Sunday, September 8, 2013

Thinking Backwards: the Camera

A bushy-tailed woodrat eating mystery food in the Sierras.
This photo was adjusted for exposure and sharpness.  
A scree slope seems like a barren landscape to search for wildlife. Shrink yourself. Then imagine scampering the maze beneath the jumbled rocks. Suddenly the underground landscape has warm-blooded potential.

Standing on a scree slope above 6700-foot Yuba Pass in the Sierra Nevada mountain range is a good place to take a mental leap. I wanted to photograph bushy-tailed woodrats (Neotoma cinerea) which den under the rocks but I was struggling to understand the new Bushnell HD Trophy camera. You would think that setting up trail cameras, aka as wildlife cameras, is all about the technology - the sensors, trigger, flash, and digital equipment. But you also need a feral imagination since you are not going to be there when the camera is triggered. You have to picture the animal moving in the landscape, often at night, and contrive a plan to steal a few moments of its life on a carefully set camera.

I am going to walk you backwards through the events at this scree slope because that's the mental process you have to work through when you are setting up a trail camera. I'll start by showing the photographs the trail camera caught on the scree slope that night. Then in the next post I will show how the original decisions I made in setting up the camera affected the results - for good and bad. And finally, I'll describe how immersing ourselves in the high elevation landscape on the way up to the scree prepared us for entering the hidden world of the bushy-tailed woodrat.

It was the last full day of our five-day trail camera workshop and we were retrieving the cameras we had deployed earlier in the week. The class split into two teams to visit the remote outposts in the vicinity of the Sierra Nevada Field Campus. I went with the workshop instructor, Dr. Chris Wemmer, to pick up my Moultrie camera along a creek while a classmate on the other team volunteered to pick up my Bushnell camera on the scree slope.

Food set out for the bushy-tailed woodrat.
Dogwood to the left, maple to the right, lettuce in the foreground, and cocoon in the middle.   
Hours and miles later, while pondering the misadventures of the Moultrie camera at the creek site, I realized I had forgotten to ask my classmate to observe any changes at the experiment I had deployed on the scree slope. To test the food preferences of the bushy-tail woodrat, I had set out four different food items in front of the woodrat den:  sprigs of maple and dogwood I had collected on the mountain as we hiked up to the scree slope, a cocoon I found laying loose among nearby rocks, and a bit of leftover lunch lettuce.

After a hectic morning in the fresh mountain air, the teams reassembled at the classroom and excitedly downloaded the memory cards from our cameras. I groaned when I saw that the Bushnell had 550 photos over a 24-hour period. In my wildest dreams the downloading photos would be filled with a family of woodrats leisurely feasting on the banquet I had set out for them.

Bushy-tailed woodrats have a urine ledge near their den entrance where generations of woodrats have stained the rock white.
This photo adjusted for exposure and sharpness.  
Right. The first few hundred photos were extremely overexposed daytime shots of the den entrance with no animals evident. But the nighttime photos were definitely showing a pair of eyes glowing at the den entrance. For the next hour, a long-tailed rat moved back and forth across the rocks. Sometimes with its nose down over the food ledge, sometimes perched on a rock holding something up to its mouth. The photos were not clear enough to determine what the rat was holding or eating.

The dogwood branch was not sampled by the bushy-tailed woodrat.
Even with post-processing of exposure, contrast and sharpening, the photos of the Bushnell Trophy HD are overexposed on the bright scree slope.  
Fortunately, the Bushnell took a few parting shots as my classmate was taking it down. With those as evidence and by examining the animal's movements on the nighttime photos, it was obvious that the woodrat had eaten the maple leaves and the lettuce, but not the dogwood. Perhaps the latex-like sap we had observed earlier in the dogwood leaves made them unpalatable. The quality of the day and night photos was not good enough for me to  tell whether the cocoon was missing or not. And unfortunately, I had not asked my classmate to be on cocoon alert.

