Buzz
Islands make up just 5% of Earth's total land area, yet they are home to one out of every five species of birds, mammals, and reptiles. Unfortunately, these islands have borne the brunt of over 60% of known extinctions throughout human history. Today, more than half of all endangered species on Earth are island inhabitants. Most of these species were either wiped out or are at risk of extinction due to invasive species – foreign creatures that arrived alongside humans. Early explorers of the seas played their part in this destruction, driving island mammals like the giant moa and the dodo to extinction.
However, it was the arrival of humans with their domestic animals that truly wreaked havoc on native species. Cows, goats, pigs, sheep, dogs, cats, rabbits, ferrets, stoats, weasels, foxes, and, most notably, rats. These new arrivals wreaked havoc on islands where many of the local animals had no defenses against such predators. The native birds, mammals, insects, and reptiles found themselves defenseless. In most cases, they lacked the instinctual fear of these invaders. Above all, rats were especially devastating, eliminating species one by one, either by directly hunting them or by destroying their habitats.
Only in recent decades has humanity initiated a focused effort to reclaim these islands from invasive species and protect the remaining native wildlife. Unfortunately, these efforts came too late to save many incredible species, such as the San Roque white-footed mouse and the Stephens Island wren.
The majority of the following accounts of successful island eradication projects are drawn from the compelling book “Rat Island” by William Stolzenburg. Here are ten stories of human efforts to restore the natural balance of island ecosystems by eradicating invasive species.
10. Fidra and Craigleith Islands
Typically, invasive species threatening native island species include animals like rats, sheep, or cats. However, on Fidra and Craigleith Islands in Scotland’s Firth of Forth, a different type of invader is jeopardizing the internationally significant breeding habitats of rare seabirds, such as puffins.
The invasive plant in question is tree mallow (Lavatera arbor), a tall Mediterranean species introduced to the region in the 17th century. Over time, it spread across Craigleith and Fidra, covering large portions of the islands with dense growth. This has made it increasingly difficult for puffins to come ashore and dig burrows for nesting. As a result, puffin populations on Craigleith Island plummeted from 28,000 in 1999 to just 12,000 by 2003. Typically, rabbits, an invasive species, help control plant growth, but the rabbit population was wiped out by disease, allowing tree mallow to thrive unchecked.
In 2006, a five-year initiative was launched to control tree mallow and restore the seabird populations. Volunteers worked tirelessly to remove the invasive plant by hand, clearing large areas of the islands. This effort is expected to have disrupted the tree mallow’s flowering and seed production, giving native grasses a chance to reclaim the land and helping puffins to breed in larger numbers once again.
9. Clipperton Island
Approximately 800 miles off the coast of Acapulco, Mexico, lies the small Clipperton Island. Only about a square mile in size, sailors have been visiting Clipperton since at least the 1700s. They discovered an isolated island with few trees but an abundance of crabs and various bird species, including boobies. Over the centuries, multiple attempts to settle Clipperton ended in failure, yet the pigs left behind by the settlers remained. These pigs thrived on crabs and bird eggs. By the late 1950s, most of the crabs and boobies had been wiped out.
A man named Ken Stager visited Clipperton to conduct a wildlife survey, bringing a shotgun to shoot birds for a museum collection. However, upon witnessing the devastation the pigs were causing to the bird population, he decided to use the shotgun to eliminate every single pig. After his efforts, 58 pigs were killed. Today, Clipperton is thriving again with hundreds of thousands of boobies and a growing crab population.
8. Galapagos Islands
There is no other place on Earth more revered by biologists and naturalists than the Galapagos Islands. It was here that Charles Darwin solidified his theory of evolution, observing the distinct wildlife that varied from one island to the next. However, one of man’s destructive four-legged creatures – goats – roamed across this pristine natural haven. Previous attempts to eradicate the invasive goats had failed, as no matter how many hunters arrived, some goats always managed to climb higher and escape, only to reproduce and repopulate the island.
