Mustelids: stoat, weasel or ferret? How to tell the difference.

The Mustelidae is the largest and most diverse family of carnivorous mammals. They include the 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.

There are two simple ways you can identify which mustelid might be in your area:  tracking tunnels and scat. The Pest Detective website has the best examples for stoats, weasels, and ferrets (scroll down the page a bit).

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Left to right: weasel, stoat, ferret
Left to right: weasel, stoat, ferret