Turtles could be key to River Murray carp virus clean-up

Could turtles help clean up the environment after the release of a carp virus in the River Murray?

A researcher has spent the past two months trying to find out.

Claudia Santori had two pets as a child: Tarta and Ruga, from the Italian word for turtle – "it's funny how little things like that make you passionate".

More than 20 years later, she has just finished a stint at the Riverglades and Paiwalla wetlands near Murray Bridge, researching her favourite animals for the University of Sydney and the Nature Foundation SA.

Despite decades of population decline due to road kills and egg-eating foxes, there are still hundreds of long-necked, short-necked and broad-shelled turtles living in the wetlands.

She counted 160 individuals over 18 days of trapping, though she said they would once have been five times more numerous.

Her work focused on the role turtles play in the natural environment, including the degree to which they helped keep the water clean by eating dead fish.

"In the water (dead fish are) out of sight, out of mind," she said.

"A lot of animals die in the water and you never see them, so you don't know.

"It takes a lot of animals to keep the water clean and drinkable; without them you'd have a lot more nutrients, blue-green algae and more turbidity."

By submerging dead carp in two types of boxes – one open, one sealed off with mesh – she attempted to establish whether those that could be eaten by turtles disappeared more quickly.

She had yet to analyse the information she collected, but her early findings suggested the carp were eaten more quickly in areas where she had found more turtles, and especially adult short-necked turtles.

"It's not all black and white, but I think definitely turtles have an important role," she said.

"But the numbers now are so low in some areas the impact isn't as much as it used to be, which could have repercussions if the water quality (problem) goes on."

She ultimately hoped to establish what would happen to the river if the turtles disappeared, and strengthen the case for saving them.

"I hope they will be back," she said.

"I don't know if the carp will ever be gone, but I hope (turtles) will be able to come back to their original numbers, live side by side ... and be the protagonists of the ecosystem again."

How to spot a turtle nest

Unless you're a fox, the best way to find a turtle nest is to stumble across a female building one: a hole in the ground as deep as the individual is long, covered over with soil, typically in an area of sand or low vegetation.

Long-necked and short-necked turtles build their nests at the beginning of November, often after rainy weather, and their eggs hatch around Christmas.

Broad-shelled turtles nest around Easter, but their eggs take up to a year to hatch.

Tragically, most turtle nests are dug up by foxes within a day or two.

But they can be protected with a layer of chicken wire, with holes big enough for the babies to get out, laid down after the female has left.

Even nests which have been dug up can remain viable - a couple of locals reportedly found several eggs remaining in a nest they had checked, and incubated and hatched them.

A wetland the size of Paiwalla might contain 100 nests with 20 eggs in each.


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