Feral pigs can do a lot of damage to native vegetation, bird life and insect life and some community groups are trying to tackle the problem in their patch to reduce the impact on the flora and fauna they are protecting.
The QEII website has some information on feral pigs and a trap design. There are also youtube videos from the USA and Australia that a Forum member has found useful plus some useful pdf information. DOC has corral traps in operation at Stony Bay at the top of the Coromandel if you want to look at a working version.