Research overview: spatial mark-resight and unmarked spatial capture-recapture

Building on spatially explicit capture-recapture, spatial mark-resight and unmarked SECR methods estimate density when few or no animals can be individually identified, exploiting the spatial pattern of detections across a camera array rather than individual identities. This overview describes how these models infer the number and arrangement of activity centers that best explain spatially correlated counts, sometimes aided by a marked subset, telemetry, or partial identity information such as sex or natural marks. It discusses the strong assumptions and data demands involved, and the active methodological development aimed at making them robust. For faintly marked cats like pumas and many small felids, these approaches promise rigorous density estimation without complete identification, and they represent a frontier in recognition-limited camera-trap analysis.