Will Predators Lose Their Marbles? Preliminary Results

[willowflat_warrior]

The original post was Feb 16, if you want some background.

Between March 9 and September 3, I trapped a total of 40 rats (ship and brown/Norway) in my snap traps trialing the “marble technique” (MT). So far, not a single rat has been able to move or remove a marble from a bait cup without being killed. I was confident that the trial would be successful, but I wasn’t expecting a perfect score!

The difference in performance between the 2 models of snap trap that I used during the trial was significant.

Supervisor Max
The D-Rat Supervisor Max tunnel made by Connovation, was almost perfect during the trial. My 2 Supervisors killed 11 rats between them and at least 40 small rodents. Over 4 months, there was only 1 dry-fire between the two.
D-Rat Supervisor Max – Connovation

Because I use a high concentration of traps, a lot of rats were intercepted by tunnels before they reached one of the Supervisors. If I was using fewer traps, I’m sure that my kill total would have been 30+.

Supervisor Tunnel Tips
1 of my Supervisors is inside a small shed, while the other one is underneath a large Totara. Because Supervisors are made out of light plastic, I mounted mine onto pieces of timber to stabilize them for predators and to make it harder for non-target species to disturb them (like a scavenging cat). The pieces of timber that I used were scraps, the equivalent of a 40cm long piece of 4x2. A thinner piece of timber could be used, provided it’s reasonably heavy.

Supervisors aren’t cheap (about $40) and mounting them onto new timber would make them even more expensive for a single trap, depending on your access to timber. However, if you’re trapping around the house or a small area in the bush, scrub, etc., 1 or 2 Supervisors using the MT, could be very effective. The D-Rat trap’s sensitivity lever, combined with the MT, would allow trappers to reduce small rodent numbers far more effectively than any other model of rat snap trap that I’m aware of.

Notes:
When disarming the D-Rat trap inside a Supervisor, I use my left hand to prevent a dry-fire, by slowing down the setting lever. Using an old sock to fire the trap also works.
Because the D-Rat’s setting bar sticks out to one side, there’s a chance that it won’t fit inside some tunnels.

Any Kess-style model of snap trap should work well with the MT, so you don’t have to buy
D-Rat traps. Being inside a tunnel specifically designed to hold the trap, may make a difference, though.

T-Rexes and Tom Cats
The MT increased my kill rate by about 50% and there was a small increase in small rodent kills, perhaps 25% more than normal. With fewer dry-fires than normal, the odds of creating trap shy predators will have decreased and my traps will have suffered less damage.

When small rodents have been able to consume the excess lure around the base of the marbles, without firing the trap, I’ve still been able to kill rats. Clearly, rats are capable of smelling the lure that remains underneath them marbles, something that I was concerned about when I began the trial. Presumably, even a tiny gap between the base of the marble and the top of the bait cup, is all that’s required for them to detect a lure. With conventional trapping, I’ve never trapped a rat in a snap trap that small rodents and/or insects have completely eaten the lure(s) out of.

Lure Options
The best base lures to use with the MT, are ones that are sticky, because they hold the marble in place. Peanut butter and Nutella are the go-to options for most trappers, but my go-to lure is tallow. It isn’t sticky, but it’s greasy enough that marbles stay put. In cold weather, tallow sets like concrete.

It will be easier for predators, including small rodents, to move marbles if Goodnature lures or egg mayo are used, because they aren’t as sticky, but marbles should still be difficult for predators to move or remove without being trapped.

Cost
Marbles only cost a few cents apiece and will last forever, but some will go missing.

Savings
Using the MT, my edible lures went way further than normal, because they weren’t constantly being eaten by predators, small rodents, and insects during pre-feeds and when my traps were armed.

Underneath the marbles, my lures have stayed fresh for ages, because they’re protected from the elements. In wet/humid weather, the marbles have only allowed a small amount of moisture to reach the lure underneath them (if any), so very little of it gets soggy or goes moldy.

In hot weather, lures can go stale quickly, robbing them of a lot of their scent. Underneath marbles, lures should retain their moisture, keeping their scent fresh. Even inside hot tunnels, it should take a long time for marbles to absorb enough heat for the lures underneath them to be affected. I haven’t used the MT in summer, so I’m waiting to find out how well lures do in the heat.

