S1, E3: Australia is being overrun by an invader. At as many as twenty-three million strong, feral pigs have already caused untold damage, and further destruction is inevitable if they're not stopped. Highly intelligent, hardy, and adaptable feral pigs are thriving in the land down-under. Here, they're endangering native species, spreading disease, destroying farmland, and even attacking people. Deliberately introduced by humans centuries ago, now its up to humans to keep their populations in check. Scientists and citizens are now resorting to a range of methods to defend their country.