Greetings all.
We have taken over a predator trapping network at Mahinerangi windfarm in Otago and have replaced all the old Fen mk5 traps with doc150’s, 200s, Timms etc etc. The resource consent issued by Clutha district council requires that we achieve no greater than 10% “residual trap interference” over the course of the year for each target predator (hegehog, stoat, ferret). This effectively means any disturbed/dislodged/sprung-empty trap counts as a missed kill. Trap interference is calculated as number of traps sprung-empty divided by total number of traps. (I have not seen this methodology used before to determine network effectiveness, but would be keen to know if others have?!) We have pigs (feral), deer (feral and domestic), and cattle within the network paddocks and covenant, all of which have the opportunity to knock and dislodge traps by either scavenging or just inadvertently. We currently only have one months data for this network but have already had several traps interfered with. We can muck around with better placement and deploying a couple of trail cams etc to see what’s happening, but I don’t see how its going to be easily remedied, ongoing. Does anyone out there have experience with trap interference being a “bottom line” in your outputs, or should sprung-empty traps just be noted as such with the main data being overall catches/traps and trap effort? How does trapnz determine whether or not a trap network is effective in terms of the way it treats the data? Any help appreciated!
Hi Matt I have been doing this for over 20 years and I have never heard of such a requirement, I would never take on a project under such conditions.
you might be able to do some work re positioning traps tunnels etc but you also want them in the best position to catch target species so moving may compromise that, Pigs or cattle are inquisitive and only have to knock a 200 box and the trap would go off, also with the 200’s if they are double sets you will get some sympethetic firing every time one traps goes off
One thing that was found with Trail Cameras when a row of Sentinels kept getting sprung and NO catch was that a couple of Red Hinds were licking the lure off the bait blocks, slow learners as the traps going off didn’t deter them.
Obviously I don’t know the reasoning behind the condition but will be hard to meet some of the ZIP Lincoln work in about 2018 had about 13% of 200’s set off no catch by rats
good luck
Thanks dave. Reading further through the annual trapping reports submitted to council by our client, i see in the latest report (2023/24) they have now “interpreted” this to mean interference per 100 trap nights. They did this differently in the previous 2 years which gave them all those high percentages, i.e. sprung emptys per monthly check gave you over 18% trap interference, however if you extrapolate over 100 trap night this means at least 3 checks in that time frame, therefore reducing your “interference” to often less than 1% overall. Im still not convinced it makes sense on this basis, and theyve unlikely had any advice from council regading this change of method or interpretation of method, so i guess we’re sort of problem solved at this point. Thanks for your reply.
That’s an interesting method @matt_8, thanks for sharing!
A percentage of trap-nights lost to interference makes a lot more sense, I think. I assume it is measuring whether any given group has frequent-enough checks (and trap maintenance) to be effective under the specific site conditions? Some documents say things like “traps must be checked every X weeks and calibrated yearly” but if it’s formulated as “an average trap must be available-to-catch for 90% of the year, check/repair/calibrate as often as needed to make that happen” each group can tailor their method to their site.
Now I want to get out my calculator and see how our project is doing on %-active-trap-nights! 
In a national park: many of our traps on publically accessible tracks are staked down. A stake is driven into the ground and the trap screwed to it with a couple of hex head roofing screws.
More upfront expense, but lower cost in the long run.
The regional council is being obtuse. I could understand a requirement about by-catch of native birds, but little else makes sense.
Thanks greg. I should have mentioned all our doc boxes are secured with 2 pieces of rebar and fencing staples to the box. Timms traps are harder to secure well. Ive thought about using the same sort of double rebar approach but using lacing wire to secure, or stainless zip ties.
Hi what I do on 200 and 250 boxes is to use 2 pieces of 20mm angle Iron 335 long with a point on one end, I drill a 6mm hole near the top drive them in down the side of box to about 75mm off the ground and secure with a 25mm Tek screw, when I want to move one it is easy to undo the Tek screw
I get 18 stakes from a 6 metre length works out about $1 per stake, But the steel supplier generally just gives me a few length for fee for conservation projects
cheers
@matt_8, what are you targeting with the Timms traps, and are you using them in the open area or forest? The conservation groups in my area have been shifting from the traditional ground placement for Timms traps to tree-mounted traps, but since you said it’s a wind-farm perhaps there aren’t many options for mounting traps off the ground?
Cats and possums. Cat timms just have a slightly enlaged keyhole (done with a jigsaw) and baited with a chunk of bunny. Tussock country so barely a tree in sight. A few pines around so we may look at screwing some to a board and screwing that to a tree, however in my experience they dont really like being orientated that way as it allows the trigger to flop forward. We did get a fairly large cat in a double 150 the other day
Greetings all,
We have recently taken over a predator trapping network at the Mahinerangi windfarm in Otago and have replaced all the old Fen Mk5 traps with DOC150s, DOC200s, Timms, etc. The resource consent issued by the Clutha District Council requires that we achieve no more than 10% “residual trap interference” over the course of the year for each target predator (hedgehog, stoat, ferret). This effectively means that any disturbed, dislodged, or sprung-empty trap counts as a missed kill. Trap interference is calculated as the number of traps sprung-empty divided by the total number of traps.
I haven’t seen this methodology used before to determine network effectiveness, but I’d be keen to know if others have experience with it! We have pigs (feral), deer (feral and domestic), and cattle within the network paddocks and covenant, all of which could potentially knock or dislodge traps, either by scavenging or inadvertently.
Currently, we only have one month of data for this network, but we’ve already encountered several traps that have been interfered with. While we can try better trap placement and deploy a couple of trail cams to monitor the situation, I’m not sure how easily this will be remedied in the long run.
Does anyone out there have experience with trap interference being a “bottom line” in your outputs, or do you just note sprung-empty traps as such, with the main data being overall catches/traps and trap effort? How does TrapNZ determine whether or not a trap network is effective in terms of how it treats the data? Any insights would be greatly appreciated!