Erayz dipped in apple cider vinegar

This is a continuation of a Nov '21 post ‘Mouldy Bait? Potassium Sorbate’. I would have continued that discussion except for not knowing if a reply to a months old thread gets the same attention as a new post. A NZ covid refugee from Canada, in the past two years I have been eight months full time volunteer predator trapping in the Ruahines, Taranaki, and in Northland. Erayz has been a favourite 200 lure, except for how quickly it can turn into a mouldy blob. That is only worsened when a mouldy piece is removed and a fresh square is no doubt inoculated with spores when it’s placed. Vinegar kills mould but the gen is that vinegar is a deterrent and shouldn’t be used in a trap. Not true says my trials and I hope this post will encourage more vinegar trials to further investigate its pros and cons.

My first trial (on a whim) was to peel and pickle three eggs in apple cider vinegar. Two of three docs baited with those got three rats in about a week. (Not recommending that, the egg deteriorates quickly.) Then I put out Ferrafeed prefeed and sprayed half of it with a 20% (4 to 1) water, apple cider vinegar solution. In the photo the top half of the carton was liberally sprayed - until it was running off. As the photo shows the vinegar sprayed portion was preferred. The small dish in the centre is undiluted ACV placed there to add to the vinegar smell. Three such cartons were put out and each was covered with a plastic hood. The result was the same in all three and ditto when the same experiment was repeated using white vinegar. All of the Ferrafeed was consumed. In two of the cartons the dish of vinegar was moved suggesting that it was indeed rats present not mice.

My final trial was to dip 20 squares of Erayz in the 20% apple cider vinegar for a few seconds. Those were put out in 20 DOC 200’s. In the five months I had been tending those traps only three stoats were caught using eggs. Erayz had never previously been used. The previous baiting was of fresh minced hare and prior to that cut up fresh chicken with feathers attached. Neither of those baitings got anything. The dipped Erayz however scored a weasel and a stoat. (Each of the traps also contained an egg placed two weeks prior.) Another 20 squares, of no vinegar treatment Erayz, were put out on the only other line in the work group area that had caught stoats. That as something of a control. My expectation was that those traps would at least get a rat to show that Erayz does work. They got nothing. I was confident the vinegar treatment would not deter rats but was uncertain about stoats. Plenty of vinegar in egg mayo though and it’s said to work.

The Erayz was not fresh. It had been mailed from Hastings to Northland and would have had time out of refrigeration before that. I’d guess it had been two weeks total without refrigeration. When it was dipped it became a lot softer. I wanted to try hanging it on wires and it softened enough that for some pieces I had to squeeze it back together to give it enough support for the wire to hold it. What was odd that half way through the day the smell coming from the plastic bag, was not vinegar but that of fresh Erayz. I say the vinegar dip rejuvenated it! I would like to be able to confirm that with more trials but this truly was my final trapping trial. I am now back in Canada.

I would like to be able to say that the vinegar dipped Erayz stayed mould free for x days longer than undipped. I forgot though to ask my mates to check on two pieces, dipped and undipped I’d left as a check for that. I only remembered that yesterday. It’s been 24 days and both pieces were equally mouldy. They will be trialling more Erayz dipped in stronger solutions of both vinegars. I have seen some terribly mouldy traps. If you are tending anything similar I hope this will inspire you to get some straight white vinegar and give them a scrub. Perhaps do it first in ever second trap. Would like to hear of subsequent catches.

Hi there Ron,

That is interesting about the vinegar. I just wanted to share with you what we do in our project to help prevent Erayze from going mouldy that may be a little less labour intensive to what I see you doing with your bait. To promote airflow around the bait we have these little mesh bait cages in each trap that stay hooked to a screw in the side wall. (Actually having it hang on the end of the trap above the end mesh is even better) This is not our finest example, but just from a trap I happen to have outside my house at the moment. only allowed me to add one photo unfortunatley.


