Dugong Totally Explained

Everything about The Dugong totally explained

The dugong (Dugong dugon) is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's Sea Cow (Hydrodamalis gigas) was hunted to extinction in the 18th century. It is also the only sirenian in its range, which spans the waters of at least 37 countries throughout the Indo-Pacific, though the majority of dugongs live in the northern waters of Australia between Shark Bay and Moreton Bay. In addition, the dugong is the only strictly-marine herbivorous mammal, as all species of manatee utilize fresh water to some degree. The dugong is heavily dependent on seagrasses for subsistence and is thus restricted to the coastal habitats where they grow, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as bays, mangrove channels and the lee sides of large inshore islands. although dugong hunting also has great cultural significance throughout its range. The dugong's current distribution is reduced and disjunct, and many populations are close to extinction. With its long lifespan and slow rate of reproduction, the dugong is especially vulnerable to these types of exploitation. a member of the manatee genus previously defined by Linnaeus. It was later assigned as the type species of Dugong by Lacépède and further classified within its own family by Gray and subfamily by Simpson.
   The word "dugong" derives from the Tagalog term dugong which was in turn adopted from the Malay duyung, both meaning "lady of the sea". Other common local names include "sea cow", "sea pig" and "sea camel". The body is sparsely covered in short hair, a common feature among sirenians which may allow for tactile interpretation of their environment. The dugong has paddle-like forelimbs which aid in movement and feeding, while its fluked tail provides locomotion through vertical movement. The teats are located just behind the forelimbs, similar to their location in elephants. Like the Amazonian Manatee, the dugong lacks nails on its forelimbs.
   Unlike the manatees, the dugong's teeth don't continually grow back via horizontal tooth replacement. The dugong has two incisors (tusks) which grow posteriorly until puberty, after which they first erupt in males. The female's tusks continue to grow posteriorly, sometimes erupting later in life after reaching the base of the premaxilla. The full dental formula of dugongs is:
Like other sirenians, the dugong experiences pachyostosis, a condition in which the ribs and other long bones are unusually solid and contain little or no marrow. These heavy bones, which are among the densest in the animal kingdom, may act as a ballast to help keep sirenians suspended slightly below the water's surface.
   Dugongs are generally smaller than manatees (with the exception of the Amazonian Manatee), reaching an average adult length of 2.7 metres (8.9 ft) and weight of 250 to 300 kilograms (550 to 660 lb). An adult's length rarely exceeds 3 m, and females tend to be larger than males.

Distribution

Remaining populations of dugong are greatly reduced, although they once covered all of the tropical South Pacific and Indian Oceans. Their historic range is believed to correspond to that of certain seagrasses., but their status is currently not well known.
An endangered population of 50 or fewer dugongs survives around Okinawa.

Ecology and life history

Feeding

Dugongs are particular about their diets, with certain 'fields' of sea-grass cropped. Dugongs are referred to as 'sea cows' because their diet consists mainly of sea-grass. Unlike manatees, dugongs are exclusively benthic feeders. The muscular snouts of dugongs are more dramatically tapered than those of manatees. Their primary feeding mechanism is uprooting sea-grass by digging furrows in the sea-floor with their snouts. Dugongs in Moreton Bay, Australia are omnivorous since they choose to eat invertebrates such as polychaetes when the supply of their choice grasses decreases. They will also go to any fresh water sources for drinking. Without these fresh water sources, many wouldn't survive. The amount of these fresh water sources, however, is beginning to decline. The dugong population is predicted to enter a steep decline. However, many scientists are working to prevent this potentially cataclysmic blow to the entire dugong population. Currently, this effort is proving futile, as the dugong population isn't showing any increased population numbers.

Migration

During the winter, a few herds of dugongs will move to warmer places in the northern countries, such as bays and canals. Dugongs also live in warmer waters of many other countries near the Equator.

Reproduction

Gestation in the Dugong lasts around 13 months, and results in the birth of a single young. The calf isn't fully weaned for a further two years, and doesn't become sexually mature until the age of 8-18, longer than in most other mammals. As a result, despite the longevity of the Dugong, which may live for fifty years or more, females give birth only a few times during their life, and invest considerable parental care in their young.

Importance to humans

Ancient interaction

There is a 5000-year old wall painting of a dugong, apparently drawn by neolithic peoples, found in Tambun Cave of Ipoh city in the state of Perak, Malaysia. This was discovered by Lt.R.L Rawlings in 1959 while on a routine patrol in the area. This dugong image together with some thirty other images were painted using haematite, a type of red colouring easily available in the area to ancestors of the Orang Asli living in and around Tambun.
When seen from above, the top half of a Dugong or Manatee can appear like that of a human woman. Coupled with the tail fin, this produced an image of what Mariners often mistook for an aquatic human. So, some say, was the origins of the mermaid myth.
During the Renaissance and the Baroque eras, dugongs were often exhibited in wunderkammers. They were also presented as Fiji mermaids in sideshows.

In the Bible

The dugong is referred to in the Bible by the phrase "sea cow" in several places in Exodus (for example, 25:5

& 26:14

) and in Numbers. Dugong hides may have been used in the construction of the Tabernacle, if dugong is an accurate translation of the biblical animal Tachash.

Dugong in captivity

Worldwide, only five dugongs are held in captivity. Two are the featured attraction of Toba, Mie Toba Aquarium in Japan; the third, named Gracie, is at Underwater World, Sentosa Island, Singapore; and the last two are found in Sea World on the Gold Coast, Queensland, Australia.

Conservation

Dugong are hunted for food throughout their wildlife range, usually for their meat and blubber. Also, the seagrass beds which the dugong depend on for food are threatened by eutrophication caused by agricultural and industrial runoff. Due to their shallow water feeding habits, dugong are frequently injured or killed by collisions with motor vessels. Because of their large size, they don't have many natural predators. These include sharks, killer whales, and saltwater crocodiles.
The U.S. and Japanese government want to build a new base on a coral reef close to Henoko, in Nago prefecture, Okinawa. This plan has generated strong protests from Okinawans who are concerned that the local environment, home to the dugong, would be ruined. Greenpeace stepped-up its campaign protesting the Okinawa base expansion in the summer of 2007, as authorities recommenced their airbase development plans .
Around the waters of Papua New Guinea, natives have been known for hunting dugongs. However, they also hunt dugong's predators, such as sharks.

Fiction

In the novel Twenty Thousand Leagues Under the Sea by Jules Verne the French Canadian harpooner Ned Land kills a dugong, an animal considered very dangerous and tasty, as food for the crew of the Nautilus. In the sequel to this book The Mysterious Island, a dugong is also present on the island where the protagonists are stranded after their spy balloon flight from the American Civil War.
   The Dugong is also the real-life basis for the Dewgong, a fictional species of aquatic Pokémon.
   The Dugong is also referenced several times throughout the Aubrey & Maturin series of books by Patrick O'Brian, as well as the now extinct Steller's Sea Cow and the Manatee.
   In the Japanese manga One Piece, Luffy and his crew meet a group of Dugong while on the island of Alabasta.

Further Information

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