How Australian conservationists’ tunnel vision lets turtles swim to freedom
Eastern long-necked turtles are known for their “ridiculously cute grin”, says Nick Dexter, and a much less charming ability to release a pungent stink to ward off predators.
But what they’re not good at, unsurprisingly, is climbing fences.
So when conservationists devised a plan to create a fox-proof haven for endangered eastern quolls using a circular fence, they realised they had a problem.
Dexter is the conservation manager at Booderee national park on the south coast of New South Wales, where one of the water sources vital for the turtles would be inside the four-kilometre fence, creating a major risk for the area’s turtle population.
The solution? Turtle tunnels filled with water.
“They do seem to be finding them on their own now, but we patrol the fence regularly and if we see a turtle we’ll take it to the nearest tunnel,” said Dexter.
“The tunnels look a bit like a small bathtub – sometimes the turtles just seem happy to sit there.”
Nineteen eastern quolls were released inside the fence in April. The species once common in the south of Australia is thought to have been extinct on the mainland since the 1960s and now exists in the wild only in Tasmania.
“Even before we built the fence, we knew we had an issue,” said Rob Brewster, Worldwide Fund For Nature Australia’s rewilding manager. “There are hundreds of the turtles. They’re long-lived and we had to look after them.”
The fence encloses 84 hectares and a mix of bush, woodland, heath and forest that includes a botanic garden and the 10-hectare lake. Outside the fence is a swamp area and Lake Windermere that the turtles move between to find water and food.
A trial of the tunnels was carried out with enough success to roll them out. The nine tunnels are spaced out around the fence and sunk into the ground. To get through, the turtle walks down a slope and into the water down a small step, and swims under mesh that keeps them under water.
Rangers have been monitoring the tunnels and have seen turtles exiting them more than 70 times.
Other species have also been hanging around the water holes created by the tunnels – bandicoots, cockatoos, kookaburras and an echidna have all been seen on cameras.
“Some animals seem to be using them as makeshift water holes. We’ve seen gang-gang cockatoos stopping for a drink and one little echidna waddling around the fence line and enjoying a bath every few hundred metres,” Brewster said.
The design of the tunnels appears to provide easy negotiation for the turtles and, so far, foxes have not got into the enclosure and the quolls haven’t escaped.
AJ Van Oploo, an Aboriginal ranger in the park, said: “We don’t want foxes in or quolls getting out. Just one fox could kill a lot of quolls so it’s imperative we have the fence.
“It’s out-of-the-box thinking. We’re reintroducing a species, but we don’t want to take out another. It had to be fixed.”
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Just as encouraging are results of recent monitoring of the quolls. Some females were carrying young in their pouches.
Fences are a well-used solution in reserves in Australia to protect threatened species from feral pests, including foxes and cats that continue to decimate native wildlife.
A previous attempt to introduce quolls to the park in 2018 and 2019 failed. Without the protection of a fence, the marsupials perished because of foxes, dogs, pythons and cars, Brewster said.
“We’re building so many fences, but we have to think about how we innovate to solve problems,” said Brewster, who hopes the design could be used to reduce the effect of other fences where freshwater turtles are trying to move around.
“Sometimes our actions to protect one species can have unintended consequences for others. But this time, it’s nice to know both the quolls and turtles will be happy,” he said.
