A hundred sheep were brought to Socorro Island, which is part of the Revillagigedo archipelago in the Pacific Ocean off the coast of Mexico, in 1869. Initially introduced to provide food for the island’s small population, the sheep multiplied rapidly over the next century due to the lack of natural predators. By 1960, their numbers had grown to about 5,000, causing significant environmental damage. The 13,200-hectare island, which is volcanic in origin, has lost 30% of its vegetation cover, with more than 2,000 hectares of native plants disappearing due to overgrazing. The local flora had evolved over thousands of years without large herbivores, making it especially vulnerable to the impact of the sheep. The effects of the overgrazing were not limited to plants. Several unique species of birds, including the Socorro dove (Zenaida graysoni) and the Socorro parakeet, have since disappeared from the wild. Feral cats, which were also present on the island, further threatened endemic birds and lizards. The Townsend’s shearwater, a seabird that nests on the island, is now classified as critically endangered due to these combined pressures. Between 2009 and 2012, the Grupo de Ecología y Conservación de Islas, an environmental group focused on island conservation, launched a campaign to eliminate the sheep from Socorro Island. The effort involved killing 1,762 sheep in total. Helicopters were used in the first phase to kill 1,257 of them, while ground teams tackled the remaining groups in the island’s more difficult terrain. Biologists used "Judas" sheep—those fitted with radio collars—to track the last remaining animals, and detection dogs helped locate the final ones. By June 2014, the island was officially declared free of wild sheep. Since the eradication, satellite images taken between 2008 and 2013 show that 1,452 hectares, or 11% of the island’s total area, have recovered vegetation. The soil has also shown improvements in nitrogen, organic carbon, and phosphorus levels. While the return of plants does not necessarily mean the full recovery of the original ecosystem, Socorro Island demonstrates that removing an invasive species can lead to visible ecological recovery within a few years.