Spatially explicit maximum likelihood methods for capture-recapture studies

Borchers and Efford provided the rigorous likelihood-based foundation for spatially explicit capture-recapture, formalizing how to estimate density when detectors such as camera stations have fixed locations. They derived a full likelihood treating animal activity centers as a spatial point process and detection as a declining function of distance to each detector, accommodating different detector types including proximity detectors like cameras. This gave practitioners a statistically efficient, model-based alternative to Bayesian implementations and ad hoc buffering, with estimable detection parameters (sigma and baseline encounter rate). The framework is implemented in the widely used secr R package. It is the standard maximum-likelihood reference for SECR and is cited throughout camera-trap density studies of tigers, jaguars, leopards, and other individually identifiable cats.