How to detect hibernating hedgehogs

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MFB

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.
 
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oracacle

Senior Member
load cell to monitor weight.
you may have to take into account changes that may happen with various environmental variable such as wind and rain.
hedgehog is normally around 250-600g so should be able to detect that.
they should also still be emitting IR radiation
also look into detecting there breathing using air sensor - I have no idea where to start on this, but its an idea

never used a load cell myself but I ma sure someone here has.
 
techElder

techElder

Well-known member
What about snow load? Or something similar? That would be a problem with weighing the buggar.

What about using a broken beam detector? Only turn it on occasionally to save power.

Or you could do what we do with hog traps. We put another floor in the cage/box that pulls a cable that trips the door closer.

You could put a switch under the floor (the floor is hinged on one end) that triggers your hedgehog "alarm".

PS. What the heck is a hedgehog, anyway, and why are you providing them a home in winter?
 
O

oracacle

Senior Member
you could use a false floor with a load cell. environment issues would be negated then.

hedgehogs are small prickly fella that hibernate over winter. they are in decline in the UK (don't know of they reside anywhere else), so providing them with a safe heaven that gives them safety from things like foxes will help their numbers.
 
S

SteveDee

Senior Member
Interesting question. I have also just installed a DIY hedgehog box for the first time.

Hedgehogs tend to be noisy sleepers during the summer, but I doubt that they make any noise during hibernation (otherwise a microphone might work). For the same reason they probably don't expel much carbon dioxide or methane. And (according to Wikipedia) their temperature drops from 30-35C down to about 2C when hibernating.

A camera or photocells within the box would be a waste of time as they fill the box with dead leaves.

A strain gauge might work, if the weigh-platform covers the whole area where the hedgehog is likely to sleep.

Sad to say that the best solution is probably to fit a hatch that you can open and take a look! But not much scope for a Picaxe.
 
M

MFB

Senior Member
Thanks for the very useful suggestions. I might go for the hinged floor approach, but activating a microswitch rather than the more complicated load cell. This could just activate an LED on the roof or send "hedgehog/No hedgehog" information via a PICAXE based wireless link. Unfortunately, its not possible to had an inspection panel to the dome version of the RSPB designed den.

I quite agree that video camera would not help, because it would just look like an episode from the old BBC "Rag, Tag & Bob tale" children's series (for those that can remember that far back). The pile of leaves effect would also make IR temperature or beam detection problematic.
 
techElder

techElder

Well-known member
If these "hogs" are like our hogs (most likely not), then the floor really needs to be attached somehow; thus the hinges will do this.

If you are going to use switches, then you must allow for the floor getting jammed with "fill the box with dead leaves".

It is still a neat engineering task.
 
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binary1248

Senior Member
My granddaughter had one for a pet. They are like a tiny porcupine. You can hold one in the palm of your hand. If you startle one (a pet) it snaps out it's quills (brings them to near vertical from its body) and they can prick you, it hurts but not enough to puncture the skin. I found out the hard way when I went to pick up my granddaughter's and surprised it. The 'hog' part of it's name is misleading, as it doesn't look any thing like a pig/hog.
 
B

BeanieBots

Moderator
I was very intrigued to see this thread as my wife and I have been running a small home hedgehog rehabilitation centre for the last 20 years.
Knowing the occupation of hibernation boxes has also been an issue for us.
When not hibernating, a simple temperature sensor works fine. Just compare to ambient.
We have several boxes with camera + microphone. During the summer, the nesting material is light and the camera can be used.
As soon as weather turns colder, the nesting material gets crammed in and the camera is of no use. The microphone can be used when they are awake but it can't detect the breathing of a hibernating hog.
More recently, all the hogs that we receive from local vets and/or rescue centres have been fitted with RFID tags.
In collaboration with a local rescue centre, I am currently developing an RFID system that will send a text via a GPRS module every time a tagged hog passes through the sensor.
The challenge with RFID is getting any sort of range.
I was hoping to get a system that would work when the hog passed over/under or past the antenna but this has proved to be unreliable.
So, far, the only reliable system is one using a large coil antenna and getting the hog to pass through it.
This would work in a hibernation box if the coil was placed such that the hog was in or close to the centre of the antenna.
I will be fitting coils to all our boxes soon but they will be located around the entrance tunnel to detect entry exit rather than occupation.
Two coils could be used to determine which direction the hog went in but that would be a rather expensive option.

@Tex .. A hedgehog is one of the few things we have that you guys don't!
 
premelec

premelec

Senior Member
BB - Tex has armadillos! I suggest wobble plate with reed switch or hall effect sense unit - load cell seems overly complicated...
 
