TURTLE TUNNELS PROVIDE SAFE PASSAGE FOR MIGRATING REPTILES

Conservationists reintroducing eastern quolls to mainland Australia faced a big problem: the fence needed to protect quolls from foxes would potentially kill a population of eastern long-necked turtles.

Their innovative solution is a series of water-filled tunnels that keep out feral predators but allow the turtles to travel between waterholes.

Nine ‘turtle tunnels’ have been built underneath the 82-hectare fence that encloses the Botanic Gardens in Booderee National Park on the NSW South Coast.

And the structures are already proving popular with more than just turtles.

Sensor cameras have captured bandicoots, cockatoos, kookaburras and one opportunistic echidna investigating the watery entrance to the tunnels.

“Some animals seem to be using them as makeshift waterholes. 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,” said Rob Brewster, WWF-Australia’s Rewilding Program Manager.

While the echidna’s antics have provided some laughs, it’s the response from eastern long-necked turtles that has conservationists celebrating.

In the nine months since the tunnels were installed, monitoring has shown turtles are successfully transiting under the fence to complete their seasonal migration.

“We have long known that turtles use the network of swamps and lakes at Booderee, feeding and fattening in the swamps and migrating to the permanent lakes when the swamps dry out. It was imperative that we maintained access for turtles to these waterbodies. Along with regular patrols, we are satisfied with the turtle tunnels as a solution,” said Nick Dexter, Booderee National Park Country and Conservation Manager.

The four-kilometre-long conservation fence was erected in Booderee Botanic Gardens in November as part of a project to reintroduce endangered eastern quolls to mainland Australia.

The fence is designed to protect quolls from feral predators like foxes, but the project team realised it would pose a problem for another native species.

The fence around the Botanic Gardens sits within an ancient migratory route for eastern long-necked turtles, who travel between water sources and nesting sites at Lake McKenzie and Lake Windermere.

Without a solution, the turtles would be unable to complete their migration and at risk of overheating and dying.

“We had to design something that would allow turtles to migrate across the fence line without allowing foxes to get in or quolls to get out,” said Mr Brewster.

The team settled on a design resembling a bathtub - a two-metre-long, 70-centimetre-deep swim-through system that could be sunk into the ground underneath the fence.

The tunnels would be filled with water to deter foxes and quolls from entering, and an underwater mesh opening would be installed at the midway point to prevent larger animals from moving through the tunnel.

The design underwent a series of trials with eastern long-necked turtles near Kangaroo Valley.

After watching a succession of turtles successfully (albeit slowly) navigate the tunnels, the team knew they’d cracked it.

The tunnels were ready to be put into use at Booderee National Park.

“It’s important that no species is left behind when we're saving threatened species - everything has a role to play in our culture and ecosystems,” said AJ Van Oploo, an Aboriginal ranger who helped to install the turtle tunnels.

Booderee rangers have been monitoring the fence line for turtle activity since the tunnels were installed late last year.

Over 123 days of monitoring, they recorded 73 instances of turtles successfully exiting tunnels.

In more good news, while sensor cameras captured the echidna and several birds taking a dip in the water, they recorded no evidence of foxes attempting to enter the tunnels.

It is hoped the tunnel design can now be used and modified to mitigate the impact of conservation fences across parts of Australia where freshwater turtle migration occurs.

“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,” said Mr Brewster.

The eastern quoll reintroduction project is a collaboration between Parks Australia, Wreck Bay Aboriginal Community Council, WWF-Australia, the National Parks Conservation Trust, Australian National University, Taronga Conservation Society Australia, Tasmanian Quoll Conservation Program’s Devils @ Cradle and Trowunna Wildlife Sanctuaries, and Aussie Ark’s Barrington Wildlife Sanctuary, with support from Foundation of Australia’s Most Endangered Species (FAME), Shoalhaven City Council, and Bremick.