An island ark
A cat-detection team is doing important work on Dirk Hartog Island
By Nicole Gill
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The stars are bright over Western Australia’s Dirk Hartog Island, which sits within the Shark Bay World Heritage Area. Zoologist Sue Robinson shovels muesli into her mouth without enthusiasm, wipes dew off her quad-bike seat and corrals her gear for the morning’s work. From newly built kennels, half a dozen dogs of varying shapes and sizes bark at the pre-dawn blackness, the din almost drowning out the snap of canvas in the 4 am breeze. In the tin shed that serves as a mess hut, Robinson’s partner, wildlife biologist Mark Holdsworth, has a black coffee in one hand and is also busy rummaging for freshly charged radios, phones and GPS receivers. Together, Robinson, Holdsworth and the dogs form the cat-detection team, which is working to rid Dirk Hartog Island of feral cats as part of the Western Australian Department of Parks and Wildlife’s Return to 1616 project.
Four hundred years ago, on 25 October 1616, Dutch explorer Dirk Hartog set foot on what is now Australian soil, becoming only the second European to do so. (The first was Willem Janszoon, who visited Cape York in 1606.) Hartog’s boat, the Eendracht, had been swept off course while en route to Java and arrived on the island known as Wirruwana by the Malgana people. Hartog and his crew spent a few days scouting the local area and then resumed their journey, but not before installing a small pewter plate inscribed with a few details of their expedition and arrival date. It is the oldest physical evidence of Europeans in Australia.
The state of the landscape that Hartog and his crew observed has since become a baseline, in nature conservation terms, for what is wild, natural and desirable, especially in recently colonised nations. For generations, whatever state the landscape was in when the first white man stepped off the boat was considered “wild”. But as environmental writer Emma Marris explained in her book The Rambunctious Garden, this perspective effectively relegates indigenous people’s landscape-management practices to a status on par with grazing by native animals.
At first glance, the Return to 1616 project seems to align with this view. The WA Department of Parks and Wildlife states that the aim of the 20-year program is “to restore the vegetation and habitats of Dirk Hartog Island National Park to how Dirk Hartog would have seen them in 1616”.
This is no simple task. The sand island is huge – more than 80 kilometres from north to south, and 14 kilometres at its widest point – and for much of the year it’s scoured by harsh sun and hot, dry winds. Everything has to be brought to the island by plane or barge, and there are few comforts available for those working in the field. “There’s no point complaining about the wind,” Robinson says. “At least it keeps the sandflies and mosquitoes away.” After only a week on site she is already a mass of itching, suppurating blisters, courtesy of bites from the local insects, and there are still five weeks of fieldwork to come.
A lot has changed since Hartog’s visit. His namesake island has been a base for pearlers, fishers and graziers, and is clearly marked by human enterprise. The Malgana people’s ongoing relationship with the island was formally recognised by a native title agreement in 2009. As part of the agreement, Malgana representatives agreed to work with national parks and private landholders to ensure responsible management of the island’s ecosystems, and to address environmental concerns.
The island was run as a pastoral property from the 1860s – all over the island, rusting lengths of wire coil around dried-out fence posts, and old irrigation pipes line the roads – and the last remaining sheep were only removed in 2013. They, along with introduced goats, trampled the island’s vegetation down to a buzz cut, underlain in places by a tatty carpet of introduced weeds. All of these invasive species are targeted for removal as part of the Return to 1616 project.
At the cat-detection team’s camp, everything is held together with cable ties and dusted with a liberal coating of sand and mouse shit. Common house mice skitter underfoot. Perhaps surprisingly, these mice are not targeted as part of the project. Although island-wide mouse eradication has been successful elsewhere, any rodent removal here would be complicated by the fact that a handful of native marsupial mice still live among the feral species.
