Thinking Backwards: the Animal

The bushy-tailed woodrat leaving its den in the scree slope at night.  

We climbed the side of a mountain at Yuba Pass, found the sought-after den entrances, and now it was time to mount a trail camera in order to take photos of the bushy-tailed woodrat (Neotoma cinerea). It was the third day of our wildlife camera trapping workshop at the Sierra Nevada Field Station, and we had already experimented with many techniques for mounting trail cameras on trees or on stakes driven into the ground. But the bushy-tailed woodrat lives in screes slopes which have no trees or soil. When you've got lots of rocks, you use rocks.

As one of my classmates in our trail camera workshop described, setting a camera is like walking onto an empty theatre stage. You've read the lines but now you must flesh out the play by imagining the future actors and scenery.  With a new camera in hand and rocks underfoot, I needed to conjure up my next few steps. At the high elevation, I felt closer to the ground, the animal level, but the logistics of technology were slipping away.

Rocks stained white from urine flag the otherwise hidden entrance of a bushy-tailed woodrat den.   

Dr. Chris Wemmer, the workshop instructor, had previously explained that bushy-tailed woodrats choose a flat rock near the entrance to their underground den to pee before they venture outside to forage. Over time, these become coated with white. It took awhile and a lot of wandering, but I found a white urine ledge tucked into a dark opening on the scree slope and carefully examined the open ground around it to detect the woodrat paths.

Then the task was to find a location that faced the paths yet would not directly expose the camera lens to glare from the low morning or afternoon sun. Because the ground was so uneven, I needed to pile rocks to form a level foundation outside the den and then build a sturdy stone castle around the stake to hold it in place. After 30 minutes of setting and resetting rocks, I finally attached the Bushnell Trophy HD camera to a small tripod and then wired that onto the round steel stake protruding out of the rock fortification. Mounting a camera on a tripod has the advantage of allowing micro-adjustments to aim and tilt the camera without moving the carefully rigged stake. 

Bushnell Trophy HD camera mounted on a tripod wired to a stake.
These round steel stakes are commonly used on construction projects to secure wooden forms in which concrete is poured. They are sturdy although heavy to carry into the field, and have holes drilled through them which can be handy for attaching wires or nails for mounting a camera.  

When I told an associate I was going to a five-day trail camera workshop, he lent me his new Bushnell Trophy HD camera and told me to come back with detailed advice on how to use it. It's kinda sensitive he said. What does that mean, I wondered.

After playing with the Trophy Cam at the Dipper Ranch the week before the workshop, I knew it meant: many false triggers in bright light and on hot days, overexposed photos, and fuzzy focus at close distances. False triggers are when a trail camera takes photos even when there is no apparent animal to trigger the sensor. The sensors of most trail cameras are programmed to trigger when they detect either or both movement and a temperature difference in front of the camera. Usually this is an animal but sometimes waving vegetation or even warm air rising off the ground can trigger the sensor.

My first test of the Trophy cam in the Dipper backyard triggered over 10,000 photos in a 48-hour period. Yikes, have you ever tried to review 10,000 photos? Most of them had no animals with only a few showing deer drinking from the birdbath.

A yearling buck checks the moon - one of the few animated photos during the test of the Bushnell Trophy HD camera in the Dipper backyard.  

However, color photos in the afternoon shade and the infrared black and white photos at night of the Dipper deer were mostly crisp and the Trophy camera seemed to be capturing movement in quick series rather than big gaps as with some of my other trail cameras. I liked the superior speed and definition of the Trophy cam but my inclination was not to use it on hot days, in bright light or aim it for short distances. 

The scree slope was all these things: bright, hot, and the most stable place I could find to place the stake was about 40" from the urine ledge which in the cam-trap world is close range. On the other hand, the woodrats would be out at night and are relatively small mammals (13-16" body length including tail), so I wanted the camera to frequently trigger at small movements.

I was anxious to capture photos of the Sierran bushy-tailed woodrat so that I could compare them to the closely related San Francisco dusky-footed woodrat (Neotoma fuscipes) which I had been observing at the Dipper Ranch in coastal California. I didn't want to miss a single pee, nibble or whisker twitch. So I took a risk. Instead of concentrating on the technical strengths and weaknesses of the camera from my previous tests, I kept imagining the nightly antics of this Sierran woodrat and defaulted to settings of greater sensitivity for the motion-detection sensor and for greater infra-red (IR) illumination at night.

Native plant samples, a cocoon, and organic lettuce set in front of the urine ledge as bait.  

Onto the next decision. Should I use bait? I often don't use bait but this set was going to be up for such a short period, it would be a shame to climb all that distance and not get any photos of a bushy-tailed woodrat. Why not use the maple and dogwood leaves I incidentally shoved into my pocket earlier as we made our way up the mountainside? And how about the cocoon I found in an odd place on the scree slope? And a piece of lettuce left from lunch? I arranged the different food types in separate piles on an open space in front of the urine ledge. A little experiment - perhaps I could figure out the food preferences of the bushy-tailed woodrat, particularly whether it would eat the cocoon or not.

