100,000 Rats, 42 Tonnes of Poison — And One Slightly Nervous World Heritage Island
By Bernard LaganMarch 25, 2013
Here’s the plan: Stop rats from killing rare species, with a poison-packing flying squadron carpet-bombing virgin rainforest. It’s worked before. But is this really the way we save the planet?
Dr Ray Nias is a gently spoken zoologist who plots massacres from his small office on the edge of bushland in Sydney’s suburban northwest.
His employers — a northern California-based group of activist scientists, Island Conservation — favour a stealth poison that causes animals, mostly rats, to begin seeping blood from their insides. Because death may take up to a week, rats that slink off to die have never learned to connect the little emerald-green cereal pellets to their end. The laced bait is poured from helicopters using satellite guidance to fly a patchwork grid so precise that at least one lethal bait will fall within every two square metres of ground below.
Sometimes the rat killers are aided by a country’s armed forces. Governments often chip in millions. For a mass extermination to be successful, every last rat must take the poison. After the rats are gone, island saviours can set about reversing the reign of the rats by scouring the planet for the nearest relatives of the creatures the rats forced to disappear. And bringing them home.
On Australia’s Lord Howe Island, far out in the Tasman Sea, there are an estimated 100,000 black rats, all descended from a few that scrambled ashore from a broken ship’s organ in the winter of 1918, when the island trader SS Makambo ran aground and stayed stuck on a Lord Howe beach for nine days. The shipwrecked rats gorged on the island’s birds, lizards and insects, and multiplied, quickly bringing about a wave of extinctions; Lord Howe’s Tinted Thrush, its native warblers, fantails, white-eyes and starlings disappeared. And its native owls. All fell to the swarming rats.
So, too, did one of the world’s largest and strangest insects — the Lord Howe land lobster, a black stick insect as long as man’s outstretched hand, which doesn’t need males to reproduce. These were believed to have been lost forever until, in 2001, a tiny group of females was found clinging to the soaring, rat-free volcanic rock, Ball’s Pyramid, which thrusts out from the sea like a blade, 23 kilometres off the island’s coast.
Lord Howe’s spectacular red-crowned parakeets had been wiped out before the rats arrived — hunted down by farmer settlers who cursed their raids on early crops. But the rats would have got the parrots anyway. Long-ranging seabirds such as the Kermadec Petrels fled, flying on to outposts too far off for the rats to swim to. They never returned.
Now the rats’ time on the island is just about up. Nias, who is a director of the not-for-profit Island Conservation, is among those coming for them. Over the past 18 years, Island Conservation’s small band of scientists has choreographed mass killings. They have been spurred by the development of faster-acting, stronger poisons; global satellite-positioning technology that enables helicopter pilots to stay within one metre of their computer-plotted flight paths when dropping baits; and the realisation that time is fast running out to save endangered species forced into their last refuges — the world’s most remote islands.
Island Conservation staff, working out of buildings at Santa Cruz on the coast south of San Francisco, have also had to battle seething animal-rights activists, doubting, combative fellow scientists and embittered island residents in their missions to rid islands of the destructors brought by man. These include donkeys, sheep, cats, dogs, foxes and mice.
The pioneers of island mass eradications — the New Zealand Department of Conservation — honed their techniques in distant, empty territories, away from the public gaze. They went to islands off Alaska’s howling Aleutian Peninsula, the remotest parts of the Pacific Ocean, forgotten corners of the Caribbean and lonely, wind-tossed islands in southern New Zealand. They have shot, trapped and poisoned pigs, goats, arctic foxes and rats — the greatest predators of all — by the million.
The group chose to work on islands because islands have a disproportionately large number of the planet’s disappearing species. They make up less than 5 per cent of the world’s land area but harbour 20 per cent of all the planet’s bird, reptile and plant species. And just about all of the world’s known extinctions have occurred on islands, as they are the last refuge for many species.
It was in the year 2001, on an empty, chilly sub-Antarctic outpost, 700 kilometres south of New Zealand, that the tide really turned for those committed to large-scale, mass extermination of island invaders — Campbell Island became the site of the largest rat extermination ever attempted. Back in the 19th century, this was an island of roughneck sealers and whalers, and when they left, feral animals stayed; these included wild cattle, cats, and the greatest menace, the Norway rat. Although the cats and cattle were later removed, many doubted that the rats could ever be eradicated.
Campbell lies within the latitude of the Furious Fifties — a region of screaming winds and winter snowstorms. It is also, at 11,300 hectares, a big island. It has wild, sheer cliffs and tumbling, treacherous escarpments. Hand baiting such a large, craggy island was highly unlikely to reach every rat, and the difficulties of using helicopters to drop poisoned baits seemed insurmountable. The island was so far south, the cost of shipping helicopters, fuel and supplies would be enormous. And there was only a narrow window to drop the baits; it would have to be in the mid-winter period when rat numbers were lowest and they were unlikely to be breeding. Mid winter was also when the bird species, such as skuas, that might be accidentally poisoned by the baits, were off the island. The island’s big albatrosses, which posed an airborne threat to the helicopters, and the rock hopper penguins which would be terrified by the noise, would also be elsewhere at that time of year.
