Endangered Mary River turtles in decline, new research finds

The Mary River, home to the ‘bum-breathing’ turtle, has an unidentifiable killer swimming in its waters which is suspected to be swallowing the endangered species.

Experts fear the rare Mary River turtles are being swallowed by a mystery killer leaving the aquatic creatures in alarming decline.

Also known as “bum-breathing turtles”, the species has been in decline for decades with efforts to reduce the impact of predators and ecosystem changes dating back to the early 2000s.

Tiaro Landcare Group, which has investigated the species for years, fears now the Mary River turtle is being eaten by a predator.

Between 2015 and 2018, a field study on the population unveiled there was a very low number of immature turtles residing in the Mary River, particularly in the lower catchment.

The Tiaro Landcare Group has been working with the Charles Darwin University to find out why.

“One strategy that we’re testing is to grow them until they’re about 10cm long then release these headstarter turtles and then test them,” project leader Marilyn Connell said.

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A Mary River turtle hatchling.

The turtles were equipped with tags to monitor their movements within the river and track their survivorship.

While a current analysis has not been completed, indications show the tags travelling faster in the water than what the species is capable of.

This has led to a conclusion that the turtles have been swallowed by a predator, leaving the equipment inside their belly.

“So far, it’s not good news and we’re not sure what it is,” Ms Connell said.

Marilyn Connell has concerns for the declining Mary River turtle population. Picture supplied by Marilyn Connell.

Ms Connell said the turtles are not the only species in the Mary River with declining offspring.

The lungfish, found in the Burnett, Mary and Brisbane River, the white-throated snapping turtle in the Fitzroy, Burnett and Mary River and the Mary River cod species are all being threatened by low immaturity rates.

The Tiaro Landcare Group speculate the mystery killer may cause significant issues for multiple aquatic species in coastal rivers of Eastern Australia.

The group is currently looking for partners to help investigate the identity of the predator and research solutions.

“We can’t decide what to do until we know what it is,” Ms Connell said.

Ms Connell encouraged locals to become a “turtle messenger” and care for the environment and river banks to protect the “uniqueness part of the Mary.”

The Lungfish, Mary River cod and white-throated snapping turtles are threatened species within the Mary River.

“Be proud of the creatures we’ve got in the river and help the next generation value and treasure them,” she said.

The group has worked on protecting the species since 2001 and together with Gympie, Fraser Coast and Sunshine Coast councils runs control programs for wild dogs and European red foxes during nesting seasons.

Tiaro Landcare Group project leader Marilyn Connell said the organisation’s program had been “quite successful” – thousands of Mary River turtles have hatched thanks to the program.

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It is expected that 90 to 100 per cent of hatchings would have failed otherwise, Ms Connell said.