Dugong



 

The Dugong is a large marine mammal that belongs to the same mammalian order as manatees. The species in this order, known as Sirenia, are sometimes called sea cows and are thought to have evolved from an ancestor related to elephants. Found in the Indo-West Pacific region, Dugongs are believed to have spawned mermaid legends after sailors spotted them at sea and mistakenly identified them as half-fish/half-human creatures. Dugongs are considered highly endangered globally and The Singapore Red Data Book (2008) has classified them as "critically endangered" locally.

Description
The Dugong has a streamlined body with a rounded head, resembling manatees. The dull brownish-grey skin is thick, smooth and sparsely covered with hair. Its mouth is on the underside, facing downwards, and there are stiff bristles on the upper lip. The two nostrils are at the front of the face. Adults have a pair of tusk-like incisors in the upper jaw and the males use these to fight each other during mating season.

The Dugong's forelimbs are thick, paddle-like flippers that it uses for steering while swimming and for moving over the seabed during feeding. Instead of hind limbs, it has a fluked tail to propel it forward when swimming. However it has no dorsal fin. Although it spends its entire life in water, it breathes air like other mammals and needs to surface for oxygen.

It can be found alone, in pairs or in small groups of about six individuals. Living near the coast, it rests during the day in deeper waters and moves to shallow waters at night to feed. As it cannot hold its breath under water for very long, dives usually last no more than three minutes.

Reproduction
Dugongs reproduce very slowly. Females give birth only every 3-7 years, producing a single offspring (occasionally twins) after a gestation period of 13-14 months. Furthermore, Dugongs reach sexual maturity rather late at 9-10 years and may not breed until 15 years. So despite a lifespan of up to 70 years, a female Dugong will give birth only a few times in her life. After birth, which usually takes place in shallow waters, the mother will suckle her young for up to 18 months. The calf will cling to its mother's back as she grazes.

Diet
Dugongs feed on marine plants, especially seagrass. Their mouth, teeth and digestive system are specially adapted for a seagrass diet. They pull up the seagrass with their thick, flexible lips and shake the leaves to remove any sand and debris before swallowing.

They often have a favourite patch of seagrass that they will crop frequently to speed up the growth of young tender leaves, which they prefer to eat. However, as they eat large quantities of seagrass, they may travel several hundred kilometres within a few days to feed from different locations.

Distribution and Habitat
Dugongs inhabit the tropical coastal waters in the Indo-West Pacific region. They can be found in the Red Sea and in the territorial waters of African countries such as Madagascar, Tanzania and Somalia. They can also be found in Australia, China, Japan and India as well as throughout Southeast Asia, including Singapore, Malaysia, Thailand, Cambodia, Vietnam, Indonesia and the Philippines.

Dugongs have been sighted mainly in the Johor Straits off the northeastern coast of mainland Singapore. Sightings have also been recorded in the waters off the Changi coast, off Labrador Beach and around the northeastern islands of Pulau Ubin and Pulau Tekong.

Reported Encounters
13 Feb 1996
: A Dugong was found dead on Changi beach with many cuts on its body. It was almost 2.5m long.
Sep 1998 : A female Dugong calf was spotted near Pulau Ubin swimming around her dead mother, who had drowned in a fishing net. She was taken to the Underwater World Singapore as she was deemed too young to survive on her own in the wild. Named Gracie, she is now a star attraction at the oceanarium.
5 Jul 1999 : A 2.5m-long male Dugong was found dead near Pulau Ubin.
6 Jun 2006 : A 3m-long female Dugong carcass was found on the southern shore of Pulau Tekong.

Threats
Crocodiles and sharks are the natural predators of Dugongs, but humans are their primary threat. As a result of land reclamation and water pollution, beds of seagrass - their main source of food - have been degraded or destroyed. Because they feed in shallow waters, they are also often injured or killed by the propellers of passing motorboats. Sometimes, they get entangled in submerged fishing nets and drown.

Hunting is another cause of their demise. Their meat is said to taste like buffalo meat and their skin can be used to make leather or glue. They are also hunted for their thick layer of blubber (stored fat). In the early decades of the 20th century, the Orang Laut hunted them around Pulau Tekong and sold the meat to the Malays and Chinese. Although the hunting of Dugongs is no longer common in Southeast Asia, it is still taking place in other parts of their range.

Conservation
The Dugong is considered one of the most endangered animals in the world. Under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), commercial trade in wild specimens of this species is prohibited. As a signatory, Singapore protects the species listed in CITES through the Endangered Species Act. Under the Act, anyone caught importing or exporting a CITES-listed species without a valid permit is liable to be prosecuted in court and fined a maximum of S$50,000 for each animal and/or jailed for up to two years.

