discussion / Camera Traps  / 19 July 2021

How to dissociate the detector sensor from the camera in a camera trap surveyed area?

I want to film the reaction of a predator (wolf) attacking sheep equipped with a repellent. For that, I plan to place the sheep in a small enclosure keeping the sheep inside but not preventing the predator to enter. Camera traps are “ready to use” material so I am considering it but I am only interested in the footages that correspond to the predator-sheep interaction. I can’t just place them in front of the sheep that will constantly trigger them, empty the batteries and fill up the memory cards in no time before the predators would come…

If I organize a weak spot (a predator “gate”) in the fence from which the wolf can enter, I could trigger the cameras only when something goes through that gate. I need a camera filming the area but triggered when something goes through the “gate”. I didn’t find “ready to go” solutions so far for video making and only few options for picture making with DSLR cameras (or stop motion that could be used as poor quality film if many pictures are taken at short intervals...).

Doing this in Europe and relatively close to civilization, I can (and will) visit the material regularly and I might be able to get a phone/internet connection. Thief is a risk. For now, I won’t be in bear area or else, so I don’t expect too much wildlife damage on the material… Let's say I am quite new in all this material.

I have imagined the following (very to less)“cheap” solutions, what do you think ?

  • I place a camera trap on each side of the “gate”, filming the sheep area, but with a mirror in front of the sensor so that it redirects the detection range to the side of the camera, where the predator is forced to pass through and where the sheep won’t go. Note that an emergency blanket-like surface might be better at reflecting heat than a mirror. Plastic caps could be used to restrict the range of the sensor to.
  • I could try to "hack" the cameras: open them: unsolder the sensor from the camera, and solder it back but with long wires in between the camera and the sensor (with a potential risk of increasing resistance and therefore losing the sensor capacity?) so that I can place the sensor further away form the camera and in the direction that suits me while keeping all the feature of the camera trap.
  • I link any sensor that suits me (and that are available, ideal laser beam I guess for my situation) to an Arduino and connect the Arduino to the camera trap to commend it… I heard it might be possible but I am afraid that, by the time I am ready, it is the end of my research period…
  • I use a ready to use sensor (see link below for example) and plug it to a camera and try to find a way to trigger video mode and not picture, or many pictures (i.e. stop motion)… I could even put a remote control bellow a board on the floor of the gate. The passing predator, by stepping on it will trigger the camera (switch of will just happen when the camera has no more battery and that’s okay…)
  • I think they are DIY camera traps makers where, basically I could learn to do my own purpose-specific camera from scratch… but to have a reliable camera with solid and quality components… I guess you end up with something expensive and time consuming when you do this for the 1st time (and with waste and errors…).
  • Finally, maybe the most reasonable solution and best quality/prince: I could place only one connected camera trap monitoring only the gate and sending me an alert when the predator gets in. I place a surveillance camera above the sheep enclosure (with a huge battery most probably?!) recording 24h/24h and keeping 24h footages only. When the wolves gets in, I will need to go as soon as possible anyway. The camera trap will give me the time at witch to look on the surveillance camera footage and let me save the relevant part only… I know nothing about surveillance camera and I waste time online sorting out the solid information from advertisement discourses, I guess I should better visit a multimedia store to start with…

I am curious about what you think and I will keep you updated with what I do in the end! Thanks


PS: I have explored, for example, the following options (but often imagined for photographers and not scientific video making):

I'm an engineer and product designer working on wildlife conservation technology.
Group Curator
WILDLABS Event Speaker

Hi Matthieu. 

We're experimenting with adding alternative triggers to existing consumer camera traps. We'll be publishing more info in regards to that since it sounds like you have some specific triggering requirements for your camera traps. You can also contact me via private message if you have questions.


I think it would be technically possible. Something like the camera being put to sleep, and only activated when an outer sensor is triggered. I would be more worried about getting ethical approval for such a study where the aim is to have a live domestic animal being attacked by a predator in a confined space.

Matthieu Chastel
University of Antwerp
PhD sutdent Wolf-livestock cohabitation _ Predator aversion conditioning

Hi Egil, indeed, ehtcial approaval is of course needed and I will ask for it for sure! (But note that it is hard to explain farmers that I need ethcial approuval for that project aiming at reducing attacks, while they get attacks every other weeks despite fences, livestock guarding dogs and/or shepherds !!).

My guess is that the camera triggering will prove to be far less of a challenge than getting ethical approval for penning livestock where predators can reach them. If you have such a high rate of wolf attacks in free-ranging flocks then you can directly measure the decrease in rate of attacks in flocks that have the repellent vs those that do not.