Ferrets: know your pest!

Ferret (Mustela furo)

Identification and habitat
Ferrets are the largest of the mustelid species introduced and established in NZ. Male ferrets grow up to 44 cm long and females up to 37 cm. Ferrets have creamy-yellow undercoats and longer dark guard hairs which give them an overall dark appearance. Their legs and tail appear darker than the rest of the body. Their face is lighter in colour than the body, with a dark mask around the eyes and across the nose.

Habitats
While less widespread than stoats, they occupy mostly open country including scrublands, pasture, forest edges and coastal regions. They prefer drier habitats and are nearly absent in areas of high rainfall. There have been instances of them living in forests in Northland, threatening kiwi populations.

Behaviours

• As carnivores, they largely eat rabbits and hares, but will switch prey to native birds and lizards when rabbit numbers are scarce. This is the only mustelid capable of taking down an adult kiwi, which means that ground nesting birds have no chance against them.
• Mostly nocturnal and are not great climbers.
• Litters of 4-8 are born around late spring and a second litter is possible if there is an abundance of food. Average lifespan in the wild is 4-5 years.
• Ferrets are highly territorial of the same sex and use scent glands to mark their territory.

Threats – why are they a problem?

• Ferrets are a significant threat to conservation and agricultural industries in New Zealand. Ferrets prey on indigenous wildlife and they also carry bovine tuberculosis (Tb), a disease which may threaten New Zealand’s international beef, dairy and venison markets. 
• There is substantial possum-to-ferret transmission of Tb and controlling possum populations is the logical first step to managing Tb infection in ferret populations, especially at sites with low ferret density. At higher ferret densities there is evidence of ferret to ferret transmission of Tb and TBfree New Zealand considers ferret control an important part of Tb management. 
• When rabbit numbers are lowered with a control programme, ferrets will change their diet to other species, thus increasing the risk to native species temporarily. However, a study in the Mackenzie Basin showed that reducing rabbits largely controls ferret populations, so reducing predation of native fauna in the longer term.
• They will easily prey on burrow nesting bird species and are especially problematic in coastal nesting areas of penguins, albatross and other pelagic (sea) birds.
• One of the major contributors to the decline of white-flippered penguins on Banks Peninsula and skink populations elsewhere.
• Ferrets are big enough to hunt and kill adult kiwi, this is especially prevalent in Northland. They are responsible for a significant decline of kiwi populations in the north of the North Island.

Mustelids (Mustelidae) is the family name for ferrets, stoats and weasels.
Mustelids were first introduced in the 1880s to control New Zealand’s growing rabbit plagues. Unfortunately they had limited effect on rabbit populations but are now the main predator of rodents and birds over the whole country.

Doc 250 Mustelid Tunnel for Ferrets

Podi Traps for Ferrets