The New Zealanders needed to get four helicopters to the island — to ensure that they could thoroughly coat the landscape in poison within a 12-week time frame that was likely to be further narrowed by Campbell Island’s wild deep-south weather patterns. They fitted the choppers with long-range fuel tanks, dumped more fuel on islands along the route to Campbell and island-hopped the small choppers all the way down the Southern Ocean to the sub-Antarctic. They used a smaller, cheaper boat than would have been required to ship the helicopters, to carry the poison south, and converted a crumbling weather station on the island into living quarters for the human combatants.
They then killed every last Norway rat.
Very quickly afterwards, sea birds which had not bred on Campbell Island for decades returned. They included snipes and storm petrels. Amazingly, the world’s rarest duck species, the Campbell Island Teal — which was driven from the island by the rats 200 years ago and thought to have been extinct until a tiny number were found clinging on at a nearby islet — is back and thriving.
So remarkable was the saving of Campbell Island that it became a template for island rescues elsewhere.
Australia quickly followed with an attempt to wipe out all the rabbits and rats on its own sub-Antarctic territory, Macquarie Island, two years ago, using the same aerial baiting technique. (The jury is still out on its success.)
The Americans caught on, too, finally ending a 200-year rat occupation of the aptly named Rat Island in Alaska’s Aleutian chain. They too used the Kiwi-developed aerial technology.
The British, similarly inspired, are attempting the largest rat eradication ever — on the 800-square-kilometre South Georgia Island in the far southern Atlantic. Thirty-three times Campbell Island’s size, and just as empty of men, South Georgia is glacial and forbidding. It was once the world’s most teeming seabird breeding ground; albatross, penguins and gulls nested here in vast numbers, before the rats came with the seafarers in the late 18th century.
Three former air ambulance helicopters began dropping 100 million poisonous pallets on sub-Antarctic South Georgia Island on March 8 — aiming to eradicate the brown rats which arrived in the 18th century aboard ships. South Georgia’s glacial terrain means that the huge populations of the rats live in separate colonies on the island. Rats cannot cross glaciers, meaning that the rats live in isolated pockets that can, for now, be tackled separately.
But time is running out. The glaciers are retreating and scientists are racing against the clock to wipe out the rats before the retreat of the glaciers allows the rat colonies to form into a single, vast population.
The latest poison drop is intended to clear half the remaining rat infested territory on the island. The rat eradicators will return next summer to deal with those remaining.
Campbell Island confirmed the reputation of New Zealand’s small Department of Conservation as the giant of island rescues around the world. New Zealand has been the world’s ground zero for extinctions caused by rats. The last large habitable land mass to be discovered by man, New Zealand had no earthbound predators, such as wild dogs or cats, or snakes. As a result, many of its birds had evolved to be ground dwellers, and when the rats came with the Maori people those flightless birds were easily picked off. At least 51 New Zealand bird species are gone forever. A small band of New Zealand conservationists began to fight back on the small islands of the country’s wild deep south — not just against the rats but also against their public service masters who scoffed at the idea that whole islands could be purged of tens of thousands of rats.
Unsurprisingly, the Kiwis will also be involved in what is considered the world’s most complex island rescue — of Australia’s Lord Howe Island, which lies in the Tasman Sea between the two nations.
It is not the number of rats on Lord Howe, the island’s location, or its size (less than a quarter the area of Campbell Island) that make World Heritage-listed Lord Howe a challenge for experts in pest eradication. Rather, it is the island’s lawful occupants — its people and its endangered indigenous species — that make this a particularly tricky mission.
Unlike previous eradication sites, this is a well-off, inhabited island that has its own economic pulse; it has a permanent population of about 350 people, who are deeply attached to their island lives and spread across about 150 households. The island has 1,000 buildings. Tourists arriving on daily flights from the Australian mainland are crucial to Lord Howe’s economy — they number about 16,000 a year and lavish money on its hotels, guesthouses, restaurants and tours. To feed this transient population, the islanders run herds of beef cattle and dairy cows, and hundreds of chickens.
Lord Howe’s beauty is fortified by three soaring volcanic mountains. It has vast forests. Nearly half its plants grow nowhere else in the world, and there is a long list of native creatures that have entered the endangered- and vulnerable-species ledgers; these include ungainly native woodhens, lumbering land snails, native geckos, skinks and spiders, and an array of seabirds including petrels, shearwaters and terns.
