Resource Ryan Valdez, Ph.D. Apr 27, 2018

The Art and Science of Camera Trapping

The rise of camera trapping has allowed a growing number of volunteers to make significant contributions to academic research. Here’s a look at the practice, how these devices are used, and ways to get your own glimpses at wildlife “selfies” and help with ongoing research.

Our national parks and protected areas are vital habitat for numerous species of wildlife, and the ability to accurately survey and monitor them is important for their survival. A not-so-new technology is now sharply on the rise — camera trapping, a method by which a camera armed with infrared sensors is placed in the field to remotely capture time-lapsed images and video whenever the devices sense motion.

It can be difficult for wildlife biologists and park rangers to keep up with emerging threats to wildlife. Particularly with mammals, accurately documenting their presence and estimating their populations remains a challenge. Many of these species are nocturnal, travel great distances, have complex behavior and avoid humans. Additionally, species like the endangered jaguarundi in south Texas or the red wolf in North Carolina are so rare and elusive they are almost never seen. Camera traps allow people to see animals in the wild in ways that they otherwise simply could not.

One of the most important aspects of camera trapping is not just the photo itself but the valuable metadata that comes with it. Each frame of a camera-trapped image contains useful information such as the date, time, temperature and even the lunar cycle. A camera identification tag can also be watermarked onto each image to keep track of which camera took which photo in large monitoring projects.

In small numbers, camera trapping is a fun and quick way to see what’s out there. But in high volume, metadata from multiple camera traps allow for powerful analyses worthy of scientific publication. There are now several computer software programs designed specifically to analyze metadata from camera traps, and the cameras don’t necessarily need to be deployed by scientists to use the data in scientific research. Citizen scientists commonly use camera traps in activities such as BioBlitz festivals, which recruit volunteers, including schoolchildren, to count species in national parks. These crowd-sourced data can be so voluminous that any errors in animal identification made by volunteers become statistically insignificant.

The practice, first referred to as “photo-monitoring,” didn’t initially include a camera at all. In the late 1980s, U.S. wildlife biologists and park managers needed a new way to count common game species, particularly white-tailed deer. The first devices they used were made up of two small battery-operated units. A transmitter about the size of a brick sent out a thin beam of invisible infrared light that was captured by a receiver of comparable size. Separated at a maximum distance of 20-30 feet, anything that broke the beam of light would clock an “event,” which was then stored in the memory of the receiver. Instead of a photograph, a typical readout would include the date, time and number of events. Installation was a truly cumbersome process, but the devices worked well for their intended purpose — tied to trees on opposite sides of game trails, they helped estimate the number of deer in a region.

It wasn’t until the early to mid-1990s when someone finally had the bright idea to modify a standard pocket camera and attach it to the receiver so that whenever an event occurred, it also triggered a photograph. The early days of camera trapping required significant planning to accommodate three electronic units with additional cords and a tripod, and anyone using this device quickly learned that wild rodents love to chew on the thin electrical cables, abruptly terminating the whole operation. To complicate matters, these older models used slide film, so you wouldn’t know the results of your efforts until that film was taken in to be developed — a costly and inconvenient process.

Years later, more advanced models would finally include the motion detector, camera lens and battery pack in a single unit — and, best of all, digital photography now allows users to see the images instantaneously. And no longer is a beam of light necessary, as the all-in-one unit uses range motion detection, the same technology that triggers flood lighting outside buildings when you walk by or opens the door for you when you approach the entryway to a grocery store.

With a huge international boom in the use and scale of camera trapping for scientific research, camera traps have basically replaced the need for a human to make direct observations — which in many cases would disturb the very wildlife they are attempting to observe. Camera traps are nonintrusive and designed to operate without daily maintenance. By deploying a large number of camera traps to operate simultaneously across a landscape (known as high-density camera trapping), it becomes easier to monitor wildlife movements over time and allow complex statistical analyses. The Wildlife Conservation Society and the Smithsonian Institution have led well-known camera-trapping research projects, including eMammal and other studies on iconic species such as tigers, leopards and giant pandas.

