FERRET control
Kill trappING (CURRENT BEST PRACTICE)

CREATED: 27 April 2005

TECHNIQUE

Trap layout

  • Meaningful population control requires an extensive trapping layout: place trap stations along linear landscape features (fence lines, forest edges, waterways, roads and tracks), in isolated patches of cover and other preferred microhabitat, around farm buildings and offal pits and in areas with high prey abundance.
  • Trap stations should be approximately 200m apart.

In the South Island, ferrets have large (18-760ha), often over-lapping home ranges. Note: ferret home ranges vary substantially between sites.

  • A more intensive trap station layout may be necessary (e.g. around individual nests or in small forest blocks) to ensure adequate protection of the species being protected.

There must be enough traps available to be confident a ferret will encounter a trap.

  • A good track infrastructure is important and each trap station numbered for ease of relocation and data collection.

Reduces the risk of missing a trap during checking and allows capture data to be related to each trap site.

Timing of operations

  • Timing is critical and depends on the species being protected, and the biology of ferrets and their prey at the site.

e.g. To protect kiwi chicks, ferrets need to be controlled all year because adults, chicks and eggs are vulnerable. e.g. To protect yellow-eyed penguins, control ferrets for >6 months of the year from laying in September to March when the chicks fledge.

Effective use of traps

  • Traps should be left out permanently.

Capture rates of female ferrets are faster where permanent traps are used, and permanent traps catch more ferrets.

Trap checking regimes need to consider:

  • Trap occupancy rate (of both target and non-target species),
  • Field life of the bait used.

Timing of inspection regimes vary from weekly between January and May; to monthly between June and December. Localised site protection inspections may need to take place on a more frequent basis (i.e. daily).

EQUIPMENT

Trap type

Key elements are: catch effectively, kill humanely, easy to use and maintain, light weight, portable and cheap.

  • The DOC 250 is recommended.

These traps have passed the National Animal Welfare Advisory Committee (NAWAC) guidelines for use as ferret kill traps.

Maintenance of traps

Traps

The DOC 250 traps is galvanised or mad[1]e of stainless steel so do not require initial treatment.

Examples of protective coatings are:

  • Dipping the traps in melted preserving wax,
  • Nothing (in dry conditions),

Traps in use

  • Traps should be regularly cleaned with a wire brush.

Removes mould, fur and bits of dead animals and allows for identifying what has escaped from an empty sprung trap.

  • Un-sprung traps should be set off at 4-6 weekly intervals.
  • A formalised maintenance regime is important. Traps should be regularly maintained, including checking for worn pivots, weakened springs.

Tunnel/Cover

Kill traps must be set in a tunnel or under a cover. A tunnel has three functions: i) orientates the animal relative to the trap, ii) protects the trap and iii) keep out non-target species. It must have the following:

  • Be made of solid material.

Kiwi can poke their beaks through tunnels made of wire mesh.

  • Minimum of 600mm long. Where weka are present the tunnels need to be at least 950mm long to prevent weka accessing the traps.

This provides space for two traps with double baffles on each end.

  • Double baffles at each end.

Restrict kiwi beaks & other non-target species.

  • Open both ends.

Ferrets have access to both traps.

  • Solid anchorable design

Prevent traps being disturbed by pigs and possums.

  • Entry holes of at least 75mm x 75mm cut into baffles

Allows ferrets to enter but restricts non-targets. Correctly positioned, the holes help make the animal step onto the trigger plate.

  • Removable roof

Ease of access to check/set traps.

  • Bait is secured between traps

Ensures bait doesn’t move or get removed.

Bait and lures

Key elements are: high palatability, a field life aligned with the frequency of field checking, doesn’t attract non-targets, easy to use and cheap.

  • The most effective baits may differ with location and the natural diet of ferrets in that location.
  • Effective baits include meat (e.g. rabbit, hare, beef, possum) and fish. Fresh hen eggs can be used if stoats are also targeted.

Trapping rates are higher if an attractant is provided.

  • Baits should be replaced regularly (timing depends on environmental conditions) and disposed of away from the trap.
  • Pre-baiting traps may increase capture rates.

SKILLS REQUIRED

  • Managers need a good working knowledge of ferret ecology and the prey ecology to manage operations effectively.
  • Trappers should have a good working knowledge of ferret behaviour. Specific on job training in the use of traps is essential.
  • A consistently high standard of setting traps is essential – trappers must be dedicated to the work.
  • Trappers need sound bush navigational skills involving compass and map reading.

