The Galapagos once destroyed invasive goats to save giant tortoises

At the end of the 20th century, the Galapagos giant tortoise living on the archipelago of the same name off the coast of Ecuador was in danger of extinction. From more than 250,000 individuals in the 16th century, their numbers dropped to just 3,000 in the 1970s, mainly due to hunting by humans. Turtles are relatively slow and defenseless, so are easy to collect and keep on ships, where they can survive for a year without food, providing fresh meat for sailors. In addition to overhunting, humans also brought with them the biggest invasive species to the island’s fragile ecosystem, the goat. This seemingly harmless herbivore devours all available vegetation, including many rare plants, and competes with native animals for the island’s scarce resources. As goats ate away the trees on the islands, the Galapagos tortoises began to disappear.

In 1995, authorities decided to eradicate goats in the Galapagos to save the island’s native flora and fauna. Two years later, the Isabela project was outlined, according to which they would destroy goats and donkeys on Isabela island, pigs, goats and donkeys on Santiago island, and goats on Pinta island.

In 1999, a group of gunners searched for footprints on three islands and shot goats from a helicopter. This was one of the most advanced extermination programs of its time. Within a few years, 90% of goats were wiped out with relative ease. But as goats become fewer, they also become harder to detect. The remaining goats learned to be wary of hunters, and began to hide in bushes, caves or lava tubes. The remaining 10% of goats are increasingly difficult to remove. To completely eradicate goats, hunters must use another method called “Judas goat”.

A herd of several hundred goats was collected, sterilized, injected with hormones to make them go into long-term heat, fitted with radio-monitoring collars and released on the islands. Because goats are social animals, they instinctively seek out other goats. Through tracking Judas goats, hunters can track down the remaining goats. Once they found a herd, they would shoot everyone except the Judas goats so they could continue looking for more hidden goats. They leave the goat carcasses to decompose so that the useful nutrients the goats consume on the island can return to the ground. Taking away goat meat will remove nutrients from the island forever, according to Dr. Karl Campbell, operations manager of the Isabela project.

More than 200 Judas goats were deployed on Santiago island and another 770 on the larger Isabela island for two years. In 2006, they were the only goats left on the target islands. The invasive goat herd only has 20-30 goats left on Santiago Island and 266 goats on Isabela Island. They are allowed to live on the island for monitoring purposes.

After the Galapagos Islands were cleared of goats, the trees began to recover. Small trees began to grow back from the stump left by the goats. Plateau shrubs, forest trees, cacti and many endemic species increased in number. Combined with captive breeding, giant tortoise populations also recovered.

The Isabela Project is the world’s largest island regeneration effort to date. In 7 years, more than 140,000 goats were wiped out from half a million hectares of land at a cost of 10.5 million USD. The last few hundred are the hardest to kill and cost the most money. The success of the Isabela project prompted conservationists to conduct eradication programs on three other islands. Combining aerial shooting, hunting dogs and Judas goats, they killed an additional 10,000 goats between 2006 and 2009.