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Dugong, Dolphin Round Out Endangered Animal Coins
 | By Dennis G. Rainey, World Coin News
June 25, 2008 |
This column is Part Three of the three-part series on Malaysian marine animals that are considered endangered. In this part I will discuss the following mammals, all depicted on 2006 25 sen denomination coins: dugong (Dugong dugon), KM 105, IUCN Vulnerable; Irrawaddy dolphin (Orcaella brevirostris), KM 107, IUCN Data Deficient; and bottlenose dolphin (Tursiops truncatus), KM 108, IUCN Data Deficient. According to the IUCN's definition of a Data Deficient listing for a species, "A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. A taxon in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking." It does not imply a threatened nor safe from extinction status.
Dugong
The dugong's Malaysian name is duyung/dugong. The dugong and three species of manatees comprise the small group of mammals belonging to the Order Sirenia. Sirenians have heavy bulky bodies, front limbs with paddle-like flippers, lacking hind limbs, no dorsal fin and a flattened tail fin that is whale-like in shape.
Dugongs have thick, tough, almost hairless skin colored dark gray above and whitish below. They average about eight feet long and 650 pounds. There are records of 13 feet length and some 2,000 pounds. Adults use the flippers to "walk" through the pastures of sea grass they feed upon. Huge upper lips hang over the smaller lower lips, an adaptation for grazing sea grass. The small mouth opening is directed downward. The dentition is flattened, and in old dugongs only two molars remain in each side of each jaw. The skeleton is dense and heavy, enabling them to stay submerged when feeding. Eyesight and hearing seem to be good. It can swim up to about 13 miles per hour, but when foraging for food it swims slowly. They do dive in deeper water, sometimes staying submerged up to eight minutes. Dugongs are gregarious, and in areas where they have not been disturbed herds of several hundred may be found. A few areas in northern Australia is known for these aggregations. Its diet consists almost entirely of numerous species of sea grasses. Sexual maturity usually occurs at 9 to 10 years of age, but not before 17 in some. A single young is born underwater and can swim after birth to the surface to breathe. The young hold on to the mother's back while she feeds, and go up when she rises to breathe. They nurse underwater. If lucky, a dugong may live to the age of 70.
Dugongs inhabit coastal areas in Old World tropical and subtropical seas and infrequently visit estuaries and freshwater rivers. The historical distribution is vast, comprising 37 countries from the Red Sea to Vanuatu Islands in the western Pacific Ocean. (See Nauru 1995 $50, KM 11 and Tuvalu 1994 $20, KM 20 for their coins depicting the dugong). However, the present distribution is disjunct, closely tied to available sea grasses, and any worldwide population estimates are totally unknown due to lack of surveys in 23 countries. In the 14 countries, short surveys have been made primarily from the sea surface. As far as I can determine, aerial surveys have been made only in Saudi Arabia in 1986 (estimate of 1,800 dugongs), northern Australia and along the coast of Sabah, East Malaysia. Many - perhaps most - surveys depended on interviews with fishermen. There are no accurate surveys along the African coast, but since those coasts (possible dugong habitat) resemble those in Saudi Arabia, it has been "guessed" that about the same number lives there. This brings the total to 3,600 in the western region of dugong distribution. Only one small population exists in northwest India.
Dugongs occur in Peninsular Malaysia, Sabah, maybe Sarawak, Singapore and Brunei. Most recent records in Peninsular Malaysia are in the extreme south in the Johor Bahru region, capital of the state of Johor, within walking distance of Singapore via bridges and roads. Islands off the east coast of Johor have extensive beds of sea grasses. There is good evidence that a resident small population (10 or so) live there. There are 78 seagrass sites on east and west coasts of Peninsular Malaysia and in Sabah and Sarawak win East Malaysia with 14 species. Interviews with fishermen indicate another small population exists at a site on the west coast, but dugongs are rare in Peninsular Malaysia.
Aerial surveys along the coasts of Sabah revealed seven groups with 17 dugongs. A few reports exist about dugongs caught in gill nets in northern Sabah. Their occurrence in Sarawak is questionable but some may persist on the Brunei coast.