I originally found the tan-colored cocoon (in the center of this photo) resting loose among the scree rocks. Although I didn't see any urine ledge at this location, there were scales stripped from fir cones and other bits of vegetation and loose soil as if this was another type of den entrance or exit.  

I was curious to determine if the vegetarian woodrats ate cocoons. I knew that grizzly bears in Glacier National Park move to high elevations in the summer to forage on army cutworm moths that aggregate beneath talus slopes. Did bears eating moths under talus in the Rocky Mountains indicate that woodrats eat cocoons in scree of the Sierra Nevada Mountains? It sounds preposterous now, but at 7000 feet, it seemed like a logical possibility.

Logical for someone who celebrates summer by occasionally reading science-fiction or a murder mystery. You see, my original source for the moth-eating grizzly bear diet was Blood Lure  a novel by Nevada Barr. A friend introduced me to the fictional character of Anna Pigeon years ago and now I like to take the petite ranger with me when I travel in the summer. She gets into trouble in one National Park after another, but while she is solving the mystery, she always shares a lot of interesting and accurate natural science and history of said park. Light summer reading for a nature nerd.

Bushnell Trophy HD camera erected on the set facing the den entrance. Camera is above and to the right of black-grey backpack.

Dr. Wemmer says it often takes him an hour to set up a trail camera at a new site. Between climbing the mountain side, searching for a urine ledge, building a rock castle around the camera mount, placing the four-course bait, and pondering all the settings on the Trophy cam menu, it had taken me nearly 3 hours to get the camera in place on the scree slope. I figured that was just about right for a novice, and surely Anna Pigeon, also subject to overanalyzing, would have taken that long too. Hopefully all the time and effort would result in some good bushy-tailed woodrat photos and insight to their behavior.

If you've read the previous post, Thinking Backwards: the Camera, you know that I made a mistake in selecting the settings for the Bushnell Trophy HD camera on this set. By pushing the sensitivity of the settings, I ended up with many false triggers and overexposed photos. Although I could partially compensate by post-processing the photos, they were not clear enough to determine whether the bushy-tailed woodrat ate the cocoon or not. But I did get some photos of the nocturnal beast and a little information, and with that I am generally pleased.

I would not have known about the urine ledges as a way to look for bushy-tailed woodrat den entrances without checking references or talking to someone knowledgeable about the local wildlife.

To ensure yourself the best conditions for capturing wildlife on your trail camera, it is important to know the habits of your target animal. If possible, you should study up on the local wildlife before you head out into the field. If you are lucky, you can tag along with a helpful wildlife biologist like Dr. Wemmer. Once in the field, you need to be alert and constantly interpreting the landscape for sign. Although I was trying to apply my ecological knowledge from the coast and with a closely related rodent species, I would not have been nearly as successful without the advice of someone who knew the local species.

Dusky-footed woodrat arranging the stick nest it has made in the firewood pile at the Dipper Ranch.  This photo was taken by a different trail camera, the Moultrie BirdCam 2.0 which I will be describing in a future post.  

This is similar to strategies used by traditional bow and gun hunters, however, you need to further interpret any information about an animal's presence to find field conditions that will work well with your camera. After all, when the animal shows up on the set, you will not be present to make adjustments. It's great if you have a location to which you can return and make adjustments after viewing a first round of photos. But we don't always have the opportunity to repeatedly visit a remote site, review and adjust, so sometimes you just need to apply the lessons you've already learned with that camera and/or from a previous similar site.

I encourage you to think backwards when setting up a trail camera - camera, animal, landscape - but it needs to be an integrated process rather than focusing on just one of those. Don't get overwhelmed with visions of cute, dancing bears in your head. Even moth-eating ones.

To be continued as Thinking Backwards: the Landscape.

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.
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My traveling companion, Anna Pigeon, courtesy of Nevada Barr, Blood Lure, Berkley Books, 2001. Hilarious biography here.  Barr:"I didn’t go in the Park Service until I was 36 years old.  I want to encourage women to do what they want, what they love.  And, I want to encourage people to take care of parks.  . . . I hope they’ll think 'Oh yeah, I read about that and it sounds like a cool place.' " Yep.

Steven P. French, Marilynn G. French, and Richard Knight, Grizzly bear use of army cutworm moths in the Yellowstone Ecosystem, International Conference on Bear Research and Management, 9(1):389-399, 1994.

Hilary Robinson, Relationships between army cutworm moths and grizzly bear conservation, 2009.

Felisa A. Smith, Neotoma cinerea, Mammalian Species, No. 564, pp. 1-8, American Society of Mammalogists, 1997,