The amount of lure that I require per trap is way less than normal. Instead of luring every trap for a pre-feed and every trap when they’re armed, once I’ve done a pre-feed, the lure underneath the marble is safe once the traps are set. When I make a kill, I remove the marble from the trap and leave the lure underneath it as a pre-feed. Depending on how much interference your traps experience, the savings could be significant.

Risks?
I’m confident that it will be very difficult for rats and mustelids to move or remove a marble without being killed, but they will be able to remove marbles from tunnels when a trap has been fired by another animal. Some predators will discover that a marble isn’t actually the egg of a small bird, once they’re taken it to their nest or den, but others will find out while they’re still inside a tunnel or near the entrance. Do marbles on the forest floor pose a risk to wildlife?

I contacted several ornithologists, asking if they thought that marbles would pose a risk to kiwi. They didn’t think that kiwi would be harmed, because marbles are perfectly round and smooth. It’s manmade objects like nails and screws that are dangerous to them. Carnivorous birds, like blackbirds and thrushes, will discover that the shell of the egg that they’ve found can’t be cracked, and abandon the marble.

The herpetologist that I contacted, said that lizards, geckos, and skinks aren’t capable of swallowing marbles, even if they wanted to.

Unless you happen to find an abandoned marble inside a tunnel or on the forest floor, it will either be buried away inside a den/nest or disappear into the forest floor over time.

Participation
Please help me to collect more data. I think that I’ve come up with an easy, cheap way to make snap traps more deadly, but I need to find out if my results are normal or out of the ordinary.

Cheers.

[davidnblake36]

Do you put lure on the marble? Or just underneath it?

[willowflat_warrior]

You overfill the bait cup with your lure and then press the marble down on top of it, leaving a ring of the lure exposed between the top of the bait cup and the base of the marble. You just reminded me that I need to add a few photos.

[alecmilne.nz]

What a wonderful idea, many thanks. Common sense when you think about it but those always seem to be the best solutions

[dan_percy]

You are a genius! my one thought is once the exposed bait it removed by insects water etc if the rats can still smell it?

[willowflat_warrior]

The rats here have had no difficulty detecting the lure underneath marbles. So far, about 25 rats have been killed in traps where small rodents have eaten all of the exposed lure. With their powerful sense of smell, even a tiny gap will allow predators to smell the lure underneath a marble.

I hope that you give the marble technique a go (it’s hardly expensive!). I’d like to find out how it works for other trappers, using different traps, lures, tunnels, habitats, etc. I’m especially keen to find out if white marbles are an effective way to kill more stoats and weasels in snap traps. As a base lure, I recommend using Goodnature’s Meat Lovers’ at this time of year, because it doesn’t go bad, insects don’t eat it, and you’re more likely to kill mustelids with it than a lure like PB.

Cheers.

[falconz]

The marble in the cup of T-Rex traps have been amazing. Good results even after the top layer had been cleaned up by insects or “softly licking rodents”.
Great suggestion and thank you for it.

[willowflat_warrior]

Thank you for experimenting with marbles. My results, so far, have been so amazing, that I had expected to receive a lot of feedback from trappers trying marbles. It’s not as if marbles are expensive or hard to find.

A potential advantage of small rodents licking up the exposed lure, is that they leave saliva behind, on the bait cup and the base of the marble. I read in a study, that rodents are very attracted to the scent of saliva, because it indicates that fellow rodents have found a good source of food. Rodents are very social animals, so there’s the added appeal of potentially meeting another rodent at the food source. That’s why it’s wise to leave half-eaten lures in bait cups, instead of re-luring them.

The scent of rodent saliva in snap traps is also a good way to lure mustelids to traps, of course. Combine rodent saliva, a small “egg”, and the lure underneath it, and you’d think that snap traps would kill a lot more mustelids.

Once you’ve collected a decent amount of data, I’d be interested to find out the difference in kill rates is between your normal and marble traps is. If you post again, please include some photos.

Cheers.

[christina.g]

@willowflat_warrior Are all your traps sitting horizontally, or are any tree-mounted? I’m curious about whether marbles would fall out of vertical tree-mounted D-rat traps, or whether a sticky-enough lure would hold them in (at least till the insects and/or summer heat reduce the stickiness).

[willowflat_warrior]

My snap traps are all horizontal. PB and Nutella might be sticky enough to hold a marble, but I’d be surprised if something like Goodnature’s Meat Lovers’ could. In warm, dry weather, a base lure like PB will harden as it dries out, which should hold the marble in place.

