Unexpected Visitor (Bobcat!) in Camera Trap

This past winter, we spent some weeks trying to pin down the location of a bobcat den in our back forest. It was an exhilarating chase that I likened to a game of Battleship, where we would place game cameras in the forest at some locations based on educated guesses, and once we got lucky with a strike, we’d follow up a few days later with additional close placements to see if we could narrow things down. Because the several miles of stone wall in our woods is laid out on north-south and east-west axes, I thought we might be able to use these grid strikes as a sort of x and y axis method of narrowing down where those kittens must be. We would just need to inventory our hits and use some software to map the strikes. 

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Bobcat on west bank of Rappahannock River with Fones Cliffs in background, otter scat in foreground

In Vermont, bobcats like to den up in talus piles below rocky slopes. We thought that would narrow things down. Well, all that effort didn’t work out. We got some nice night shots of the behinds of various bobcats, but no evidence that we were ever close to a den site. 

Fast forward half a year, and while on vacation at my in-laws in Virginia I set up a camera by the creek we use to get into their marsh. I’d noticed that at one particular location, there was a beaver or otter slide, and I wanted to find out who was using this entrance.

I set up a cheap camera (Canon SL-1) with a decent lens (the new Tamron 35mm VC) hooked up to an intervalometer that would keep taking pictures during the diurnal periods every few seconds. This was all stuck on a solid tripod, set up low to the ground, just above what I thought might be the height of a confused beaver who might draw himself up to look to see what that device was clicking at him. 

I set the camera up so that the path through to the creek was visible, and the cliffs across the river too, hoping that the winding creek would compose a leading line down to the subject, whoever that was going to be. At the bottom of the frame, I left in two old scats that I thought might be nice foreground objects, and potentially an aid in identifying the creature. 

I put the focus on the border of the tree line, expecting an animal would stop just about there to observe the field before entering, and then I set the aperture quite narrow so as to increase the depth of field and the odds that whatever I caught might be in focus. I set it to f/10, which is the point on that camera where things start going downhill sharpness-wise due to diffraction.

I then left it for 36 hours, allowing most of the scent to wear off. With that aperture, the camera was taking mostly 0.5 second exposures during the critical periods, so anything that was moving was going to show a good bit of motion blur. 

And then I got very lucky. Instead of the critter who created the slide, I captured the bobcat who was quite possibly hunting that critter. Of the 30 or so images captured, only three showed the cat completely still, and only one of those – the one pictured above – composed the way I’d intended. The rear of the cat obscured part of the creek, eliminating that serpentine leading line, but with wildlife, you have to take what you can get. 

I sharpened a few parts that were very slightly motion blurred in the half second exposure, cloned out a couple pieces of grass that had blown into the frame and did some small color corrections and exposure adjustments, but other than that, it’s as it appears out of the camera. It was shot in JPEG to maximize the number of frames I could take on the memory card.

Possibly pregnant bobcat using old stone wall (in VT) to move silently at night

A couple notes for people trying out this sort of wildlife photography:

– There are two major schools of thought on these camera traps: either take tons of photos on intervals, or use a triggering mechanism to take a few photos only when an animal triggers something. I find that the interval method – while more tedious – affects animals less, as they appear to aclimate to a regular click, so long as it is frequent enough, rather than a sudden barrage of clicks. I also find that I learn very unexpected things by going through the thousands of photos. That review process can be made quick by creating a movie of the frames and viewing them at 24 per second. 

– You will conduct three to ten setups like this for every one time you find you get something useful or interesting. Don’t put up a couple camera traps and then give up when you don’t find anything. 

– Find natural constrictions to place the camera. This one worked precisely because it was one of the few ways to cross from the creek side to the field side of the line of trees without much hassle and – critically – making a lot of noise. 

– If possible, photograph that constricted crossing area from the side, so that you needn’t worry about creating a very large depth of field in focus. The example with the bobcat shows that sometimes it’s worth trying it the wrong way, but in general, you’ll get many out-of-focus frames when you try to catch a creature coming toward you or away.

– It actually helps to have real data on the forest. A forest inventory done by a forester will show stands of timber delineated by soil types and tree species, often also stonewalls and other features relevant to where a bobcat might roam. Clearcuts and patch cuts are great for prey species, like rabbits. A timber cruise done on modern forest inventory software will also generally include a graphic map of all these features, and more often than not refer to the history of timber treatments on the property.

– Finally, the most useful people to consult when trying to find a cat like this is the farmer who farms the land, and the hunter who hunts it. It’s unlikely either will have been deliberately seeking out a relatively obscure non-game species like a bobcat, but those are the people who will have seen it.

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