Some traps seem 10 times more effective than others (and other interesting things we have learned from our new camera tool)
The main purpose of our camera and trapping over the last four weeks has been to test the new camera set up and get as many videos of predators as possible. We can then tag them in a way that artificial intelligence can learn the difference between predator species.
In the last three weeks we have caught the following:
• 4 x possums
• 9 x hedgehogs
• 1 x cat (of course we let it go and did not bait for cats (only peanut butter!))
Our camera was sitting in front of the following traps:
• Good Nature possum - automated air powered trap
• Good Nature rat - automated air powered trap
• Rat poison station - basically just a tunnel that rats go into to eat poison
• Timms Trap - spring action kill trap
• Live Capture - trip plate cage - NOTE it is a legal requirement that if you use this sort of trap you need to clear every day.
The photo below shows the set up. Green object in front is weather protection for the camera. Two good nature traps on the tree. Yellow trap is Timms. Green box is rat bait station. Cage is the live capture trap.
All the animals we caught were ALL the Live Capture Trap which is the first time we have tried this. We caught a vastly higher number of animals than we did last year at the same place because of the live capture trap.
The way we measure trap effectiveness is by recording how often the trap kills the predator for every time we see one on camera. To date we have been getting a kill rate as low as 1%. For example, we would see 100 possums on camera for every time one would be killed (https://cacophony.org.nz/existing-predator-traps-work-little-1-time). The Live Capture Trap seems to be running at about 10-20 times more effective (although we are using a very small sample size, for now). This means about 1 in 5 times we see a possum on camera it is captured.
For hedgehogs, the kill rate seems close to 60-70% of the time which means you can very quickly eliminate a lot of hedgehogs.
Both the Timms and Good Nature have both caught possums last year but nothing yet this year. The possums go up and down the tree in the video all the time but avoid the Good Nature and Timms traps.
We have updated our tool effectiveness table below
Some other observations are noted below - happy to hear how what we are finding matches with your experiences
There are s..t loads of hedgehogs around
Previously we would see hedgehogs on our camera footage and I assumed it was the same one each time (I’m not sure I want to do this enough to be able to tell the difference!) However, over three weeks we eliminated nine hedgehogs from the same spot!
Why are we eliminating hedgehogs? They are very destructive to native fauna. One hedgehog was found with 283 weta legs in its stomach http://www.doc.govt.nz/nature/pests-and-threats/animal-pests/hedgehogs/
There seems to be scent trails leading to the trap that attracts everything
It seems there is a very strong scent trail towards the trap. Interestingly, dogs instantly go up to the trap when they get on the property. Particularly after a possum or cat has been in the trap there is a noticeably pungent smell near the trap. New science studies (http://predatorfreenz.org/predator-scent-may-key-developing-long-life-lu...) seem to indicate that even predator smells are of interest to potential prey. This is a good indicative result for the idea of a lure and elimination device that could remove multiple predators.
Mice seem to be sensitive to scent in a negative way
The only time we saw mice near the trap was on the days after rain - maybe removing scent (human or other)? Mice are certainly around the property, as the bait stations are being regularly eaten.
Possums do not seem to learn trap wariness
One possum was caught in the live capture trap while his/her friend was not. After clearing the trap of one possum, the second one (presumably the same one that visited the captured friend) came to check it out and got caught the second night. Although, this is a small sample size and may have not been the sharpest possum.
Infrared (IR) light seems no issue for possums, hedgehogs or mice
In this set up we have an IR light on full time and there did not seem to be any noticeable impact from this. We have yet to see a rat or stoat but the wariness of the IR light will be tested further.
Any lure idea can be tested objectively
All of the things we are testing at the moment are suggested by others and it is a great way to actually see what works. One experienced trapper suggested Natural Liquorice was a great bait. We did catch a couple of possums with this as a bait but could show video after video of them walking straight past it too. If you have any bait ideas, whether visual, food or other (for possums in particular) let us know and we can try it out.
We are currently testing:
• Good nature paste
• Flour blaze
• Oats in peppermint oil
• Peanut butter
• Eggs (as a visual lure)
A device that could target and kill without a physical trap would be remarkably effective
The most common reason that the possums in particular don’t get caught in a trap is they just walk on by despite there being fresh food both outside and inside the traps. If we had a device that could track and then squirt poison on them it could be close to 100% effective instead of as little as 1-10%
Note that all of these observations are from a ridiculously small data set, but the aim is to create the automated detection tool that will be able to verify all of these sorts of observations much more systematically to be able to rapidly gather statistically significant data.