Judas goat

A Judas goat is a trained goat used in general animal herding. The Judas goat is trained to associate with sheep or cattle, leading them to a specific destination. In stockyards, a Judas goat will lead sheep to slaughter while its own life is spared. Judas goats are also used to lead other animals to specific pens and onto trucks. They have fallen out of use in recent times, but can still be found in various smaller slaughterhouses in some parts of the world, as well as conservation projects.

Cattle herders may use a Judas steer to serve the same purpose as a Judas goat. The technique, and the term, originated from cattle drives in the United States in the 1800s.

The term is a reference to Judas Iscariot, an apostle of Jesus Christ who betrayed Jesus according to the New Testament.

Goats tracking feral goats
The phrase has also been used to describe a goat that is used to find feral goats that are targeted for eradication. The Judas goat is usually sterilised, outfitted with a transmitter, painted in red, and then released. The goat then finds the remaining herds of feral goats, allowing hunters to exterminate them. The podcast Radiolab dedicated a portion of its episode on the Galápagos Islands to how feral goats affected the environment on the islands and how Judas goats were used to help return the islands to nature. This technique is now used to target other invasive species, such as camels in Australia, pigs in America, rats in Mexico, and raccoon dogs in Europe.

Goat eradication on San Clemente Island
Endemic species on San Clemente Island have been degraded by feral goats since 1875. Under the administration of the United States Navy, a program of intensive eradication between 1972 and 1989 eliminated 28,000 goats on the island. Some feral goats were able to find cover in the rugged terrain and eradication efforts were hindered by frequent naval bombardment operations. Between 1989 and 1991, a dozen radio-collared Judas goats were used on the island to locate the remaining feral goats. 263 goats were killed.

Project Isabela in the Galápagos Islands
Project Isabela was a goat extermination initiative in the Galápagos Islands that started in 1997 and ended in 2006. Approximately 140,000 goats were living in the wild on the islands and threatening the local ecosystem. Goats were killed by gunmen in helicopters and on foot. Judas goats were used to lure the remaining goats to their death. The project cost 6 million dollars.