Hi all, I was just re-reading the Wikipedia pages for rattus exulans, rattus norvegicus, and rattus rattus, as you do, and one of those pages talked about rats being sensitive to ultrasound, with baby rats and mating females making ultrasonic calls.
So naturally I wondered if there had been any research into using ultrasonic lures for rats, or trials of them.
Does anyone have experience, or know of research into ultrasonic lures?
Edit:
I see there is a paper by Jones and Sandoval in a very recent issue of NZ J Ecology.
Skimming, it seems they did not get value for money from their equipment, using deluxe ultrasonic speakers that cost 385 euros a pop. For the price of 20 of them, you could fly to Shenzhen, explain what you want, and come back with 1000 or more custom-tuned ultrasonic piezo transducers in four weeks. And the electronics and software to drive them and 3D printed PPS enclosures, in all likelihood.
With 1000 or 10,000 units, you’d be able to A-B test different rat vocalisations, different repetition cycles, different diurnal cycles and/or different placements.
Your edit contains the most recent paper looking at this. I know that there have been a few theses and experiments that have looked at audio lures for possums and mustelids (this study looked at audio lures in pen testing and wild environments).
Agree that the relative cost of a proven product would drop as production increased. If you could get a company interested in the upfront engineering cost, the unit cost of a small audio lure system could be quite manageable. But the relative cost is still high and interaction rates low compared to toxin, which makes it less likely to be adopted.
I had in mind using ultrasonics as a durable lure for trapping. Specifically in our projects with many traplines.
We are using fresh rabbit meat chunks, which in summer last about 18 hours before the maggots get too big. In winter they go mouldy.* (This is in Taranaki, plenty of humidity.)
If we had good lures that lasted six months in the field before recharging, that would be eight or more trap servicing runs without having to carry bags of rabbit meat, and maybe 30 seconds saved per trap per visit. Adds up when you’re doing more than a hundred in a day.
(It’d be even better with self resetting traps…gotta have dreams).
We have had a bit of a shortage of rabbit in recent months too. Around here, erayz doesn’t seem to draw in the crowds like fresh rabbit does. Nor does the Goodnature meatlovers’. Not useless but not as good.
I could bodge up some small lightweight ultrasonic lures if I could get detailed specs on piezo transducers. Add a flashing white LED and they might attract mustelids too. I’d set them to only operate for an hour sometime after dark to save battery.
Maybe I’ll explore the other idea–using small (10kg) cargo drones to drop in baits, trap consumables (mesh) and supplies at various points on the traplines, to enable week-long trapping-and-line-pruning runs. Save the driving to and fro. Can’t see DoC being too happy about that one, though. More dollars and more regulations.
* Coating the rabbit baits with beef dripping does help quite a bit–thank you @willowflatwarrior!–but it’s a bit messy and slow. And by the last half of the line, the baits have been rubbing in the bag and the dripping has mostly flaked off. I suppose we could try to industrialise the coating process, and switch to rigid containers.
I had a play with this a couple of years ago, made a prototype. There are surprisingly numerous papers on vocalizations of various rats (and mice), including in different social contexts (fear, normal social interactions etc). A lot of it is ultrasonic.
My prototype mimicked “happy” rats, until a motion sensor detected movement, then fearful rats. Used a microcontroller to drive the speaker in the different ways required.
Only tested briefly in field with camera trap. Feral cats seemed fixated, only stoat captured on camera did not show much interest, but numbers might be too low to know. Possums, rats and hedgehogs all seemed interested (weird about the possums?) Pet cats and dogs went nuts, more so than with the audible “squeakers” you can purchase.
Then ran out of time! Going to do more testing this year hopefully. Suitable ultrasonic speakers are under $5 on aliexpress, $15 on digikey. AA batteries lasted a long time.
@bluewave I don’t know if the tech is something you would be willing to share, but I’m sure there are many on this forum who would be interested in trying something like this out.
As far as attractive noise profiles, I reckon a candidate would be mouse nesting noises since so many of our target predator species would target a mouse nest.
