On a summer evening in 2001, two men set out to scale Ball’s Pyramid, a jagged spire of rock off the coast of Lord Howe Island, a remnant volcano 480 miles northeast of Sydney, Australia. They were looking for an insect that hadn’t been seen for more than 70 years.
Earlier in the day the men had found impressively large insect droppings in the leaf litter beneath a tea tree about 200 feet up the rock. Now, shining their flashlights on the tender tips of the shrub, they saw what they were hoping for: two golden-brown stick insects, both adult females. A little later, they found a third, a green nymph.
It was one of the discoveries of the century. An insect thought to be extinct was surviving on an 1,844-foot pinnacle with little more to live on than a few dozen spiky-leafed plants. And it’s no pip-squeak. Fancifully known as the tree lobster, the Lord Howe Island stick insect is the size of a cigar and weighs as much as a sparrow. The males have thighs like a New Zealand rugby player.
This jumbo insect was once so common it was used as fish bait by the island’s residents. How it went from ubiquitous abundance to clinging to existence on a shark fin of rock in the Pacific Ocean is the story of islands everywhere. It’s the story of introduced predators: rats.
Invaders ravage a Pacific paradise
Rats have been responsible for more ecological unraveling than any other animal except humans. They are the ecological Grim Reaper. Their presence on islands invariably leads to extinctions and radically reduced populations of birds, amphibians, reptiles, and invertebrates. They also harm plants by eating fruits, seeds, and germinating seedlings.
But Lord Howe Island has recently shown the tables can be turned on rodent invaders. Eradicating them provides an ecological reset and the opportunity for endangered species such as the supersize stick insect to make a comeback. “It’s amazing what’s unfolding,” says Hank Bower, a Lord Howe environmental manager for 15 years.
Rats had been part of Lord Howe’s life for more than a hundred years. They arrived in the classic way: by deserting a sinking ship. In 1918, the S.S. Makambo, an island-trade steamship, ran aground at the northern end of the island. The ship was refloated, but not before rats had come ashore. With no natural predators on the island, their numbers exploded. Within two years, they had eaten the stick insect—and several other species—to oblivion.
All told, six bird species, 13 invertebrate species, and two species of plants were lost. The rodents also made life difficult for Lord Howe’s human inhabitants. Along with mice, which were already on the island, the rats contaminated homes, gnawed electrical cables, besieged gardens and orchards. They also devastated the only significant export—the seeds and seedlings of endemic kentia palms, a popular indoor plant—by devouring the wild seed stock.
To try to control rat numbers, the island’s administration placed a bounty on their tails. Residents shot rats, hunted them with dogs, poisoned them, and introduced several species of owl—a misguided attempt at biological control that backfired when the owls displayed a taste for native prey.
These efforts scarcely dented rodent numbers. An island paradise designated a World Heritage site in 1982, Lord Howe was ecologically damaged and at risk of losing more species.
Residents were closely divided over eradication
Ridding islands of predators was once thought impossible. But over the past 70 years, more than a thousand islands have been cleared. No island now seems beyond redemption. The biggest success so far is South Georgia, the size of New York’s Long Island, which was declared rat free in 2018.
Could Lord Howe join these revitalized islands? Geographically, there was no reason why not. Much larger islands, with equally precipitous terrain, have been cleared. The benefits would be many: restored ecological integrity, the recovery of threatened species, a story to attract environmentally minded tourists, and the permanent removal of a disease-carrying, garden-raiding, fruit-ravaging, house-infesting pest. Islanders could look forward to throwing away their traps and never having to dispose of a dead rodent again.
But there was a snag: Most of the islands where rats have been eliminated were uninhabited. The presence of people makes eradication an order of magnitude more difficult.
The most effective approach—aerial bombardment with rodenticide—is not feasible on an island with a human population. The problem is not the risk of accidental ingestion by people and their companion animals and livestock. Nor is it the challenge of dealing with infrastructure, such as buildings, which might harbor rodents. These issues can be addressed. Even the existence of agriculture, which can provide rodents with alternative food sources so that they might not get around to eating a poison bait, can be accommodated.