And there are also 100,000 rats and tens of thousands more mice which are voracious eaters of Lord Howe’s plants and bird eggs. The mice have been known to swarm by the hundreds and attack sea bird chicks. The rodents have divided the islanders.
No-one has so far attempted to use aerial baiting to eradicate rats and mice on such a developed island that also sustains a large human population and a vital tourism industry. But in the winter of 2015, helicopters are due begin the first of two low-level, precisely guided sweeps across Lord Howe Island, dropping about 42 tonnes of green cereal pellets laced with lethal brodifacoum, the anti-coagulant that causes internal bleeding and eventual death.
Some — such as the island’s best-known naturalist, Ian Hutton, who has discovered tiny seabird chicks mortally wounded by rats, who has found the smashed birds’ eggs, and who sees daily evidence of the rats’ ravaging of the island’s plants — desperately want the helicopters to come and spread the poison.
“Some people say, ‘Oh well, the rats have happened and that’s too bad. But those rats, they have to eat something every night so they predate on birds’ eggs, lizards, snails, crickets, plants. It’s all going on every night,” says Hutton.
Others demur. Rob Rathgeber, a semi-retired business consultant, who spreads his time between Sydney and the island, says that while he accepts that some rats must be killed, in order to control their numbers, there is no need for their total eradication on Lord Howe: “There is a very, very valid point that the rat is now in sync with the environment over there. And if you remove it, it causes all sorts of problems.”
He also fears the unknown possible long-term effects on humans of brodifacoum — the anti-coagulant in the rat baits that causes death by bleeding. Conservation scientists counter that the risks to humans are minimal and an antidote is readily available.
It was depressingly clear only three years after the SS Makambo foundered in 1918 that the rats that had fled the ship would devastate the island’s plants and creatures. A local naturalist, A R McCulloch, wrote: “One can scarcely imagine a greater calamity in the bird world than this tragedy which has overtaken the avifauna of Lord Howe Island.”
The islanders tried to turn back the rat tide, offering a sixpenny bounty per rat’s tail, and organised large rat-hunting parties using dogs, clubs and guns. Their desperation eventually led to a chain of ecological train wrecks on Lord Howe. In the 1920s, for example, Masked Owls — which are ferocious rat hunters and killers — were brought up from Tasmania and quickly thrived. But they also became fearsome predators of the endangered native birds that the islanders have been striving to save from extinction — the woodhens and the Providence Petrels. Now the owls themselves have been declared pests; they’re being culled and will eventually also be exterminated.
These days, the islanders’ use of commercially available poisons to control mice in their homes and the rats around their properties has become so prevalent that it also results in the death of native wildlife — including the hard-done-by woodhens, which have only recently been nurtured back from the brink of extinction. Some of the birds are dying from secondary poisoning; from eating the dead and dying poisoned rodents or the bait.
In fact, the quantity of poisoned bait thrown at rats and mice every year in the populated areas of Lord Howe almost equals the amount per hectare that will be used in the eradication planned in 2015. There is also a race against another ecological clock: brodifacoum is already among the poisons routinely used by islanders and there is concern that the island’s rodents could become immune to it before the mass eradication — the $9 million cost will be funded by the Australian federal and New South Wales governments — can be started.
The deaths of native birds through secondary poisoning throws up one of the most vexing issues faced by those planning the Lord Howe rat eradication. They already know from trials on the island with dummy baits that some of the island’s still fragile native species — the woodhens in particular — will eat the poisoned baits after the helicopter drop. They will undoubtedly die. And some other native birds — such as the Pied Currawongs — will also die from feeding on the masses of dead rats, as the poison that killed the rats accumulates in the birds’ livers.
The problem is that nobody knows how many birds might be accidentally killed, but previous exterminations offer some ominous indicators. When New Zealand aerial-bated Kapiti, a 2,000-hectare island bird sanctuary north of Wellington, there were significant declines in the call rates of wekas — a bird closely related to Lord Howe’s woodhens. Some research says the population was decimated. And up to 20 per cent of the island’s native parrots — the kaka — may have died. Brodifacoum was used on Kapiti.
The worst backfire as a result of baiting occurred in Alaska. In the thaw of 2009, scientists made their way across the Bering Sea to check the results of their work on Rat Island in the Aleutians. During the previous winter it had been aerial-bombed with brodifacoum baits by a team which included the ace New Zealand helicopter pilots, mountain flyers used to the Alaskan weather; winds that tossed choppers as if they were darts. Organisers of this baiting were confident that in breaching Rat Island’s remoteness and Arctic conditions, they’d opened up a new frontier for island eradications.
The return party found that they had indeed killed all the rats. But they were chilled to discover Rat Island’s beaches littered not only with the corpses of gulls, but also with the great carcasses of bald eagles — America’s national symbol.
