Acoustic capture-recapture methods for animal density estimation

Abstract

Capture-recapture methods are one of the two most widely-used methods of estimating wildlife density and abundance. They can be used with passive acoustic detectors—in which case acoustic detection on a detector constitutes “capture” and detection on other detectors and/or at other times constitute “recaptures.” Unbiased estimation of animal density from any capture-recapture survey requires that the effective area of the detectors be estimated, and information on detected animals' locations are essential for this. While locations are not observed, acoustic data contain information on location in a variety of guises, including time-difference-of arrival, signal strength, and sometimes directional information. This talk gives an overview of the use of such data with spatially explicit capture-recapture (SECR) methods, including consideration of some of the particular challenges that acoustic data present for SECR methods, ways of dealing with these, and an outline of some unresolved issues.