Trap Performance and Cost - comparing manual, AT220 and A24 traps

The Bluff Hill Motupohue Environment Trust has a trap fleet comprising 1,148 manual traps, 134 AT220 traps, and 394 A24 traps. We set out to answer the question: how do trap performance and costs compare between those three trap types? This builds on the earlier report which examined AT220 trap performance.

The attached report provides the answer - which might surprise you! The cost per kill on a manual trap is $27.90; the cost per kill in an AT220 is $4.26. There’s quite a bit of nuance in those figures… but if you’re planning a major trap purchase, you might find the report useful.

Let’s get a conversation going!

Cheers David

Trapping Performance and Costs - AT220, A24 and Manual Traps.pdf (687.0 KB)


Very interesting report thank you. What a challenge the mice are with your bait only lasting a couple of days! Keep up your great mahi & make the most of the bonus of being situated on a small peninsula!


Thank you so much for sharing this valuable data - this is a great help for small groups like ours.

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Awesome Mahi! Thanks!

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Thanks - that’s awesome! Very interesting and I’m sure will be very useful for evolving projects.

With regard to Trap.NZ we note the comment about converting sensor trigger events into trap kill records - that’s definitely something we are looking at. Sensors on self-resetting traps are becoming more common, but even with kill trap sensors there is the need to automatically associate the trigger time with the trap record.

And we are also planning to follow up with Goodnature about getting their data into Trap.NZ - our APIs are a bit more mature now so it should make it easier for them. Though I personally think the “Smart Cap” totally defeats the purpose of having a self-resetting trap when you have to visit the trap to get the data! I don’t know why they chose Bluetooth over LoRa.


seems a bit oversimplified here. It assumes each trap kill is of equak value. For example the DOC traps are for Mustelids and none of the self resetting traps are proven to be effective on mustelids or cats for example. For rat control you start hitting some huge costs per ha as outlined by the bay bush report. Mixing up your tools has an advantage and not undervalued.


Kia ora Rolf. It’s already a 17 page report - there’s a ton of detail that’s been edited out to focus on the performance / cost measure. Other reports (Bay Bush being a great example) go through the species aspects. Your point about kill values is valid… particularly the mustelid and cat point - they are indeed reluctant to engage with AT220 traps. That said, they scavange from under the AT220… and so a mop-up campaign with legholds under the AT220 is then a good way of taking advantage of that behaviour.

I endorse your point about needing a mixed fleet to tackle specific predator species. My main point about costs of manual traps stands… those targetted mustelid and cat kills will impose a higher (and necessary) cost. Your point about rat kills is less valid… the cost per kill is the cost to focus on… and automatic traps are far deadlier to a rat population than manual traps. Of course, if you have the data and analysis that contradicts that, please publish it… because we need fact-based reporting!


What an excellent report David! It’s great to see a lot of the nuances in there too. Like mice eating the A24 lure and being too light to trigger it. And if they do trigger it, it can be from above creating a false kill trigger.

Did you trying putting a trail camera on a few of the automatic traps to marry up the data with actual events to get a feel for accuracy? I’ve seen rats get hit with A24 and run away - not sure if they died subsequently.

For more frequent checks (defeats the purpose for some) I just reuse the old A24 ALPs and squeeze some choc in from a bulk pack (or just Nutella). The pest is killed before they get to it, so not much is needed. I get that some prefeed is helpful though. That’s also a quick way to check if the gas is gone - so is the lure! Only applies to more regular checking though. Surely they/we can source cheaper digital strike counters. They say the strike counter battery can’t be replaced (why would they design it that way?) but I find you can pry them open and replace the battery no problem.

I would have considered putting the spare battery in the costs for AT220 as it sounds like it is needed for remote operations. We haven’t got an AT220 yet, so I don’t know how significant that is.

An issue for some with the auto traps is that they can become a target for thieves, depending on the area. They’d need a good resale market to do it more professionally though.

Thanks for sharing!


Thanks Cam - appreciated! Yes, we have watched trap interactions using regular trail cams and the Cacophony Thermal camera. It gives us confidence that the triggers correlate reasonably well with kills… although the A24 does occasionally trigger without killing - particularly with small mice.

We’ve got a local engineering company building us a test hose with a valve for A24s - allowing a single gas cylinder to be used to test multiple traps for slow bolt retraction and other leaks.

One of the other benefits of the Celium network is theft / vandalism identification. If we see multiple daytime ‘strikes’ along a line, that’s typically a sign of vandalism. We then have a specific date / time to share on Facebook. That in itself is something of a deterrent. We’re going to be trialling the Cuddeback grid camera system to then be able to put a face to the damage.

An excellent report thanks! Interesting the impact of a low predator density on the project, both economically and philosophically. We are a way from achieving a low predator density!
I agree with the points on A24’s. Our policy now is vising the traps 3-4 weekly, testing the gas by triggering the trap from the top and replacing gas as required. We find Smooth (blue) lure around the trap, in the throat of the trap and in the cap helpful. I use a cut off gas canister and an air compressor to test for leaks and trap function. We use generic gas at very good rates from our local MyRide bike shop. I have never considered the environmental aspect of the bait cartridges and baskets sound a good option. We have abandoned the chirp system for the reasons stated.
We use tea strainers in our DOC200’s to prevent mice stealing bait – they work well. We run some with mouse traps but we are more concerned with rats. It’s really interesting about the mouse problem when the rats are controlled. We have a number of DOC200’s in plastic boxes which protect the bait in the egg box. We have some 3d printed spikes (like a golf marker) to hold the bait (usually Erayse) up out of the egg cup which fills with water.
We also have a 3d printed tray which fit in the Timms/Flipping Timmy traps for another lure option.

Thanks for sharing this report! We’ve been working a lot of the with A24s since our project started in 2020. We ran a camera trial with the main purpose being to confirm whether the strike report data actually correlated with a kill and not just something bumping the trap! What we ended up seeing from the trial was smaller rats and mice visiting the trap and struggling to get into the cavity or trigger the trap. We are currently trialling a work-around which is attaching the AT220 webbing to the inside of the A24 trap cavity to see if that helps them work their way up into the trap. I’ve also noticed that the newer models of the A24 have a smaller entrance into the cap which might help kill mice.

Hi Clyff - we’ve started doing the same thing here as the gas is often leaking and the timer on the app is just so unreliable. It does mean we’re wasting gas to run the checks but I think that’s a worthwhile waste to ensure the trap is functioning. We also have stopped using the pouches due to their waste and put a long-life lure in the top if they’re not checked weekly (we have volunteers checking most of our traps once a week so we’re able to use a short-life bait in most instances). We did notice that we got an increase in mice getting stuck in the cap as a result so have been trialling a wire mesh system and a little wooden plug that makes the entrance to the cap a lot smaller to reduce the likelihood of a mouse getting into the cap and increases their chance of putting more weight down onto the trigger so that they get hit. The downside is that they often jam up the strike bar and burn through the gas!

Well I am going to get Pest Free Kaipatiki Trust to review this! I am currently trying to do some analysis and dashboards after moving all their historic records to TrapNZ.