 The Galápagos National Park Service systematically culls feral predators and competitors . Goat eradication on islands , including Pinta , was achieved by the technique of using " Judas " goats with radio location collars to find the herds . Marksmen then shot all the goats except the Judas , and then returned weeks later to find the " Judas " and shoot the herd to which it had relocated . Goats were removed from Pinta Island after a 30 @-@ year eradication campaign , the largest removal of an insular goat population using ground @-@ based methods . Over 41 @,@ 000 goats were removed during the initial hunting effort ( 1971 – 82 ) . This process was repeated until only the " Judas " goat remained , which was then killed . Other measures have included dog eradication from San Cristóbal , and fencing off nests to protect them from feral pigs . 
