Distance sampling with camera traps

Howe and colleagues adapted distance-sampling theory to camera traps, providing a way to estimate density of unmarked animals from the distances at which they are detected in front of the camera. By measuring or modeling how detection probability declines with distance and angle within the camera's field of view, and accounting for the time animals spend in the detection zone, the method yields density without individual identification or assumptions about movement speed. Demonstrated on Maxwell's duikers, the approach offered an alternative to the Random Encounter Model with its own data requirements, notably calibrated distance estimation. It expanded the toolkit for recognition-free density estimation and is a widely cited methodological reference now applied to numerous unmarked mammal populations in camera-trap surveys.