Trapping Ocelots with a Camera
Automatic motion detectors help biologists get photos of rare cats and other elusive species.
By Sheryl Smith-Rodgers
Darkness falls at Laguna Atascosa National Wildlife Refuge near Brownsville, in South Texas. Through a clearing in the woods, an ocelot emerges, cautiously smells the air and then plops down on the ground, rolling and rubbing lazily on its back like a house cat.
Suddenly, a brilliant light flashes, illuminating the sleek, spotted feline and its brushy surroundings for a mere second. Just as quickly, the darkness returns. Oblivious, the ocelot rubs in the dirt a while longer, then jumps up and vanishes into the night.
A week or so later, Linda Laack, a wildlife biologist at the refuge, grins at a photograph of the ocelot, caught off guard that night, relaxing. Flipping through a stack of snapshots, Laack pauses to peer at another picture of an ocelot. This one is wide-eyed, slightly crouched, its head bent down, nose nearly to the ground.
The pictures are among thousands taken by remote 35 mm film cameras set up at select sites at the refuge and activated by infrared beams or motion sensors. Their mission: to “capture” the elusive ocelot, the region’s endangered carnivore.
“It’s a lot of fun, interesting and exciting,” Laack says of the scientific method called camera trapping. “It’s a great way to survey for specific animals, like ocelots. If we didn’t have cameras for surveying areas, then we’d have to use live traps, which are more expensive and time consuming. Cameras are less invasive to the animal.”
Occasionally, though, animals must be caught. “There’s still a place for trapping and attaching radio-collars in our work if we need to learn more specific information about behavior, habitat use or movement patterns,” Laack explains. “That type of information can’t be gathered by cameras alone.”
This year, an intensive camera-trapping study will attempt to determine exactly how many ocelots inhabit the 65,096-acre refuge. “There are about 50 to 100 ocelots left in South Texas,” Laack says. “We estimate that there are 30 to 40 in and around Laguna Atascosa.”
Using cameras to “trap” animals has been around for more than a century. George Shiras III developed and used trip-wire photography of animals at night for the first time in 1899. His stunning photos were published in National Geographic in 1906. In the 1920s, rudimentary camera traps documented the presence of tapirs on Barro Colorado Island north of the Panama Canal.
Generally, biologists use camera traps — such as models marketed by TrailMaster and CamTrakker — to inventory species at specific locations as well as determine species density, animal activity and behavior. By comparing spot patterns and other distinguishing marks, scientists can identify individual animals.
Camera traps aren’t perfect. Waving grass or birds flying by can trigger a camera. Batteries wear down, flash units break down, film rolls run out. Animals can even wreak havoc with equipment. Especially raccoons.
“They love to play with the cameras,” Laack says. “We’ll get a picture of a raccoon far away, then one of it closer up, then a picture of its face. Then the camera gets knocked over.”