Swimming against the tide

Swimming against the tide

Aquatic life is divided into two categories, marine and fresh water species. It is normally believed that marine animals are flesh-eating animals. Surprisingly however, there is a marine mammal called the dugong, which is a herbivore.

The dugong, along with the manatees (commonly called sea cows), is one of the four living species of the order sirenia. It is the only living representative of the once diverse family, dugongidae. It is of the genus dugong and species d.dugon, hence its binomial name is dugong dugon.

The only sirenian, dugong, in its range spans the waters of at least 37 countries throughout the Indo-Pacific. But a majority of dugongs live in the northern waters of Australia between Shark Bay and Moreton Bay.

Like all modern sirenians, the dugong has a fusiform body with no dorsal fin or hind limbs, and instead possess paddle-like forelimbs to manoeuvre. It can be easily distinguished from the manatees by its fluked, dolphin-like tail and flippers which lack nails on them.

Sirenians can easily suspend themselves slightly below the water surface as their heavy ribs and long bones act as a ballast. An adult dugong length rarely exceeds three metres (9.8ft) and this long individual would weigh around 420 kg. But typically, an adult dugong’s weight ranges from 250-900 kg. The largest dugong recorded was found off the Saurashtra coast of Western India, and was 4.06 metres (13.32ft) long and weighed 1,016 kg.

In spite of the longevity of the dugong, which may live for 50 years or more, females give birth only a few times during their life and invest a considerable time period in parental care. Females give birth after a 13-15-month gestation, usually to just one calf.

Dugongs have a different significance in different places where its population spans. In Kenya, it is known as the ‘Queen of the Sea’ whereas in Southern China, it is regarded as a ‘miraculous fish’.

Where dugong meat and oil is a source of food in Australia and Torres Strait, in the Gulf, its tusks were useful as sword handles. The Japanese used its ribs to make carvings, while in the Philippines, the body parts of the animal are used to ward against evil spirits. In Thailand, the dugong’s tears are believed to form a powerful love potion while Indonesians considered them as reincarnations of women.

Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include hunting, habitat degradation and fishing related fatalities. With its long lifespan of 70 years or more and the slow rate of reproduction, the dugong is particularly vulnerable to extinction.

As the dugong has been hunted for thousands of years for its meat and oil, its current distribution is reduced and disjunct and many populations are close to extinction. The IUCN (International Union for Conservation of Nature) lists the dugong as a species vulnerable to extinction, while the Convention on International Trade in Endangered Species (CITES) limits or bans the trade of derived products.

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