Then came Karl Campbell, an Australian with a new strategy: using goats against goats. He and his team shot as many goats as they could, and to lure the remaining ones out of hiding, Campbell employed a clever tactic. He used specially selected female goats, called Judas Goats, which were radio-collared and released to attract the male goats into the open. With a coordinated assault involving hunters, dogs, and helicopters, they successfully killed every single goat on Santiago and Isabela Islands—approximately 160,000. This was the largest goat eradication operation in history.
7. Breaksea Island
The kakapo is a large, flightless parrot native to New Zealand. Isolated on the island, with few predators other than raptors, the kakapo evolved into a forest-dwelling bird weighing up to nine pounds and standing three feet tall. Unfortunately, it was decimated by early island settlers, dogs, stoats, and most significantly, by native mice and non-native rats introduced by humans. Eventually, only a small number of kakapos survived. To ensure the species' survival, they required a secure refuge where the last few birds could breed and thrive.
In their efforts to save the kakapo, conservationists and scientists sought an island free of rats and isolated enough that rats could not swim to it from nearby landmasses. One possibility was Breaksea Island in Fiordland, New Zealand, a rugged 400-acre island overrun by millions of brown rats. Despite the doubters who claimed it was impossible, two men, Rowley Taylor and Bruce Thomas, were determined to rid Breaksea Island of rats. They believed in their skills and in the potential of a newly available rat poison that could change the game.
The poison in question was brodifacoum, a much stronger anticoagulant rat poison than its predecessor, warfarin. Like warfarin, it caused rats’ blood to stop clotting, but brodifacoum was hundreds of times more potent. Only one gram was needed to kill even large rats, and the poison was effective enough to ensure that no rats survived, reproduced, or developed resistance, unlike warfarin, which had led to resistant rat populations in the past.
Taylor and Thomas first tested their plan on the smaller Hawea Island. They carefully tracked every rat trail and set up bait stations every forty meters. The brodifacoum poison worked perfectly, killing every rat that consumed it. This success proved they could eliminate rats from an entire island, albeit a smaller and less challenging one than Breaksea.
Despite their success on Hawea Island, government officials doubted they could achieve the same result on the larger and more rugged Breaksea Island. With only three weeks to complete the task, Taylor and Thomas scouted rat trails and set up 744 bait stations across the island. Once the rats became accustomed to the bait stations, they filled them with brodifacoum. In just 20 days, they had eradicated every rat on Breaksea Island. A month later, not a single rat remained. The project marked a milestone in island conservation, and by 1990, over 40 New Zealand islands had been cleared of rats using this innovative method.
6. Baja Islands
The Baja region is home to over 250 islands, nestled between the Pacific Ocean on the west and the Sea of Cortez on the east. These mostly uninhabited, desolate islands represent living examples of Darwin’s theory of evolution, each hosting unique species of birds, mammals, insects, and lizards found nowhere else. However, unlike the more famous Galapagos Islands, the Baja islands were also overrun with invasive species like rats, rabbits, goats, burros, and cats. Since humans arrived, 19 native species have already been driven to extinction.
Bernie Tushy and Don Croll set out with a mission to do on the Baja islands what Rowley Taylor and Bruce Thomas had done on the other side of the world. Armed with brodifacoum, a potent rat poison, they set to work tackling the rodent issue. However, the real challenge lay with the cats. To deal with these elusive predators, they called on a skilled trapper named Bill Wood. Having perfected his skills with bobcats, Wood was enlisted by Tushy and Croll to help rid the island of feral cats. Reluctant at first, Wood quickly realized that eradicating these destructive species was his true calling. Along with Brad Keitt and Josh Dolan, they formed the Island Conservation and Ecology Group, supported by volunteers from both the US and Mexico. Within five years, the group successfully removed invaders from nine islands, including clearing San Roque and Rasa Islands of rats, Natividad Island of rabbits, and San Benito Islands of goats and burros. Additionally, they eradicated feral cats from seven islands and helped protect around 88 species unique to the Baja islands.
