Caught in the trap! Remote cameras with electronic beams are the newest tools for biologists investigating mysteries in the wild

International Wildlife, Nov-Dec, 1997 by Fiona Sunquist

Remote cameras with electronic beams are the newest tools for biologists investigating mysteries in the wild

During the winter of 1991, Ullas Karanth drove slowly along a narrow forest road listening to the signal of a radio-collared tigress. At one point, he stopped his Jeep and climbed out, checking for tracks. To his amazement, not one but two sets of tiger footprints marked the dusty road, and from their size, neither appeared to belong to the radio-collared tigress he knew was nearby. "How can I ever catch another 20 tigers?" he muttered despairingly.

Karanth, a research ecologist with the Wildlife Conservation Society in New York, was trying to estimate the number of tigers living within the boundaries of India's Nagarahole National Park, but the tracks of new, unknown and uncollared animals kept showing up on the roads and trails, confusing his tally. Then a novel thought occurred to him. If he were studying mice, he would have set out a grid of tiny box traps. What if he used a grid of cameras, or photo traps, to count tigers?

Counting wildlife--one of the most basic jobs for a wildlife ecologist--is still often a vexing task guided by hunches, vague clues and educated guesses. Cameras left in the bush could add a new precision, Karanth realized. Not only did he proceed to deploy the cameras, but his subsequent use of them, in combination with complex but realistic computer models, has set the standard for scientists who need to count hard-to-find species.

Karanth's camera traps also typify the widespread use of a sometimes low-tech technology that increasingly has provided biologists--as well as photographers, educators, hunters and the police--with a powerful new way to look at the wild world. These remote photographic devices, in which an animal crossing an electronic beam triggers an automatic camera, produce a self-portrait of the animal. With that comes the photographic evidence to solve all sorts of scientific riddles and related questions.

Little wonder that the remote camera has become an important tool for biological fieldwork. With their sophisticated electronics and lithium batteries, new miniature units with motor drives can be set to photograph almost any size creature, from a mouse to an elephant. Even tiny fleas too fast to watch with the naked eye trigger the camera as they fly or leap, providing often-stunning records of natural behavior.

Using cameras to "trap" animals actually goes back to the turn of the century. In 1906, nighttime nature shots by pioneer wildlife photographer George Shiras appeared in National Geographic--photos set off by a trip wire. About the same time, Indian forest officer F. W. Champion had abandoned his shotgun for a camera and had begun to photograph some of India's more elusive, nocturnal wildlife, producing astonishing portraits of wild tigers.

But unwieldy equipment and technical limitations made execution difficult for these early photographers. Champion needed a party of porters to carry his cumbersome plate camera, heavy tripod and flash equipment. The flash, a metal box filled with about .9 kilograms (2 lbs.) of magnesium powder, also could be downright dangerous. When fired by a spark from a battery, the magnesium exploded, illuminating the scene with a brilliant white light. The burst usually frightened away all the wildlife in the area and sometimes set fire to the surrounding vegetation.

As cameras became more sophisticated, wildlife photographers advanced the technique and the technology. In 1948, British natural history photographer Eric Hosking began to photograph birds in flight. Hosking's friend, engineer Philip Henry, had developed an electric flash that was powerful enough to stop the action. But when the system was set up, they discovered a human limitation. A small bird flying past the camera was in the picture for about one-tenth of a second. Hosking simply could not make his eye, brain and shutter finger work fast enough to trigger the camera when the bird was in the middle of the frame. "My first results were a fine crop of disappearing tails, half heads, empty bushes and clear skies," writes Hosking in his autobiography, An Eye for a Bird.

The solution, Hosking and Henry decided, was to get the birds to trigger the camera themselves. Using the same principle that makes some automatic supermarket doors open (a break in a light beam interrupts an electrical circuit and triggers the opening mechanism), they adapted a photoelectric cell to activate the camera. The results were extraordinary scenes of birds in flight, individual feathers sharp as a pin.

In 1970, British photographer Stephen Dalton cranked the level of difficulty up a notch. He began using remotely triggered cameras to take high-speed photographs of insects in flight. His most difficult assignment: to photograph a jumping flea. A shutter speed of a 500th of a second is fast enough for most flying insects, but for a leaping flea it was hopeless. "They take off at something like 2 or 3 Gs," says Dalton. "I had to do it in total darkness. When the flea leaped, it broke the beam and triggered the flash. The shutter was already open."