Awesome, thanks Ben. I only had a quick look and I couldn’t find any specs like frequency response and drive requirements at the time. I guess I need to invest more time.
Any reason you didn’t go on to try it as a trap lure? Just the time required, or did something else about it stop you? Target species interest is great, but what matters is kill rates.
My thoughts were to bodge something up, and if/when it works and is affordable, do a ruggedised compact design and get JLCPCB or one of their competitors to make a few dozen of them. (I’m not going to be able to finance 10K or even 1K of them by myself.)
Do you have the recordings still?
Re stoats, from reading around they are not definitely known to hear ultrasonic and they rely on vision and smell more than hearing. So I’d add a sparkling LED for them.
Rats have 20/600 vision, really bad, and are red-green blind, but can see slightly into UV apparently. Hearing is great. Smell is their best sense but the poaukus don’t have a great reputation around here.
Just time was limiting - and lack of instant obvious success on stoats (and my crude testing would have only detected the most amazing success - while very useful success probably wouldn’t have registered). I was solely thinking about stoats at the time- but cats are strongly on our radar at the moment also.
There is a bit published on mustelid and cat hearing abilities. A paper from 1985 shows Mustela nivalis (least weasel) hears to 60.5kHz. Very recently (2026) a short communication reports that NZ stoats vocalise in the 22-28kHz range, so you can be sure they can hear that too. (New Zealand Journal of Ecology 50(1):3640). Wikipedia reports up to 64kHz for house cats.
Given a great deal (majority?) of the vocalisation of rodents is ultrasonic - would expect mustelids and cats to be able to hear it.
…I haven’t looked up possum and hedgehog data!
I have some recordings I can share - complicated by fact I was also testing a motion lure (fake rat - looked surprisingly realistic!) - which seemed attractive to cats especially.
The circuit to drive an ultrasonic speaker, do timing etc etc is simple and low cost. But with all things like this, unit cost scales enormously with volume. Something that costs $50/unit at 100 units costs $4/unit at 100k units, or thereabouts! Making some prototypes by hand (with Chinese PCB) and a 3d-printed case is probably what I will try next…time permitting.
Edit: The other reason I neglected this was that our project also needed remote trap monitoring, so I prioritised that (it’s in the field now). There are existing systems out there, but we had some specific requirements (in particular, we are a charity and don’t want ongoing subscription charges, which can cost more than the initial purchase over time).
Just read the paper you linked - thanks, an interesting read.
Yes, the approach there is good for research (playing recorded USV), but probably expensive for mass production. My prototype mimicked rat sounds by simply calculating and playing frequencies and frequency shifts, it wasn’t a recording.
Did you get specs on your transducers, or have you got a lab capable of measuring them? (That would be awesome!)
I have seen a bunch on AliExpress, ultrasonic rat repellers they are sold as, but there are no specifications.
We can dream about remote monitoring. Ours is a low funds project. It’s also in damp Taranaki forest - we’d have to climb big emergent trees to install PV panels to power the radios for a useful self monitoring system. And the radios themselves too. LoRa may be great, but it can’t get around the physics of radio waves.
Edit - I’ve seen videos of Ukranian drones controlled with fibre optics rather than radio to evade jamming. Apparently 10 kilometre spools of hair-thin optical fibre are cheap now. I like LoRa technically but the prices are a bit steep. If I had time and money, that’d be another thing to try. On the non-public traplines anyway.
@gregvp my one concern with that in a bush environment would be whether it’s practicable to bring the fibre back in again or whether it would snag on the vegetation and not respool. After using hip-chains with cotton thread to lay out lines in the bush, we were told to collect as much of the thread as possible afterwards, even though it was biodegradable. Apparently our manager had once come back to a line and found a dead ruru entangled in the left-behind thread
Have bought some of the common 4140 ones off aliexpress for further testing, I expect they’ll work. I’ll report findings here if/when I get some up and running.