H

Haku

Senior Member
Great little creatures, occasionally see them roaming around a local cul-de-sac when walking home at night. Some can be quite noisy.

Could you use a PIR sensor if it's sensitive enough? Get the Picaxe to store the trigger time so you can see in minutes/hours/days the last time it was tripped.
 
M

MFB

Senior Member
Again, thanks for the comments. It seems there are lots of techniques for detecting hedgehogs in a den during the summer (temperature, pir, microphone etc ) but during hibernation not much is happening. Currently plan to go with a hinged floor activating a microswitch but welcome alternatives..
 
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oracacle

Senior Member
depending on the entrance you could use a 2 IR beam type setup. you would need a tunnel for them to enter through and the direction could be detected from the order the beams are broken - this would give you a reason to use a picaxe.
 
M

MFB

Senior Member
oracacle said:
depending on the entrance you could use a 2 IR beam type setup. you would need a tunnel for them to enter through and the direction could be detected from the order the beams are broken - this would give you a reason to use a picaxe.
Click to expand...
I often find reason an inadequate tool.
 
J

johndk

Senior Member
Seems no one has mentioned the possibility of a capacitive "touch" sensing. Seems like that could be made to work, especially during the cold months when humidity will be low. I'm thinking perhaps a touch pad on the bottom of the box.

I know they're not the same, but here in Maine we have groundhogs (wild), about the size of a large cat. They're farm pests because of their appetites and their burrowing ... but they are good eating!

John
 
J

jims

Senior Member
johndk...down around Cape Elizabeth we called them woodchucks and the sure liked our squash. JimS
 
M

MFB

Senior Member
johndk said:
Seems no one has mentioned the possibility of a capacitive "touch" sensing. Seems like that could be made to work, especially during the cold months when humidity will be low. I'm thinking perhaps a touch pad on the bottom of the box.

I know they're not the same, but here in Maine we have groundhogs (wild), about the size of a large cat. They're farm pests because of their appetites and their burrowing ... but they are good eating!

John
Click to expand...
Some people in the UK do eat hedgehogs. I understand the trick is to cover them with mud and bake them in a open fire, then crack open when nicely done. I hasten to add that this is not my motivation for buying a hibernation den!
 
H

Haku

Senior Member
MFB said:
Some people in the UK do eat hedgehogs.
Click to expand...
Too many years ago when I was a kid I was given a pack of hedgehog flavoured crisps, they tasted horrible, probably because they weren't actually hedgehog flavoured, just flavoured crisps by a company called hedgehog.
 
A

AllyCat

Senior Member
Hi,

IMHO an "analogue weighing system" would be a superior solution because adaptive software can discriminate the arrival/departure of one or more inhabitants from any "background" effects such as the addition of debris or bedding materials. Also, a (micro-) switch based method is likely to need careful mechanical design and calibration of the threshold switching weight.

However, a conventional "load cell" may not be needed. I don't think that a single "Touch" pad would detect the addition of a small "body" above it, but I envisage a variable "parallel plate capacitor" in the form of a "mattress" covering the whole floor. The compressible dielectric might be plastic/rubber foam or even straw, with "sheet" conductors each side made of metal(ised) foil or a thin wire mesh/grid.

I'm using a similar principle to detect a valve open/closing. My "capacitor" is two metal plates a few cms in area and a few mm apart (with air inbetween). The PICaxe can detect a change in the spacing of around 1mm (a difference of less than 1pF). Of course there may be long-term drift in the Touch value, but a "step change" (arrival/departure) over some seconds or minutes could be easily detected.

Cheers, Alan.
 
S

SteveDee

Senior Member
My box has a floor, an entrance hall & a bed-sitting room.

I could add photo-cells inside the hall, but wouldn't be able to tell whether it had been tripped by a hedgehog or a rat!

HedgeHogBox.jpg
 
A

AllyCat

Senior Member
Hi,

JimPerry said:
So no base as the description says the little critters are free to dig down :confused:
Click to expand...
MFB said:
I might go for the hinged floor approach, but activating a microswitch rather than the more complicated load cell.
Click to expand...
My suggestion was really related to MFB's comment above from page 1. The "tunnel" entrance might be amenable to multiple "touch" sensor hoops and a small PICaxe, but like any sequential optical beam break method could become confused by "indecisive" movements or unexpected visitors. However, a simple "floor load" measurement a few minutes later could help to give confirmation of occupancy. I presume hedgehogs are not as destructive as squirrels. :(

Cheers, Alan.
 
hippy

hippy

Technical Support
Staff member
As AllyCat suggests, you could perhaps go for multiple sensors; a light beam detector or similar to detect ingress and egress, a pressure mat or load cell to determine occupancy, and a PIR to monitor activity.

