How to detect hibernating hedgehogs

jims

Senior Member
I've been debating with myself if I should mention this...but here goes. If it weren't for the WW2 hedgehogs this conversation would probably be quite different.
Search (WW2 hedgehogs) on google images to see what I mean.Jims
 

SteveDee

Senior Member
.....that's similar to how I started nearly 20 years ago...
Maybe we should have started 20 years ago when hedgehogs were common here. I'm confident we don't/won't have a resident in our box, because we would have seen the usual evidence dotted around the garden during autumn if there had been any around.

Five or six years ago we had a "hedgehog-cam" (a Maplin iR camera inside a baked-bean tin). The hog used to visit the cat food that we provided at the same time most nights, but didn't eat much of it compared to the mice, rats, cats & slugs. We always seem to encourage the wrong diners.
 

techElder

Well-known member
Thanks, Bear. That makes a difference.

The original request is still unresolved.

I am now at a loss about how to tell when it is occupied.
-X- Counting the comings and goings. You would be counting visitors while the "hogs" are hibernating.
-X- Weight by cell or switch. They pack so much in that the space would be always compressed.
-X- Light. Too much junk in the space.
-X- Temperature. Hibernation means "no" relative temperature.
-X- Sound. They stop making noise while hibernated.
-X- Photos of naked female "hogs". Temperature might now work, but for only half the population. ... Well, mostly half.
-X- XRAY. Probably cause mutant "hogs" in the future. PICAXE doesn't have the power to analyze films.
-X- Eddy current. "Hogs" are non-ferrous.

Here's a thought. Don't laugh. At least not out loud.

Since the critters want to build a home in the box by bringing in other material and make their own space, could you pre-form the space for them so they wouldn't bring in "stuff?" I'm imagining Styrofoam cutout areas within the walls of the box with a path to each "home."

Then you have a place for sensors within the Styrofoam.

OK, BB, you're getting red in the face from holding in your laughter. :D
 

rq3

Senior Member
Having recently purchased a hedgehog hibernation box, and mounted it in the garden, I am now at a loss about how to tell when it is occupied. Initial thoughts about installing a PICAXE based wireless telemetry unit drew a blank when I realised that during hibernation hedgehogs drop their temperature to match the ambient environment and only rarely wake up and move about during the winter. What then to monitor?

I would therefore welcome any ideas for a non-invasive approach to detect whether a hedgehog box is occupied. Thanks.
Totally off the wall thought, since just about everything else has been proposed. Gas sensors. There are cheap electrochemical sensors for lot's of stuff. CO2, O2, ethanol, methanol, formaldehyde, hydrogen sulfide, etc., etc. Do hybernating hedgehogs, um, pass wind? Any other odd physiological emissions? Hybernating bears sweat phenol compounds, and stink.
 

MFB

Senior Member
Thanks, Bear. That makes a difference.

The original request is still unresolved.



-X- Counting the comings and goings. You would be counting visitors while the "hogs" are hibernating.
-X- Weight by cell or switch. They pack so much in that the space would be always compressed.
-X- Light. Too much junk in the space.
-X- Temperature. Hibernation means "no" relative temperature.
-X- Sound. They stop making noise while hibernated.
-X- Photos of naked female "hogs". Temperature might now work, but for only half the population. ... Well, mostly half.
-X- XRAY. Probably cause mutant "hogs" in the future. PICAXE doesn't have the power to analyze films.
-X- Eddy current. "Hogs" are non-ferrous.

Here's a thought. Don't laugh. At least not out loud.

Since the critters want to build a home in the box by bringing in other material and make their own space, could you pre-form the space for them so they wouldn't bring in "stuff?" I'm imagining Styrofoam cutout areas within the walls of the box with a path to each "home."

Then you have a place for sensors within the Styrofoam.

OK, BB, you're getting red in the face from holding in your laughter. :D
Thanks Tex, very good summary of the suggested technique and reasons why they probably would not work. Quite like the latest idea about using an electronic nose but would imagine there would be quite a complex mix of fumes in the den (decomposing vegetation ext).
 

BeanieBots

Moderator
@Tex. Hogs are very fussy about where they hibernate and often do it next to or under any human supplied box. They also come in quite large range of sizes. Sometimes there will be more than occupant. (four is the most I've ever seen together). So, a pre-defined space is unlikely to be very appealing but I've never tried it so who knows?

