For January’s Science Update, also featured in The Snapshot monthly e-newsletter, we explored the accumulation of Snapshot Wisconsin photos over time and how the number of photos taken fluctuates with the seasons. To date, our data set contains more than 24 million photos, and their content is a vital component of the Snapshot Wisconsin project.
The bar chart above indicates that over half of the photos are blank. This can be attributed to the fact that our cameras contain a motion trigger function, which is designed to capture wildlife as it moves through the frame. However, this mechanism only detects movement and cannot differentiate between animals and vegetation. This means that on windy days during the spring green up period, thousands of blank photos can be captured. Occasionally cameras will malfunction and continuously take blank photos without being triggered by motion. This issue was more prevalent with earlier versions of our cameras; the model we currently use does not take as many blank photos. Additionally, over time volunteers have learned that trimming vegetation in front of their camera helps prevent blank photos.
Every day at 10:40AM, the cameras are programmed to record a time lapse photo. This is not only to document the “spring green up” period and the “fall brown down” period, but also to sync ground-level measures of greenness with satellite data. These photos are primarily used by our partners at UW-Madison and compose 7% of our data set.
It is not uncommon for our trail camera hosts to trigger the camera themselves during check events, which is the cause of most of the 3% of photos that are tagged as human. Although these photos are removed from the data set prior to analysis, they can be helpful in instances where the camera has been recording photos with the wrong date and time. A photo of a hand in front of the camera combined with the date and time reported by the volunteer at each check event are enough for us to adjust the date and time for the whole set of photos.
Twenty percent of the Snapshot Wisconsin photos are untagged, meaning they have yet to be classified as blank, human or animal. Many of these photos will be sent to the crowd sourcing website, Zooniverse, for classification. We hope to implement a program to automatically classify photos to work through this backlog as well.
Finally, about 14% of Snapshot Wisconsin photos are of confirmed animals. In the graph above, we have broken down which species appear in these photos. Deer are by far the most common species, appearing in about two-thirds of photos, followed by squirrels, raccoons, turkey, cottontail rabbits, coyotes, and elk. The remaining 8 percent of animal tags are divided up across 34 categories including other bird, opossum, snowshoe hare, bear, crane, and fox. Elk may have a higher proportion of triggers than expected because Snapshot Wisconsin cameras are placed more densely in the elk reintroduction areas than in other areas of the state.
Before joining the Snapshot crew, I worked on a long-term fisher (Pekania pennanti) monitoring project in a beautiful section of Northern California, called the Klamath-Siskiyou eco-region.
Our study focused on one of two endemic populations of fishers on the West coast found in Northern California and Southern Oregon. Fisher populations declined in the 1800s and early 1900s due mainly to trapping and habitat loss. This study was undertaken 11 years ago in response to a petition to list the fisher as a federally endangered species (which was ultimately overruled).
The goals of the project are to better understand the size and robustness of the western fisher population, explore species interactions between meso-carnivores (such as gray fox and ringtail), and investigate fisher responses to wildfires. It’s a very dynamic and exciting project to work on, with lots of valuable questions to explore.
We used baited, corrugated plastic boxes at 100 historical locations to track our fisher populations. The boxes were fitted with a metal track plate covered in contact paper and ink, along with a glue strip that caught hair from critters passing through the box.
Every day for three months, my co-worker and I would set off into the woods to collect track plates and hair snares. This usually meant 10-12 hour days of driving around the Klamath National Forest, punctuated by steep hikes to retrieve samples in the forest.
Even though we never outright saw the feisty fishers, we began to expect “visits” from them at our boxes. We collected tracks and hair from the same boxes every week. The fishers certainly appreciated the chicken and cat food we left as bait for them! Our weekly box checks became like meeting up with old friends. At one site, I collected a female’s tracks and hair every week for two months. She never made a mess of the bait or destroyed the box (which I greatly appreciated)!
All in all, I had a terrific experience that helped me to understand the importance of non-invasive sampling (i.e., sampling that does not require capturing animals – like the camera trap method used in Snapshot Wisconsin)!
If you are still curious about the non-invasive sampling boxes, check out this video of the box setup.
The following post is by a guest blogger, Caitlin Henning, Communications Specialist at the Wisconsin Department of Natural Resources Office of Applied Science. Currently, her primary project is the WDNR’s landmark Southwest Wisconsin CWD, Deer & Predator Study. Thanks for the information on this project, Caitlin! Read More…