Dugongs
Common name: Dugong
Scientific name: Dugong dugon
Family: Dugongidae
Status: Vulnerable
In Australia, dugongs (Dugong dugon) are found in northern coastal waters, generally living in shallow, calm, wide, protected bays. Their distribution stretches from Shark Bay in Western Australia, over the northern coastline and down the Queensland coast. Moreton Bay Marine Park is the southern limit of dugong populations along the east coast of Australia.
Surveys show that the waters of the Torres Strait and Hervey Bay have higher densities of dugongs. The Great Barrier Reef region supports globally significant populations of dugong, and is one of the reasons the area was given World Heritage status.
The dugong is the only plant-eating mammal that lives its entire life in the marine environment. Dugongs and their relatives are more closely related to elephants than any marine mammal.
These shy, slow-moving creatures, spend most of their day feeding on seagrass which is why they’re often called ‘sea cows’. An adult will eat about 30 kilograms of seagrass each day. Dugongs have relatively poor eyesight, so rely on the sensitive bristles covering the upper lip of their large snouts to find and grasp seagrass.
As dugongs feed, whole plants are uprooted leaving telltale tracks behind. Known as ‘cultivation grazers’, dugongs feed in a way that promotes growth of Halophila ovalis – their preferred seagrass species. Uprooting the seagrass promotes nitrogen fixation, aerates the sea floor and increases the amount of organic matter to the area, therefore encouraging regrowth of the seagrass. Halophila ovalis is a fast-growing seagrass that is high in nitrogen and low in fibre.
Growing to about three metres in length and weighing as much as 500 kilograms, dugongs are an essential element of Aboriginal and Torres Strait Islander people's living maritime culture.
Dugongs mature at between 10 and 17 years of age and can live for up to 70 years. A cow only reproduces every 3 to 7 years. After giving birth, she nurses and nurtures her calf for 1–2 years. Being mammals, dugong calves suckle milk.
Threats
Dugongs are classified as vulnerable to extinction by both the International Union for Conservation of Nature (IUCN) and the Queensland Government's Nature Conservation Regulation, and their populations are in steady and ongoing decline.
A report from James Cook University (JCU) TropWATER reveals a long-term decline in dugong populations along the Great Barrier Reef, spanning from Mission Beach to Bundaberg, and Hervey Bay in the Great Sandy Strait.
Aerial surveys most recently conducted in 2022 confirm that this declining trend has persisted for almost two decades, despite Australia's renowned global status as the host of the world's largest population of these marine mammals.
Boat strikes, accidental entanglement in fishing gillnets and marine debris, habitat degradation due to coastal development, and water quality can all pose a threat to dugongs.
Dugongs also face unique challenges due to their long lifespan and their slow reproductive rate. As a result, the loss of even a single dugong from anthropogenic causes can have a significant impact on their population.
Conservation actions
There are a number of measures in place and actions underway to help protect the dugong, from Go Slow areas in Queensland’s southern marine parks through to research projects to further understand behaviour of the species.
A recent commitment to better conserve the Great Barrier Reef’s threatened, endangered and protected (TEP) species, including dugongs as well as dolphins, turtles and sawfish, for example is the phasing out of gillnets for commercial fishing in the Reef by mid-2027. This will reduce risks posed by gillnet entanglement, including animal injury or death. In the meantime, a new gillnet-free zone has already been established in the far north of the Great Barrier Reef from Cape Bedford to the tip of Cape York providing protections from the risks of gillnetting for dugongs in this area.
As part of the new zoning plan for the Great Sandy Marine Park, the increased proportion of highly-protected zones to conserve the park’s marine life, including seagrass meadows will help support dugongs. The new zoning plan also includes the removal of commercial large mesh gillnets and ring nets from certain areas, while new and expanded Go Slow areas provide more comprehensive protection for dugongs (and turtles) from the risk of boat strike.
Queensland Parks and Wildlife Service (QPWS) and researchers from James Cook University TropWATER are also partnering on activities that support dugong and marine turtle populations in the Great Sandy Marine Park. This includes working together to monitor the abundance of seagrass meadows as well as projects examining light availability within the Great Sandy Strait, a herbivory exclusion study looking at how marine life feeding on seagrass impacts recovery, and seagrass seed bank availability. Seagrass surveys are also being undertaken in the Moreton Bay Marine Park by Science Under Sail Australia and QPWS.
Work by other partners and organisations includes a dugong aerial survey project by James Cook University’s TropWATER to monitor the distribution and abundance of the species along all of Queensland's coast, supported by the Australian Government’s Reef Trust and the Great Barrier Reef Foundation. Sea World also undertakes dugong conservation and research projects relating to the dugong.
How you can help
One of the biggest threats to dugongs is getting hit by boats and other watercraft traveling too fast over shallow waters. When dugongs come to the surface to breathe they can be hard to spot.
If you’re out on a boat, always ‘go slow for those below’, especially in shallow or seagrass-rich areas. You can also help by being careful not to damage seagrass by careless anchoring or operating your boat in shallow water where boat wash or propeller damage can occur.
To report marine animal strandings (of sick, injured or dead turtles, dolphin, dugongs or whales) call 1300 130 372.