@rq3. You might be onto something. Hogs are very smelly but they all smell different depending a lot on their location and diet. Also, the smell varies and can be used to determine some varieties of parasite they might be hosting. Unfortunately, hogs have not been studied in depth like many other creatures have so there is no information like there is for bears. I know Reading University are doing a lot of studies relating to Hog DNA so I will try and contact them to see if they have any information about 'emissions'.
Do they pass wind? You bet they do! When feeding a juvenile, I was half expecting to get a little damp, I did not reckon on getting an eyeful of solids. Doing the sums that equates to a human being able to fire a 'lump' over 25 foot!
 

Circuit

Senior Member
I'm sure everyone knew you were only kidding.
Hogs are very much in focus in the UK at the moment. Unfortunately, this is because of their rapid decline in numbers. It is believed that there are only one million of them left. Although not yet on the official endangered list, I doubt it will be long before they are. In the sixties and seventies, almost every domestic household with a garden shed had a hog living under it. More recently, hardly any households have seen one. We have done several presentations at local schools and hardly any of the kids have ever seen one, which is really rather sad.
We loan out footprint tunnels and trail cameras to interested parties to see if they have any hog (or other) activity in their gardens. It was amazing how much uptake there was on this and we still have a waiting list.
Hibernation box occupancy is not as simple as it sounds which is why my current endeavours are based around RFID but even if your hogs have been chipped (obviously, only those that have visited the vet are) it is still far from job done. Just putting a scanner on the side of the box does not work. The hog must actually pass through the coil. I've been in contact with a RFID manufacturer and they have produced an "extra sensitive" version but even that struggles to get through the layers of a damp nest to the chip inside the hog. (and yes, it is driven by a PICAXE for the ID decode and data logging with "send text on activity" soon to be added.)

Meanwhile, keep the ideas coming. This is of national interest, not just us guys! Experts up and down the country have been asking the very same question.
Totally fascinating in all respects. But tell me, do you have problems with visiting badgers? I own a small wood and hedgehogs were often to be sighted. Then badgers built a sett in a neighbour's garden (all the gardens are rather large around here) and we watched the demise of the hedgehogs...literally! Badgers are the one predator that can open a rolled up hedgehog. My niece and nephew used to come back from walking the wood with what they referred to as "hedgehog shells" - all that remained after the badger had partly unrolled the hedgehog and eaten it from the inside to the out. Badgers are increasing rather too successfully in the UK at the moment and one theory is that this increase is inversely proportional to the hedgehog population.
 

BeanieBots

Moderator
Badgers DO eat hedgehogs and they also both compete for the same food source. Badgers will only eat hogs when food is short.
There is plenty of video footage to show badgers & hedgehogs eating side by side, so no, I don't think the increase in badgers is responsible for hedgehog decline.
The main reason is believed to be agricultural changes and the fencing off of domestic gardens. A hedgehog requires 12-15 gardens to forage. Many gardens these days are isolated by fencing and the hogs cannot roam freely. Also, nice neat gardens with no leaf litter and/or log piles offers no food and/or places to nest/hide.
Seen many thrushes recently? They suffer the same problem as hedgehogs. They both eat food poisoned by slug pellets and then die of the poison themselves.
As usual, the biggest reason for decline of almost anything is us. Decline of the urban hog is almost entirely due to reduced access. During our recent surveys we visited many gardens where the residents had no sightings in their gardens. One simple question was all it took. "How would a hedgehog get into your garden?".

Anyway, I could go on & on about hedgehogs but there are plenty of other forums for that.
Meanwhile, any other contributions regarding hibernation detection are always welcome.
 

julianE

Senior Member
Perhaps use microwave to detect a hog.

http://www.ebay.co.uk/itm/HB100-Microwave-Sensor-10-525GHz-Doppler-Radar-Motion-Detector-for-Arduino-/261474644988?hash=item3ce11a73fc:g:aSwAAOxyi-ZTaucx


The detector can be mounted on the side of the box from the outside. Hedgehog, being mostly water, would absorb the microwave signal whether hibernating or awake.
Provided that the nesting material is dry it should not interfere much with the microwaves.

It's not a very simple solution but it's a complicated problem. I have the sensor but haven't had much time to work with it. There is a goodly amount of information on the sensor particularly over on the parallax forum.

Good luck on a very cool project, I do remember a time when hedgehogs were plentiful in Europe, sad to hear of the decline.
 