Threats to dugongs include habitat loss due to coastal development reclaiming many sea grass meadows. Land reclamation stirs up silt, killing not only sea grasses but coral reefs as well. Development also brings pollution. The Johor Baharu city (population 876,000) region (see above) gets 16 million foreign tourists annually, and the growth rate of the city is one of Malaysian's highest. It is also one of the biggest industrial centers in Malaysia. In the region of Sandakan on the east coast of Sabah, destruction of forests to establish palm oil plantations results in pesticides and sedimentation washing down rivers to pose a threat to sea grasses. Dugongs have been caught in fishing gill nets and traps in the Johor Straits area. Illegal dynamite fishing is a threat in Sabah. Historically, hunting dugongs for their flesh was common up to the 1970s, but they are now so uncommon that hunting has declined. Pleasure boats have increased greatly, and some dugongs have been killed by propellers.
Dugongs are protected in Malaysia and must be released if caught. The penalty for hunting, killing or being in possession of their meat is two years in jail and a fine of $6,600. However, there is no official policy for managing dugongs in Peninsular Malaysia. The University of Malaysia at Sabah does have a research program under way. Engaged in dugong research is the Marine Mammal and Whale Shark Working Group that consists of universities, Departments of Fisheries in Peninsular Malaysia and Sabah, the World Wide Fund for Nature (WWF), Malaysia and others.
Irrawaddy Dolphin
The Irrawaddy dolphin's Malaysian name is Lumba-lumba Empesut. This dolphin was first described from a specimen from the Irrawaddy River in Myanmar (Burma). They occur discontinuously along coasts in shallow brackish waters at mouths and upstream of rivers in southeast Asia and Australasia. Freshwater populations are in the Ganges and Irrawaddy and extend as far as 1,429 miles upstream and in the Mekong (in Cambodia, Laos and Vietnam) and Mahakam (in Indonesia) Rivers. On the Asian mainland, the dolphin occurs in the Bay of Bengal and then east to Palawan (Philippines). It may exist in China. It has been recorded in Sumatra, Java, river mouths of Sabah, Sarawak and Brunei, Kalimantan (Indonesian Borneo), Sulawesi, New Guinea and northern Australia.
The Irrawaddy's rounded head lacks a beak unlike the bottlenose dolphin outlined below, and its closest relative may be the killer whale. The average length is seven feet and weight is 254 to 287 pounds. It feeds on fish, squid and crustaceans.
There are no population size estimates for the species worldwide. The largest number is probably in northern Australia. There is evidence that this dolphin is fairly common throughout Sarawak waters and in all river estuaries. In one estuary, as many as 30 have been sighted. Many fishing trawlers throw back unwanted fish to the somewhat spoiled waiting dolphins.
In some areas such as Vietnam they are sacred and are released if caught in nets, but in some parts of India they are hunted for food. Some are caught incidentally in fishing nets in India and in anti-shark nets in Australia. Habitat degradation by timber industries, dams and gold mining are serious threats in some freshwater areas, and coastal degradation that produces pollution is becoming more and more a threat. Over-fishing of the dolphin's food resources in some major rivers is a major threat. Much more research into its ecology in Malaysia is greatly needed.
Bottlenose Dolphin
Lumba-lumba is the Malaysian name for the bottlenose dolphin. I was unable to find any relevant information about this dolphin in Malaysia. The bottlenose dolphin is close to being a cosmopolitan animal, but recent evidence claims there are two species involved. Animals in the tropical Indian Ocean are Tursiops aduncus and elsewhere are T. truncatus. At this time I do not know which form is in Malaysian waters, so I will not discuss this dolphin in Malaysia further. It is undoubtedly protected in Malaysia.
Elsewhere they are killed for their flesh (e.g. Japan), killed for bait for shark fisheries in several areas and are supposed competition to fishermen in Japan. Incidental catches in fishing nets kill a few to several hundred annually depending on the area. Tursiops in the North and Baltic Seas, western Mediterranean and Black Sea may be threatened, but worldwide this species is not in danger of extinction.
Author's note: An Aug. 8, 2007, newspaper article stated that the Chinese Baiji dolphin is likely to be extinct. This freshwater dolphin occurred only in the Yangtze River. Pollution and over-fishing created food shortage for the dolphin. See these two coins in the Standard Catalog of World Coins in the People's Republic of China section: 1988 10 yuan (Y 166) and 1996 5 yuan (Y 730).
Comments and questions are welcomed. Contact me at denrain@charter.net.
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