The ferrets in NZ that are feral ere not brought over by the ships. I tend to believe the only ones still alive are the Hybrids. "It has been claimed that New Zealand has the world's largest feral population of ferret-polecat hybrids.[17] In 1877, farmers in New Zealand demanded that ferrets be introduced into the country to control the rabbit population, which was also introduced by humans. Five ferrets were imported in 1879, and in 1882--1883, 32 shipments of ferrets were made from London, totaling 1,217 animals. Only 678 landed, and 198 were sent from Melbourne, Australia. On the voyage, the ferrets were mated with the European polecat, creating a number of hybrids that were capable of surviving in the wild. In 1884 and 1886, close to 4,000 ferrets and ferret hybrids, 3,099 weasels and 137 stoats were turned loose.[18] Concern was raised that these animals would eventually prey on indigenous wildlife once rabbit populations dropped, and this is exactly what happened to New Zealand bird species which previously had no mammalian predators." [Posted in FML 7029]