Martin Foote has been battling the Department of Conservation over the use of 1080 on Mt Pirongia in the western Waikato. He is a strong advocate for an environmentally-friendly approach to possum control, namely trapping and hunting. A key to carrying out this harvesting of the resource effectively, is an understanding of how the animals behave.

by Marty Foote

Possum behaviour 

Possums have natural infiltration and movement pathways, which can be established by trapping possums and recording where they are caught. Where possums have not been controlled and have created stable populations and territories, the places they move through, feed, play, socialise etc… are clearly defined by runs, territory bite marks, scratched trees indicating play/socialising areas, dropped fruit/leaves and faecal pellets under feed trees. This is where possum harvesters invest all their harvesting efforts and is where contractors catch the bulk of the possums.

Slum dwellers and travellers 

However, these territorial and resident possums are not the possums that a low density possum contractor is interested in. The most important possums are the possums that are living in the slums and the travellers. Slums are in poor quality habitat and slum dwellers are forced to live in substandard housing. When the dominant possums are taken away the slum dwellers move into the better accommodation and will be caught in the obvious resident trap-sets. 

Travellers are possums (usually young, but also older possums being kicked out of a territory) that are on the move. 

Travellers will move in ways that are defined by the physical environment, the possum is moving through, and the infiltration/movement corridors can be established by

  • laying trap-lines, with closely spaced traps
  • recording where the travellers are caught. 

The trap-sets that catch travellers are normally different from the trap-sets that catch residents.

Once the movement corridors have been defined, the permanent traps are placed where it is known travellers have been caught. Permanent traps are also placed in areas where there is a good seasonal food resource that has been utilised by resident possums, in order to catch any possums that elude the traps set for travellers.

Vocal communities

Possums are very vocal communicators and it is the vocal calls that let other possums know what is going on. Leghold-traps have the ability to call possums to them, with the old trapper adage being “the best lure is a possum caught the night before”, which means that any possums, within hearing distance of an angry possum caught in a trap, will be inclined to investigate and will come back the next night to be caught in the now reset trap. 

When possum populations are very low (after effective control) vocal calling becomes very important, when possums are looking for mates, and they will travel long distances to find partners, just the same as possums, in very high densities, will travel long distances to a food source, such as a farmer’s swede paddock or an old man pine when the pollen bursts in the late winter.

DOC contracts for wild animal control are not working

DOC’s preferred method of wild animal control is to use prescriptive input contracts that define the work that a contractor will do, in the hope that desired wild animal density results will occur. 

Unfortunately, input contracts are so tightly prescribed that actual wild animal behaviour plays very little part in the contracted work being done.  

Consequently wild animal control becomes a gamble that may, or may not, achieve the desired density targets.  What’s currently happening with the use of aerial 1080, is that at least 30% of the operational area fails to achieve the wild animal density targets set by DOC.