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Posted October 27, 2012 | comments Leave a comment

Cameras in the woods

The camera in this plastic housing attached to a tree takes digital photos when body heat and movement are detected. Courtesy photo

This photo of a bobcat was captured by a camera trap. Courtesy photo

Richard and Sybille Stromberg

By Richard and Sybille Stromberg

Since August we have been participating as citizen scientists working with researchers at the Smithsonian Institution and North Carolina State University to document mammals in our area. The project is called "eMammal."

We have been placing camera traps - an infrared-activated camera ¬- in the Shenandoah National Park other areas in northern Virginia and North Carolina. The photos help researchers answer questions about mammal distribution and are used to answer conservation and ecological questions.

Before cameras were used, researchers walked trails to record observed species, tracks and other signs of an animal's presence (e.g., feces, scrapes, dens). But this often failed to record animals that live at low densities or are wary of humans, and it works best for only the largest species. Recent advances in camera technology allow surveying elusive and rarely seen mammals ranging in size from mice to forest elephants.

The camera traps we are using are digital and have infrared sensors. When they detect body heat and movement, they take a series of 10 photos and keep taking them until the animal leaves the camera's detection range. The result is a filmstrip of the animal's actions. Multiple photos increase our ability to identify the animal and to count how many animals are in a group. The camera is protected by a plastic housing with a grill over the front. The housing has a hole in the back through which a plastic-covered cable with a lock on one end is passed. The cable can be cinched tightly against a tree and locked.

The project's longterm goal is to estimate animal density. The cameras are placed in sets of three: one on a trail, one within soundscape of the trail (50 meters), and one beyond sight and sound of the trail (200 meters). The one on the trail will capture the human trail users, but photos of people won't be retained - only the numbers of people passing by will be kept for statistical purposes. The number of animals detected at each distance from the trail will enable estimation of the influence of trails on animal distribution.

Besides Shenandoah National Park, cameras are being placed this year in Antietam National Battlefield, Cunningham State Park and Catoctin Mountain Park in Maryland; Manassas National Battlefield, Mason Neck State Park and Thompson Wildlife Management Area in Virginia; Rock Creek Park in D.C.; and Harpers Ferry National Historical Park.

In Shenandoah National Park, cameras are placed along Keyser Run Fire Road, Sugarloaf Trail, Upper Thornton River Trail, trails on the west side of Mathews Arms Campground and our section, Tuscarora-Overall Run Trail. Locations and photos can be found on the EMammal Facebook page.

We started in August and will pick up the cameras for the last time in November. Next year the program will start in April. Every three weeks, we move the cameras to new spots. We are given coordinates use a GPS to locate each spot. Each time we move a camera, we remove the memory stick and put in an empty one and replace the batteries. At home, we download the photos, identify the animals and then upload the photos to the project's central storage.

Our first deployment on Aug. 8 was at the upper end of the Tuscarora-Overall Run Trail, not far from the Appalachian Trail. We moved the cameras on Aug. 31. From Aug. 8-31, the cameras on the trail and 50 meters from the trail each took 300 photos, 30 10-photo sequences. The camera 200 meters away had 850. The camera on the trail took photos of three hikers during that time.

The second deployment on Aug. 31 was further down the trail, beyond the connection to the Mathews Arm Campground. This time we had 930 photos from the 50-meter camera and 1,060 from the 200-meter camera, but the camera on the trail had 5,272 photos! It had filled up the memory stick and stopped taking photos on Sept. 15 because this section of the trail is the main access to Overall Run Falls, the highest waterfall in the park, so we got many photos of people walking by. We moved the cameras on Sept. 23 further down the same trail, closer to the falls. It had similar numbers: 5,337 on the trail, 520 at 50 meters, and 930 at 200 meters.

White-tailed deer appear most often in the photos. The next most prevalent occurrence is black bears. They often rubbed against the tree or the camera. Once they knocked the camera askew and they have broken off the carrying handle on two of our ameras. Once a big bear trotted by with two cubs.

We have also seen chipmunks, raccoons, opossums, and bobcats, mostly at night. One bobcat appeared in daylight and posed on the trail. A mouse came out several nights. One morning a flicker and, later, a wood thrush sat on the ground. Squirrels appeared during the day. Then there was the bear that relieved himself right next to the camera...

Guest columnists Richard and Sybille Stromberg live southwest of Front Royal. Richard is a Master Gardener and both love native plants and hiking. Email them at info@nvdaily.com.

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