These native mice are the exception though. Island species tend to show higher levels of predator naivety than their mainland counterparts – they’ve never learned to be afraid. Since cats arrived, and the sheep and goats flattened the flora, ten of a total of 13 native mammal species thought to have been here when Hartog landed have vanished: the western barred bandicoot, the chuditch (aka the western quoll), the brush-tailed mulgara, the dibbler, the greater stick-nest rat, the desert mouse, the Shark Bay mouse, the heath mouse, the woylie and the boodie. These animals will form the focus of the second phase of Return to 1616: the re-introduction of what has been lost. It’s hoped that the native burrowing critters will increase water penetration of the island’s dry soils, consequently upping seed germination rates and helping native plants re-establish.
Increasingly, offshore islands in Australia and abroad are being utilised as biological arks: places safe from introduced species and other threats. The mammals to be re-introduced on Dirk Hartog Island are being bred on the mainland for release once the island is clear of feral species. This is where the cat-detection team comes in. Robinson, Holdsworth and the dogs are not here to kill cats – a separate crew has been baiting, trapping and shooting the remnant cats and goats – but rather to make sure that none still remain.
Robinson loads Bax, a lanky Belgian shepherd, into the travel cage on the back of her quad bike and heads out to the east coast. The island is crisscrossed with rough tracks, many cut specifically to provide access for the various eradication-related activities. They link a network of motion-sensing cameras, often set up at water sources or on natural corridors, which snap photos of cats and goats, or the occasional cat trapper doing push-ups for the amusement of his office-bound colleagues.
Still in darkness, Robinson and Bax pull up on the eastern edge of the island. She fits the dog with a muzzle, a working collar and a reflective collar. He is also equipped with a transmitter that records where he’s searched for evidence of cats. Along a coastline, one cat’s range can extend for 30 to 40 kilometres.
Most days, each handler will do two 10-kilometre surveys, each with a different dog. The dogs walk even further, swinging back and forth under the coastal scrub, occasionally startling a native quail or dozing lizard from beneath a spinifex clump. The dogs’ welfare is of utmost importance. They are muzzled at all times outside their kennels, but should a dog somehow eat a bait, each handler carries a blister pack of small, white pills: emetics to be inserted under eyelid or tongue. Also on hand is an intravenous kit containing antivenin in case of snakebite. Both of Bax’s front legs bear a small shaved patch in preparation for the life-saving injection. The team’s early morning starts are largely to reduce the risk of snakebite, but also help to beat the heat.
Bifurcating the island just south of its midpoint is a feral-proof fence, roughly 3 metres tall. It’s electrified via two wires at knee and shoulder height, and is set deep into the ground to prevent animals from burrowing under.
In the midday sun, we drive across to the western end of the fence, where we see what Robinson describes as “delicious, oil-dripping, poisonous chipolatas”. These Eradicat baits – sausages impregnated with 1080 poison – hang from the fence at 20-metre intervals. While Western Australian animals are moderately immune to 1080’s active constituent, sodium fluoroacetate (the compound occurs naturally in a range of local indigenous plants), the baits are still positioned to prevent non-target species taking them. These ones are freshly hung, and are still dripping with the fat that has attracted the local shingleback lizards. One has climbed about a foot up the fence, from where it launches itself in a futile attempt to snag a sausage.
Later, Holdsworth and Bozo the chocolate labrador will find a cat skeleton. They bring home the skull, still encased in leathery skin that clings to it like dried seaweed on a rock. By the time Robinson, Holdsworth and the dogs leave the island after a month of searching, the only other cat signs they’ll have found will be a handful of old, dry scats. It’s a good sign that the southern sector remains cat-free.
Despite the name, Return to 1616 is not really about returning Dirk Hartog Island to an Eden-like past. Once the island is officially clear of feral cats and goats, two species of hare-wallaby will also be introduced, along with the ten mammals that previously lived here. It’s hoped they will form insurance populations – part of a new world of conservation in which rapid habitat loss, aggressive invasive species and climate change have forced conservationists to consider whether what Hartog saw 400 years ago is really what they want to create.
It isn’t possible to go back, anyway, and not just because a perfect, static past never existed. The landscape has changed. The climate has changed. Only the stars remain the same. It is possible, however, to go forward, creating small pockets of breathing space for nature. One island at a time.