Camera trap

A camera trap is a weatherproof camera fixed to a tree or post, with a sensor that detects heat and movement. When an animal walks by, the camera takes a photo or a short video, day or night, using an infrared flash that does not disturb most animals. Researchers leave the cameras for weeks or months and collect the images.

Cameras are especially useful for cats because most are secretive, nocturnal and live at low density. Many have individual markings, such as the stripes of a tiger or the rosettes of a leopard or jaguar, which let scientists identify each animal. By recording which individuals appear, when, and in which place, they can estimate population size using capture-and-recapture methods. Cameras also reveal rare sightings, such as a black panther in a forest, and they show how animals use paths and wildlife corridor routes. Rangers can also use them to detect illegal activity, as in anti-poaching work.

The method has limits. Cameras can be stolen or damaged, results depend on where they are placed, and images do not show all the animals present. Camera-trap photos of wild cats have also helped to teach the public about species most people never see.