Environment

Weasel

Weasel.Weasel.

Common names:
Weasel, mustelid

 

Scientific name:
Mustela nivalis vulgari

 

Regional classification:
Cost recovery and community control

 

 

Description

Weasels are the smallest and least common mustelid in New Zealand. 

Weasels are the smallest of the three mustelids - weasel (left), stoat (middle) and ferret (right).Weasels are the smallest of the three mustelids - weasel (left), stoat (middle) and ferret (right).

 

Size and colour

Males grow up to about 20 cm. Their fur is brown with white under parts, often broken by brown spots. Their tails are short, brown and tapering.

 

Breeding

If plenty of food is available, weasel numbers can increase dramatically as female weasels reach sexual maturity at three to four months, and can produce up to 12 young a year.  If food is short, numbers can just as quickly fall off.

 

Field sign

Mustelid scats (droppings) are long and thin, often with a characteristic tapering twist at each end.  They are filled with fur, feathers and bone fragments and are hard and black when dry. 

 

Mustelids secrete onto their scats a thick oily yellow powerful smelling fluid called musk.  Scats are often placed in conspicuous positions such as in the middle of a track as a sign to other mustelids in the area.

 

Mustelids characteristically eat the flesh from the neck and head area of their prey.

Why are they a problem?

Mustelids feed on small animals including:

  • rabbits
  • rodents
  • possums
  • birds

They also feed on whatever opportunity offers, including:

  • eggs
  • lizards
  • frogs
  • insects

They have also been implicated in the transmission of TB to cattle.

Recommended control methods

The English Fenn trap is the best method of trapping mustelids.  It is a steel spring trap which kills small animals by breaking their backs.  These traps can be ordered from the Northland Regional Council. 

 

Fenn traps come in two sizes:

  • Mark 4 is a smaller size best suited to small weasels and stoats.
  • Mark 6 trap will handle the larger ferret, and is also suitable for smaller animals.

Both traps are RSPCA approved.

 

Placing the trap

Good trap sites for mustelids include:

  • wood piles
  • small animal tracks that pass under fences
  • piles of stones
  • rabbit burrows
  • small drain pipes.

Other areas include the edges of ponds and streams and under trees where the vegetation is short.

 

Making a tunnel

Mustelids cannot resist tunnels and frequently run through pipes, over logs, and in and out of holes. Setting your trap on a run, inside a pipe or tunnel, or down a rabbit burrow, will increase your chances of catching a mustelid.

 

You can make a tunnel out of drainage pipe, wood, field tiles, sticks etc.

 

The tunnel should be about one metre long and wide enough for the trap to be sprung inside of it:

  • 20 cm wide and 17 cm high for Mark 6 traps;
  • 15 cm wide and 13 cm high for Mark 4 traps.

The tunnel should have sides and a top – no bottom. Setting two traps in one tunnel may be more effective.

 

Setting the trap in a tunnel prevents accidental catches of other species and prevents children from stumbling over them.

 

Traps should be set in places used by mustelids or where they have been seen.

 

Baiting the trap

The best bait for mustelids include:

  • fresh rabbit
  • liver
  • eggs
  • the entrails of poultry
  • fish flavoured cat food also works well

Place twigs and stones around the trap to guide the animal to it. Place the bait on or behind the trap in such a way so that the animal must walk over the trap to reach it.

 

A piece of bait or fish can be dragged around on a piece of string to make a scent or blood trail leading to the trap.

 

Baits should be replaced every two to three days, or in hot weather, every day.

Note:  All traps must be checked at least once every 24 hours under the Animal Protection Act 1960, Section 6.

 

Shooting

Mustelids are often encountered while spotlighting rabbits and possums and can be shot, although shooting alone is not an effective control measure.  

 

Poisoning

There is no poison available which private individuals can use on mustelids.  Occasionally mustelids die of secondary poisoning after eating the carcasses of rabbits and possums killed by poison.

 

Find out more: Download pest animal control publications

More information

For further information or control advice please contact one of our Biosecurity Officers at the Northland Regional Council on 0800 002 004:

  • Whangarei: Carl Cooper and Steve Henderson
  • Dargaville: Paul Ralph
  • Kaitaia: Mike Knight

 

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