Dugong dugon 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Sirenia Dugongidae

Scientific Name: Dugong dugon (Müller, 1776)
Common Name(s):
English Dugong, Sea Cow
French Dugong
Spanish Dugon

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2bcd+4bcd ver 3.1
Year Published: 2015
Date Assessed: 2015-07-12
Assessor(s): Marsh, H. & Sobtzick, S.
Reviewer(s): Hodgson, A., Pilcher, N.J. & Kwan, D.
Marsh et al. (2011) made a crude estimate of the Dugong’s extent of occurrence (EOO) as 860,000 km2 based on potential habitat (waters <10 m deep in its known range). This spans approximately 128,000 km of coastline across at least 37, and up to 44, countries and territories. Although the Dugong still occurs at the extremes of its range, Husar (1978) and IUCN (2009) list the Dugong as extinct in the waters of several islands including: the Maldives, the Lakshadweep Islands, Mascarene Islands of Mauritius and Rodrigues, and Taiwan (Husar 1978). Although this species may only have been vagrant at some of these islands (e.g. Taiwan, Hirasaka 1932), there is historical evidence of substantial Dugong populations off Mauritius and Rodrigues Islands; these populations were harvested in the 18th century (Cheke 1987). Cheke quotes historical accounts of a dugong fishery on Rodrigues in the 1730s. There is also anecdotal evidence that the area of occupancy (AOO) of the Dugong has declined in many parts of its range, especially along the coasts of east Africa and India.

The only reference site is the urban coast of Queensland between Cooktown and Brisbane, Australia where a 40 year time series of catch rates in nets set for bather protection indicates that the Catch Per Unit Effort (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 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. However, there are sites in Australia that support large populations of Dugongs (e.g. Shark Bay, Torres Strait) where it is unlikely that such a decline has occurred (Marsh et al. 2011, unpublished).

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, subsistence hunting, habitat loss from extreme weather events that are likely to be exacerbated by climate change, human settlement and agricultural pollution. 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. Nonetheless there is evidence of ongoing decline in Dugong numbers (Sobtzick et al. 2012) along the urban coast of the Great Barrier Reef Region largely attributed to habitat loss associated with extreme weather events.

Marsh et al. (2011) undertook a regional assessment of the Dugong and concluded that the East African population was likely ‘Endangered’; Red Sea and Gulf of Aden ‘Data Deficient’; Arabians Gulf ‘Data Deficient’; Indian sub-continent and Andaman and Nicobar Islands ‘Endangered’; continental South East Asia ‘Endangered’; archipelagic East and South East Asia ‘Data Deficient’; Western Pacific Islands ‘Data Deficient’; and Palau and the Japan (Ryukyus) as Critically Endangered. The most recent assessment of the Australian population (Woinarski et al. 2014) concluded it was ‘Near Threatened’. The Dugong’s confirmed range states include a mix of developing and developed countries and territories including countries and territories with a very high Human Development Index (HDI), countries with a high HDI, countries with a medium HDI and three countries with a low HDI (Marsh et al. 2011). The outlook for Dugongs in countries with a very small Dugong population and/or a low HDI must be poor. These countries include Brunei, Cambodia, China, Comoros, Djibouti, Egypt, Iran, Japan, Kenya, Madagascar, Mayotte, Mozambique, Myanmar, Papua New Guinea, Singapore, Sri Lanka, Sudan, Tanzania, Viet Nam and Yemen. Nonetheless, four countries/territories with a very high HDI (Australia, New Caledonia, Qatar and the United Arab Emirates) support substantial populations of Dugongs (hundreds or thousands; Marsh et al. 2011), although even among and within these countries/territories the prospects are uneven. Because of the uncertainty associated with the assessment of the status of the Dugong, we suggest that the classification should remain as Vulnerable.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Dugongs inhabit coastal and island waters between East Africa and Vanuatu between latitudes of about 27° north and south of Equator. Spanning approximately 128,000 km of coastline (860,000 km2) across at least 37 and and possibly occur in an additional seven states and territories (Marsh et al. 2011, N. Pilcher pers. comm).