Camera traps don’t just capture animals — they can also help catch poachers. New models use black LED bulbs that are virtually invisible at night while actively recording images and video. These are the preferred camera traps to use where there is a high probability of humans on the landscape, thus reducing theft. Camera traps are also commonly used as personal security devices in homes and offices and are fairly standard tools in more covert security field operations.

There are over 15 major brands of camera traps on the market, including well-reviewed manufacturers such as Reconyx, Browning, Stealth Cam, Spypoint and Bushnell. Some camera traps are better for harsh weather conditions, others can remain untouched for months in the field by using high-quality lithium batteries or solar panels, and most can record high-definition video and audio. There are even camera traps that can send images instantly to a cell phone enabled through Wi-Fi and cellular networks. Whatever the medium-to-large mammal, there is a camera trap that can document it. Their decreasing costs and increasing reliability make them ideal tools for scientific research and field biology.

Now, the technology is easy for anyone to use, whether a wildlife professional or a home enthusiast. These guidelines can help you get started.

  • Keep the face of the camera from pointing at the path of the sun, as direct sunlight can damage sensors and quickly heat the inside of the camera unit and drain its batteries.
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  • Clear moving grass, branches or any mobile objects from the front of the camera’s range, or it may continuously take photos from detecting their motion. This can become quite important while sampling in high wind.
  • Avoid attaching a camera to thin trees, as they can sway in the wind, triggering the unit’s motion detectors.
  • Fasten cameras securely to their base (tree or pole), as wildlife may get curious and carry them off.
  • If you are targeting large carnivores, you might need a metal casing to protect the camera from being chewed apart or broken.
  • Camera traps set too close to the ground can be triggered by heavy rain and become covered in soil splatter.
  • If the camera trap can be easily seen by a person (e.g., in plain view on the side of a trail), consider securing it with a metal cable lock to deter theft.
  • Even a camera securely locked to a tree can have its front panel opened, exposing the batteries and digital card. Small luggage locks are good options to secure that front hatch.
  • Prior to deployment, leave camera traps and all accessories outside for at least a week to rid them of human scent.
  • Test your camera’s ability to photograph you by conducting a “walk test” in front of it before setting it.
  • And lastly, before you leave your newly deployed camera trap in the field — don’t forget to turn it on! All too often this is the greatest source of anguish and embarrassment as you return excitedly to collect images a month later — in my case, with a handful of students in tow.

Just as important as it is to document rare and elusive wildlife, camera traps help us better understand the distribution and abundance of the more numerous species such as white-tailed deer and coyotes and migratory wildlife such as pronghorn antelope in the Greater Yellowstone Ecosystem. The National Park Service has been investing in camera trapping to add value to its Inventory and Monitoring Division, a series of 32 regional networks that gather and analyze information on animals, plants and ecosystems across the country to keep national parks healthy. Some project examples include:

  • Documenting wildlife as a standard practice for national BioBlitz surveys.
  • Understanding wildlife movement and connectivity in the Greater Yellowstone Ecosystem.
  • Exploring the nocturnal wildlife of the Sonoran Desert.
  • Monitoring the activity of wildlife responding to large-scale wildfires.
  • Documenting the physical disturbance of natural resources from bison in the north rim of the Grand Canyon.
  • Analyzing how wildlife use the Appalachian Trail.
  • Monitoring wildlife that live along the Blue Ridge Parkway.
  • Photo-documenting the population of mountain lions in the Santa Monica Mountains.

NPCA also deploys camera traps to better understand the diversity and behaviors of wildlife beyond the boundaries of national parks, including Great Smoky Mountains National Park, Yellowstone National Park, First State National Historical Park and Petersburg National Battlefield.

About the author

  • Ryan Valdez, Ph.D. Senior Director, Conservation Science & Policy

    Ryan Valdez serves as Senior Director of Conservation Science for National Parks Conservation Association. As a member of the Conservation Programs team, he facilitates the application of multidisciplinary science to help protect US national parks.

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