Dugong dugon

Taxonomy (Name)

Picture

Distribution, Range

Coastal and Island waters between East Africa and Vanuatu between latitudes of about 27° North and South of Equator. See Marsh et al. (2002).

IUCN

Map

Country

Status

International Status

IUCN Red List Category

VUIUCN

Justification

The dugong's range spans at least 48 countries and an estimated 140,000 km of coastline. We have used two relatively crude relative indices of extent of occurrence: (1) length of coastline, and (2) area of continental shelf with a depth of <10 m. We then assembled the evidence for all countries in the dugong's range based on the review of the status of the dugong throughout its range conducted in 2002 with the assistance of more than 100 experts (Marsh et al. 2002) plus additional literature published since that time (see Tables 1.1 and 1.2 in attached PDF). The results of this synthesis are summarized in Table 2.1 (see attached PDF). This synthesis indicates that the dugong is declining or extinct in at least a third of its range, of unknown status in about half its range and possibly stable in the remainder ? mainly the remote coasts of the Northern Territory and Western Australia.

The only reference site is the urban coast of Queensland where the most robust quantitative data on population trends are available and a 40 year time series of catch rates in nets set for bather protection indicates that the CPUE in 1999 was only 3% of that in 1962 (Marsh et al. 2005). This CPUE is considered an index of dugong decline in the region from all causes during this period. This decline and modern aerial survey estimates of dugong abundance were used to backcast the population in the region in the early 1960s (which would be expected to have been lower than that at the time of European settlement as a cottage commercial industry for dugong oil had existed at several locations along this coast since the 1850s. The extrapolation suggested that the region supported 72,000 (95% CI 31,000, 165,000) dugongs in the early 1960s compared with an estimated 4,220 (95% CI 2,360, 8,360) dugongs in the mid 1990s. The seagrass habitat in the region is currently insufficient to support 72,000 dugongs, a result which suggests that the habitat had also declined (unlikely) or that the shark net CPUE has overestimated the decline (see Marsh et al. 2005). If the magnitude of this decline was robust and typical of the entire range of the dugong, the dugong would qualify for being classified as Critically Endangered at a global scale.

As summarized in Table 2.1, the major causes of the dugong's decline along the urban coast of Queensland are still present in most of the dugong's range as follows: gill netting 87-99%, subsistence hunting 85-98%, human settlement 82-85%, agricultural pollution 80-89%. The magnitude of these threats is likely to be greater in most other parts of the dugong's range than in Queensland. The Queensland coast supports a low human population density relative to most other parts of the dugong's range and has a well developed system of marine parks and pro-active management. There is also anecdotal evidence that the area of occupancy of the dugong has declined in many parts of its range, especially along the coasts of east African and India where anecdotal evidence suggests that it is at high risk of extinction.

Even in the regions where we have classified the status of the dugong as stable, this classification is unconfirmed. Much of the northern Western Australian and some of the Northern Territory coast has never been surveyed for dugongs and there are no accurate estimates of the Indigenous harvest. The sustainability of this harvest must be questioned as it has been shown to be unsustainable by population modeling in remote parts of Queensland and Torres Strait (Heinsohn et al. 2004, Marsh et al. 2004).

Genetic information on dugong stocks is limited. Recent work based on mitochondrial DNA and microsatellite markers (Brenda McDonald, unpublished data) indicates that the Australian dugong population is not panmictic. There is clear evidence of two maternal lineages, which have a geographical basis apparently reflecting the existence of the Torres Strait land bridge between Australia and PNG, despite the flooding of this land bridge some six thousand years ago. The Australian dugong population still has a fair degree of genetic diversity indicating that recent losses are not yet reflected in the genetic makeup of the population. There is some evidence of gene flow between dugongs in Australia and Eastern Indonesia.

To date, there has been little effective management intervention to reduce anthropogenic impacts on the dugong, apart from legislative protection which is almost ubiquitous throughout its range. Management plans have been developed for some 22-24% of the range (mainly in Australia) but are in place in only 18-22% of the range. The dugong is protected by marine protected areas in 22-23% of its range (again mostly in Australia) (see Table 1.3 in attached PDF).

Because of the uncertainty associated with the assessment of the status of the dugong both on the Queensland coast based on the CPUE data (Marsh et al. 2005) and the rest of its range, we suggest that the classification should remain as Vulnerable A2bcd.

Follow the link below to see the tables referred to in the text.

IUCN

CITES

Appendix IIUCN

CMS

National Status

Ecology Discription

Appearance

Habitat

See Marsh et al. (2002). IUCN

Population size

Total population size is unknown. See Marsh et al. (2002). IUCN

Behavior

Diet

Reproduction

Threat

Major Threat(s)

See Marsh et al. (2002). IUCN

Conservation and Measurement

International

The species is listed on CITES Appendix I. IUCN

National

Conservation law

Protected Area

Other Coservation Projects

Citation

Baillie, J. and Groombridge, B. (comps and eds). 1996. 1996 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

De Iongh, H., Kiswara, W., Kustiawan, W., and Loth, P. 2007. A review of research on the interactions between dugongs (Dugong dugon Muller 1776) and intertidal seagrass beds in Indonesia. Hydrobiologia 591: 73-83.

Groombridge, B. (ed.). 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 1990. 1990 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 2008. 2008 IUCN Red List of Threatened Species. Available at: http://www.iucnredlist.org. (Accessed: 5 October 2008).

IUCN Conservation Monitoring Centre. 1986. 1986 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN Conservation Monitoring Centre. 1988. 1988 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

Marsh, H., De'ath, G., Gribble, N. and Lane, B. 2005. Historical marine population estimates: triggers or targets for conservation? The dugong case study.

Marsh, H., Penrose, H., Eros, C. and Hugues, J. 2002. Dugong Status Report and Action Plans for Countries and Territories. Report Series. Early Warning and Assessment , United Nations Environment Program UNEP/DEWA/RS.02-1.

Scott, P. 1965. Section XIII. Preliminary List of Rare Mammals and Birds. The Launching of a New Ark. First Report of the President and Trustees of the World Wildlife Fund. An International Foundation for saving the world's wildlife and wild places 1961-1964, pp. 15-207. Collins, London, UK.

Thornback, J. and Jenkins, M. 1982. The IUCN Mammal Red Data Book. Part 1: Threatened mammalian taxa of the Americas and the Australasian zoogeographic region (excluding Cetacea). IUCN, Gland, Switzerland.

UNTAET. 2000. Regulation No. 2000/19 on Protected Places. United Nations Transitional Administration in East Timor.

World Wildlife Fund Eastern African Marine Ecoregion. 2004. Towards a Western Indian Ocean Dugong Conservation Strategy: The Status of Dugongs in the Western Indian Ocean Region and Priority Conservation Actions. Dar es Salam, Tanazania.

IUCN