fox

 

Foxes are causing a “catastrophic” situation for Australia’s freshwater turtles. Along the Murray River, foxes are decimating turtle populations by digging up nests to eat eggs and capturing reproductive females.

This situation is exacerbated by the turtles’ long lifespan juxtaposed with their young’s vulnerability to predators, creating an aging population that conceals the severity of the issue, says University of Sydney emeritus professor Mike Thompson.

Thompson, whose fascination with turtles began in the 1970s, now works on the 1 Million Turtles citizen science project from his semi-retirement in the Adelaide Hills.

The eastern long-necked turtle, the most common species in the Murray, has seen a population decline of 90% since 1980, with potentially higher losses in South Australia. This significant decline has prompted the federal government to consider listing the species as vulnerable.

Similarly, the Murray short-necked turtle, already listed as threatened in Victoria and vulnerable in South Australia, has suffered a 69% decline over the same period.

“The catastrophic decline is largely due to predation by foxes,” Thompson says. “The foxes in some places dig up all the nests and eat all the eggs. Other native predators eat the eggs as well.

“Also, the foxes often take and kill the reproductive females when they’re coming out of the water to nest.”

Research indicates that Australia’s 1.7 million foxes kill approximately 300 million native mammals, birds, and reptiles annually. A 2022 Australian National University study found that foxes, spread across 80% of the mainland, have been recorded killing 108 different species of reptiles, including turtles.

Thompson says that turtles, which take about a decade to reach reproductive maturity and can live up to 100 years, are particularly susceptible.

“The turtle population has been going down for a long time but it’s masked because they live for such a long time,” he says, adding that fewer and fewer juvenile turtles are being spotted.

Freshwater turtles face additional threats from habitat loss, fire, drought, pigs, water infrastructure such as carp traps, and being struck by vehicles or boats.

“[And] carp have made big changes to the aquatic environment which we think has negatively impacted the nurseries of turtles,” Thompson says.

The 1 Million Turtles project aims to hatch a million eggs and return the turtles to the water, utilising TurtleSat to collect data and pinpoint locations of turtles, their nests, or remains.

Efforts to mitigate fox predation have intensified, with increased culling and the construction of fox-proof fences around nesting sites. The project is also experimenting with artificial islands where female turtles can nest safely out of foxes’ reach.

An article co-authored by Thompson and other experts, published in Australian Zoologist, noted that 11 of 25 freshwater turtle species are listed as threatened by at least one state or the federal government. The article highlighted the scarcity of long-term population comparisons, with significant declines observed in both the eastern long-necked and Murray short-necked turtles.

The authors emphasised the importance of citizen science projects in addressing data and funding gaps to protect these vulnerable turtle populations.

“My back of the envelope calculation suggests a million [turtles released] isn’t nearly enough,” Thompson sys. “For the Murray, it might be 10 million.”

 

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