Environment

At certain times of the year, volunteers can be found roaming Canberra’s bush reserves bearing raw chicken carcasses – all in the name of saving the local apex predator. By Suzannah Marshall Macbeth.

Saving Canberra's goannas

A goanna with its mouth open basks on a rock under a clear sky.
A Rosenberg’s monitor.
Credit: Ken Griffiths / Alamy

In the dappled shade of gum trees at the edge of Mount Ainslie Nature Reserve, a stone’s throw from the back fences of suburban Canberra, a trestle table is attracting a lot of attention from people out for their Sunday morning walk. On the table are three goannas. They aren’t going anywhere – they’re freeze-dried and beautifully mounted – but they are lifelike enough to attract a second glance from almost everyone who walks by.

Two of them are tree goannas, also known as lace monitors, a species no longer found in Canberra. The third is a Rosenberg’s monitor, or heath monitor, a handful of which still live in the connected Mount Ainslie and Mount Majura nature reserves – 1139 hectares of protected bush just a couple of kilometres from the city centre.

During Covid-19 restrictions, I was one of many Canberrans who retreated to the network of fire trails and foot tracks that crisscross the Mount Ainslie and Mount Majura reserves. The area is well used by walkers, runners, dog walkers, cyclists and occasional horse riders, many of whom are aware of the birds, shinglebacks and kangaroos but never may have seen one of the powerful Rosenberg’s monitors, which can grow up to 1.5 metres in length.

At last count, there were no more than seven known goannas living in Ainslie–Majura. Whether this remnant population can survive so close to Canberra’s centre, surrounded by suburbs, farmland and roads, and threatened with attack by foxes and dogs, is the question driving retired ecologist Don Fletcher’s work leading the ACT National Parks Association goanna project. The first step, with the help of the 20-odd volunteers who have turned up to the reserves every Sunday morning, is to find out how many are actually there.

I accompany volunteer John Brickhill to an area with signage about “unexploded ordnance”. We hike into the bush to find the camera traps, where half a chicken torso is attached to a stake with a camera pointing at it. Over the course of a week, some of these “baits” have dried out, been picked clean or disappeared entirely, depending on which enterprising creature has had a go at it. Our job is to replace the bait – at certain times of the year on a Sunday, 18-20 volunteers can be found wandering around carrying chicken carcasses in plastic containers – and change the memory card and batteries in the camera.

The cameras are motion-activated but can’t distinguish goannas from everything else, so after the survey is over, volunteers will sort through a couple of million photos. Among countless pictures of ravens, possums, foxes, wallabies, grass blowing in the wind and faces of concerned volunteers checking the camera’s orientation, hopefully there’ll be a few goanna faces – familiar ones and, Fletcher hopes, some new ones too.

Back at the volunteer rendezvous point, Fletcher chats to passers-by about Rosenberg’s goannas. Most people who stop are shocked to hear that goannas still live here.

“They lie still among the timber,” Fletcher says. “They can be right there and you won’t see them.”

Hannah Windley was involved in establishing the Ainslie–Majura goanna research project two years ago in her then role with the National Parks Association, and is back as a volunteer. She shows me the intricate face markings on the freeze-dried specimens. “Because each face has a different pattern, we’re able to identify individuals.”

As we chat, Windley has one eye on the walkers passing by and winces when she sees dogs off lead. “Even if a dog doesn’t attack a goanna, their mere presence can change the goanna’s behaviour,” she says.

Ironically, the role predators play in changing the behaviour of their prey is part of the reason why goannas are so significant as the largest remaining native predators in some Australian ecosystems.

“We know from looking around the world in history that the largest predator in a system is incredibly important,” Fletcher says. “There can be very, very few of them, and so you would underestimate the importance of those few, but they have a big effect on the things they prey on, which in turn have an effect on the things they hunt or eat or consume, so on down the ecosystem.”

Fletcher refers to the well-studied example of the reintroduction of wolves to Yellowstone National Park in the United States. The presence of the apex predator, the wolf, affected the behaviour of elk, which in turn changed the vegetation composition along rivers, with flow-on impacts for beavers, insects and other species. These changes helped re-establish balance in an ecosystem that was struggling due to excessive browsing of elk on sensitive river vegetation.

“We don’t have that level of knowledge about the system here, because goannas haven’t been well studied,” Fletcher says.

He and the ACT National Parks Association also run a goanna research project in the Naas Valley in Namadgi National Park – prime goanna habitat where numbers have grown alongside increased fox-baiting in recent decades. Yet there are still many unknowns about goannas, such as how often they breed and how severe a threat dogs and foxes pose to the adult populations.

“A female will lay 12 eggs, most of which will hatch, and then there’s tremendous mortality – but there’s another vulnerability as well that we don’t know much about,” Fletcher says. “When [the female goanna] is laying, for quite a few hours she has her head poking out of a termite mound and she’s in a trance. You can walk right up to her and she doesn’t show any sign of noticing you’re there or being afraid.” It’s likely that female goannas are extremely vulnerable to foxes while they’re laying eggs.

Late last year, Minister for the Environment and Water Tanya Plibersek announced a Towards Zero Extinctions strategy for threatened species, but Rosenberg’s goannas are unlikely to be on her worry list. They are listed as critically endangered in Victoria, and vulnerable in New South Wales and South Australia, but are considered secure in south-west Western Australia, which means they are not vulnerable under national frameworks. (They have not yet been considered for listing in the ACT.) This reflects the changes to the Environmental Protection and Biodiversity Conservation Act, whereby species that are secure in part of their range are automatically excluded from federal listing.

“In a way that’s a response to ‘there’s just so much to list’,” Fletcher says, “but it’s misguided, because the way in which things become extinct is not, generally speaking, by the entire population all suddenly going down. It’s piecemeal – this population, then that – they blink out in little bits and pieces across their range. So the fact that [Rosenberg’s goanna] is secure in south-west WA really isn’t a reason to not worry about them in the ACT or at Ainslie–Majura.”

As for the rationale for protecting this population, he says, “of course there’s the intrinsic interest in the individual organism, but the ecological reason is best expressed by the idea that if you start taking apart a clock and you’re hoping to put it back together again, then don’t lose the parts – keeping all the components is a pretty fundamental thing for any complex system.”

In Canberra, goannas are part of a tussle between humans, their pets and feral introduced animals. Globally, people and livestock account for more than 90 per cent of land-dwelling vertebrate biomass – spaces and resources for wild animals are rapidly shrinking.

Fletcher hopes for measures to make Ainslie–Majura safer for the goannas, for instance by controlling fox numbers, as he’s seen the damage from attacks they’ve suffered. In January, he and some volunteers caught a male goanna, nicknamed Rum, with the intention of fitting a GPS pack so they could monitor his movements and find out more about his behaviours. Instead, they discovered three gaping slashes on his neck and throat, oozing blood and fluid, with a chunk out of his tail from an older injury. Luckily, a trip to the vet and some careful dosing of antibiotics allowed Rum to return to the mountain, even making appearances at one of the camera traps.

Between such rescue missions, monitoring camera traps and working with researchers in Namadgi National Park, an incredible number of volunteer hours goes into keeping an eye on the ACT’s Rosenberg’s goannas. Hiking the beautiful trails of Ainslie–Majura to find the camera traps, with a potential reward hidden on those memory cards, I can see how the volunteers get hooked. With their help, this precious piece of the complex ecology of Canberra’s woodlands might have a fighting chance.

This article was first published in the print edition of The Saturday Paper on June 3, 2023 as "The hills are alive".

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