Countries occurrence:
Australia; Bahrain; Brunei Darussalam; Cambodia; China; Cocos (Keeling) Islands; Comoros; Djibouti; Egypt; Eritrea; India (Andaman Is., Laccadive Is., Nicobar Is.); Indonesia; Japan (Nansei-shoto); Jordan; Kenya; Madagascar; Malaysia; Mayotte; Mozambique; New Caledonia; Palau; Papua New Guinea (Bismarck Archipelago); Philippines; Qatar; Saudi Arabia; Seychelles; Singapore; Solomon Islands; Somalia; Sri Lanka; Sudan; Tanzania, United Republic of; Thailand; Timor-Leste; United Arab Emirates; Vanuatu; Viet Nam; Yemen (Socotra)
Regionally extinct:
Mauritius (Rodrigues - Native); Taiwan, Province of China
FAO Marine Fishing Areas:
Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – western central
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Five countries/territories (Australia, Bahrain, Papua New Guinea, Qatar and the United Arabian Emirates) support substantial subpopulations of Dugongs (thousands) with tens of thousands of Dugongs in northern Australia/Papua New Guinea alone (Marsh et al. 2011, unpublished). The percentage of mature individuals is likely to vary between various subpopulations, but is likely to be somewhere between 45% and 70% (Marsh et al. 2011). Genetic information on Dugong stocks is mostly limited to the Australian region. Recent work based on mitochondrial DNA (Blair et al. 2014) shows that the Australian Dugong population is not panmictic. The Australian population still has high genetic diversity, indicating that recent population declines are not yet reflected in the genetic makeup of the population. Seddon et al. (2014) used microsatellite markers to demonstrate low, but significant, population differentiation within a regional in southern Queensland. Further data (D. Blair unpublished data) using the same genetic markers indicate considerable differentiation between southern and northern Queensland populations. Preliminary population-genetic and phylogeographic studies on Dugongs outside Australia are ongoing. These studies suggest strong regional differentiation. Australian populations are largely distinct from those elsewhere; populations in the Western Indian Ocean (Red Sea, Persian/Arabian Gulf, East Africa) are rather uniform and with limited genetic diversity; Madagascar might harbour a distinct lineage. The situation for the Indo-Malay Region is unclear but possibly more than one historical lineage occurs there. Thailand (Palmer 2004, L. Parr unpublished data) and Australia (McDonald 2005, Blair et al. 2014) are home to distinct matrilines that possibly diverged during Pleistocene sea-level fluctuations, but are now able to mix geographically within those regions
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Habitat requirements for Dugongs include coastal areas, shallow to medium deep, warm waters (15-17°C minimum with behavioural thermoregulation), seagrass beds supporting sub-tropical and tropical species of seagrass, particularly low fiber species (Hines et al. 2012, Marsh et al. 2011). Dugongs show great variability in movement patterns and migration, depending on the study area and the influence of seasonal temperature or rainfall on regional ecosystems. Long-distance movements by Dugongs along the Queensland coast are well-documented (Sheppard et al. 2006), even though Dugongs do not appear to undertake regular migrations and individual movements are individualistic (Sheppard et al. 2006, Marsh et al. 2011, Gredzens et al. 2014). Cope et al. (2015) used pedigree analysis based on individual genetic markers to infer the movements of Dugongs between locations in southeast Queensland including Moreton Bay and Hervey Bay. They found that approximately 30% of assigned parents had at least one offspring found in a different locality, implying recent movement of the parent or offspring. This analysis suggested markedly more movement between localities than detected through repeated direct sampling of individuals (Seddon et al. 2014) or through telemetry (Sheppard et al. 2006).
Generation Length (years):22-25
Movement patterns:Nomadic

Use and Trade [top]

Use and Trade: Archaeological evidence confirms exploitation of Dugongs by early humans. As long as 6,000 years ago, Dugongs on the small island of Akab in the United Arabian Emirates were hunted for food (Méry et al. 2009). Excavations in the Torres Strait, Australia, has revealed that Dugong hunting in this region dates back at least 4,000 years and possibly up to 7,000 years (Crouch et al. 2007, Wright 2010) and that the harvest has been substantial for at least 400–500 years (McNiven and Bedingfield 2008). Although hunting is now legally banned in most countries, there are important exceptions for the subsistence use by traditional peoples. In Australia, the Dugong hunting rights of ‘Native Title Holders’ (indigenous people who can prove continuous connections to their traditional land and sea country) have been consistently upheld by the courts in a series of landmark decisions since 1993. Dugong hunting still has considerable cultural significance to coastal Aboriginal and Torres Strait Islander peoples across northern Australia, and Dugong meat is considered by these groups to be the one of the highest value traditional foods. Some subsistence Dugong hunting is also allowed in the Pacific states of Papua New Guinea (restrictions apply), Vanuatu and New Caledonia (restrictions apply), where Dugongs are still of great cultural and dietary significance.Commercial exploitation of Dugongs occurred intermittently at various places along the coast of Queensland, Australia, from 1847-1969 (Daley et al. 2008). Numerous products are still obtained from Dugongs and used for food, folk medicine, cooking/lubrication, aphrodisiacs, amulets/charms/jewellery, carvings, religious artefacts, leather products and other (Marsh et al. 2011). Trade in Dugong (and all other sirenian) products is regulated or banned by the Convention for Trade in Endangered Species (CITES). Dugongs are currently listed on CITES Appendix I.

