On a remote Pacific island, conservation teams trapped and removed exactly 131 feral cats, expecting a slow, fragile recovery for the wildlife those predators had been hunting to the edge of oblivion. Instead, the ecosystem rebounded with a speed and complexity that surprised even the scientists who had argued hardest for the operation. What unfolded after those 131 animals were taken off the landscape is now reshaping how I think about invasive predators, extinction risk, and the limits of our ecological models.
The story centers on Japan’s Ogasawara Islands, a subtropical archipelago that has become a global test case for what happens when humans try to rewind an ecosystem that has been distorted for decades. By following the data from this experiment, I can see why some researchers now say the reaction of The Ecosystem “exceeds all predictions,” and why others are warning that even a spectacular recovery does not erase deeper genetic scars.
The remote island where a conservation gamble paid off
For decades, the Ogasawara Islands, a UNESCO World Heritage Site located about 1,000 kilometers south of Tokyo, have been a living laboratory for the collision between introduced predators and uniquely vulnerable island species. On Chichijima, one of the main islands in the Ogasawara chain, domestic cats that arrived in the late twentieth century slipped into the forests and cliffs, turning into a population of stealthy hunters that targeted ground nesting birds and small reptiles. Between 2010 and 2013, conservation teams on Chichijima embarked on what one scientific group later described as a Conservation Gamble Pays, committing to trap every last feral cat they could find.
The logistics were daunting. Field crews set cage traps along ridgelines and coastal terraces, tracked animals with cameras and radio collars, and worked with local residents to identify strays. According to detailed reconstructions of the project, the rescue mission focused on trapping every individual predator that could be located, because leaving even a handful of breeding cats would have allowed the population to rebound. In the end, the teams removed 131 animals from the island, a figure that appears again and again in the scientific reporting because it marks the threshold at which the ecological balance finally tipped back toward the native species.
How 131 predators nearly erased a bird, then triggered its comeback
The stakes of that number become clear when I look at what was happening to one of the island’s signature birds. Since the trapping and removal of cats from Japan’s Ogasawara Islands, a native animal that had been pushed to the brink of extinction has begun to recover. Earlier accounts describe how this bird, once numbering in the hundreds, had dwindled to fewer than 80 individuals as the cats learned to raid nests and ambush adults on the forest floor. One synthesis of the cat removal work notes that When conservationists removed 131 feral cats from the island, they were racing a clock set by basic rules of genetics and survival.
That genetic dimension is crucial. By the time the last cats were trapped, the bird’s population had fallen so low that inbreeding and random events could have finished the job even without predators. One analysis of the project explains that fewer than 80 individuals remained, a level at which harmful mutations can accumulate and reduce fitness. Geneticists studying the Ogasawara case have warned that such mutations, known as deleterious variants, can persist even after predators are gone, a point underscored in work linked to KyotoU researcher Daichi Tsujimoto.
The ecosystem’s reaction that “exceeds all predictions”
What stunned many observers was how quickly the island began to heal once the last cat was gone. Reports on the project describe how, after 131 predators were removed, the response of The Ecosystem went far beyond what standard models had forecast. One synthesis of the data notes that When the feral cats were evacuated, nesting success for the threatened bird climbed, juvenile survival improved, and vegetation that had been suppressed by overgrazing herbivores (which the cats had indirectly favored) began to rebound. Another account of the same project frames it as Wild Cats Evacuated, The Ecosystem, Reaction Exceeds All Predictions, emphasizing how the cascade of changes rippled through insects, seeds, and soil.
Parallel coverage of the work on Chichijima describes how the removal of 131 stray cats triggered shifts that were “way beyond expectations,” including a rapid uptick in activity by small reptiles and invertebrates that had been heavily preyed upon. One detailed narrative of the rescue mission highlights that The rescue mission was designed around the idea that only total removal would allow such a response, while another section of the same reporting stresses that When conservationists removed cats, they were also erasing a predator that had arrived in the late twentieth century and never belonged in that food web at all.
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*This article was researched with the help of AI, with human editors creating the final content.
