Acoustic localization of terrestrial wildlife: Current practices and future opportunities

• Published in: Ecology and evolution Vol. 10; no. 13; pp. 6794 - 6818
• Main Authors: Rhinehart, Tessa A., Chronister, Lauren M., Devlin, Trieste, Kitzes, Justin
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.07.2020; John Wiley and Sons Inc; Wiley
• Subjects: acoustic localization system; Acoustic noise; Acoustics; Algorithms; Animal behavior; Animals; Arrays; Automation; autonomous recording units; Background noise; bioacoustics; Classification; conservation; Estimates; Habitat utilization; Localization; microphone array; Microphones; Position (location); Recording; Review; Reviews; Sound; Species classification; Terrestrial environments; Time lag; Time synchronization; Vocalization behavior; Wildlife; Wildlife conservation; Wildlife habitats; wildlife monitoring; wildlife monitoring; conservation; autonomous recording units; bioacoustics; microphone array; acoustic localization system
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.6216

Autonomous acoustic recorders are an increasingly popular method for low‐disturbance, large‐scale monitoring of sound‐producing animals, such as birds, anurans, bats, and other mammals. A specialized use of autonomous recording units (ARUs) is acoustic localization, in which a vocalizing animal is located spatially, usually by quantifying the time delay of arrival of its sound at an array of time‐synchronized microphones. To describe trends in the literature, identify considerations for field biologists who wish to use these systems, and suggest advancements that will improve the field of acoustic localization, we comprehensively review published applications of wildlife localization in terrestrial environments. We describe the wide variety of methods used to complete the five steps of acoustic localization: (1) define the research question, (2) obtain or build a time‐synchronizing microphone array, (3) deploy the array to record sounds in the field, (4) process recordings captured in the field, and (5) determine animal location using position estimation algorithms. We find eight general purposes in ecology and animal behavior for localization systems: assessing individual animals' positions or movements, localizing multiple individuals simultaneously to study their interactions, determining animals' individual identities, quantifying sound amplitude or directionality, selecting subsets of sounds for further acoustic analysis, calculating species abundance, inferring territory boundaries or habitat use, and separating animal sounds from background noise to improve species classification. We find that the labor‐intensive steps of processing recordings and estimating animal positions have not yet been automated. In the near future, we expect that increased availability of recording hardware, development of automated and open‐source localization software, and improvement of automated sound classification algorithms will broaden the use of acoustic localization. With these three advances, ecologists will be better able to embrace acoustic localization, enabling low‐disturbance, large‐scale collection of animal position data. Acoustic localization can be used to locate a vocalizing animal spatially using an array of time‐synchronized microphones. We comprehensively review applications of acoustic localization for terrestrial wildlife. We describe trends in the literature, identify considerations for field biologists who wish to use these systems, and suggest advancements that will improve the field of acoustic localization.