Threats [top]

Major Threat(s): Threats to Dugongs vary between different populations as detailed in Marsh et al. (2011) and Hines et al. (2012). Major threats include:
  • Incidental capture in fishing gear (e.g. gill nets), shark nets for bather protection, IUU fishing especially if meat is subsequently sold (see Pilcher et al. 2014, for a detailed rapid assessment based on questionnaires to provide information on conservation hotpots for Dugongs in 18 countries in four geographic areas: Pacific, Southeast Asia, South Asia and East Africa, with 6,153 respondents)
  • Hunting: legal (i.e. culturally sanctioned) and illegal
  • Boat strikes and boating activities (e.g. acoustic pollution)
  • Damage/modification/loss of habitat caused by human settlement on coasts, shipping, trawling destructive fishing, natural processes (e.g. cyclones and tsunamis)
  • Threats to seagrass (including untreated sewage disposal, coastal dredging and reclamation, inshore commercial trawling, agricultural pollution)
  • Chemical pollution (e.g. oil spills and heavy metal loads)
  • Climate change (extreme weather events and high temperatures)
The major drivers for incidental capture in fishing gear and illegal hunting are poverty and declining fish stocks. Dugongs are legally protected in most of their range. However, enforcement is typically weak or non-existent. The imperative of artisanal fishers to break the law is increased by the opportunity to sell both Dugong meat (Robards and Reeves 2011) and valuable commodities such as swim bladders and shark fins (Marsh et al. 2011). Artisanal coastal and riverine fisheries are vital to the livelihoods and food security of coastal peoples, especially in the tropics (Batista et al. 2014), including most Dugong range states. On a global scale, such fisheries catch the same amount of fish for human consumption as commercial fisheries, yet employ some 25 times the number of fishers (over 12 million people; Chuenpagdee et al. 2008, Batista et al. 2014). Gill nets are significant threat to many marine mammals including dugongs (Read et al. 2006, Moore et al. 2010, Pilcher et al. 2014). Some Dugong declines coincide with the introduction of monofilament nylon gill nets (Muir and Kizka 2012). However, it is often very difficult to convince the fishers or the fisheries managers to take the capture of Dugongs seriously. When Dugong population sizes are low, their capture in fisheries is a rare event, which becomes rarer as the Dugong population declines. Coastal development represents another important driver. Significant seagrass loss leads to Dugongs having reduced food resources, delayed reproduction and starvation (Marsh et al. 2011). The impact of chemical and noise pollution on Dugongs is unquantified. (Marsh et al. 2011).

Climate change is projected to lead to altered coastal environmental condition and increases in severe tropical storms and flood events that could affect both Dugongs and their seagrass habitats exacerbating the effects of the other drivers listed above (see Marsh et al. 2011 for details).

Conservation Actions [top]

Conservation Actions: Dugongs are covered under three international conservation conventions: The Convention on Biological Diversity (CBD), the Convention on the International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on Migratory Species of Wild Animals (also known as CMS or the Bonn Convention). Dugongs are also included in the Coral Triangle Initiative (CTI), goal five (Threatened Species). Additionally, the Convention on Wetlands (the Ramsar Convention) protects some important Dugong habitats.

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. Protected area initiatives aim to protect Dugongs in many range states (Marsh et al. 2011) and are most developed in Australia. Most of the marine protected areas outside Australia with the potential to protect Dugongs are ‘paper parks’ where laws and regulations exist but are not implemented. Strategic Action Programmes/Strategic Plans/Action Plans to protect Dugongs have been developed by countries in the Red Sea and Gulf of Aden region (Gerges 2002), Indonesia (de Iongh et al. 2009a, 2009b) and South Pacific Regional Environmental Programme (SPREP; Gillespies 2005). However, effective enforcement of conservation regulations is a problem throughout most of the region because of poverty, lack of resources and personnel. The most pressing need is for alternative sustainable livelihoods that address poverty and provide incentives for conservation. The most promising initiative is the UNEP Dugong, Seagrass & Coastal Communities Initiative (see

Citation: Marsh, H. & Sobtzick, S. 2015. Dugong dugon. The IUCN Red List of Threatened Species 2015: e.T6909A43792211. . Downloaded on 25 September 2018.
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