Say Cheese! Camera Traps and Ecology

November 30, 2016 PLOS Blogs Biodiversity Citizen Science Climate Change Collaboration Conservation Ecology Public science communication

You may have already seen the pictures from the Gardner Police Department’s camera trap by now, but if not, they are going to make your day.

And while today’s news cycle is giving us some comic relief, camera traps have proven to be an incredibly useful and powerful tool for ecologists. They allow ecologists to gather information about wildlife to an extent that was previously nearly impossible. Camera traps limit disturbance to wildlife populations, can be deployed in remote areas, capture information at all hours for long periods of time, and can survive under grueling conditions. It is a much more forgiving protocol than having a poor researcher huddled in a blind in the rain. So how do they work?

camera_trap_diagram — From Rovero et al. 2013.

A camera trap is a camera that is remotely-triggered, typically by movement. They have evolved considerably since their advent in the 1890s when George Shiras developed a method where a trip-wire controlled flash camera was set-off when an animal would walk in front of the camera. The first animal “selfies.”

Today, camera traps are more sophisticated and range in price from a few dollars to several hundred or more. There are two types: infrared and incandescent. Infrared cameras take color day time pictures, but monochromatic night time pictures. Incandescent cameras have a bright flash that provide color night time pictures. There is a trade-off. With the flash comes the increased risk of frightening the animals you are trying to observe, but with infrared, there is some lose in clarity.

A comparison of night time pictures taken with an infrared camera (top) and an incandescent flash camera (bottom).

Ecologists have used camera traps to great utility. Dr. Nyeema Harris, Assistant Professor at the University of Michigan, utilizes camera traps to track and quantify the distribution and spatial dynamics of carnivores across Michigan—from the wilds of the Upper Peninsula to the city of Detroit. Asia Murphy, a Ph.D. student at Penn State University, has used camera traps to show how ground-dwelling forest birds, small mammals, and lemurs in Madagascar are faring in the face of habitat degradation. There are also widespread research networks focused on bridging knowledge and combining resources.

One of these networks, is the Cougar Network, an organization that focuses on studying how cougars interact with their habitat. You may recognize the Cougar Network from everyone’s favorite camera trap game, Cougar or Not?, headed up every Friday on Twitter by Dr. Michelle Larue, Research Ecologist at the University of Minnesota. In Cougar or Not?, Larue will post a photo and keep everyone in suspense as they guess wildly for a couple of hours before she reveals the answer (which is usually “not a cougar”). I am pretty sure a couple of weeks ago I mistook a bobcat for a moose. It is much harder than it sounds. The game is a wildly fun and successful science communication endeavor. Check in around 12:30 EST every Friday for more.

Besides offering interesting pictures to look at, with some old-school ecology and hardcore math, ecologists can get some major science from camera traps. In PLOS One alone, there has been recent work to quantify the seasonal and daily activity patterns of mammals in Japan, research into mesocarnoviores in China, and work on niche partitioning in Brazilian wetlands. Over 590 results show up on Web of Science, with publications using camera traps increasing every year.

camera_trap_pubs — Number of publications found on Web of Science by year using the search term “camera trap.”

There is some question about the of protocols associated with ecological information collected by camera traps. Many publications focus on clarifying and establishing these protocols to help standardize the data and metrics calculated from camera trap data. Dr. Brent Pease and colleagues present a new paper in PLOS One, Single-Camera Trap Survey Designs Miss Detections: Impacts on Estimates of Occupancy and Community Metrics, that compares detection rates of species based on differences in the number of camera traps used in a study.

Continued refinement of techniques and technology surrounding camera traps will continue to catalyze work in ecology. As this field grows and matures, we will learn more about our world and its inhabitants. Till then, the ecologists will be in the lab sorting through all those pictures trying to figure out if that is a cougar they are staring at.