STANDARDS

Animal Welfare Act 1999

  • Under the Animal Welfare Act 1999, the NAWAC developed a standard as a draft guideline for testing kill traps. It is recommended that only traps that have passed the NAWAC guidelines are used, because traps that have not passed may eventually be prohibited or restricted.

SUSTAINING CONTROL OVER THE LONG TERM

  • Monitoring of conservation outcomes is essential to judge effectiveness of the control programme.

Control operations are useless unless outcomes are achieved.

  • Achieving outcomes from predator control are long term and often control must take place for 5 years+ to get results. Funding must be in place for long-term control.

Ferret populations are cyclic within and between years. This can result in years when anticipated outcomes are not achieved.

  • Baits may have to be alternated and/or combined over the duration of control programme.

Ferrets are flexible and opportunist in their diet, so a change in abundance of their normal prey can cause a rapid shift to alternative food resources.

  • Good data collection helps operations to be more effective and efficient over the long term. What is recorded depends on what the project wants to know. Typical questions are: What trap sites catch most /least? How much trap effort is generally required to achieve the outcome in this block?
  • Trapping rates are highest in late summer to autumn, but at this time of the year mainly juveniles are trapped, leaving enough breeding animals to maintain abundance.
  • It is important to maximise trap efficiency by selecting the correct trap type, bait, layout, seasonal timing, and length of operation.

LIMITATIONS

  • There is no “window of opportunity” post control as numbers quickly return to pre-control levels.

Ferret populations recover rapidly through immigration.

  • Intensive trapping of large areas is very labour intensive but is sustainable and responsible.

INFORMATION

Recommended reading

  • Lavers, R. B. Clapperton, B. K. 1990. Ferret In C. M. King (Ed.) The Handbook of New Zealand Mammals, pp. 206-224-206. OxfordUniversity Press, Auckland.
  • Clapperton, B. K. 2001: Advances in New Zealand mammalogy 1990-2000: Feral ferret. Journal of the Royal Society of New Zealand 31: 185-203.

References (some references of interest):

1.Clapperton, B. K. 2001. Advances in New Zealand mammalogy 1990-2000: Ferret. Journal of The Royal Society of New Zealand31(1):185-203.

2.King, C. M.; O'Donnell, C. F. J.; and Phillipson, S. M. 1994. Monitoring and control of mustelids on conservation lands. Part 2. Field and workshop guide. Department of Conservation Technical Series 4, Department of Conservation, Wellington, New Zealand.

3.Caley, P.; and Morriss, G. 2001. Summer/autumn movements, mortality rates and density of feral ferrets (Mustela furo) at a farmland site in North Canterbury, New Zealand. New Zealand Journal of Ecology25(1):53-60.

4.Byrom, A. E.; Spurr, E. B.; and O'Connor, C. E. 2002. Ferret Neophobia to traps. Contract Report LC0102/082, Landcare Research, Lincoln.

5.Moller, H.; and Hamilton, B. 1999. Predator control: the game keeper's gift. inFish and Game New Zealand.

6.Clapperton, B. K.; Minot, E. O.; and Crump, D. R. 1989. Scent lures from the anal sac secretions of the ferret Mustela furo L. Journal of Chemical Ecology15:291-308.

7.Warburton, B. 2001. Traps and trap-testing. in Walker, A., editor. Proceedings of Mainland Island Hui, Omapere 20-23 August 2001. Department of Conservation.

8.King, C. M.; Griffiths, K.; and Murphy, E. C. 2001. Advances in New Zealand mammalogy 1990-2000: Stoat and weasel. Journal of The Royal Society of New Zealand31(1):165-183.

9.Ragg, J. R. 1997. Tuberculosis (Mycobacterium bovis) epidemiology and the ecology of feral ferrets (Mustela furo) on New Zealand farmland. Unpublished Ph.D. University of Otago, Dunedin, New Zealand.

10.Caley, P. 1996. The efficacy of trapping for reduced ferret abundance. The Royal Society of New Zealand Miscellaneous Series36:73.

11.Barlow, N. D.; and Norbury, G. L. 2001. A simple model for ferret population dynamics and control in semi-arid New Zealand habitats. Wildlife Research28:87-94.

12.Thomas, M. D. 2001. Kill-traps for stoat (Mustela ermina) control. Research Investigation No. 3412, Pest Control Research Ltd., Christchurch.[2]

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created: 27 April 2005