AllyCat

Senior Member
Hi,

Yes, I think the problem with that particular sensor is the words "Doppler" and "Motion"; it outputs a low audio frequency proportional to the speed of movement. If my calculations are correct, 100 Hz corresponds to about 3 mph (i.e. path length changing at 6 mph) at 10 GHz. Also, I think the assumption that the general environment will remain "dry" may be rather optimistic.

However, a "microwave" solution just might be possible. A microwave oven (that is optimised to heat water) uses a frequency near to 2.4 GHz, which is very similar to the frequency used by WiFi and Bluetooth (not a coincidence). If one puts two cups of water in a microwave oven, then each heats at only about half the rate of a single cup.

So, one might put a "dummy" hedgehog (i.e. the equivalent volume of water) in the "house" and measure its temperature rise (relative to ambient). It would probably be necessary to metallise most of the house to make a "microwave cavity" and then a typical WiFi transmitter might have sufficient power to heat the hog(s) efficiently. Of course we (or at least most of us) don't want to "cook" the hog, nor even heat him/her enough to affect hibernation, so the temperature rise would need to be much less than 1 degree. Perhaps a pair of DS18B20s could detect this, but a custom differential thermometer would be better.

However, I still believe the most promising method so far is to continuously "monitor" the entrance and exit. I'm drafting a more detailed proposal which I hope to post in due course.

Cheers, Alan.
 

julianE

Senior Member
I'm liking the LIGO method, I was just having a conversation with a physicist friend about gravity waves, for years I thought gravity acted immediately was surprised to find out it propagates in waves like everything else.

I will read up about the sensor I linked, for some reason I thought that it could be made to work with motionless objects as a range finder tho the doppler method is the prefered.

I'm not sure how the more sophisticated wall stud sensors work, I know that most use capacitive method of detecting a stud but there was an innovation to use radar technology for detection, could be another venue to try.

I do like using a WiFi or bluetooth transmitter for detection, very elegant.
 

MFB

Senior Member
Again, amazingly original ideas. However, I'm not totally comfortable with bombarding animals with even low power microwaves.

Could an inductive loop around the den (pulsed intermittently to save power) be used to detect a hedgehog? Should be relativly simple to build a loop and see what effect, if any, sticking an arm through it had.
 

AllyCat

Senior Member
Hi,

Yes, I'm often entertained by the number of people prepared to wander around for hours on end with a >1 watt microwave generator clasped to their ears (aka a mobile phone). ;)

I think an induction loop can only work with conducting materials not skin, bone or blood, etc.. I did once consider "tagging" material by using Nuclear Magnetic Resonance for a "consumer" project. But when you do the maths, the required magnetic field strengths (or the resulting radio frequencies) are horrendously high.

Ultrasonic detection of heart or lung movements might be a possibility, but I believe the sensors need to be "coupled" into the body using direct contact and oil.

Cheers, Alan.
 

rq3

Senior Member
I'm liking the LIGO method, I was just having a conversation with a physicist friend about gravity waves, for years I thought gravity acted immediately was surprised to find out it propagates in waves like everything else.

I will read up about the sensor I linked, for some reason I thought that it could be made to work with motionless objects as a range finder tho the doppler method is the prefered.

I'm not sure how the more sophisticated wall stud sensors work, I know that most use capacitive method of detecting a stud but there was an innovation to use radar technology for detection, could be another venue to try.

I do like using a WiFi or bluetooth transmitter for detection, very elegant.
The more I thought about this, the more I like your capacitance method, vs. my chemical sniffer approach. I know that it is possible for the Picaxe "touch" routine to be exquisitely sensitive (8 inch detection range) and with thought it can be made self calibrating. Perhaps a hybernation box with a grounded metal plate floor, and a metal plate internal roof connected to a "touch" pin could work. I've actually held a hedgehog. It's a spiny little beast roughly the size of my closed fist. But it's a water filled animal, and assuming (dangerous, I know) that the nesting material it drags in is relatively dry, it should give a pretty hefty capacitance effect when sleeping between two capacitor plates. Even if the plates are stuffed with dry leaves and grass.

To the OP, how big is the hybernation box? If you've said, I apologize.
 

julianE

Senior Member
I read more about the microwave sensor and it can be made to output a voltage proportional to the rf signal received but it does not seem to be very reliable. As mentioned, it's really meant for doppler so needs motion.

I've been reading about theremins and that would be another way to detect an animal. It works by hand motion changing the capacitance of a tuned circuit, it is able of detecting picofarad capacitance change. Might be too complicated a circuit.

