Australia remains one of the last places on earth where dugongs can still be found in significant numbers, with over three-quarters of the overall population residing here. They spend most of their day grazing on seagrass in the shallow, tropical waters, yet it is these shallow waters that endanger their very existence. There was a time when traditional hunters saw dugongs as an inexhaustible resource. Hundreds of herds could be seen in many places across the dugong’s range in the shallow waters from East Africa to the Western PaciƤ c Islands. Today is sadly not that time as the IUCN Red List has listed dugongs as vulnerable to extinction with population numbers worldwide becoming increasingly fragmented. Dugong, which means ‘lady of the sea’, is a species of a marine mammal and the only entirely vegetarian marine mammal on the planet whose prime food source is seagrass. They are a passive and gentle species, sometimes referred to as the ‘sea cow’ as, like cows, they move slowly, grazing on underwater grasses day and night. Dugongs may be seen to resemble whales (if viewed from behind), a largely overweight sea lion or possibly a face resembling that of a dolphin, yet they are more closely related to elephants than to any of these marine mammals, while their closest living aquatic relatives are manatees.

Professor Helene Marsh from James Cook University and one of the world’s experts on dugongs says that dugong threats vary depending on that particular area at question and that there are still some places where dugong numbers are still relatively unaÆ¡ ected. “There are places like Torres Strait, which is the dugong capital of the world and probably has been the dugong capital of the world for 7,000 years as there is just a lot more habitat there than anywhere else. Our long-term data would suggest that the population in this area is stable.”

Australia remains one of the last places on earth to have a large proportion of the remaining dugong population, making it the largest and globally most important refuge for the dugong. However, there are still certain population numbers in this part of the world that are also suơ ering and in decline.

Marsh explains that those areas on the urban coast of Queensland where there are cities and towns provide evidence of a signiƤ cant decline in the dugong population. “The decline is complicated but it involves loss of habitat, animals being caught in shark nets, boat incidents, animals being caught in bycatch for commercial fisheries, and hunting.”

Extreme weather in Queensland over the past decade, namely storms and cyclones, has also had a large impact on the availability of seagrass, which has led to an increase in dugong deaths from malnutrition and ill health. 

“When you get extreme weather events, you get the soil washing into the oceans, which become more turbid. The seagrass can’t grow so there is a really hard problem to address”, said Marsh. 

Andrew Simmonds, the Great Barrier Reef Marine Park Authority’s project manager for species conservation, says that some of dugongs’ lifehistory traits make them “all the more vulnerable”. Although dugongs can live up to 70 years, they have a delayed sexual maturity and a very low reproductive rate which is largely dependent on the availability of food and other individuals. “Their reliance on inshore habitats further increases their exposure to human-related and land-based threats”, said Simmonds. 

Coastal developments along the Great Barrier Reef have also had an impact on the dugong population due to direct disturbance and loss of seagrass habitats, which they are extremely dependent on.

“There is quite a lot of work being done on trying to allow humans to live alongside dugongs and the rest of the marine ecosystem but I don’t think we have solved the problem. There is certainly concern about the loss of seagrass from grazing land in particular as well as a water quality problem that is being aơ ected by increased sediments, nutrients and pesticides in catchment runoơ ”, said Marsh.

Simmonds believes that the best thing we can do to help protect the dugong population is to reduce pressures on our oceans. This can be done in the form of preventing debris from entering coastal waters; abiding by local zoning rules which stipulate how and where you can Ƥ sh; abiding by boat speed limits to avoid boat strikes; and reducing run-oÆ¡ nutrients, pesticides and sediments from the land, which will help improve the health of seagrass meadows. “If each individual threat is looked at separately, some can seem relatively small, but once you combine them the pressures can have a substantial impact.”

In the Great Barrier Reef Marine Park, measures have now been stepped up to protect dugongs. Restrictions have been imposed in 16 Dugong Protection Areas on the type of Ƥ shing gear that can be used and prohibiting the use of some types of Ƥ shing nets. Dugong habitats are also taken into account in the Great Barrier Reef Marine Park Zoning Plan, which determines how and where certain activities can take place out on the water. As a result, about 96 percent of high conservation value dugong habitats are protected from extractive industries such as Ƥ shing. In addition, the Queensland Government has also changed many of its shark control nets to drumlines so as to reduce the number of incidental capture of dugongs. But is this enough? Projections say that if dugongs continue to decline at the current rate, they will become extinct within the next forty years. 

Simmonds believes that if dugongs were to disappear from our planet, it may have a range of cascading impacts on seagrass meadows and marine ecosystems more broadly. “The grazing of seagrass by dugongs plays a role in determining the abundance and species composition of seagrass meadows. They are an important component of the wider reef ecosystem, as not only is seagrass the main food source for dugongs and green turtles, it also provides nursery habitat for many fish, it can capture large amounts of carbon and helps trap and stabilise large amounts of sediment.”

The future for these gentle giants appears to be fragile, with population numbers taking many years to recover. Australia therefore forms a crucial part of this species’ survival, as if they were to disappear from these waters they will, most probably, disappear altogether.

As featured on Australian Wildlife Society Magazine.