Can animals hear camera traps?
Camera traps in their modern form are still relatively new and are generally thought to not disturb wildlife at all.
However, a very interesting scientific paper was published in late October this year, titled 'Camera traps can be seen and heard by animals'.
The title says it all; this was a study which sought to discover firstly if camera traps do give off any sound outside the frequencies humans can hear, and whether any animals can hear these frequencies. They also looked at whether some animals may be able to see the infrared light emitted by the LEDs.
The study found that camera traps do emit a high frequency sound, although very quietly. This sound was more prevalent when the batteries were low too. It should be noted though that some camera trap models were not tested - including Bushnell and Ltl Acorn.
They also found that the frequency emitted can be heard by 'most mammals' - among those animals is the red fox.
This is the first time anyone has proved that some animals can actually detect camera traps purely through audio signals.
And it made us think; has a fox, or any other animal, appeared to detect one of our cameras despite it being supposedly undetectable? One video immediately sprang to mind, captured this year in 'Kennedy Wild Bird Food Forest', as part of our Yorkshire Pine Marten Project;
The fox clearly doesn't like our camera trap, once it realises its there, and quickly turns and leaves. We initially thought it must have caught a slight reflection of itself in the no-glow IR cover with a the dusk light lingering; but perhaps it was picking up on the high frequency sound emitted...
That kind of reaction is quite rare and not something we see very often. In fact a vixen passed in front of this camera trap before this male and didn't appear to notice the camera at all.
Although many mammals may be able to hear camera traps, the study notes that with the constant background noise in in-situ environments it is unlikely that they hear them constantly. The animal would also have to be fairly close to the camera traps to actually pick up the sounds.
There is another possibility however - that the fox could actually see the infrared light emitted, as well as hear the ultrasonic sounds. This is very difficult to prove , but this study argues that nocturnal animals in particular are able to see infrared light emitted by camera traps. It is likely that no-glow models reduce this likelihood however.
Roe deer especially seem to take notice of our cameras; sometimes it may be due to scent that we've left behind, but some pictures make us wonder. For example, this is an image taken a few years ago of a roe buck with an old ProStalk camera trap;
The camera had been there for at least a week by this point, and the infrared flash wasn't the issue as it was taken during the day. But the buck is clearly looking directly at the camera - can he hear it? Even at approx. 5 metres away?
This area of research is definitely one to keep an eye on, and without being able to just ask the animals if they can hear our camera traps when out in the forests and fields, it's a difficult question to answer.