Efficacy of Acoustic Triangulation for Gray Wolves

Abstract

ABSTRACTAcoustic triangulation is a unique, relatively noninvasive monitoring approach that can inform our understanding of a species’ distribution in time and space. Acoustic triangulation relies on standard triangulation techniques to determine the location of an acoustic event. Howl surveys are frequently used to survey wolves (Canis lupus) and other canids. We evaluated the efficacy of acoustic triangulation for estimating the location of wolves. We measured precision and accuracy of acoustic triangulation using an experimental mock howl survey and field data collected with wild wolves in northern Wisconsin, USA (2014–2018). Precision of acoustic triangulation was similar to triangulation with ground‐based radiotelemetry for both pooled data and individual wolves at specific times, although the 2 techniques did not result in similar predicted locations. Distance from the howl source was the most consistently significant factor influencing the efficacy of acoustic triangulation. Error ellipse size was 33 times smaller at distances <1 km. Wind speed also reduced the accuracy of acoustic triangulation for mock howl surveys. Precision for modified howl surveys with wild wolves improved with the number of bearings. We estimated a mean bearing error of 13.2° (±2.1, 95% CI) for single bearings and a maximum distance of 1.76 km (range = 0.96–1.76 km; = 1.41 km) detection for audible anthropogenic howls. Such information can be applied to howl survey data to generate more fine‐scale location information for wolf‐pack home sites. Acoustic triangulation of wolves can provide high‐quality location information in areas where wolves are not monitored with radiocollars. © 2020 The Wildlife Society.