5. Anacapa Island
The Anacapa Islands, part of Channel Islands National Park off the coast of California, consist of three rugged rocky outcroppings in the Pacific Ocean. Remote and isolated, they were once an ideal sanctuary for many species, especially seabirds. However, the arrival of humans and rats devastated the ecosystem. Rats wiped out populations of Xantus’s murrelet, a small seabird, and harmed grasshoppers, lizards, and wildflowers. In an effort to save what remained, the U.S. government sought help from its southern neighbors and the Island Conservation and Ecology Group.
In New Zealand, large islands had been cleared of invasive species using helicopters to drop vast amounts of brodifacoum, a potent rat poison. However, in the U.S., with its stricter environmental regulations and animal rights groups like PETA, such methods would be met with resistance. Additionally, Anacapa Island was home to the Anacapa deer mouse, a species that needed protection. The challenge was to eliminate the rats without harming the deer mouse or other predators, like raptors, that might consume the poisoned rats.
After years of planning, the conservationists decided to trap and relocate the Anacapa deer mice and raptors to protect them from the poison. The helicopters were ready to drop the brodifacoum, but animal activists intervened, leading to a prolonged court battle. Eventually, the judge allowed the operation to proceed. The helicopters dropped the poison, and soon Anacapa was rat-free. Once the poison had taken its toll, the deer mice were reintroduced to the island. Subsequent visits showed no sign of rats returning, and species like Xantus’s murrelet, salamanders, lizards, and grasshoppers began to return to the island.
4. Tahanea Atoll
Not all island eradication efforts involve large-scale, military-style operations. Some, like the successful project on Tahanea Atoll in the Tuamotu Archipelago of French Polynesia, are driven by small teams of passionate individuals. The goal here was to eliminate rats from the atoll in order to save the endangered Tuamotu Sandpiper, or Titi. Once widespread across the Tuamotu Archipelago, this small shorebird had been reduced to only four known colonies due to the destructive predation of invasive rats.
A dedicated group of people took action to help the Titi. Before tackling the rat problem, they first needed to capture and protect the Titi on Tahanea Atoll. For three weeks, they carefully sheltered 18 of these precious birds while the atoll was cleared of rats using poison. Thanks to their efforts, Tahanea Atoll is now a rat-free sanctuary for the Titi.
3. Rat Island
After the fox was eradicated from Kiska Island, the rat population exploded, posing a serious threat to the least auklet, one of the smallest seabirds at just three ounces. While small in size, the least auklet made up for it with massive colonies on Kiska Island. However, as the rats grew in number, they devastated these colonies. The rats would kill dozens, sometimes hundreds, of auklets, stacking their bodies while consuming only the brains and eyes. As Jones and his fellow conservationists saw these disturbing piles of bird carcasses, they realized that the next enemy they had to fight was the rat. A more challenging battle began: they needed to eradicate the rats from Kiska and other islands to prevent the extinction of the least auklet and other bird species in the coming decades. As Jones noted, the number of birds killed by rats in the Aleutian Islands far exceeded the deaths caused by the Exxon Valdez oil spill.
Kiska Island spanned one hundred square miles, positioned in one of Earth's most unforgiving and wind-battered regions. The journey to reach the island was an immense challenge, fraught with peril. It would require a fleet of ships and helicopters, each leapfrogging from one island to another, transporting fuel, supplies, and rat poison mile by mile.