My trial with vinegar stemmed from recommendations that veg brought home from the store should be dipped into a 15% vinegar solution to prolong it’s shelf life. The Erayz I had was half way gone by time I put it out. It needs more trialling but it certainly seemed to me that the vinegar dip rejuvenated it. Hopeful that’s the reason for the success. But even more hopeful that, as in the case with the rat vinegar trials, the vinegar proves to be not a deterrent but an attractant.

I like the idea of hanging baits. Your rack would also be easy to remove and clean when it does get mouldy. If you use eggs as well, I suggest trying some traps with the eggs elevated. A uni study has it that captive stoats showed far more interest in an elevated egg with it’s potential to fall and break than one on the flat.

Oh pardon. Royden is Ron. Didn’t realize I wasn’t logged in as me. Have looked to delete that account but haven’t figured out how yet.

I can state for a fact that rats are, indeed, very attracted to egg mayo. If you’ve had quiet traps for a while, bait them with some, and there’s a good chance that you’ll get kills overnight. Both times I’ve switched from my normal rotation of baits to it, there’s been a significant spike in kills. I’ve read several times that rats are deterred by vinegar, but ZIP researched a range of lures and chose to use mayo in their dispensers, because rats, stoats, hedgehogs, and possums all love the stuff. The vinegar takes if a few days longer to grow mold than other baits, as do Goodnature lures (which work very well in snap-traps, BTW).

Dipping Erayz in ACV is a good idea, because it will appeal more to rats than if white vinegar was used. Studies have shown that rats are attracted to yeast, so I’m going to try malt vinegar at some point.

I’m very proud of you for the work you’ve done here trapping. Please come back!

Can you post a link to the study, please? I’d love to read it. Cheers.

Ooops! The last line was for Ron-Sherk, I don’t know how that happened. Still, I’m proud of every trapper, including you, Royden!

No worries W_W just one me with two accounts. (The other not wanted??) I tried egg mayo in a number of 200’s in the Ruahines without any success. At the time I was trying various baits in cloth pouches to slow down the flies. Tried chicken hearts, chicken liver, rabbit mince and the egg mayo. Everything dried out soon enough but the mayo lasted longest. I put it in pouches made from the commercial kitchen wipes. (What I know as J cloths.) I could squeeze the pouch and the mayo would squish out to the surface so it seemed a good way to present it.

As we know switching up the baits seems to be effective too but for both stoats and rats my experience says that erayz (until it molds) is tops. The fresher the better - like any bait. (Every trap almost always has an egg as well.) My trapping days are done but based on what I mentioned above I would be trialling redipping erayze in vinegar after say a week or more - before any mold starts to grow. Now though that wouldn’t be only to slow down mold but to confirm that the vinegar somehow freshens the erayz. I would be trying both vinegars, no reason to think that white wouldn’t work equally well. The Ferrafeed I sprayed with 20% white vinegar was totally consumed as well. One reason for trying both would be because I think the white has more acetic acid?? For cleaning existing mold in traps it might be the better choice. Wouldn’t want to assume that the slight difference in smell makes any difference. I’m hoping anyone using erayze tries what I did. But do it in ever second trap so there’s something of a control.

I’ll find the study link and add it as a reply to your request. I have a Wordpress travel journal website and I intend to use some pages there to post relevant trapping info I’ve both read and trialled. I hope to do a page of all the pertinent studies I’ve read and note their main conclusions. (A tip for anybody searching google. Always add ‘pdf’, if it’s the facts you’re looking for.) I did start a facebook group but google doesn’t search facebook. I only tested this site a little, so this might not be correct, but it seemed to me that a Trap NZ topic title was much easier to find than a text string from a post. Not good if good trapping tips get seen and then get buried forever. This is something that I feel PF2050 should be correcting. They should be soliciting proven trapping tips from all the trapping groups and presenting them in an easy to search site. But they should also be encouraging trials that include controls. Not as strict as those in a uni study but something to say, this is the result ‘with’ and this is the result of a roughly equal number of traps without.