The core problem with inhabited islands is political: getting people to agree to an eradication project and support its execution. On Lord Howe, a slim majority of the 350 residents embraced the idea; the rest did not. Some opponents of the project believed eradication could not be achieved and so should not be attempted. Others were alarmed about the health implications of dropping tons of rat poison from helicopters. Some claimed the project would drive away the tourists who are the backbone of the island’s economy. Some mistrusted the board in charge of the island’s administration. Some mistrusted the project’s scientific advisers. Some mistrusted the science itself.
Mistrust is fertile soil for misinformation. A number of bizarre theories circulated: The eradication campaign was an experiment by the New Zealand government to test rodent poison on a human population as part of its plan to eliminate predators in its own country; the project was part of a long-term scheme to remove people from the island so that it could revert to nature—“First the rats, then us,” they fretted; a cabal of ecologists with shares in the rat-poison company were lining their pockets at Lord Howe’s expense.
Detractors claimed that far from revitalizing the island’s ecology, the project would “poison paradise.” When the issue was put to a vote in 2015, 52 percent of the islanders came out in favor, and the $10 million eradication project finally began in June 2019, almost 20 years after the idea had first been floated.
Meticulous planning leads to success
The operation, funded jointly by the Lord Howe Island Board, the New South Wales government, and the federal government, involved aerial distribution of rat poison in uninhabited parts of the island, the deployment of some 20,000 bait stations in areas of human settlement, and hand dispersal of baits in a buffer zone between the two areas.
Logistically, it was one of the most complex eradication campaigns ever undertaken. Two island bird species—the endemic Lord Howe Island woodhen, a flightless, chestnut-colored rail, and the native pied currawong, a mostly black relative of the magpie—were considered at risk of ingesting poison on account of their size and inquisitiveness, so some were held in captivity. Most chickens were either removed from the island or housed in a rodent-proof facility. As a safety precaution, all the milk from dairy cows was destroyed daily.
The crux of any island eradication is that every predator must encounter a bait. There can be no exceptions. This required the project team to place baits in more than 600 structures, from houses to hotel rooms, sheds to shops, and in roof spaces where rats or mice might be living.
Meticulous execution paid off. By late October 2019, no rodents could be found, and the island’s plants and animals began to flourish. Biologists speak of species being “released” from predator pressure. I think of it as liberation ecology. The woodhen population, which in the 1970s dropped to as low as two dozen birds, has more than trebled to an estimated 800 birds today, and the black-winged petrel, a burrow-nesting seabird, has also seen a boost.
Prior to rat eradication, the petrel’s nesting success was as low as 2.5 percent. Surveillance cameras trained on the burrows had shown that rats were taking the eggs and chicks. In 2020, nesting success jumped to 67 percent. The species itself is not at risk—there are an estimated 10 million black-winged petrels in the world—but they and other seabirds play an important role in island ecosystems by transferring nutrients from ocean to land.
When predators are eliminated, overlooked and underappreciated species often rebound and become noticed and celebrated. Such was the case with some endemic land snails. There are an incredible 70 species found only on Lord Howe—Australia’s highest concentration of land snail diversity. Snail numbers plummeted after rats arrived. Several species, including the gorgeously named exquisite pinwheel, were driven to extinction, while others fell to critically low numbers.
In 2016, during a snail survey across the island, researchers found only one specimen of a related pinwheel snail in two weeks of scouting. In 2020, after the eradication, they found 73. Similar increases were observed in other snail species, and one was rediscovered after not having been seen for more than a hundred years.
Lord Howe sees an ‘ecological renaissance’
Islanders have been surprised by the speed of the recovery. “I wouldn’t have believed it could happen so quickly,” says mountain guide and fifth-generation islander Jack Shick. In the past, visitors would be lucky to see a woodhen. “Now it’s the first bird they see,” he says. “And they’re popping up in places where you’d never find one before.”
Woodhens are not the only birds staging a comeback. Silvereyes, gray ternlets, green-winged pigeons, and golden whistlers are all responding to the lack of predators. “I’ve been guiding people up Mount Gower [Lord Howe’s tallest peak] for 30 years, and I’ve never ever heard baby golden whistlers calling,” says Shick. “Over the past 12 to 18 months I’ve been hearing the babies calling in the mountains, which is fantastic.”