With foresight, the conservationists decided to tackle a smaller island first before attempting the colossal task of eradicating rats from Kiska Island. One island in the Aleutians seemed to almost shout – 'come and rid me of my pests!' Rat Island, though only a tenth of the size of Kiska, was set to become the third-largest rat eradication project in history if successful. After four years of meticulous planning, on September 17, 2008, the rats on Rat Island had only a brief period left to live. Some of the best helicopter pilots in the world would drop brodifacoum from the skies, while teams on the ground spread it manually. Every inch of the island was thoroughly treated with rat poison. While this successfully eradicated the rats, it tragically led to the death of numerous raptors who consumed the poisoned rats or the tainted bait. Nonetheless, the mission was a triumph, and the bird populations began their recovery. The restoration of Rat Island’s ecosystem remains the largest and most ambitious project of its kind ever undertaken in the Northern Hemisphere.
2. Kiska Island
The Aleutian Islands, located in the Bering Sea of the North Pacific, were once home to a variety of unique species, until human presence altered the balance. The arrival of humans spelled the end for the Steller’s sea cow, a massive relative of the manatee, which was driven to extinction just 14 years after its discovery. The flightless spectacled cormorant, another victim of human interference, also became extinct. Fur hunters drove the sea otter and northern fur seal to the brink of extinction. However, the most devastating impact came with the introduction of the fox to the Aleutian Islands. Native to Alaska, the fox had not inhabited the majority of the Aleutian Islands until humans transported them across the Bering Strait. Once introduced, the foxes ravaged the islands, preying on everything in sight. Ground-nesting ducks, sparrows, wrens, and the Aleutian honking goose were among the many victims. By the time the first American naturalist visited, almost all of the islands' native plants and animals were in decline, many already extinct. The foxes consumed everything from crabs and mussels to moss berries and birds.
Kiska Island holds the distinction of being one of only two islands, along with Attu Island, in the Aleutian Island chain to have been captured by the Japanese Imperial Army during World War II. For fifteen months, the American and Japanese forces fought over these isolated and remote islands in the Bering Sea. On August 15, 1943, the combined American and Canadian forces were set to retake Kiska and Attu in what was known as K-Day. However, unbeknownst to the Allies, in the dead of night, the Japanese quietly evacuated their soldiers by submarine. When the Americans and Canadians launched their final assault, the Japanese forces were gone, but their rats remained. Although the rats weren't the first to be eradicated on Kiska, the foxes would be dealt with first.
Among the American troops stationed on these islands, one soldier fell in love with the desolate, cold, windswept beauty of the place and decided to stay. This was Robert Jones Jr., known as 'Sea Otter' Jones. After assessing the situation on the islands, he witnessed firsthand the devastation that the foxes had caused to the native species, just as the previous American naturalist had reported. Jones resolved to act and make the islands safe for the wildlife again. He set about eliminating the foxes, using poison, leg traps, and rifles. By 1960, Jones had achieved his first victory, clearing Amchika Island of foxes. However, had he arrived in time to save the Aleutian cackling goose? It seemed not, as none were found alive. Yet, in one of the most remote islands, a colony of the odd honking geese was discovered. By 1964, Jones had turned his focus to Kiska Island and again eradicated the foxes. Wherever Jones succeeded in this endeavor, the island’s wildlife began to recover, including the Aleutian cackling goose. It seemed that mankind had reversed the fate of the native species on the Aleutian Islands. However, the rats had their own plans lurking beneath the surface.
1. Campbell Island
Campbell Island, spanning 44 square miles, was about to become the largest landmass to undergo rat eradication, thanks to the dedication of New Zealander Pete McClelland. By the early 2000s, rat eradication on Pacific islands had become a well-practiced process, but Campbell Island's size and isolation—440 miles from the nearest land in the Southern Ocean—posed a new level of challenge. McClelland spent five years meticulously planning the operation, treating it as a military campaign in many ways. He and his team would have just one chance to eradicate the rats, knowing that failure would mean the rats would triumph.
In June 2001, the mission to liberate Campbell Island from its rat infestation began. By mid-July, after extensive aerial distribution of brodifacoum, it was estimated that over two hundred thousand rats had been eliminated. Years of follow-up surveys confirmed the success of the operation—no rats were found. At that time, Campbell Island became the largest island ever to be successfully rid of rats.
