Pre‐screening acoustic and other natural signatures for use in noninvasive individual identification

Abstract

Summary 1. Common ecological tasks, such as wildlife monitoring, adaptive management, and behavioural study, often make use of natural signatures (e.g. animal calls or visual markings) to identify individual animals noninvasively. However, there is no accepted method for pre‐screening candidate natural signatures to select which signatures are the best‐suited for this purpose. In this paper, we suggest a pre‐screening checklist and focus on the challenge of assessing a candidate signature’s individuality. 2. Individuality is critical, as the use of low‐individuality natural signatures can lead to misidentification of individuals and therefore bias estimation of population parameters and population response to management actions. An information‐based metric of individuality could assist researchers with selecting suitable signatures by allowing comparison among candidate signatures and providing an estimate of how many individuals may be reliably discriminated using a particular signature. 3. Before an individuality metric can be used to pre‐screen natural signatures, the metric must first be calculated from preliminary sampling and must be robust to typical sampling concerns. We used field‐collected animal vocalizations as well as simulations to test how robust the metric is to variation in sampling design. 4. We found that the metric is fairly robust to the number of animals sampled and the number of sessions (e.g. calling bouts) analysed, but that it is sensitive to the number of observations per session. 5. Synthesis and applications . Managers and researchers could save time and energy and improve the accuracy of estimates (such as abundance, survival, or population response) based on individual identification by first pre‐screening candidate natural signatures for their individuality. As long as the number of observations per session is controlled, the relative values of the individuality metric can be meaningfully compared. The metric can thus be used as a tool to estimate relative individuality and so facilitates a difficult step in choosing a natural signature for noninvasive individual identification. We include instructions on how to calculate and interpret the individuality metric.