Are Dugongs and Manatees Related?

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Gray in color. Short oval shape. Two flippers and a tail. These are the features found in both manatees and dugongs. But the similarities do not end there.

Manatees and dugongs are large-bodied, slow-moving and docile herbivores found in shallow water areas in warm coastlines and some freshwater bodies. They spend most of their day floating elegantly in water, taking several hours grazing on sea grasses and swimming gracefully with their powerful tails and flippers. Because of their slow nature and grass-eating tendencies, both manatees and dugongs are called sea cows, and their large size and gentle but curious nature makes them attractive creatures.

Belonging to the same order: Sirenia

Manatees and dugongs are mammals of the order Sirenia—that is, sea cows. The word Sirenia comes from Greek mythology to describe mermaids. The first sailors were persuaded to believe that these creatures were sirens (mermaids), hence the name of the order. Sirenians are unique marine animals because they are strictly herbivorous.

Manatees and dugongs are the two presently existing families of the order Sirenia. Among manatees, there are three living species, while just one species of dugongs is currently in existence—though researchers have shown that dugongs are the ones with the most subspecies (19).

The four living species of the order Sirenia are the Amazonian Manatee, the dugong, the West Indian Manatee and the West African Manatee. By the year 1768, there was a third family of the order Sirenia, the Steller’s Sea Cow, but it went extinct just 27 years after its discovery following massive hunting. The Steller’s Sea Cow was closer to dugongs than to manatees.

How big are they?

Dugongs and manatees have a relatively long snout, horizontal tail (like whales and dolphins) and short round paddle-like flippers. They can grow to 4 meters in length and weigh up to 450 kilograms. However, manatees are generally larger than dugongs, weighing 400-500 kilogram and growing to a length of 3.6 meters. Dugongs rarely grow longer than 3 meters and weigh on average 420 kilogram.

While manatees have horizontal tails with just a single lobe to move up and down as the animal swims, a dugong has a fluked tail with two separate lobes joined together in the middle. Manatees have divided upper lip and shorter snout for gathering food and feeding on plants, while dugongs have broad, short, trunk-like and downward facing snout with a slit for the mouth that’s useful when feeding off ocean floor.

Dugongs have overgrown incisors set at the front of the mouth and resembling small tusks. The incisors are usually only obvious in adult males. Manatees lack incisors and instead have marching molars (hind molar progression). Actually, manatees continually grow molars in the back quarters of their mouths such that when the front teeth grind down and ultimately fall out, the molars fully emerge and push new teeth forward.

Social life

Manatees and dugongs are solitary animals though they have different approaches when it comes to mating partners. For instance, manatees are devout polygamists with males having several partners. Female manatees give birth at the age of 3-5 and have successive births every 2-3 years. On the other hand, a female dugong lives with only one male for years. Females begin to give birth at the age of 10 and continue to do so every 3-5 years.
Dugongs spend their entire life in shallow, sheltered coastal areas such as bays and mangrove swamps. They never leave saltwater. But manatees can live in both freshwater and saltwater. In fact, although the West African and West Indian Manatee reside primarily in saltwater and migrate to warmer freshwater areas in winter, the Amazonian Manatee resides only in freshwater. Nevertheless, neither manatees nor dugongs can survive in cold water. They have to make the journey to warm water areas every winter.

Threats faced

Dugongs and manatees are highly vulnerable mammals. Both are exploited for bones, meat, oil and skin. Both face dangers such as accidental entrapment in fishing lines and nets, being hit by boats and ingesting plastic. They are also threatened by loss of habitat when mangroves are cleared, wetlands destroyed and rivers dammed.

Manatees and dugongs are close cousins. They have a lot in common, are incredibly wonderful creatures and great to spend time with in the water. At Captain Mike’s, we love these mammals and sharing information about them. We offer manatee tours in Crystal River, Florida for those who would like a memorable and delightful day in the water. For more information about manatees, manatee tours, kayaking and scalloping trips in Crystal River, Florida, visit the Captain Mike’s swimming with the Manatees website.

Swimming with the Manatees boasts the best water adventure in Crystal River, Florida with lots of things to do for you and your family. For more information, contact us online, or call us at (352) 571-1888.

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