Northern Australia

Australia’s Marine Turtles

By Justin McCaul

Australia is home to 6 of the world’s seven species of marine turtles. All are listed as either vulnerable or endangered under Australia’s Environment Protection and Biodiversity Conservation (EPBC) Act. They are also listed as either endangered or critically endangered under the International Conservation Union’s (IUCN) Threatened Species List.

Above: Loggerhead Turtles are distinct from other species because of the large size of their heads.

The six species of marine turtle found in Australia are: Green (Chelonia mydas), Hawksbill (Eretmochelys imbricata), Olive Ridley (Lepidochelys olivacea), Leatherback (Dermochelys coriacea), Loggerhead (Caretta caretta) and the endemic Flatback (Natator depressus). Their survival is threatened by boat strike, illegal and unmanaged fishing, habitat destruction, pollution, and rising seas and temperatures.




Above: Green Turtle that has finished nesting heads back to the ocean at dawn, Heron Island

ACF staff member Justin McCaul got more than he bargained for when he accepted an invite to help collect data on Australia’s endangered marine turtles. First flying to Torres Strait and then taking a boat to an uninhabited island within the Great Barrier Reef Marine Park he participated in the trip with two other groups of dedicated volunteers on tow different island – Milman Island and Heron Island.

The monitoring trip is funded by Earthwatch Institute and organised by Ian Bell of the Queensland Parks and Wildlife Service (QPWS).

January is seasonally very wet in the tropics and the day of departure is no exception. However the flight does provide a glimpse of the spectacular Cape York Peninsula coastline and in shore islands.

After an over night stay on Thursday Island we set of on a Great Barrier Reef Marine Park Authority (GBRMPA) boat to head for Milman Island. During the five hour trip we stay close to the coast and eventually round the most northern point of Australia – the tip of Cape York Peninsula.

Milamn Island is a remote and uninhabited, densely forested sand cay in the northern most section of the Great Barrier Reef Marine Park (see map). It is a favoured nesting area for both Hawksbill and Green turtles. A ten year population biology study on Milman Island (1990 – 2000) identified a 4% decline in the nesting population of Hawksbill turtles.


Despite its great distance from urban areas, islands such as Milman used to be visited regularly by people from both the Torres Strait and the mainland. Also, until it gained status as a Green Zone within the Great Barrier Reef Marine Park rezoning exercise in 2004, it was visited by commercial fishers. Today it is now off limits to all but national parks staff and researchers.


Above: Milman Island

Worldwide, the number of Hawksbill turtles has been severely depleted as a result of excessive over harvesting for their shell. Japan in particular has a large jewellery and crafts industry in Hawksbill shell. As with the hunting of whales, Japan is presently engaged in an international lobbying effort to get a core group of countries – mostly in the Pacific and the Caribbean - to support an overturn of the ban on trade in Hawksbill turtle.


Above: Passing by the northern most point on mainland Australia - Cape York Peninsula.




Above: Measuring the carapace of a Hawksbill turtle.

As part of a strategy to involve Indigenous people in conservation, also participating in the monitoring trip was a number of students from the Torres Strait. All do marine studies a part of their curriculum, and most have worked with marine turtles before.



Above: Students from the Torres Strait observe QPWS Conservation Officer Ian Bell perform a laparoscopy on a Hwksbill turtle.

Eating marine turtles, especially Green Turtles, is part of Torres Strait Islander culture. The young students all felt that traditional hunting of turtles needed to be better managed, and although they believed most people in the Torres Strait do the right thing, they know some people are taking too many turtles. They participate in research trips such as this one so they are able to then educate other people in the Torres Strait about the importance of managing marine turtles in a sustainable manner.

Late afternoon is the time when hatchlings emerge from the sand and scurry down the beach headed for the ocean. Waiting for them are flocks of seagulls as well as small inshore reef sharks. The high level of predation – including feral pigs, dogs and in some cases goannas – has lead researchers to estimate that only 1 in 1000 hatchlings survive through to adulthood and breeding age.



Above: A green turtle hatchling makes its way down the beach

Above: …and makes it to the ocean. Hatchlings however face many predators on land and in the water leading to estimates that only 1 in 1000 make it to adulthood.

Earthwatch Institute and QPWS invite me to participate in monitoring work taking place on another island within the Great Barrier Reef Marine Park further south – Heron Island.


Above: Heron Island

Despite the presence of a large number of people on Heron, species such as Green and Loggerhead turtles continue to make their annual nesting trek to the island.


Above: Hatchlings emerging from the sand in late afternoon.

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