However, more important is the preservation of the Dugong's feeding grounds as the loss of seagrass habitats is now a major cause of the dwindling local population. None of the areas where Dugongs have been reported are currently protected as a designated "marine nature area". But in December 2001, the government deferred its plan to reclaim land at the Chek Jawa Wetlands, thus saving the area's abundant seagrass beds from destruction. Chek Jawa is located on the eastern tip of Pulau Ubin and Dugong sightings have been reported there.

Variant Names
Scientific name: Dugong dugon
Common names:
- English - Dugong, Sea Cow
- Danish - Dugong
- Dutch - doegong
- Finnish - Dugongi
- French - Dugong
- German - Dugong oder Pazifische Seekuh
- Italian - Dugongo
- Spanish - Dugon, Dugong, Dugongo
- Swedish - dugong, sjöko



Author
Valerie Chew



References
Convention on International Trade in Endangered Species of Wild Fauna and Flora. (n.d.). CITES species database. Retrieved April 21, 2009, from http://www.cites.org/eng/resources/species.html

Davison, G. W. H., Ng, P. K. L., & Ho, H. C. (Eds.). (2008). The Singapore red data book: Threatened plants & animals of Singapore. Singapore: Nature Society (Singapore).
(Call no.: RSING 591.68095957 SIN)

Dolphins fly in by Charlie to Underwater World. (1999, July 18). The Straits Times. Retrieved March 7, 2011, from NewspaperSG.

Francis, C. M. (2007). A photographic guide to mammals of South-East Asia. London: New Holland.
(Call no.: RSING 599.0959 FRA)

Francis, C. M. (2008). A field guide to the mammals of South-East Asia. London: New Holland.
(Call no.: RSEA 599.0959 FRA)

International Union for Conservation of Nature and Natural Resources. (2008). Dugong dugon. Retrieved April 20, 2009, from http://www.iucnredlist.org/details/6909

Lim, L. (2001, December 21). Ubin's nature beach gets a reprieve. The Straits Times. Retrieved March 7, 2011, from NewspaperSG.

Lim, L. (2001, December 29). Pulling together to turn the tide for Chek Jawa. The Straits Times. Retrieved March 7, 2011, from NewspaperSG.

Male dugong found dead near P. Ubin. (1999, July 6). The Straits Times. Retrieved March 7, 2011, from NewspaperSG.

Ng, P. K. L., Murphy, D. H., Lim, K. K. P., Chou, L. M., & Lane, D. J. W. (1995). A guide to the threatened animals of Singapore. Singapore: Singapore Science Centre.
(Call no.: RSING 591.529095957 GUI)

Ng, P. K. L., & Wee, Y. C. (Eds.). (1994). The Singapore red data book: Threatened plants and animals of Singapore. Singapore: Nature Society (Singapore).
(Call no.: RSING 574.529095957 SIN)

Sivasothi, N. (2006). Dugong carcass washed ashore on southern Tekong. Retrieved April 20, 2009, from http://rmbr.nus.edu.sg/news/index.php?entry=/news/20060608-dugong_tekong.txt

Tan, R., & Yeo, A. (Eds.) (c2003). Chek Jawa guidebook. Singapore: Simply Green.
(Call no.: RSING 333.91716 CHE)

Three-year-old Dugong Gracie moves to new home. (2001, January 25). Channelnewsasia. Retrieved April 21, 2009, from Factiva database.

Yeow, P. L. (1996, February 15). Dugong found dead on Changi beach. The Straits Times. Retrieved March 7, 2011, from NewspaperSG.


Further Readings
BBC Science & Nature. (n.d.). Dugong, sea cow. Retrieved April 20, 2009, from http://www.bbc.co.uk/nature/wildfacts/factfiles/3073.shtml

Lee, S. S. (1972, July 14). Carcass of a 500lb sea cow found on beach. The Straits Times. Retrieved April 21, 2009, from NewspaperSG database.

Ministry of National Development. (2001, December 20). Deferment of reclamation works at Tanjung Chek Jawa [Press release]. Retrieved April 21, 2009, from STARS database.



The information in this article is valid as at 2009 and correct as far as we are able to ascertain from our sources. It is not intended to be an exhaustive or complete history of the subject. Please contact the Library for further reading materials on the topic.

Subject
Endangered species--Singapore
Dugong--Singapore
Nature>>Animals
Wildlife
Science and technology>>Zoology>>Endangered animals

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