Dugongs (Dugong dugon) are a protected species of large marine mammals that resemble manatees. Dugongs belong to the order Sirenia of placental mammals. They have robust, torpedo-shaped bodies covered in tough, wrinkled, and sparsely-haired skin. Surprisingly, the elephant is the closest relative to both dugongs and other members of the sea cow family than any other marine mammal.
Throughout history, dugongs have been hunted by human beings. Today, hunting practices have resulted in an extreme decline in their population. They are considered to be near extinction or threatened by most scientists. The dugong is a species of cultural significance and an endangered species of wild fauna.
Appearance
The dugong has no dorsal fin or hind limbs and makes use of its forelimbs/flippers to paddle through the water. It also has a fluked tail with deep notches.
The nose, or snout, is downturned, with a cleft upper lip – an adaption that allows it to feed more easily on grass as it floats through the water. Its small eyes restrict its vision, making it more essential to navigate its environment via other means.
They also have some of the densest bones of any animal, which helps them remain just below the water’s surface.
Compared to its sheer size the brain is relatively small. This is likely because of their herbivore nature, which did not require them to evolve complex hunting abilities.
There are minimal sexual differences between males and females, as their body structures are nearly identical. The male’s testes are not externally visible, and the main difference lies in the positioning of the genital aperture concerning the umbilicus and anus.
Often, their body shapes are compared to those of dolphins. But dugongs are far bulkier and do not move as smoothly as dolphins do. They also have short hair.
Dugongs are obligate breathers, which means they need to surface regularly to breathe air and will rarely venture out into deep waters. They have a specialized muscle called the diaphragm, which helps them control their buoyancy and enables them to move vertically in the water column.
Did you know…
Dugongs can exhibit both solitary behaviours but are mostly social animals. While they are typically found alone or in small groups, they occasionally form larger aggregations in areas with abundant food sources. They communicate with each other using a variety of vocalizations, including chirps, whistles, and clicks. These vocalizations are essential for social interactions and maintaining contact with other species.
Habitat
Dugongs spend most of their time in the grassy sea beds of these warm latitudes, where they can find the most to eat. They can be found in warm coastal waters where grassy meadows are common. Their population concentration centers around living in bays, mangrove channels, and the waters around inshore islands.
They can be found up to a depth of 10 meters, although if the continental shelf remains shallow, they have sometimes been observed to travel up to 37 meters from the shore in search of seagrasses such as Halophila spinulosa. Higher latitudes dugongs are also known to take on long-distance migrations during the winter to find warmer waters.
The dugong is found throughout the warm waters of the Indian Ocean, the western Pacific Ocean, and the Southern Pacific, all the way to the eastern coast of Africa. The Persian Gulf has the second-largest population globally.
They can thrive in brackish waters and stretches with higher water quality, such as Queensland’s urban coast or Western Australia’s.
Before their populations became vulnerable, they were found in various places worldwide. They used to live off the coast of East Africa, the Red Sea, and the Mediterranean Sea. They were even seen near the Gulf of Thailand. In recent years, only a small number have been found in the waters of Borneo, scattered throughout the Malay archipelago.
Diet
The dugong is a herbivore, as are all sea cows. It eats a wide variety of seagrass and doesn’t have any advanced hunting capabilities. They ingest the whole plant, including the roots. They also turn to algae when sources of grass are diminished. There are also examples of sea cows eating jellyfish and shellfish on occasion.
Cultivation grazing is also observed in them, where they exhibit a preference for feeding on rapidly growing, nutrient-rich seagrasses. They tend to favor eating more younger plants and less fibrous strands of seagrasses during their feeding activities. This behavior is significant as it allows them to obtain a higher nutritional value from the seagrass meadows they frequent.
They are known for their seasonal migrations in search of food and suitable breeding grounds. They follow seagrass beds as they move to different areas, covering long distances during their migrations.
Reproduction
A dugong reaches sexual maturity between 8 and 18 years of age, much older than other mammals (on average). Through the growth and presentation of tusks in the males, females become aware that a potential partner has reached maturity. Recent studies reveal that there are different ages at which females can give birth. Location and environmental factors like food availability and water temperature influence their reproductive cycle. They do not have a specific breeding season and can mate year-round in some areas.
Males defend their territories and modify their behavior to attract potential mates.
After successful mating, the female undergoes a gestation period of about 13 to 14 months. They usually give birth to a single calf, although rare cases of twins have been reported. Calving often occurs in shallow, sheltered areas to protect the newborn from predators.
Females are highly dedicated mothers, providing extensive care to their calves. The mother and calf maintain a close bond, and dugong calves rely on their mother for nursing and protection during their early life. Young ones are large when they’re born and can remain with their mothers, nursing, for up to a year and a half.
Threats
The Steller’s sea cow, a common ancestor and the only other species belonging to the Dugongidae family was hunted to extinction in the 1700s. Today, the international trade of dugongs is strictly prohibited due to their worldwide decline.
Due to the large size, juveniles do not have any natural predators. However, they are threatened by coastal sharks, killer whales (orcas), and other large predators like saltwater crocodiles. Although they are protected throughout their range, there are still incidents in which these creatures are killed or accidentally captured.
They are believed, as a species, to be vulnerable to extinction due to overfishing. The species has been hunted for its meat, oil, and more for centuries. It regularly gets trapped in fishing nets, causing disruption, injury, and sometimes death.
In addition to the physical threats, dugong populations are also impacted by the increasing levels of plastic pollution in the ocean. Plastic debris contaminates their habitats and food sources.
According to the international union for conservation of nature and natural resources the status of Dugong is critically endangered.
6 More Facts About the Dugong
- It is the closest living relative is the manatee.
- They have been seen to exhibit playful behavior and interacting with floating objects, seaweed, or other marine creatures, showing curiosity and intelligence.
- The dugong brain is only 0.1% of the animal’s body weight.
- The largest individual recorded was 4.06 meters long and 1,016 kilograms. This mammoth of a dugong was found on the Saurashtra coast of west India.
- Dugongs, specifically Sirenians, are the only extant herbivorous marine mammals today, which have also evolved to live completely in the water.
- The color can change due to various algae growing on their skin.
FAQs
Are dugongs extinct?
No, they are sometimes described as vulnerable or threatened. Other times, organizations or individuals have classified them as near extinction. Throughout history, they have been hunted by human beings. This still occurs, to some extent, to this day. However, their territories are all protected by various organizations hoping to save the animals from extinction.
Are dugongs called sea cows?
Yes, dugongs are a species of sea cow. They take their nickname from their diet—seagrass. They spend their days grazing on grass on the seabed, not unlike real cows in a field.
How many dugongs are left in the world?
There are believed to be around 30,000 dugongs left in the world. The largest populations are in the waters around Australia.
Do sharks eat dugongs?
Yes. Sometimes, some species of coastal shark prey on dugongs. But they are not overly threatened by marine predators. They are at far more risk from hunters and human encroachment on their habitats.
Can dugongs attack humans?
Dugongs are arguably one of the friendliest creatures in the animal kingdom. They are known to swim with divers, eat sea plants, and interact with humans. It is safe to say that a dugong is unlikely to attack a human.
