BHMET runs a fleet of around 1,500 manual traps, 400 A24 automatic traps, 100 AT220 automatic traps and 100 AT520 automatic traps. Corrected Catch Rates (i.e. catches per 100 trap nights) are an important metric for us… but we’re struggling to integrate automatic trap statistics.
Historically, I haven’t been too troubled because just using manual trap results, I have a proxy for automatic trap results - in other words, the rapid decline in predator kills we see in our manual traps is largely because of the way higher kill rates in our automatic traps.
But we’re now at a stage where I need an integrated statistic… that includes all trap types.
Two major problems: how to integrate automatic trap results into Trap.NZ and then how Trap.NZ handles automatic traps in calculating ‘trap nights’.
Integrating automatic trap data into trap.nz is an absolute nightmare in any circumstances. But with a fleet of 400 A24s (only 100 of which have Smart Caps), 100 AT220s, and 100 AT520s, it’s an insurmountable barrier. If any other projects have experience of this, I’d love to hear from them! I’m contemplating manually adding results by ‘smearing’ six-monthly reports across evenly spaced dates - in other words, if our six month AT220 report says 12 ‘small’ kills and 3 ‘large’ kills, I assign 1 mouse per month, 1 rat per month and 1 possum every other month (since that’s the ratio found from carcass checks). But that’s a LOT of work. Perhaps I’m better off not trying to do the statistics in Trap.NZ: perhaps Excel is a better bet - so export the manual stats from Trap.NZ and then integrate the automatic trap stats in Excel? Any ideas (that don’t involve code!)?
For manual traps, the trap night figure is calculated based on assuming that a kill occured halfway between two visits… so if 30 days elapsed between two service visits and a kill was recorded on the second visit then the assumption is that the trap killed on day 15 and was unavailable for the remaining 15 days of the cycle. But that’s clearly not the case with automatic traps… but does Trap.NZ account for that in the ‘trap night’ calculation for automatic traps?
You are doing a great job highlighting a basic issue with data collection.
Maybe Trapnz needs to discuss the issue with statisticians and programmers.
Rather than relying on trap data, I use camera trapping data to track predator numbers. Cameras are an additional expense but it isn’t necessary to monitor every trap.
To date our camera data is proving very effective and appears to reflect the inverse of trap activity - more predators caught equals less camera triggers.
Great point raised and would love to something back from Trap.NZ on this.
Also, I am a manage across two projects and an administrator for another
when looking at the AT220 Telemetry Reports. it read the data from across all three. And as there is no way to separate the data out. thus, make’s things hard when looking at triggers. (I have to select the individual traps)
There also needs to be some way to edit the telemetry data at the back end to simplify the reporting process. currently we have 1,470 All triggers and 195 Possums. this is around three times the total for last year and were only in May.
Short answer is trap nights work best for single fire, non remote monitored traps, as that is what it was designed for.
We would have to make a bunch of changes to make that report useful for self resetting traps. It would have some similarities to trap nights (to capture time in the field as an effective trap), but it would likely mean a new report with a different set of data captured.
We are working on methods / reports to improve the value derived from self resetting traps.
I suggest that this conversation needs expanding to become a long answer because this cuts to the heart of being able to compare the effectiveness of different trap types… which needs a consistent metric.
I need to measure several things:
Our overall trapping progress - are we seeing kill rates (measured by kills per 100 trap nights) decline consistently across our area of interest?
Our species-specific trapping progress - are we seeing each target species decline consistently across our area of interest?
Our individual trap performance - how are individual traps performing? Do we need to move under-performing traps?
Trap type effectiveness - how do different trap types compare in their effectiveness?
At present, I can only measure 1,2 and 3 for manual traps. Which as I mentioned before is okay as long as I have an equal distribution of manual and automatic traps because my manual trap stats are an acceptable proxy for my automatic traps.
But 4 is a critically important measure for investment. If I’m putting a funding application together, it’s critically important that I can justify why I’m selecting a particular trap type. Given the high capital cost of automatic traps, I need evidence.
I can gather that by having an entirely seperate set of spreadsheets for A24s, AT220s and AT520s… and then compare overall metrics (AT220s have an catch/100Trap Night averages of 6.0 overall and 0.43 for possums versus the same area manual trap averages of 0.7 and 0.09 respectively… a massive difference). But it would be so much easier if Trap.NZ could handle that.
Another thing that we are grappling with is that the AT220 traps will fire several times each night to clear any beam obstructions until the pest drops out of the trap. This is inflating our rats count. The possums are recorded differently by an accelerometer so should be accurate. Apparently the detail of the telemetry can be examined to determine false triggers but I haven’t worked out out how to do that. I’ve asked NZ auto traps to put up some explanation.
Hi there. The AT220 will preform a “clearing fire” if at the beginning of the night the sender eyes are blocked. This clearing fire is usually enough to clear any remains blocking the sender eyes.
It will only preform one of these clearing fires - this is usually enough to remove the remains, and if not additional fires will not help. It will however repeat this if the eyes are still blocked the following night, in hope to remove the blockage. It will do this until the eyes are cleared, or battery runs out.
These clearing fires are tallied in the “All Cycles” count when using the app, not the “Triggers”, so shouldn’t be inflating your rat counts.
Hope that helps.
Hi David,
Important issue you raise, I be misunderstanding your issue but it seems to me that the data you require is stored in the AT220 log. Maybe easy (automatic?) downloading of this log into TrapNZ would solve the problem. It would identify accurately the date and time of any catches.
Maybe your query should be directed to NZ Autotraps?
For what it’s worth I don’t have the number of AT traps that you do but I use excel to record catches, entering data when I clear the traps and get an average over time.