Torres Strait – Dugong capital of the world!

Dugong (Dugong dugon) are air-breathing marine mammals of global conservation significance, that can grow up to three metres, weigh up to 400kg and live for at least 70 years. Females reach sexual maturity at six years, and produce a calf only once every 2.5-5 years thereafter. Gestation period is 14 months, but calves suckle milk from their mothers for 18 months after birth. Dugongs’ main food source is seagrass, but they also eat invertebrates such as worms, sea squirts, and shellfish ^[1].

Torres Strait contains the largest Dugong habitat on the planet^[2]! About one fifth of the global range for dugong occurs in Australia, and a significant proportion of that occurs in Torres Strait, which is home to 58% of the high-density habitat for Queensland ^[2]. This immense Torres Strait dugong habitat, which is also home to the largest continuous seagrass bed in Australia ^[3], supports a large and genetically healthy dugong population, of between 12-28000 animals, with the exact number being difficult to confidently determine due to logistical challenges of remote aerial surveys, and the complexity of correcting for possible biases in the survey method, including calculating how many animals might be missed in dirty water when they are not at the surface and visible to observers ^[4].

This map layer shows the areas where most of the dugongs (Dugong dugong) live in the Torres Strait region^[7]. Dark areas show where more dugongs were seen and light areas show where no dugongs were seen.

Torres Strait Islanders have a long and extensive relationship with all aspects of their sea country, including Dugongs. Dugongs are especially important, and hold a prominent place in cultural protocols, traditional ecological knowledge, daily livelihoods, and diet. Archaeological evidence suggests that Torres Strait Islanders have hunted dugong for at least 4000 years ^[5], and the level of harvest is suspected to be sustainable because there is no evidence for population decline from aerial surveys over time ^[2,4]. However, due to some uncertainties over the estimates of the Torres Strait population mentioned above, and a lack of accurate total estimates of the harvest size through time, it is wise to be cautious about the current level of harvest. The ongoing sustainability of the dugong (and turtle) harvest is so important to Torres Strait Islanders, that the TSRA sea program and Traditional Owners from 14 communities have taken action, and developed community based dugong (and turtle) management plans ^[6]. Sustainable dugong harvest is also supported by the Torres Strait Treaty between Australia and Papua New Guinea, and domestic Australian legislation ^[2].

While hunting pressures may be considered a threat to dugong in Torres Strait, the majority of this hunting occurs outside the remote areas of highest dugong density. Studies combining hunter behaviour and dugong density data suggest that only one third of the high density dugong habitat in Torres Strait is ever hunted ^[2]. Dugong in the southern areas of the Great Barrier Reef may not be hunted as much, but they must contend with far greater risks from cyclones, habitat loss, water quality decline from development along the coast, and boat strikes. Overall, dugong are much safer in Torres Strait ^[2].

No wonder Torres Strait is known as the dugong capital of the world!

1. Souter D (2009) Dugongs. e-Atlas, Australian Institute of Marine Science.

2. Marsh H (2013) Dugongs are safer in Torres Strait than in Townsville. The Conversation.

3. Taylor HA, Rasheed MA (2010) Torres Strait dugong sanctuary seagrass baseline survey, March 2010. 22 p.

4. Marsh H, Hodgson A, Lawler I, Grech A, Delean S (2008) Condition, status and trends and projected futures of the dugong in the northern Great Barrier Reef and Torres Strait; including identification and evaluation of the key threats and evaluation of available management options to improve its status.: James Cook University.

5. McNiven I, Bedingfield A (2008) Past and present marine mammal hunting rates and abundances: dugong (Dugong dugon) evidence from Dabangai Bone Mound, Torres Strait. Journal of Archaeologia Science 35: 505-515.

6. TSRA (2013) TSRA Sea Program.

7. Grech A, Marsh (2013) Torres Strait Dugong distribution and relative density - Spatial model of aerial surveys from 1987 - 2011 (NERP TE 2.1, JCU). e-Atlas.