Conservation experts have implemented various measures to eliminate 140,000 goats over seven years, aiding the recovery of the Galapagos giant tortoise.
By the late 20th century, the Galapagos giant tortoise, native to the islands of the same name off the coast of Ecuador, was at risk of extinction. From a population of over 250,000 in the 16th century, their numbers dwindled to just 3,000 by the 1970s, primarily due to human hunting. Tortoises are relatively slow-moving and have poor self-defense mechanisms, making them easy to capture and sustain on ships, where they could survive for a year without food, providing fresh meat for sailors. In addition to overhunting, humans also introduced the most significant invasive species to the fragile island ecosystem: goats. This seemingly harmless herbivore devoured all available vegetation, including many rare plants, and competed for scarce resources with native wildlife. As goats stripped the islands of their greenery, Galapagos tortoises began to vanish.
Galapagos Giant Tortoise. (Photo: Flickr).
In 1995, authorities decided to eradicate goats in the Galapagos to save the islands’ native flora and fauna. Two years later, the Isabela Project was launched, aiming to eliminate goats and donkeys on Isabela Island, pigs, goats, and donkeys on Santiago Island, and goats on Pinta Island.
In 1999, a team of marksmen scoured the three islands, shooting goats from helicopters. This was one of the most advanced eradication programs of its time. Within a few years, 90% of the goat population was relatively easily wiped out. However, as the number of goats decreased, they also became harder to detect. The remaining goats learned to be wary of hunters, beginning to hide in dense brush, caves, or lava tubes. The remaining 10% became increasingly difficult to eliminate. To completely eradicate the goats, hunters had to employ a technique called “Judas goats.”
A herd of several hundred goats was gathered, sterilized, and injected with hormones that induced long-term estrus. They were fitted with radio-tracking collars and released onto the islands. Since goats are social animals, they instinctively seek out other goats. By tracking the Judas goats, hunters could locate the remaining goats. Once a herd was found, they would shoot all but the Judas goats, allowing them to continue seeking out hiding goats. They left the remains of the deceased goats to allow the nutrients consumed by the goats to return to the earth. Removing the goat carcasses would permanently deplete the island’s nutrients, according to Dr. Karl Campbell, the manager of the Isabela Project.
Over 200 Judas goats were deployed on Santiago Island and 770 more on the larger Isabela Island over two years. By 2006, they were the only remaining goats on the target islands. The invasive goat population had dwindled to just 20-30 on Santiago Island and 266 on Isabela Island. They were allowed to remain on the islands for monitoring purposes.
After the Galapagos Islands were cleared of goats, vegetation began to recover. Small trees started to regrow from the stumps left by the goats. Populations of highland shrubs, forest trees, cacti, and numerous endemic species increased. Combined with captive breeding, the population of giant tortoises also rebounded.
The Isabela Project is the largest island restoration effort in the world to date. Over seven years, more than 140,000 goats were eradicated from half a million hectares at a cost of $10.5 million. The last few hundred goats proved the most challenging to eliminate and consumed the most resources. The success of the Isabela Project motivated conservationists to carry out eradication programs on three other islands. Combining aerial shooting, hunting dogs, and Judas goats, they eliminated an additional 10,000 goats between 2006 and 2009.
