Status of the World Dugong Population by Country
(4 of 4)
Purpose of this page is to provide the country-by country information, accessible through The Map.
Okinawa Islands is thought to be the northernmost limit of the dugong range. It has been verified that a small number of dugongs live throughout the year in the sea area between Kin Bay and Ada, Kunigami Village. Six of them were sighted from the air along the Eastern coast within 12 minute period. A photo of three dugongs, apparently a family, was taken off-shore Kayou in Nago City. In the Kin Bay also, a parent dugong and a cub were photographed. These findings indicate that dugongs breed in the above sea area. The same area is also rich in sea grass colonies.
In other areas, such as Sakishima, no trace of dugongs was found. It is concluded, therefore, that the Okinawa dugongs form a small local population living mostly along the Eastern coast of the Okinawa Island and that they are under threat of extinction.
Japan and The United States government are planning to construct a U.S. Marine Corps sea-based air station off the eastern coast of the city of Nago, where seagrass is growing, in the northern Okinawa Island, as a tradeoff for the Air Station at Futenma, Ginowan city. This might destroy the habitat of the dugong, marine biologists have warned.
The proposed heliport is intended to replace the site at the U.S. Marine Corps' Futenma airfield that is to be returned to civilian control next year. According to Senzo Uchida, director of the Okinawa Expo Aquarium, since 1965 there have been 13 cases in which dugong were caught in fishing nets or their carcasses have been discovered on beaches in Okinawa. Of the 13 cases, 11 were along eastern coast of the main Okinawa island, he said. In December 1995, a female dugong was caught in a net five kilometers north of the planned heliport construction site. In January this year, a male dugong became stuck in a net eight kilometers south of the site. In the government's initial research into the construction of the helicopter base in September, researchers surveying the area by helicopter spotted a dugong swimming in the area, where seaweed abounds. Dugongs feed mainly on seaweed.
Seven researchers have started a project to find out more about the dugong's connections to Okinawa. The group said. "If our study finds that the heliport will have a negative impact on the preservation of dugong lives, the government should reconsider the plan." The group will also study the impact of noise and other factors on the mammals.
On 5 August 1993 the Service published a proposed rule to list the dugong population off Palau as endangered. The proposal noted that the population is declining and currently numbers fewer than 200 animals. The Service identified illegal hunting as the primary threat to the population and noted that hunting pressure, coupled with the species' low reproductive rate, could lead to the extinction of the population by the end of this decade. The proposed rule also cited threats associated with habitat loss.
Dugongs have been reported to occur in significant concentration around the entire coast and islands of Papua New Guinea.
Of the countries in dugong's range, only Australia and Japan are developed countries, so I think Australia and Japan have special responsibilities for dugong conservation. (Helene Marsh)
Australia is the last bastion of the dugong as it can still boast the largest remaining dugong population in the world. Recent surveys suggest that the total for Australian waters is in the tens of thousands.
However, surveys along Australia's Greet Barrier Reef reveal a crash in the populations of dugong. From a 1987 estimate of 3,500 numbers are now feared to have dropped to just over 1,700 - a decline of more than 50%. The reasons are likely to involve a complex mixture of traditional (legal) hunting, habitat loss and drowning in commercial gillnets ans shark nets.
Shark Bay's population of 10,000 is among the world's largest single aggregation. Favourable conditions exist here for studying the animal's behaviour.
Biologist Paul K. Anderson of the
University of Calgary recently discovered that males
stake out barren pieces of territory called leks.
They vigorously defend their leks in hopes of
attracting females, which venture forth only to mate.
The intrusion of a challenger can mean violent combat
between males, behavior that contradicts the popular
image of these mammals as gentle giants.
During summer the dugongs thrive in the
warm shallow waters near the eastern shores of Shark
Bay, where they dine on the starchy underground
rhizomes of the tropical seagrass Halodule uninervis.
But winter brings hard times for them. When the water
temperature in the shallow gulfs get below 18oCelsius
they move approximately 140 kms out to inshore water
behind Dirk Hartog and other islands, where oceanic
water mixes with the now cooler waters of the bay,
producing temperatures above 18o, which dugongs need
to survive. Here they only find a seagrass called
wireweed or Amphibolis antarctica, a southern
seagrass which does not store starch , so the dugongs
must survive in the cold winter on a poor diet. There
are indications that the animals get over the winter
months by deliberately supplementing this poor
vegetarian diet with animal food such as bottom
Beginning with efforts in 1999 by Dr. Nick Gales, dugongs within Shark Bay have successfully been caught and GPS locational tags deployed. After a year of trials and fine-tuning, five GPS tags were deployed for a 6-week period from August last year. All units were successfully retrieved by a remote release mechanism and were full of location positions. The subsequent plotting of the data showed the extent to which these five animals used areas of Shark Bay. Time-depth recorders (TDR's) were also attached to the harness system around the dugong's tail, allowing us to gain insight into the diving behavior of those animals as well as their movements.
With GPS now giving <5 m accuracy, the August 2000 deployment facilitated some fine-scale habitat analysis of those areas where the tagged dugongs had been concentrated. With seagrass analysis expertise from Edith Cowan University we are using videographic techniques to determine seagrass composition and cover within high-use dugong areas. Plotting dugong positions into Arcview with baseline seagrass data, distribution maps are produced which, used as management tools, will assist in the decision-making process for proposed developments within the Bay.
With the receipt of this grant the project will continue on for at least two more years, with at least four deployments each year. The working relationship established between all parties and the local community has been one of the highlights of the program. In the years to come we hope to apply the Shark Bay model with indigenous communities further north and up into the Kimberley region, and begin a program in those areas to understand the movements of dugongs along the entire Western Australian coastline. - Dave Holley (Marine Fauna Zoologist, Dept. of Conservation and Land Management, Technology Park, 17 Dick Perry Ave, Kensington, Western Australia 6151; phone (08) 9334 0290 Mb: 0417 952 118; fax: (08) 9334 0278; e-mail ) (Geo Australasia Jan 1999 and other sources)An aerial survey carried out in July 1999 suggested a total dugong population of over 13,000 dugongs in Shark Bay. A plausible but unproven explanation for this sudden increase may be a large-scale movement, presumably from the Exmouth area following cyclone Vance.
In Australia, dugong are protected by state and federal legislation which permits only indigenous peoples to legally hunt them. This law was initiated when traditional hunting of dugong was carried out by netting or spearing from a raft, however, now equipment includes harpoons with detachable heads and dinghies with outboard motors. These modern methods have allowed traditional hunting techniques to increase the number of animals taken and have the potential to substantially impact on local populations. Some Aboriginal communities now recognize the problem of declining populations and are looking at managing the impacts of their hunting practices.
To adequately conserve our current dugong populations a high level of protection must be given to both dugong themselves and their vital sea grass habitats. Strict regulations and control over coastal developments and boating activities, the banning of gill netting, removal of shark nets, cessation of inshore trawling in sea grass communities and modified Aboriginal hunting laws should all be incorporated in to a management concept to ensure that future populations of Dugong dugon in our Australian waters can be maintained.
Apparently there are still a number of
dugong around some islands of the western Pacific
such as Vanuatu (estimated population 400) and the
Philippines <<>> Africa + Middle East