The Mustelidae is the largest and most diverse family of carnivorous mammals. They include otters, badgers, weasels, martens, ferrets, minks and wolverines. Three types of mustelids were introduced into New Zealand during the mid-1870s when rabbits become a serious agricultural pest in New Zealand. Farmers demanded that mustelids, the natural enemies of the rabbits, be introduced. Despite the protests of bird experts, ferrets (the largest), stoats and weasels (smallest) were released throughout pastoral areas.

Far too late, after many official protests, the government changed its policy on mustelids in 1903. However, it was not until 1936 that all legal protection for mustelids was removed. Because of their behavioural characteristics and sizes, and because of the complexity of predator guilds in different locations, each of these mustelids requires slightly different management strategies in different locations.