Their doughy, whiskery, pudgy appearance is a far cry from the slender, alluring stereotype of mermaids.
However, that is precisely what dugongs were formerly thought to be in legend.
Legend has it that dugongs, which are marine creatures in the order sirenia, once enticed male-starved mariners in search of female companionship, thus giving origin to the mermaid tale.
So, what exactly are they, and how do these benevolent behemoths fend off those who would do them harm?
What Are Dugongs?
The dugong is special since it is one of the last herbivorous marine animals.
How did the Dugong get its name?
Dugong dugon is its formal scientific name.
Europeans likely adopted this name because it was similar to the local Visayan term for the species, one of the local dialects spoken by the people of the present Philippines.
Closest Relatives
The dugong is the sole surviving member of its family, the Dugongidae, and one of only four remaining members of the order Sirenia, among which are three species of manatees.
Steller’s sea cow, another family member, became extinct in the 18th century due to excessive hunting.
As of today, fossil evidence has identified 19 different genera within this family.
The sea cow’s closest relatives are elephants, even though the two animals couldn’t seem more different.
It’s estimated that the two populations split apart more than fifty million years ago.
The first Sirenians were likely quadrupedal amphibious mammals that could quickly transition between land and sea.
It’s possible these herbivores, which lived in very shallow waters, reached roughly hippopotamus size.
Habitat
The majority of these creatures can be found in the tropical regions of the Pacific and Indian oceans.
They like to hang around in tropical coastal areas.
In addition to their native Australia, dugongs can also be found in Madagascar, India, and Thailand waters.
Although marine in nature, they have been known to make the landward trek, particularly to locations with brackish water (a combination of salt and fresh water).
The dugong prefers calm, shallow water from the dangers of storms and waves.
Further offshore, they may swim when the continental shelf is broad and shallow.
Due to their proximity to the coast, dugongs are sometimes threatened by larger boats and other human activity.
Breeding
Female dugongs typically have one calf every three to seven years, and the birth takes place underwater.
For the first year or two of its life, the calf remains close to its mother, nursing from her teats and learning from her.
Dugongs mature between the ages of 4 and 17 years.
Due to their slow reproduction, extended parental care, long intervals between offspring births, and reliance on seagrass, dugongs are particularly susceptible to human exploitation.
Do Dugongs Have Natural Predators?
An individual dugong is an attractive prey for a variety of sharks, crocodiles, and killer whales that frequent coastal waters due to the dugong’s peaceful nature.
Calves are especially defenseless in their first year of life, making them an easy target for predators.
Have Humans Ever Hunted Dugongs?
Humans have hunted dugongs for thousands of years because of the high demand for oil, skin, and meat.
However, dugong populations have sometimes flourished despite this human threat. Nonetheless, the species’ precarious situation worsened with the advent of mechanized hunting in the 18th century.
International regulations have improved protections for the species against illegal hunting, but it is still at risk from several other dangers.
How Does A Dugong Protect Itself?
Dugongs are not well-suited for life in combative situations due to their lack of acute senses and self-defense measures.
Due to their inherent disadvantages, these beings have been driven to adapt to an unforgiving ecosystem, learning how to live despite the odds always being against them.
They have adapted both physically and behaviorally to survive in harsh environments.
Navigation
Since dugongs lack several highly developed senses, they have modified their behavior to make it easier for them to obtain food and go around.
They can’t see very well, so they use their bristly snouts to feel their way around the ocean floor in search of food.
This aids the dugong in its search for food in the muddy, turbid waters in which it generally lives.
Predator Avoidance
Tiger sharks are one of only a few predators known to have a notable effect on the behavior of dugongs.
Researchers have found that when there are many tiger sharks around, the number of dugongs eating in the shallows drops.
This study adds to the growing evidence suggesting that dugongs avoid tiger sharks by moving to deeper water.
Let’s assume tiger sharks keep showing up in dugong feeding grounds in large numbers.
If this is the case, dugongs will keep going to the same deeper refuges they’ve been using to avoid sharks, even if they don’t have enough food there.
This means that avoiding predators is a top priority for dugongs.
As an additional line of defense, dugongs assess the safety of their environment not by the density of predators but by the ease with which they may escape to deeper water.
The capacity to flee is more important to dugongs than obtaining the richest and most abundant food source.
Cropping and Excavating
The dugong does not always have the luxury of picking a safe eating spot.
Therefore, dugongs have adapted certain self-defense mechanisms to ensure their continued existence in their preferred habitat, where predators actively target them.
A dugong will resort to cropping as the first line of defense when threatened.
While foraging outside their protected areas, cropping is a protective strategy used by dugongs.
Predator avoidance is the go-to strategy for dugongs, as it saves energy and generally succeeds when put to use.
Dugongs use a second defense mechanism called “excavating” to protect themselves from predators while gaining access to the seagrass that grows at deeper depths.
This strategy has several advantages, but the detritus generated by digging it out can be a magnet for predators.
For this reason, dugongs must dig in places with a low density of predators.
And because it can only be employed while the seagrasses are thriving—between February and May—the excavation mechanism is less effective.
Communication
Because of their restricted sensory capabilities, dugongs have evolved their social interactions to rely on sight and touch when they are close and sound when they are farther off.
They rely heavily on their eyesight for mating, using elaborate visual displays to woo potential partners.
Their entire bodies are covered in the same sensitive bristles that line their snouts, allowing the animals to interact simply by brushing up against one another.
Dugongs use a range of noises like barks and chirps to communicate with each other when they are separated by distance.
As a result, their hearing has evolved to be considerably more acute than their vision.
Cautious Dispositions
Due to a lack of defensive mechanisms, these organisms have developed strategies to avoid confrontation.
Due to human exploitation of their meat, teeth, and other resources, dugongs are now critically endangered.
Since then, dugongs have learned to be wary of and avoid interactions with other species, including humans.
Sources:
- https://oceana.org/marine-life/dugong/
- https://www.dcceew.gov.au/environment/marine/marine-species/dugongs
- https://www.americanoceans.org/species/dugong/
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