Dugong (Dugong dugon)

Dugongs are believed to have been the basis of mermaid legends when glimpsed swimming in the water from a distance. They could hardly be described as beautiful but they do have a certain grace underwater. The world's largest population of dugongs - over 10,000 animals - feed year-round in Shark Bay, the southern limit of their range.

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About the Dugong

The dugong (Dugong dugon) is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's Sea Cow (Hydrodamalis gigas), was hunted to extinction in the 18th century. It is also the only sirenian in its range, which spans the waters of at least 37 countries throughout the Indo-Pacific, though the majority of dugongs live in the northern waters of Australia between Shark Bay and Moreton Bay. The dugong is the only strictly-marine herbivorous mammal, as all species of manatee utilize fresh water to some degree.

Like all modern sirenians, the dugong has a fusiform body with no dorsal fin or hind limbs, instead possessing paddle-like forelimbs used to maneuver itself. It is easily distinguished from the manatees by its fluked, dolphin-like tail, but also possesses a unique skull and teeth. The dugong is heavily dependent on seagrasses for subsistence and is thus restricted to the coastal habitats where they grow, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as bays, mangrove channels and the lee sides of large inshore islands. Its snout is sharply downturned, an adaptation for grazing and uprooting benthic seagrasses.

The dugong has been hunted for thousands of years for its meat and oil, although dugong hunting also has great cultural significance throughout its range. The dugong's current distribution is reduced and disjunct, and many populations are close to extinction. The IUCN lists the dugong as a species vulnerable to extinction, while the Convention on International Trade in Endangered Species limits or bans the trade of derived products based on the population involved. Despite being legally protected in many countries throughout their range, the main causes of population decline remain anthropogenic and include hunting, habitat degradation, and fishing-related fatalities. With its long lifespan of 70 years or more, and slow rate of reproduction, the dugong is especially vulnerable to these types of exploitation. Dugongs are also threatened by storms, parasites, and their natural predators, sharks, killer whales, and crocodiles.

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Scientific Classification

Kingdom: Animal (animalia)

Phylum: Chordate (Chordata)

Class: Mammal (Mammalia)

Order: Sirenia

Family: Dugongidae

Genus: Dugong

Species: Dugong (dugon)

Where can I see them?

They can be found in the following habitats:

Conservation Status

The Dugong is Vulnerable (IUCN 3.1)

  1. EX - Extinct
  2. EW
  3. CR - Threatened
  4. EN - Threatened
  5. VU - Threatened
  6. NT
  7. LC - Least concern

Population trend: Unknown

Year assessed: 2008

What's the threat?

The species has been traditionally hunted throughout much of its range for its meat, hide, oil and bones. Although commercial hunting is now banned, dugong products from indirect takes are still highly valued, and traditional hunting of the species by the indigenous peoples of Australia and the western islands of the Torres Strait continues. The species’ large size, slow swimming speed and dependence on coastal habitats make them easy targets for hunters. Researchers fear that due to other factors this traditional harvesting of the species is no longer sustainable. Habitat loss and degradation is thought to be a major threat. High levels of human population growth and rapid rates of industrialisation are occurring throughout much of the dugong’s range. Sea grass ecosystems are very sensitive to human activity and may be destroyed directly by mining or trawling, or lost as a result of dredging, land clearing and land reclamation. These activities cause increases in sedimentation and turbidity, which blocks out light and smothers the plants. Accidental entanglement in gill or mesh nets or traps set by fishermen is an indirect cause of dugong mortality. Since dugongs cannot hold their breath for long periods of time, many drown as a result of entanglement in these nets. Factors such as pollution, vessel strikes and disease may also threaten dugong populations, although their effect has yet to be quantified. The species’ life history makes it particularly vulnerable to these threats. Dugongs are long-lived with a low reproductive rate, long generation time, and a high investment in each offspring. Even under ideal conditions, simulations have predicted that dugong numbers will not rise by more than about 5% per year. A slight reduction in adult survivorship can cause a population to crash.

Information about the threat is provided by the Zoological Society of London's EDGE of Existence programme

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