Instead of mounting a snap trap with a marble vertically, you could mount one on an angle, which would reduce the odds of a marble falling out. Low tree branches might work, or you could mount a trap on the end of a thin piece of wood and prop it against a tree or a post.

I’ll see what results I get with a vertical trap.

Good Luck!

[falconz]

Thank you for the fascinating information regarding rodent saliva acting as an attractant to other rodents…even more of a reason to add a marble to the trap bait-cups as rodents will attempt to extract as much bait from the surface of the marble leaving a large surface area of trace.
We have just developed a new trapline in a greenbelt separating a rural and semi-urban area of native tree planting and grasses over a 2200 metre length including 24 tunnel-boxes (TBs) and 4 DOC200 single set boxes. Each of the TBs include a T-Rex trap and a mouse trap. The TBs and unset traps were left in the field for 2 weeks with bait on the top of the traps to eliminate the neophobia of target species.
On our first baiting run we experimented with marbles in the T-Rex traps at every second TB
Our first trapline inspection results were irrefutable, not only with the catch results, but the retention of traces of bait untouched by “lickers” and insects thereby offering a second chance of a catch.
The unmarbled traps without a catch were as clean as a whistle eliminating any possibility of a second shot at a catch.
So impressive were the results that I installed marbles to all of the T-Rex traps. The marbles I had were a bit too large for the mouse traps unfortunately but will attempt to purchase a smaller version to cover those.

I have photos available but unfortunately cannot master the art of attaching them to this forum. (Advice from anyone would be gratefully received)

Cheers

[christina.g]

@falconz Re image uploads, in this reply box I can see a symbol with a horizontal bar and an up-arrow which gives me an option to upload files when I click on it. I took a screenshot of the menu bar I see and used copy/paste to put the screenshot directly into the ‘Type here’ text box:

The image/file shows up as a line of computer code (including a file name) in the text box and as a preview picture or hyperlink next to the text box so you can see what the final post will look like.
Hope one of these methods will work for your device and you’re able to share your photos!

[falconz]

Thank you Christina for that information

[falconz]

[falconz]

The Up arrow on a horizontal bar was the key but on my device it didn’t appear in the task bar but at the bottom RH of the text box.

Thanks again for steering me in the right direction

[christina.g]

You’re welcome @falconz! Good to see that you’re getting those pests with your traps

[willowflat_warrior]

Brilliant results!

With a new line, I’d expect you to rack up some impressive results.

For pre-feeds in my T-Rexes, I smear some lure on the front of the trap when they’re unarmed. Rodents lick it clean, leaving a nice coating of saliva, which attracts other rodents and appears to reduce neophobia, given my kill rates. When I’ve armed my T-Rexes with the same lure underneath marbles, the appearance of the armed trap looking so different to an unarmed one, which could generate neophobia, doesn’t deter rats.

Yeah, mouse traps are too small for marbles to work. For one thing, I think that a marble might interfere with the trap sometimes when it fires, like getting stuck in the teeth/kill bar. An excellent alternative to marbles is raw chickpeas. They’re very hard, so they last for ages against nibbling, they’re cheap, and they protect the lure underneath them, but not quite as well as marbles do, because they’re too small to go on top of the bait cup.

Because they’re so dry, chickpeas are also mold-resistant and the mold that does grow is just a fine layer, not the mold that resembles cotton candy. I’ve very rarely had to replace moldy chickpeas, because you can just flip them over, putting the moldy side into fresh lure. Doing this with gloves is nearly impossible, unfortunately. In winter, the combination of a mold-resistant Goodnature lure and chickpeas, is an excellent long-term lure for mousetraps. Maybe 1% of the small rodents here have actually managed to have a nibble on a chickpea before they’ve been trapped.

Keep up the great work.

[willowflat_warrior]

I’ve experimented with a vertical T-Rex, mounting one onto a piece of timber. After 2 days, the marble hasn’t moved at all. The chunky PB has a very firm grip on the marble, so they should work fine vertically.

[christina.g]

Thanks @willowflat_warrior! I’ll share this with the rest of our volunteer group and see if we can get some more people trying out the marbles.

[willowflat_warrior]

Remember to do a pre-feed on the front of the T-Rexes, smearing some PB, Nutella, etc. on the front of the trap to give predators a sample. Once the pre-feeds been licked off, then arm the traps.

Please post some photos of what I hope will be numerous kills.

Cheers.