Feral pigs

Feral pigs (Sus scrofa) are classified as a potential pest problem in a number of regions and are monitored and controlled on a site-specific basis where necessary.

Pigs can reduce farm productivity by damaging pasture and young forestry plantings, preying on lambs, and spreading disease including Tb (bovine tuberculosis).

In natural areas, they can damage native vegetation, bird life and invertebrate life.

Below: Extensive pig rooting on a farm at Conway Flat, North Canterbury in 2003. With Biodiversity Condition Fund assistance, 18 landowners have been implementing a feral pig control plan prepared by Landcare Research. Photo: B MacFarlane

Extensive pig rooting

Impact of pigs

Landcare Research ecologist, Ivor Yockney, says the impacts of feral pigs in New Zealand are not well understood and have yet to be quantified, but there have been anecdotal reports of increasing feral pig populations throughout much of New Zealand.

‘It's unclear why pig numbers appear to have increased, but it may be in part due to farmers retiring pasture land for a range of reasons.

'Any increase in woody vegetation provides good habitat for feral pigs and makes them more difficult to control by hunters.’

Where numbers do build to problem proportions, an intensive knockdown programme is recommended using a combination of aerial shooting, intensive trapping, spotlight shooting and targeted ground hunting.

This should be followed by long-term sustained control using traps and hunting. Currently, there is no poison registered as suitable for pig control.

Pig traps

If well managed, pig traps can be an effective supplement to hunting.

Miles Giller, QEII North Canterbury Rep, says designs vary but the most effective can be dismantled and moved easily, are strong enough to require little maintenance and can catch several animals at once.

A suitable design

  • Panels constructed with 6mm mesh reinforcing steel (or equivalent)
  • Side and rear panels 3m long (max) by 1.5m high, front 0.75m wide
  • Mesh off-cuts can be attached off-set to lower panels to prevent piglets escaping
  • Door 0.75m wide by 0.8m high, hinged at top, opening inwards only
  • Panels anchored down with waratahs
  • Removable rods and gudgeons down each corner allow easy dismantling, transport and assembly.

Below: A weld-mesh-panel trap with an inwards swinging door. The lure can be placed in a bag hanging overhead. Assembly of this trap takes about 15 minutes. Photo: Miles Giller

Pig trap

Set the door by propping it slightly ajar with a short stick. As animals enter, the door is lifted by their brushing back, the stick falls down, and the door will swing down and close.

Once inside, pigs cannot push their way out, but other pigs can push their way in.

Below: The inwards swinging door is hinged at the top. Photo: Miles Giller

Pig trap inwards swinging door

Trap management

  • Locate on a well-ventilated open site near known pig areas, where it can be seen regularly from a distance when going about other business.
  • Open saddles or paddocks near cover are ideal. Monitoring of pig traps is less efficient in isolated or heavily forested areas.
  • For humane reasons, check traps regularly and provide shade and water.
  • Bait with smelly materials attractive to pigs (combinations of decaying animal carcases, molasses, beef fat and fermented barley are usually successful).
  • You can suspend the bait in a bag just above the trap, to maximise dispersal of smell and to minimise consumption by trapped animals.
  • Try to avoid passing close to the trap or disturbing the locality with hunting.
  • Rebait the trap every few weeks. Otherwise be patient, as it may be several days before wary pigs are willing to investigate the trap locality.
  • Shoot and remove captured animals (local hunters may be keen to do this for you).
  • Do not enter the trap while any captured pig is still alive as they can be extremely aggressive.
  • For safety reasons, never set traps in public places.

Below: A family of pigs in a trap. With an inwards swinging door, multiple catches are common as one trapped pig lures another. Overnight catches of over 20 pigs in a single trap have been recorded. Photo: Ivor Yockney

Family of pigs in a trap

Open SpaceTM Magazine No. 70, July 2007 © QEII National Trust

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