From the abstract:
Stoats ate more egg baits if they could roll (and thus break)
the egg than if eggs remained stationary and unbroken. Stoats spent longer
investigating moving baits (dead day-old chicks Gallus gallus domesticus, or
mice Mus musculus) that were attached to a pendulum, but such baits did
not elicit increased biting or chewing responses. This study demonstrates that
visual and textural bait features could improve bait consumption, that mirrors
could attract stoats to enter traps, and that movement devices could direct
the attention of stoats towards baits or control devices. All these concepts
need to be refined and field tested before being used.
Keywords: stoat, Mustela erminea, bait, lure, attractant, trapping, pest

That last sentence is a head scratcher. How else are they going to be used other than field testing???

If anyone wanted to try a mirror I’d suggest using A bit pricey at $20 but it would be enough (7x10") to make 4 and maybe 6.
I used some to replace a bicycle mirror glass. IF this is the same brand I used it has mirror on both sides although one is much poorer quality. Plenty sufficient to intrigue a stoat though. If it was propped in the middle of a double DOC it would work from both entries.

Thanks for the study info. I’d actually read this study before, but it was a few years ago. I’ve read a lot of studies over the past year about every predator species, both NZ and international, so I can’t remember everything!

Regarding eggs, I’ve read several pen trials that discovered a significant difference between the appeal of eggs to M&F stoats. Smaller females would often ignore whole hens’ eggs because they realised that their jaws were too small to puncture them. Their appeal should be enhanced if it appears as if females could kock them free.
Something that I’ve used is eggshells, scattering them near the eantrance trap as a visual and olfactory lure, encouraging predators to investigate the trap. I put stray/hay/dry moss in the back to mimic a nest, too, making it look realistic, and some feathers, If I can find any. Eggshells are quite good at reflecting starlight, so they act as a form of blaze.

Something that should catch the eye of stoats would be a mini disco ball. They’d reflect light all over the place, illuminating the lure/bait quite well on sunny days, I’d imagine, and I’d be interested to see how they’d look during a full moon. The problem is that it would also reflect light off of the trap itself. Because they scatter light, I don’t think that there would be any fire risk, either. Improperly-angled, a mirror has the potential to set a trap on fire. It would, I suspect, be a pretty good curiosity lure.

Do you live in a part of Canada where you could continue to trap rats?

I’m originally from Alberta, which is rat-free, because the provincial gov’t runs a rat-elimination taskforce to prevent invasion, due to the risk to wheat, etc. They’re like a SWAT team, swarming an area if a farmer detects one. Climate change should make this a harder job, unfortunately, because rats’ range will expand to the North.

Did you trap stoats/weasels with Erayz when it had been treated with vinegar recently?
I wonder if using a spray bottle to give Erayz a coating of it in winter would help? Salt?

I run about 25 traps on my property and neighbouring areas.I’m able to check them frequently, because they’re all within walking distance.I’d basically given up on using Erayz in winter due to mold and them going soggy, but rats probably don’t care. I’ll definitely try the vinegar. I usually trap enough rodents that I can use them as mustelid bait, and remove them before they rot, but an Erayz/carcass combo, plus an egg, should be effective.

Perhaps you could try to organize a citizen science group in NZ? You could organize bait trials here from Canada, and crunch the numbers. If a technique and/or lure/bait delived promising results, you could write up a summary of the data and contact DOC, Landcare Research, Unis, councils to see if they’d be interested in trialing anything. Put up a new post asking users if they’d experiment on your behalf. I’ll try the vinegar, and there might be some users that have responded to your past posts that would be interested.