Don’t have tools to test the output, other than using my oscilloscope to see the driving waveform, plus I can detect presence of output sound using my scope on another speaker (speakers act like microphones) - but none of it quantitative. Mostly use “units of rat-murdering terrier excitement” to assess.
AFAIK the “rat repellers” just make an ultrasonic racket, they don’t mimic vocalisations.
I doubt naked fibre optic would have the durability required for long term sensing! Plus a bit of an eco-nightmare. Birds are building nests with it in Ukraine now.
We’ve found LoRA has surprisingly good range, including in vegetation. Don’t need panels on the actual sensors, 3 x AA batteries can last for years. Do have some small (6W) panels on repeaters on hill tops. We are mostly using on live cage traps, but also some on a sample of our DOC box traps.
One interesting finding - in our location we can determine with near 100% accuracy when a box trap has caught a stoat from the sensor detection timing. If noctural- rodent. If in daylight - stoat.
Hi Greg
suggest you switch to using salted rabbit to get over the maggot problem, I have posted my 15 month trial from 2004/5 here before and should be plenty come up in a google search
I looked into going some ultrasonic tests but I didn’t have the hardware. Or the electronics know how really.
Also the thinking was that sounds around 50 khz or so would have a very short range and so likely not being in rats etc from very far away.
But I think the idea of devices (like an AI camera) playing a conventional sound, then detecting an animal and maybe playing a different lower volume sound to attract it further could be important.
Then you could bring animals in from large distances away.
There a lot to be tried in this area, it’s all really untested.
LoRa can last for years on 3xAA? That is good to know. Thanks! I did some rough calcs with what I could find for power draw many years ago when I first heard about it, and estimated 1 or 2 months. All the blogs about it that I could find had it on or near buildings, so I guess I wrote it off at the time for that reason.
Yeah, the fibre-optic idea is a bit out there. Fibre is just high-transparency glass, which is nearly all silicon dioxide, the same as rocks. It’d have to be laid on the ground and covered with leaf litter to be ecosystem friendly.
But unlikely to survive long, as you say.
Thanks for sharing about daytime/nighttime differences!
I might buy a rat repeller to take apart. The transducer itself might be fine, but the electronics driving it we would not want. My old 10 MHz scope should handle the waveforms OK I would think.
Christina, yes, the fibre optic was just a wild idea, and as Bluewave says, unlikely to last long anyway. Laying kilometres of PVC conduit for it is a non-starter.
Sad about the ruru - I’ve had a couple fly down tracks away from me. Don’t know what they were doing up in daytime! One had two little friends - a fantail, and one of the tit family - didn’t get close enough to see properly. Anyway, they flew down the track, stopped and looked at me for a while (the fantail came close), and then flew off towards a river. So silent.
Thanks, Dave, I’ll have a look. I have discussed salted rabbit briefly with a couple of the local DoC people - DoC sources the bait and distributes it to volunteers. I think they just see it as more work, and one said when they tried on one line it cut their catch rates. I didn’t pursue it with them beyond that. I do have a 25 kg bag of salt in my kitchen pantry…
We seem to be getting short of rabbit, and of volunteer time. Hence this thread - ultrasonic lures. Something we could leave out for a year, meaning that on most trips, we could save the re-baiting time on each trap. Might save 45 minutes a day and/or allow servicing an extra 10 traps. As long as it catches at least as many as we do now.
Well, and as well as saving time, you might be able to attract pests from further away.
I pest probably has to come within 5 or 10 metres of a trap to smell the lure I would think? Albeit rotting rabbit would probably carry for quite a way.
With audio lures, maybe pests would hear the lure 50 or 100m away?
easy does seem to dominate much of what happens. The work that was done by landcare many years ago in a pen trial said fresh rabbit was slightly better than salted but that was offset by salted rabbit having a longer effective life.
But what they did find was stoats did not like to eat salted rabbit, which doesn’t matter as it should be dead before it gets to the bait, but I tell people always remove the bait from the bush.
I have not got into the Audio lure discussion as it has all been done before and if I remember correctly I think someone has some funding to do more work
cheers