The "touch" pin circuit looks to be the way to go.
 

SteveDee

Senior Member
...However, a "microwave" solution just might be possible...
Strictly speaking you don't have to generate microwaves. Anything (or creature) containing water emits microwaves, and you can use this radiation to determine temperature in a completely passive way.

A few years ago I worked on this project: http://www.loma.co.uk/lo_temperature_measurement.shtml
...the only problem is that the hedgehog would have to be housed in a sealed box.
...Oh, and the Maths are horrendous.
 

julianE

Senior Member
I know that it is possible for the Picaxe "touch" routine to be exquisitely sensitive (8 inch detection range) and with thought it can be made self calibrating. Perhaps a hybernation box with a grounded metal plate floor, and a metal plate internal roof connected to a "touch" pin could work.
I made a quick mock up with two 7 cm aluminum plate squares feeding an 08M2 touch pin C.2. It's very sensitive, detected my hand with ease and to test it I also placed a small block of maple between the plates and it certainly detected that as well. I did notice that my fluorescent desk lamp had a massive effect but since the box will be sitting outside i would think interference would be minimal.
 

oracacle

Senior Member
i have only had a bit of a scan through the rest of the posts here, however while watching rude-ish tube this morning I saw a person playing a theremin. Now I am no expert, but I would think that a modified version could be used to detect the presence of a hog.

coming to think about magnetism the clever people at the VLT use a device that works on the same principle as a metal detector to keep the mirrors aligned in the main reflector. something like that maybe could be used to detect change of mass on the floor. they manage to keep the mirror aligned to ridiculous accuracy, although I am not sure how the system works and may need some metal surface to work
 

MFB

Senior Member
I think the theremin/touch pin technique is looking the most promising at the moment but changes in humidity may cause measurement issues. However, provided I look for relative changes (rather than a absolute trigger value) this approach might just work. If only I could find a cooperative hedgehog to conduct some preliminary tests.
 

rq3

Senior Member
I think the theremin/touch pin technique is looking the most promising at the moment but changes in humidity may cause measurement issues. However, provided I look for relative changes (rather than a absolute trigger value) this approach might just work. If only I could find a cooperative hedgehog to conduct some preliminary tests.

How about an orange on a stick? Roughly the same size and water content as a hedgehog?
 

AllyCat

Senior Member
Hi,

As I said in posts back in page 3, IMHO the "touch" inputs are the way to proceed. BUT beware of the limitations of a capacitive measurement. Firstly, Pure (distilled) water is indeed an interesting dielectric, but even tap water, let alone blood, urine, digestive juices, etc. are best considered as an electrical conductor. So the measurement is basically of a series of capacitors between your (or the hogs) skin (including feet) and the ground or touch plate, etc.. Whether the PICaxe earth is connected to "real" ground may make a very significant difference.

Furthermore, there will be enormous long term variations or "drift" due to changes in temperature, battery voltage, humidity/dampness, etc.,etc. Therefore we can only expect to detect rapid changes such as entrance/exit or bringing "bedding" materials in, etc., so the detector needs to operate continuously 24/7. Also, one of the (few) characteristics of the hog that we do know is its approximate weight, so IMHO the "detector" should certainly include some form of weight detection.

Unfortunately (for me) it appears that although the forum keeps an "auto-save" copy of draft posts for some hours (or maybe days), they eventually disappear, so my main proposal document has been lost. I don't feel inclined to type it all again (maybe a relief for many) so I'll just summarise the main points as:

+ A PICaxe 14M2 (maybe 20M2) requires about 600 uA, so at least 4 months from a standard set of 3 x AA Alkaline or NiMH cells. Also an EEPROM (socket) for logging and/or it makes a useful I2C "expansion interface".

+ Three spaced metal hoops over the entrance, the central one to the PICaxe (and maybe real) Ground, the other two to touch inputs to detect in/out movements.

+ A circular floor "suspended" on three "compression springs" at 120 degrees around its circumference, above a "ground" floor. Both made conductive (e.g. chicken wire or cooking foil) probably in three segments, driving 3 touch inputs to indicate floor loading (weight) and possibly location. The PICaxe probably in the middle with the whole assembly stuffed in a bin bag with an "umbilical" cable to the hoops and maybe a "beacon" on the roof. Probably also measure temperature(s) and humidity because it's "easy" and might give some useful "background" data.

