A critique of density estimation from camera-trap data

Foster and Harmsen critically reviewed the assumptions and pitfalls of estimating animal density from camera traps, focusing on how researchers define the effective sampling area and handle heterogeneity in capture probability. They showed that traditional buffer-based methods using mean maximum distance moved or home-range radii can produce widely varying density estimates from the same data, undermining comparability. The paper advocated spatially explicit capture-recapture as a more principled alternative and urged transparency about assumptions, trail-versus-random placement effects, and individual identification reliability. As a clear-eyed methodological audit, it sharpened the field's awareness of where density estimates can go wrong. It is frequently cited as essential reading for anyone interpreting or designing camera-trap density studies of carnivores.