News

By Tiare “TJ” Fridrich, Manatee Biologist

Don’t let their size fool you—despite the manatee’s unofficial title as the ‘chubby mermaids of the sea,’ manatees don’t have nearly as much fat as other aquatic mammals do. While other aquatic mammals, like seals and walruses, have a thick layer of blubber to help them stay warm, manatees only have a thin layer of fat. This is because manatees are adapted to live in the tropics, where the water temperatures are warm nearly year-round. Because manatees don’t have a thick layer of fat, they struggle to maintain their body temperature in colder temperatures. When they are exposed to water temperatures less than 68 °F for a prolonged period (typically a couple of days for an average-sized manatee), they can develop cold stress syndrome, which is like hypothermia in humans and it can be fatal. Florida manatees must seek out sources of warm water to survive the coldest weeks of the Florida winter. These sources include natural springs, power plants, and thermal basins. It is critical that manatees are able to access warm-water sites—termed ‘warm-water refuges’—because without them, manatees would not survive Florida’s colder winter months.

Before much of Florida’s natural landscape was developed in the 1800s, most manatees would have depended upon natural springs, which are connected to the Floridan aquifer, to stay warm during the winter. An aquifer is a vast, underground layer of porous rock that holds most of the water humans use in Florida, and a spring is a natural opening in the aquifer where water comes to the surface. Thankfully for our manatees, this water is a consistent 72 °F year-round. Unfortunately, human development has restricted manatees access to many of Florida’s springs, and over-pumping of the aquifer has reduced the output of springs throughout the state. Today, it is estimated that 66% of all manatees depend upon artificial sources of warm water, primarily power plants, to survive the winter. During the 60 years that power plants have supplied warm water to manatees, they have changed their natural winter migratory pattern to favor these artificial sites, while more springs have become unavailable.

This dependence on power plants poses huge challenges to protecting manatees in the long term. The primary concern is that power plants weren’t built to last forever. At some point, these power plants will go offline, and their constant discharge of warm water will disappear along with them. This raises the question: Where will manatees go when that happens? Manatees have ‘high site fidelity’, meaning that they go to the same warm-water sites year after year, and during the time their young travel with them (a period of two years), these calves also learn the same patterns as their mom. Manatees will continue to visit a site they’ve been to before, even if there is no warm water there, exposing them to cold stress during periods of low temperatures. Experts agree that a plan needs to be in place for when the plants do eventually go offline in order to avoid this outcome. Save the Manatee Club staff have joined the U.S. Fish and Wildlife Service, Florida Fish and Wildlife Conservation Commission, and other manatee conservation experts to devise a plan to protect and restore the warm-water habitats already available to manatees, while identifying other ways that we can improve the network of warm-water sites across the state. We will continue advocating for stronger manatee protections at existing sites, as well as making inaccessible sites finally available to manatees again.