From the order and timing of events you can probably determine if it is a hedgehog which has come in and hibernated, one which has come in and is active, or one ( or something else ) which has come in and then left.
 
S

stevesmythe

Senior Member
Not a Picaxe solution but I'd go for a miniature infrared CCTV camera connected back to the house via PoE network cable (or by ethernet over power (Powerline) if you've got mains power nearby). There'd be no uncertainty over whether there is an occupant and, if so, what it is. The other solutions suggested seem to involve quite a high degree of uncertainty.
 
B

BeanieBots

Moderator
All of our boxes contain IR cameras and microphones. Trust me, it's not a viable method of detecting occupation during hibernation.
I also have my doubts about any form of pressure sense because when hibernating they cram as much 'stuff' into the box as possible. It's very difficult to dig one out because it is so tightly packed and pressed firmly against all sides.
I've tried a pair of IR sensors along the sides of the entrance tunnel. This worked for about a week before they became completely blocked by grime and assorted insects. After a few months, mice had chewed the cables and that idea was completely abandoned. Hedgehogs themselves are not very destructive but they make a LOT of mess and can (and do) 'deposit' six inches up a wall and in vast quantities. Enough to block any form light sensor. This is one of their mechanisms to prevent 'others' such as rats from entering, so I don't think false triggers from rats will be an issue once it's occupied.

The capacitive approach sounds the most hopeful. It would need to be adaptive much like the way a PIR sensor works but over a much longer period (perhaps days) to overcome the capacitance change in the bedding as it changes with humidity. If I get a chance, I'll have a go at that approach with some of our current residents to see if it's viable. One of their other habits is peeing in the box. This could be an issue for a capacitive method but keeping the sensor above ground level should help.

@Steve, nice looking box but is that chipboard? If so, it won't last a season before it crumbles to nothing.
Even marine ply takes a good beating with frost, water, sun and urine cycles.
 
M

MFB

Senior Member
I'm always impressed by the level of advice on this forum and this thread is no exception, thanks.

BeanieBots seems to have unique expertise and has confirmed my conclusion that detecting a hibernating hedgehog is by no means a simple task.

Regarding the rather unkind suggestion from The Colonies, about just trapping and eating them, I would have to run that past my wife first.
 
B

BeanieBots

Moderator
I wasn't going to give Tex the pleasure of biting!
I've heard that Gypsies have been known to eat them but I doubt they make a good meal. Very little meat and all those spines to remove.
Also, they're at their fattest just before hibernation. This is also when their metabolism is at it's lowest. Hence, their guts will be full of what they've eaten. (They're insectivores).
Most are riddled with all manner of parasites too, so be sure to cook thoroughly before serving!
 
techElder

techElder

Well-known member
Actually, I like fuzzy little creatures.

So, I'm thinking that it is probably better to just go with the old ways and provide the space for them to hibernate and next year see if you have more of the little spiked critters.
 
S

SteveDee

Senior Member
BeanieBots said:
...@Steve, nice looking box but is that chipboard? If so, it won't last a season before it crumbles to nothing....
Click to expand...
Yes it is, but it only has to last until Easter to save my marriage! (Basically I'd promised all summer to make a hedgehog hibernation box. Then one Sunday at the beginning of November I had an ultimatum, and had to make something real quick using whatever I could find in the garage).
But I'm confident that the metal roof will provide enough protection for the next 4 months.
 
B

BeanieBots

Moderator
Texasclodhopper said:
Actually, I like fuzzy little creatures.

So, I'm thinking that it is probably better to just go with the old ways and provide the space for them to hibernate and next year see if you have more of the little spiked critters.
Click to expand...
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.
 
B

BeanieBots

Moderator
@Steve,
Ha,Ha.....that's similar to how I started nearly 20 years ago.
We now have a rolling residency of around 12 hogs. A dedicated out-house. 3 x 12 foot outside soft release areas. 8 x hardwired IR cameras. About to purchase a microscope so we can do our own poo samples. (lovely!).
Not to mention the totally odd lifestyle. A non weaned hog requires feeding on the hour every hour 24/7. So you get 20 mins sleep every hour for the 3 weeks it takes to get them off the bottle. Just as you get them having 4-5 hour breaks, another one comes in!
You might think it gets a bit easier now that they are starting to hibernate but no. It was a very mild autumn and there are a lot of juveniles that are too small to hibernate, so they need to be kept awake and fattened up ready for release in the spring.
 
The bear

The bear

Senior Member
@Steve,
On the marriage front, stick a scrubbing brush in the hog house. Come spring get a hedgehog from your local nursery, pet centre or friend,
and present (Give) it to your wife. Job done.
Note to Tex, I do enjoy your input. I was thinking along the same lines.

Regards, Bear..
 
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