering areas: the growing human population of Florida consumes so much groundwater that the freshwater outflow in the “manatee” springs is adversely affected.
An additional challenge for the Florida manatees is that genetically they are not well-equipped for future challenges. Their genetic heritage is narrow and diversity low, because the whole population has its origin in just a few West Indian manatees which swam to Florida from the Caribbean. In spite of the threats, the U.S. Fish and Wildlife Service expects the endangered U.S. manatee population to double another time during the next 20 years. In 2033 there would be 10,000 individuals of these aquatic mammals in the U.S. waters if everything goes well.
The three species of manatees and their relative the dugong are a specific coastal management challenge in the tropical and temperate waters of our planet. When the populations of these friendly animals are well managed, they have a high potential of becoming a major attraction for nature-oriented tourism.