Predator Free Waitahanui (PFW) has been set up as a volunteer organisation to coordinate pest control in our Waitahanui community. PFW is an extension of Greening Taupo whose objective is to improve the Taupo environment for people and native wildlife by undertaking restorative planting and pest control to create ecological corridors and increase the number of native birds in the Taupo area. For the native birds to thrive and survive within back-yards and the surrounding native bush a reduction in predators is fundamental. To stop possums damaging the native trees we will also target those creatures. PFW wants to encourage and enable individuals to undertake and support a trapping and eradication programme within the Waitahanui community and give our native biodiversity a chance to thrive.
Predators: Rats, Stoats, Weasels, Ferrets and even Hedgehogs love eggs. Most native birds breed at ground or low level, so the eggs or nestlings get eaten by these predators. Possums are also active in our community and do major damage to native trees and other vegetation.
Rats are the most common target and Stoats, Weasels and Ferrets do even more damage to the birds, but are not as common in our area, although they have been trapped. Possums are also a target but require special traps. All traps used are tested and approved by the Department of Conservation and are designed to kill the target species instantly and humanely and to make it nearly impossible for children, birds or pets to get into the traps or get hurt.
Major Missions:
Set up an effective predator eradication program in back-yards and native bush.
Get permanent and part-time residents from all back-grounds to work together.
Identify further environmental and conservation needs for the community.
At a recent trap building workshop by the Waitahanui School we have made more than 30 tunnels and these are currently distributed over various back-yards in the community. We expect to extend the project to the Waitahanui River. Tauhara College and Te Kura o Waitahanui (Waitahanui School) are supporting the project in various ways. We also work together with Iwi in the area who have committed to install traps in the surrounding areas to ensure minimal re-infestation of the village.
Catching rats on a low budget
Trapping does not have to be expensive.
In New Zealand Victor traps cost between $4.50 and $10, depending on supplier and quantities bought. These traps are good for catching rats (and the occasional mouse or mustelid) in backyards and, if necessary, in other places.
DOC 200 traps cost between $27 and $60 depending on suppliers and materials. These traps are recommended by DOC for rats, stoats and weasels.
For safety reasons and to prevent non-target animals to be caught these traps need to be set in wooden tunnel-boxes, which can easily be made from left-over timber and timber suppliers are often willing to sponsor the materials for community trapping projects in return for some publicity.
We managed to run a community project using about 60 Victor traps on a budget of $950 using mainly Victor and a few other traps. This was achieved in Waitahanui, a small village nestled on the East side of Lake Taupo, the Waitahanui River to the North and a steep hillside to the South.
To do the same with DOC 200 traps would have cost at least three times as much. With the Victor traps we caught 180 rats, 5 mustelids (4 weasels and 1 stoat) and about 100 other predators (mainly mice) in the first year. With DOC 200 traps we could maybe have caught some more mustelids, but there don’t seem to be that many of those in the area.
Experimental traps for inspiration
We involved the Waitahanui community in some planning and trap-building. A reasonable number of backyard traps are now spread throughout the village and those are serviced by the residents themselves.
We had been experimenting with double traps where the entrance would be automatically closed behind the first predator caught to force the next one to enter via the second entrance. A line of 42 double DOC 200 traps with closing doors is currently being used in the Tongariro Forest where early figures indicate, that more traps will achieve double catches this way. We even caught some single live rats, where a ‘sprung without catch’ had also sprung the second trap.
We involved Tauhara College students to develop some other new ideas for more effective and innovative traps. Some of their ideas involved a two-story trap mounted in a tree, several more or less effective double traps with closing doors, a corflute trap on a polystyrene base floating on the river, traps with ramps inside and several tunnels with doors and entrance-ways made from timber instead of mesh.
Along the Waitahanui River we did not use double traps, but as a result of the innovative ideas we compared catches for a number of traps with either
use of mesh or plywood for entrance and door
placement close to the water or further away
ramps in the box or flat floors
As a result our most successful traps do now have wooden walls and doors only, are positioned close to the water and are sunk into the ground with a door at the top and an entrance high up with a ramp leading down. These are more popular with rats than the standard Victor-trap tunnels.
Experiments with baits and lures
The standard recommended bait for Victor traps in backyard tunnels is peanut butter. We have tried various other baits and additional flavoured lures, but we have decided to continue with peanut butter.
We had a problem with peanut butter disappearing off the yellow Victor treadles without triggering the trap within one or two days. We wondered, if slugs, snails, ants or other insects could be responsible. The final conclusion was that mice must be able to lick the peanut butter off without getting caught, maybe by approaching the bait from the side or from between the kill-bar and the trigger-arm.
Initially we solved this problem by covering the peanut butter by half tea strainers strapped to the yellow treadle with the peanut butter inside. This stopped the problem, but the weight on the treadle makes it tricky to set the traps. We are now experimenting with perforated bottle-tops strapped to the treadles.
We have also used long-life ceramic lures and aerosols. The manufacturers claim that these attract various species of predators to the traps. These may indeed have a positive effect on the numbers caught, but we do not have sufficient data to confirm these claims statistically.
We know from experience with DOC 200 trap-lines in other areas around Lake Taupo, that dehydrated or fresh rabbit is a very good lure to be used in those traps. Particularly fresh rabbit seems to be good at catching mustelids (stoats, weasels and ferrets). Those areas seem to have more mustelids and dragging a dead stoat from one trap to another seems to be effective in leading more of these to the traps by their potent smell.
Dealing with loss of traps and vandalism
Some trapping projects have issues with disappearing traps, which are usually the result of theft by people who obviously are aware of their value and have a use for these themselves. The costs of most of the new sophisticated traps makes stealing them indeed interesting for those who are so inclined. This doesn’t apply to Victor and other cheap traps which are often even given away or sold for a small donation at community trap building workshops.
We did not expect to lose many Victor traps from the Waitahanui River line, but initially found several traps turned over or moved. We suspected that dogs being walked in the area could smell the peanut butter or the catches and tried to break into them.
Then we found that some traps disappeared or were thrown in thorny bushes or turned up downstream in the river. We know, that some people in the area don’t like the use of poisons for some trapping operations. We reported the problem on the community website and explained, that we do not use poisons. We got some sympathetic reactions, but the problem has not been completely eliminated.
We found better hiding places for most traps and we have modified a number of traps to be sunk into the ground with an access ramp into the box and a service door up the top. The top itself is then covered with shrubs and soil, so they are hard to find. Particularly rats seem to like this modification, so this episode has resulted in even better trapping results.
We are now planning to use high-school students again to help with more suggestions on how to measure and improve the effectiveness of the techniques used.