Shortly after appearing at the den entrance, the bushy-tailed woodrat inspects the maple branch.
This photo adjusted for exposure and contrast.  
The settings for the Bushnell Trophy HD camera on this scree set were: still photo, 8 megapixel, 3-photo captures per trigger, Infrared (IR) LED control high (32 LEDs flash), Auto PassiveIR sensitivity (camera determines the sensitivity of the sensor to infrared heat based on the current operating temperature), and NightVision shutter speed high (to freeze motion better). If you own the Trophy Cam, you can refer to the instruction manual for more information on these settings, or find the manual online at the Bushnell site.

Next, the bushy-tailed woodrat ate the lettuce.
This photo adjusted for exposure and contrast.  
My evaluation of the Bushnell Trophy HD camera is that it is a difficult camera to initially use as a novice unless all you want to photograph are large animals at night at distances greater than 4 feet (=deer). Its sensor triggers at subtle temperature differences and the IR LED flash is bright. The settings on the Trophy can be adjusted to accommodate different situations but it takes experience to understand how to adjust the multiple settings.

After an hour of sampling the food gifts, the bushy-tailed woodrat heads off to forage. The camera did not catch the woodrat coming back to this den entrance that night.
Photo adjusted for exposure and contrast.  
I have seen some fairly sharp photos of small, fast moving animals taken by experienced camera trappers on their Bushnell Trophy Cams both day and night. It is probably a matter of learning the technology and gaining experience with the camera. Dr. Wemmer said that some of the Bushnell cameras tend to overexpose at close range but this could be compensated for by either covering the flash window with some type of semi-translucent plastic film, or, with some Bushnell models, you can select a lower number of infrared lights to trigger.

The brightness of the exposed scree slope probably caused the many false trips in the daytime although I would have thought that setting the PIR sensitivity to Auto would have compensated for the hot summer rocks. Since I was shooting a nocturnal animal, this was not altogether important as I quickly scanned and deleted the hundreds of false daytime triggers.

Overexposed nighttime photo on the Bushnell Trophy HD.
Original photo except downsized for posting.  
But even the nighttime photos were overexposed for several reasons. Because the scree slope was so steep, I had to place the camera fairly close to the den entrance which was surrounded by a backdrop of rocks all of which probably reflected IR light. I was able to somewhat compensate for this with photo software after the fact by lowering the exposure of and sharpening the images. By applying my post-processing skills, I was able to obtain enough information from the digital photos to determine the woodrat's movements and interpret at least some of its eating habits. It's cocoon preferences, however, will remain a mystery.

Cocoon found among the rocks of the scree slopes.
If only Anna Pigeon had been there to solve this mystery.  
To be continued as Thinking Backwards: the Animal

This post is part of a series based on my experiences at a camera trapping workshop. To see the other posts, check the dates before and after this one, or click "wildlife camera" in the Sightings box in the right column.


  1. Yah, those whitish granitic rocks bounce back a lot of light.

    Btw - I'm sure the cocoon is still there. ;)

  2. RT: I am sure the woodrat ate the cocoon but you will have to wait for my next post when I reveal by highly scientific source, a source even you the woodrat fanatic have not read yet.

  3. Also, I was wondering if reflective surfaces act the same for regular flash and for IR light. Anybody know?

  4. The whole "IR Flash" thing is a misnomer. The flash is not putting out true infrared heat, it's a wavelength of red light just beyond the edge of the visible red spectrum of mammals, but still within the range of the CCD sensor. So you can think of its reflection/absorption properties as if it was visible light.

  5. I struggle with some of the same problems, particularly the "sun bounce" off rocks, dry leaves, etc. Living in the sunny Southwest, some times it is hard to find camera sets that won't produce these exposures.

    Your food experiments are interesting too. I'll have to try something like that.

  6. The easiest and most effective way to avoid overexposure on close subjects is to simply tape one or two layers of wax paper over the LED panel to limit the amount of light it puts out.


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