When it was later confirmed that every dead bird sampled had tested positive for brodifacoum poisoning, the scientists knew something had gone terribly awry. There had been only a few eagles on the island when the baits were dropped, but it seemed the big birds had flocked from further afield. Word must have got out among the eagles of the Aleutian Islands that there was a mass of easy prey, dead rats, on Rat Island, and the magnificent birds had flown in from surrounding islands only to meet their deaths.
Australia’s sub-Antarctic Macquarie Island harbours a different kind of cautionary tale, of ecological blowback on people’s attempts to radically interfere with a chain of predation. In the late 1990s wildlife officers stormed the island’s huge feral cat population. As expected, seabird numbers subsequently began to swell, but then came nature’s backlash — without the cats, the island’s rabbit population boomed. So, too, did those of the rats and mice. In 2006 hillsides left scoured and unstable by hordes of burrowing rabbits collapsed in heavy rains, trapping the nesting penguins below. Then, in 2010, when the first batch of brodifacoum baits were unleashed upon the rats and mice, foul weather forced the next drops to be abandoned. Unhappily, however, 400 seabirds were found poisoned. In 2011 the eradicators tried again. Macquarie Island has since exploded with life: its seabird population is again booming and vegetation is re-coating the bald hills. The island may be declared rat-free this year.
The potential for collateral casualties on Lord Howe weighs heavily on those planning the island’s mass rat eradication. The precious native woodhens — once down to no more than the 30 last of the species in the world — are vulnerable. So are the big, black, melodious-voiced Pied Currawongs — a species also native to Lord Howe. Non-native species such as ducks and the Masked Owls will also suffer.
The killing of non-target creatures is a cost of mass poisoning. The consensus among conservation scientists is that their quest to eradicate marauding introduced species is akin to war; and that some innocents will die so that many more can live. Or as Art Sowls, one of architects of the Rat Island eradication remarked to William Stolzenburg, author of the book Rat Island, after his team discovered the dead eagles: “The non-target issue is frustrating, but if you have cancer, you have to decide you are going to have chemo. Truth is, if they get all the rats, all the non-targets will be better off in the long run.”
And for Nias, not to kill the invasive animals would be to surrender ever more of the diminishing natural world: “Occasionally biologists do come with the argument that invasive species are just part of the new world, that we should just learn to live with them. Well, that just means giving up, in my view. You might as well live with pollution in rivers as part of the new world, you might as well live with climate change, you might as well let people shoot tigers to put them in Chinese pharmacies. That’s part of the new world — let it happen. We don’t take that view. We say eradication is feasible, it’s effective, produces results, so we do it.”
Lord Howe, as an inhabited island which owes its living to tourism, is more sensitive to the collateral-deaths issue. This eradication, conducted in the presence of a vocal, alert human population, will be closely watched. It will not have the cover of remoteness and inaccessibility. A disaster on Lord Howe would be felt by conservationists the world over.
So the scientists have organised a biblically inspired insurance policy — a Noah’s Ark. Before the helicopters swoop, hundreds of woodhens and Pied Currawongs will be captured and locked in cages specially built to be impenetrable to mice. Some of these will be further removed, taken to the Australian mainland for safekeeping in Sydney’s Taronga Zoo. So if, by some awful turn of events, the poisoning decimates the native birds on Lord Howe, there will be enough animals in reserve, to ensure the survival of the species. Only small numbers of the birds will initially be released back into the wild, and they will be fitted with radio transmitters to allow scientists to monitor their survival rates — before the rest of the population is allowed to join them.
Not so fortunate will be the island’s 300 chickens and its beef cattle. They’ll be slaughtered before baiting starts. The dairy herd will be locked away in a specially built barn. The island’s 40-odd pet dogs will need to be tied up or kept indoors. Lord Howe Island has no cats. Around Lord Howe’s built-up areas, the poison baits will be distributed by hand and put into bait stations.
The evolving technology used in island pest eradication — more lethally efficient poison and the use of satellite technology to ensure that no corner of targeted land will be missed by the choppers — means the success rate of island strikes is on the upswing. Island Conservation’s website reports that in the 18 years since the organisation was formed, 51 of the world’s islands have been cleared of invaders. This adds up to an area slightly smaller than the Isle of Man.
But the hope is that after the rats are gone, the lost bird populations of the past will return to Lord Howe Island. Perhaps the ocean wanderer, the large Kermadec Petrel, will take a chance and return to this shore where it hasn’t bred for decades. It’s even hoped that the relatives of land birds such as the red-crowned Parakeet, long lost from Lord Howe, will come to enjoy the sanctuary of a rat-free island.
And if these close relatives don’t come freely, people like Ray Nias are prepared to intervene and move them in. He knows that the extinct Lord Howe parakeet’s relations survive on Australia’s Norfolk Island and in New Zealand.
Says Nias: “The exciting thing for me about island conservation is that up to a point it’s about stopping damage. But it also gives you the potential to start restoring what was before.”