My trial with the erayz and vinegar was on my last field day. The work group had never used erayz but they did say they’d be trying more. If I was still trapping, next I’d be trying dipping erayz just before it starts to mold. (Spray, not dip, worth a try too.) That the vinegar seemed to freshen up the erayz was totally unexpected. More trials are certainly needed to confirm that. I’d also be trailing spraying full strength vinegar of both kinds too, along with a scrub with a dish brush, in a number of DOCs to confirm that vinegar is not a deterrent. Also to see that the vinegar does effectively kill any residual mold in the boxes. I have often left moldy erayz on the top of trap boxes and nothing touches it. Can’t conclude from that though that at some mold stage it wouldn’t still have sufficient erayz smell to attract.

Yes I would like to try to organize what you mention in your last paragraph. I’ll try contacting you with the message method available by clicking your pseudonym.

My traps are quite close to where I live, so I’m able to check them several times a week, and some of them 3-4 times. Unfortunately, Erayz turns to mush in no time, even in hot weather. Shouldn’t it dry out and become like jerky? Every other kind of meat does, and fish. What gives?

I’ll try the vinegar treatment soon. I’m going to clean out a DOC tunnel in a few days, so it’s a good opportunity to try something. Once the maintenance is finished, I’m going to spray the lid and the inside of the trap with malt vinegar (just 1 spritz each). Derived from barley beer, I think it’s the type of vinegar that rats would be the most attracted to. I’ll have the trap close enough that I can check it daily, and will leave the trap unset, because I want to find out how long it takes for any activity to occur. With egg mayo, I typically trap rats on night 1, so it may not take long for malt to attract them, either. Even if vinegar don’t turn out to be effective lures/bait treatments, it should be an excellent way to alert predators to the presence of a new trap.

The next time I put new Erayz in my traps, I’ll spray 1 piece in a double-set with vinegar, and leave the other one alone. I have a trap close to a stream, so if the sprayed piece doeswell in that tunnel, then that’s all the evidence I need!


Just to thank you for this message as since reading it I have been regularly using your apple cider treatment. Unfortunately I don’t have time to do tests and controls. However my observations are that the vinegar works well as on the first use as I got a good rat count, however over time this has come back a bit so maybe I need to make a change. One thing though is that I have not had a stoat or weasel even though I know there are a large number in the area. So I am now using PoaHu as the lure to see if this works - 2 weeks in nothing!

I’ve also given this a try, but I need to do a larger trial. I placed some in several traps as a prefeed to see how appealing it was to rats, and it disappeared overnight, so they were vinegar fans. The second batch killed a large brown rat. I’m going to make up another batch soon.

I learned, recently, that vinegar evaporates quickly, so the extra appeal that it gives bait is short-lived. With egg mayo, I trap the vast majority of predators within the first 24 hours. After that, it’s average. Something that should reduce the rate at which vinegar evaporates, is vegetable oil, which forms a coating on top of the vinegar. I’m going to try dipping Erayz in a 50/50 mix of oil and vinegar to see if the Erayz retains its vinegar smell for longer. Rats love oils, so it won’t act as a deterrent. Oils do go rancid, eventually, but it should take quite a while for this to happen in cold weather, and rats might not care. Mustelids might be deterred, though.

Regarding mold-growth, I think that vinegar must give bait a temporary acidic shield, which prevents mold spores from colonising it right away. Vinegar doesn’t leave a residue when it evaporates, so altering the pH of the surface of the bait is the only thing that makes sense to me.

BTW, if you’re having a problem with mice stealing bait out of snap traps, jam a small piece of Erayz, into the bait cup. It’s hard for them to eat it without setting off the trap. I gave my last piece a coating of vinegar, which the mice loved, and it has stayed good for ages. A very good mousetrap is the Times Up mouse trap, which you can buy at Mitre 10 Mega. I put a pair of them in a tunnel made out of timber scraps, and I’ve been killing them like crazy. It’s nice to have rat traps that actually have bait in them!

I recommend reading the PoaUku study on the Connovation website.


I have now being using the PoaUku all the way through from April to date in 20 X Doc 200 traps. Not a single mustelid ! Numerous rats though.