Manatees and dugongs – same difference, right? And no quick Google image search is going to change that perspective – after all, they look alike. But in fact, the two living mammal species that belong to the sirenian animal order are oceans apart in terms of location, biology and behaviour.
They’re classic chalk and cheese: both slow-moving herbivores that operate in similar ecosystems with similar looks and similar builds, but to the trained eyes of those who know, they have many different characteristics. There are four living species of Sirenia – the West Indian manatee, the Amazonian manatee, the West African manatee and the dugong – all referred to as “sea cows” and each found in a different area.
To understand their differences deeper, we take a look at the main, but subtle, points that separate these creatures:
Both creatures are related to the elephant, but evolution has played a part in redefining their tails to be more efficient underwater. One of the main physical differences between the dugong and manatee is the tail: Manatees have a horizontal, paddle-shaped tail with only one lobe to move up and down when the animal swims; it’s similar in appearance to that of a beaver tail. Dugongs have tail flukes with pointed projections, like dolphin or whale tails but with a slightly concave trailing edge.
With different characteristics, it appears that manatees are the more outgoing out of the two. Both are solitary creatures, but manatees are devout polygamists – having up to several female partners. Dugongs, however, stick to just the one, which they live with for life.
Scientific name: Dugong dugon
Average lifespan: 70 years
Size: 2.4 – 3 metres
Weight: 230 – 500 kilograms
Dugongs are large marine mammals that are found near coasts around the Pacific and Africa. They spend most of their lives grazing on underwater grasses, rooting for them with their bristled, sensitive snout which acts as a sub-aqua hoover. Unfortunately, due to their docile behaviour, they are easy prey to illegal hunters, and their population has been heavily reduced.
Female manatees usually give birth at three years and continue to do so every two to three years. Their gestation period is 12 months. Female dugongs differ in that they usually give birth at 10 years and only every three to five years after that. This is mainly due to their long lifespan and slow rate of reproduction.
Dugongs have short, broad, downward facing trunk-like snouts that are horseshoe-shaped with a slit-like mouth. The snout ends with a cleft, a muscular lip that aids the dugong in its foraging for seagrass – because of this it is a strictly bottom-dwelling feeder. Manatees have a divided upper lip and a shorter snout, which means that they are able to gather food to eat and also able to feed on plants growing at or near the surface of the water.
Scientific name: Genus Trichechus
Average lifespan: 40 years
Size: 2.4 to 4 metres
Weight: 200 to 600 kilograms
Manatees are voracious herbivores found throughout the Caribbean, the Gulf of Mexico and Africa. Their diet consists mostly of plants like mangroves, turtle grass and some algae. Despite their massive bulk, they are graceful swimmers in coastal waters and rivers.
Manatees inhabit the marshy areas of the Caribbean and the Gulf of Mexico (West Indian manatee, Trichechus manatus), the Amazon Basin (Amazonian manatee, Trichechus inunguis) and West Africa (West African manatee, Trichechus senegalensis). Dugongs spend their entire life in shallow, protected areas such as bays and mangrove swamps as well as the waters off northern Australia. Manatees generally live in fresh water, whereas dugongs can usually be found in marine environments.
West Indian and West African manatees have fingernails – albeit very basic ones – on their forelimbs. But Amazonian manatees and dugongs do not have any nails.
Mature male dugongs have a pair of tusk-like incisors and manatees do not. In fact manatees have no incisors, only molars which are continuously replaced. The teeth of manatees move forward like a conveyor belt: As the tooth comes forward from the back, another tooth then takes its place.
A dugong’s nostrils are further back on its head than they are on a manatee. Both are specially designed for being submerged in water. For the dugongs their nostrils act like valve openings on top of their heads, which open when they breach for air, and close when underwater.