+ If it's a reasonably secure environment, a module on the roof (e.g. a Cannibalised Solar Garden Light) could provide Solar Charging, Radio Transmitter, Daylight Detection (e.g. to synchronise the PICaxe "time"), maybe even a camera, etc.. If you don't want to build a custom radio receiver, then emulate or "hijack" a low-cost wireless temperature-humidity / weather station.

It's probably too late for this winter, but many of the above features are similar to some of my current projects, so I may have more definitive detail to offer in due course. But sadly, I haven't seen a hog in my garden for many years.

Cheers, Alan.
 

BeanieBots

Moderator
Well, I've got plenty of residents more than willing to take part in trials.
On the weight issue, they can lose up to 2/3rds during the full hibernation. This is gradual, so self calibration might get around it.
Moisture will be a bit more tricky. Don't forget, they also 'expel' a considerable amount of 'liquid' in one hit from time to time. This could have some interesting effects on any ground based capacitive plate. Two plates at the side above the 'water line' might be an option.

At the moment, the UK is experiencing a record high temperature winter. Only a handful of hogs have started hibernating and even those that have still get up around once a week for a few days before having another week's nap.

Hopefully I'll be able to try out the 'touch' method over the Xmas break. If so, I'll report back but I think the biggest challenge will be the self calibration because I am expecting to see a vast range due to humidity, urination and damp/wet bedding.

So far, the only viable option I can see is continuous monitoring (probably by motion sense IR camera) of entry/exit.
Some great ideas have been submitted but I'm not convinced they are as simple as they sound in reality.
 

MFB

Senior Member
Having willing residents should prove a great advantage and I look forward to reading the results of your experiments. Happy Christmas everyone!
 

AllyCat

Senior Member
Hi,

Yes, the EPIC appears to have two different modes of application. The skin contact method is able to detect electric signals (e.g from the heart) but the cooperation of the hedgehog seems problematic. ;)

The other is a (capacitive) movement detection mode which measures changes in the capacitance (to "ground") of a plate attached to its input. I couldn't see it explained whether it's the changed "dielectric constant" of the intervening material(s) which is sensed or just the movement of any "conductors" in the nearby field. But I suspect the latter because the human (and no doubt a hog's) body is primarily an electrical conductor. If it were not, then electric shock wouldn't be a hazard. :)

Note that the EPIC fundamentally has a hardware band-pass filter characteristic (lower corner frequency = 0.2 Hz*) so can respond only to changes up to a period of a few seconds. Therefore, probably not very different than can be (easily) achieved with a PICaxe adaptive "touch" input. "Adaptive" software may sound complicated but basically it can just compare a new measured value against a "rolling average". That could be done by maintaining the average in a "circular buffer" of recent values, or simply something like average = average * 99 + newvalue / 100 .

* The latest version of the "movement" data sheet quotes the low frequency corner as 30 Hz which is over 100 times "worse" than the earlier data. :confused:

Cheers, Alan.
 
Last edited:

hollyblue

New Member
Did you have any luck with the monitoring?

Hi,
I stumbled on this thread whilst researching the same subject - wanting to monitor a new hedgehog box.

Good discussion which seemed to cover and reject all the ideas I'd considered and more.

Hence I'm bumping the thread to see what progress there might have been since 2015.

Cheers,
Kelvin
 

MFB

Senior Member
Hi,
I stumbled on this thread whilst researching the same subject - wanting to monitor a new hedgehog box.

Good discussion which seemed to cover and reject all the ideas I'd considered and more.

Hence I'm bumping the thread to see what progress there might have been since 2015.

Cheers,
Kelvin
Sorry, after all the negative feedback I just lost the will to go on. I hope you make better progress.

Mike.
 

AndyGadget

Senior Member
A low-tech solution using a Picaxe :
One of the popular designs for a hedgehog house / hibernation box is with an entrance tunnel as per http://www.gardenersworld.com/how-to/diy/how-to-make-a-hedgehog-house/. My suggestion is a pair of (weatherproofed) opposed microswitches on top of the tunnel with a flexible rod protruding down, stiff enough to flip a microswitch but flexible enough to let a hedgehog through. One microswitch triggering is hedgie entering, other switch is hedgie leaving. Picaxe acting as a switch-triggered bistable. The switch mounting needs a bit of thought but doable, I think.

Job for the weekend : Make a couple of hedgehog hibernation boxes.
 
Top