Despite their size and stubbly snout, manatees seem cute and cuddly to many ocean visitors. These large, slow-moving marine mammals hang out in coastal areas and rivers where Florida spring-breakers can easily see them and think that it is a good idea to hop on for a ride. Not only is this and other forms of harassment such as hugging the sea creatures illegal (the West Indian manatee is listed as endangered in the United States), but it can also impact manatees’ natural behavior, changing the way they interact with humans.
All three species of manatee—the Amazonian manatee, West Indian manatee, and West African manatee—and the related dugong are considered vulnerable (defined as facing a high risk of extinction in the wild) by the IUCN Red List of Threatened Species. This is due to a variety of threats including boat collisions, hunting, habitat destruction, and toxic red tides.
It's unclear if the manatees’ sweet looks can save them. In their favor is the fact that we’re no longer deliberately chasing them down, unlike how humans hunted to extinction their long-lost relative, the Steller’s sea cow, in the 18th century. But even slight disturbances to their lifestyles can do irreparable harm.
If you see a manatee this spring break, look but don’t touch.
1. Manatees are typically found in shallow coastal areas and rivers where they feed on sea grass, mangrove leaves, and algae. These herbivores munch on food for almost half the day, eating ten percent of their body weight in plant mass every day. With weights of up to 1,200 pounds, that is a whole lot of greenery!
2. West Indian (Trichechus manatus) and West African (T. senegalensis) manatees spend their lives on the cusp between salty and fresh water. They are able to maintain the correct balance in their bodies through an internal regulation system that works with the kidney to make sure salt concentrations never get too high. It is believed that West Indian manatees require some access to freshwater (PDF) in order to stay hydrated, but they are able to easily move between the two ecosystems.
3. Warm water is a must for the West Indian and West African manatee species. With low metabolic rates and minimal fat protection from cold water, they stick to water that is 60 degrees or warmer. They may look fat and insulated, but the large body of the manatee is mostly made up of their stomach and intestines! In colder months, they find their way to warm river tributaries or warm water outputs from power plants. In 2010 at least 246 manatees died in Florida due to cold stress from the colder-than-normal winter.
4. Manatees go to the surface of the water every three to five minutes to breathe although they can remain underwater longer, holding their breath for up to 20 minutes. When they do take a breath, 90 percent of the air in their lungs is replaced (whereas humans tend to replace about 10 percent).
5. The Amazonian manatee (Trichechus inunguis) lives entirely in freshwater rivers throughout South America in the Amazon Basin. It is hard to estimate their numbers due to their secretive nature and the murky water where they often live. A fourth dwarf manatee species was described in the mid-2000s, but this claim was called into question and it is believed to actually be a juvenile Amazonian manatee. The main threat to this species is illegal harpoon hunting for subsistence.
6. Dugongs (Dugong dugon), in the same order (Sirenia) as manatees, spend all of their time in coastal ocean waters of the Indian Ocean and western Pacific and they don’t ever venture into freshwater. Although they look similar to manatees, dugongs have a more whale-like fluke compared to the round, paddle-like tail that you see on manatees.
7. The closest living relatives of sirenians are elephants. Manatees evolved from the same land animals as elephants over 50 million years ago and the fossil record shows a much more diverse group of sirenians than we have today, with dugongs and manatees living together throughout their range.
8. Humans have one round of baby teeth and then if we lose or hurt an adult tooth, a trip to the dentist is in order. Manatees, like their elephant relatives, continuously replace their teeth throughout their lives with the older teeth at the front falling out and new teeth growing in at the back of their mouth.
9. Researchers believe that the now-extinct Steller’s sea cow (the largest member of the order Sirenia) was at one point found throughout the Pacific, in waters off Japan and the U.S. west coast. In 1741, Georg Wilhelm Steller first described the sea cow from islands off the coast of Russia (in what would later be called the Bering Sea) as subsisting off of kelp and not being able to submerge underwater. Within 27 years of first being described, the species was driven to extinction by hunting and competition for their kelp food source with an exploding urchin population.
10. Christopher Columbus and other early explorers claimed to have seen female figures swimming in the ocean—the mermaids in the writings and drawings of this era. Whether they had been at sea for too long or it was a trick of the light, we now know that many of these encounters were with manatees.
11. Manatee brains are smooth (compared to our own that have the familiar ins and outs of cortical folds) and the ratio of their brain to their body size is the lowest of any mammal. They may not be as clever as dolphins, but manatees can learn basic tasks, are extremely sensitive to touch and can differentiate colors.
12. Female manatees usually have one calf every two to five years and the calf then stays and nurses for two years. Calves nurse from their mother’s teats, which are found right where the forward limbs meet the body. The calves also can start nibbling on plants at only a few weeks old.
13. If you are a mammal—whether that’s a human, giraffe, whale or rat—then you typically have seven neck vertebrae. Only tree sloths and manatees have an irregular number of vertebrae—just six for the manatee. Scientists think this may have to do with their slow metabolism.
14. Manatees have no natural predators in the wild but humans have played a large part in making all three species at risk of extinction. About half of West Indian manatee deaths are caused by humans, and most are due to boat collisions. Manatees are quite buoyant and use their horizontally placed diaphragm and breathing to control their buoyancy. This and their average speed of 3 to 5 miles per hour means that manatees are way too slow to escape from the path of a speeding boat.
Learn more about the ocean from Smithsonian’s Ocean Portal.