Equally impressive has been the recovery of plants in the island’s rainforest. The forest floor is a carpet of new saplings jostling for space and light, their presence testimony to the quantity of seeds and seedlings previously consumed by rodents. “You see a lot of berries and palm seed on the ground now,” Shick says. “We never saw that before. The rats would eat them before they got to maturity. All those seeds have the potential to germinate and grow.”
Bower, the island’s former World Heritage environment manager, calls the recovery an “ecological renaissance.” And it’s not just big-ticket items, such as island endemics. “We’re hearing crickets at night,” he says. “We rarely heard them on the island before.”
The common coastal succulent known as pigface has started fruiting for the first time. It’s one of a growing category Bower calls “never seen that before.” In July, an endemic wingless ground-burrowing cockroach was rediscovered after not having been seen since the 1930s.
But ecological liberty comes with a price: eternal vigilance. On Lord Howe that takes the form of a monitoring regime that aims to ensure the island stays rodent free. Chew cards impregnated with peanut butter (a flavor rats find irresistible), tracking tunnels with inked cards that record an animal running across them, trail cameras, and highly trained rodent-detection dogs are all part of the surveillance program. Devices are concentrated at points of entry: the island’s airport and its wharf, where a freight ship brings supplies from Australia every fortnight. Cargo is triple-checked by dogs, and the New South Wales government recently allocated $22 million for a biosecurity upgrade of the shipping infrastructure. Islanders are urged to report any sign of a rat or mouse. A monthly progress report delivered to householders carries the slogan: “Rat on a rodent: Help us protect paradise.”
Already there has been a scare. In April 2021, after rodents had not been spotted for more than 18 months, a resident saw a pair of rats scurrying across a road in the island’s settlement at night. It was a terrible blow for the project team. They quickly mounted a response, setting out additional bait stations and conducting sweeps with rodent-detection dogs. During the next three months almost 100 rats were removed.
No rodents have been seen on the island since July 2021. For nature tour operators like Shick, that fact alone is remarkable. “There wouldn’t have been a trip up Mount Gower when I didn’t see either a rat running across the path in front of me or evidence of where they’d been chewing on plants and seeds, and rat droppings all along the track,” he says. “I grew up with rats, and I know the signs, and now I can’t find any.”
Islanders weigh bringing back lost species
As the island remains rodent free, thoughts turn to species that could safely return. Some could potentially come from Norfolk Island, 500 miles to the northeast, where several closely related subspecies of Lord Howe’s lost birds remain. Gray fantail, parakeet, boobook (a species of owl)—all are potential returnees. Another is a bird in the warbler family, the gerygone (jer-RIG-gon-nee), which hasn’t been sighted since the 1920s.
For Lord Howe’s nature-minded residents, no reintroduction would be sweeter than that of the stick insect. Two years after the species was rediscovered in 2001, two pairs were collected from Ball’s Pyramid in the hope that they would breed in captivity. One pair, nicknamed Adam and Eve, was given to Melbourne Zoo. Initial prospects were not good. Eve fell gravely ill but was nursed back to health by being hand-fed a slurry of ground-up tea-tree leaves, sugar, and calcium.
Fortunately for the species, stick insect females can produce offspring without male help. Eve went on to lay 248 eggs, and many thousands of stick insects have now been reared.
A trial release of the insects is envisaged for Blackburn Island, half a mile offshore in Lord Howe’s lagoon. If that goes well, a wider reintroduction will be considered.
But caution will be needed, says Ian Hutton, a biologist, tour guide, and curator of the island’s museum. During their hundred-year reign, rats radically reshaped the island’s ecology, he says. Some of the birds lost to rats could have been predators of the stick insect. “Without that predatory cap, their numbers could get out of hand,” he says.
Maintaining ecological balance is crucial and is one reason Hutton is eager to reintroduce birds from Norfolk. “They could provide the necessary predator function,” he says.
As important as ecological balance, though, is social harmony. “It’s no good scientists imposing their ideals on a community,” Bower says. “If we’re going to do any reintroductions, we need to go to the community and have genuine consultation.”
One reason the rodent eradication project became divisive was that many residents perceived it to be an initiative from outside being foisted on them.
Yet for islanders like Shick and Hutton who are regularly in the forests and seeing the recovery, the prospect of a revived ecology is exciting. “It’s not just about killing a pest,” Hutton says, “but about how we can restore the ecosystem.”
