Though manatees are considered to be some of the bigger sea mammals, their bones are as brittle as porcelain. Manatee bones have no marrow cavity which is why their bones are so dense. With that information, manatees are more prone to fracture. Around 20 to 30 percent of manatee mortalities are a result of human-related threats–watercraft collisions. Since manatee bones are so fragile, when a boat's propeller comes in contact with a manatee it can result in scratching the manatee and causing them to scar.
The Florida manatee is a massive gray marine mammal with two front flippers and a broad, paddle-shaped tail. Studies average a manatee at 10 feet (3.05 meters) in length and 1,000 pounds (453.6 kilograms) in weight but can be as long as 15 feet (4.6 meters) and weigh more than 3,000 pounds (1,360.8 kilograms). Manatees are said to have evolved from grass-eating land mammals dating back to 50 million years ago, scientifically said to be four-legged animals that look like a cross between a pig-like creature and an otter. Now, the manatee's closest living relative is an elephant, an easy way you can see this relationship is through the fingernails a manatee has on their two front flippers.
Fossil remains of manatee ancestors show they have inhabited Florida for about 45 million years. Modern manatees have been known to be established in Florida for 1 million years (absent during the ice age). Manatees can be found in both salt and freshwater. They typically congregate in coastal waters or shallow streams and estuaries with warm temperatures and plentiful vegetation. The Florida manatee is found in coastal waters in the Gulf of Mexico and the Atlantic Ocean as well as Florida's shallow rivers, estuaries, and the Everglades. A manatee's body temperature averages at about 95°F (35°C), though manatees have layers of blubber under their wrinkly skin which is used for insulation and to increase buoyancy, it’s not enough to keep them warm during the winter months or when the waters drop in temperature. They only have 3-5% body fat! For reference, a human bodybuilder has about 10% body fat on average.
Manatees cannot tolerate temperatures under 68°F (20°C), one of the main reasons why they like to migrate into Florida’s spring waters, which stay at 72°F (22.2°C) all year around. During the warmer months (summer time), manatees migrate as warmer water temperatures allow for expanded travel. They have been reported as far north as New York City and as far west as Louisiana, although sightings in Alabama, Georgia, and South Carolina are more common.
The Florida manatee population is estimated to be approximately 6,000 individuals and continues to fluctuate due to female manatees averaging one calf every two to five years and usually beginning breeding successfully between the ages of seven and nine. Florida manatees are threatened by watercraft collisions, habitat loss due to development and pollution, and entanglement in fishing gear. Climate change also poses a serious threat in the form of fluctuating temperatures, resulting in either lethal cold snaps or unusually warm surface-water temperatures leading to more severe and frequent hurricanes and deadly red-tide algae blooms.
In 2021 the Florida Fish and Wildlife Conservation Commission reported 1,003 known deaths of manatees, the highest number ever recorded since the 1970s. The leading cause of manatee deaths relates to starvation and cold weather, but many reports show that an unsustainable number of manatees are lost each year to boat collisions alone.
Though manatees are considered to be some of the bigger sea mammals, their bones are as brittle as porcelain. Manatee bones have no marrow cavity which is why their bones are so dense. With that information, manatees are more prone to fracture. Around 20 to 30 percent of manatee mortalities are a result of human-related threats–watercraft collisions. Since manatee bones are so fragile, when a boat's propeller comes in contact with a manatee it can result in scratching the manatee and causing them to scar. One of the ways humans have tried to avoid this is by putting propeller caps on so they can’t slice the manatee, but this results in blunt force trauma which can cause a manatee's bones to completely shatter. Unlike humans and other mammals, manatees do not have the ability to reuptake their bone fragments, which leads to mortality. Many manatees do end up surviving sharp and blunt force trauma but at a cost.
When observing many manatees you will find scarring on their bodies, which can be from scratching themselves up against docs but it is most likely from boat propellers. Though it’s traumatizing for the manatee itself, it is also traumatizing for a viewer. But those scars have been beneficial for both science and everyday observation. Those marks are like tags. Each mark is uniquely different and helps scientists and viewers to track or remember specific ones, for purposes such as scientific study to find ways to prevent scarring to being able to name them for fun.
With that information, people and corporations like River Ventures, Fish and Wildlife Commission Committees, the coast guard, marine scientists, and everyday swimmers or boaters are able to come together and come up with ways to prevent the endangerment of manatees. In our beautiful Crystal River springs, we have implicated safe zones for manatees, no wake/idle zones, zones that can not be accessed by anyone or by any way, safety signs, precaution videos, and information sites as well as many others. Here you can find several ways to act and protect manatees every day. We and many others have taken action in our beautiful Florida waters to help lessen the number of injuries to manatees and you can too.