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Tracking Cryptic Animals Using Acoustic Multilateration: a System for Long-Range Wolf Detection Arik Kershenbaum, Jessica L

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Tracking Cryptic Animals Using Acoustic Multilateration: a System for Long-Range Wolf Detection Arik Kershenbaum, Jessica L Tracking cryptic animals using acoustic multilateration: A system for long-range wolf detection Arik Kershenbaum, Jessica L. Owens, and Sara Waller Citation: The Journal of the Acoustical Society of America 145, 1619 (2019); doi: 10.1121/1.5092973 View online: https://doi.org/10.1121/1.5092973 View Table of Contents: https://asa.scitation.org/toc/jas/145/3 Published by the Acoustical Society of America ARTICLES YOU MAY BE INTERESTED IN The pioneering contributions of Per Stockfleth Enger to fish bioacoustics The Journal of the Acoustical Society of America 145, 1596 (2019); https://doi.org/10.1121/1.5095405 Inverse identification of a higher order viscous parameter of rigid porous media in the high frequency domain The Journal of the Acoustical Society of America 145, 1629 (2019); https://doi.org/10.1121/1.5095403 Artificial speech bandwidth extension improves telephone speech intelligibility and quality in cochlear implant users The Journal of the Acoustical Society of America 145, 1640 (2019); https://doi.org/10.1121/1.5094347 Characterizing horizontally-polarized shear and infragravity vibrational modes in the Arctic sea ice cover using correlation methods The Journal of the Acoustical Society of America 145, 1600 (2019); https://doi.org/10.1121/1.5094343 Swept-frequency ultrasonic phase evaluation of adhesive bonding in tri-layer structures The Journal of the Acoustical Society of America 145, 1609 (2019); https://doi.org/10.1121/1.5094764 Investigation of ultrasonic backscatter using three-dimensional finite element simulations The Journal of the Acoustical Society of America 145, 1584 (2019); https://doi.org/10.1121/1.5094783 Tracking cryptic animals using acoustic multilateration: A system for long-range wolf detection Arik Kershenbauma) Department of Zoology, University of Cambridge, United Kingdom Jessica L. Owens Cooperative Predator Vocalization Consortium, Daytona Beach, Florida 32174, USA Sara Wallerb) Department of Philosophy, Montana State University, Bozeman, Montana 59717, USA (Received 17 September 2018; revised 12 February 2019; accepted 15 February 2019; published online 28 March 2019) The study of animal behavior in the wild requires the ability to locate and observe animals with the minimum disturbance to their natural behavior. This can be challenging for animals that avoid humans, are difficult to detect, or range widely between sightings. Global Positioning System (GPS) collars provide one solution but limited battery life, and the disturbance to the animal caused by capture and collaring can make this impractical in many applications. Wild wolves Canis lupus are an example of a species that is difficult to study in the wild, yet are of considerable conservation and management importance. This manuscript presents a system for accurately locating wolves using differences in the time of arrival of howl vocalizations at multiple recorders (multilateration), synchronized via GPS. This system has been deployed in Yellowstone National Park for two years and has recorded over 1200 instances of howling behavior. As most instances of howling occur at night, or when human observers are not physically present, the system provides location informa- tion that would otherwise be unavailable to researchers. The location of a vocalizing animal can, under some circumstances, be determined to within an error of approximately 20 m and at ranges up to 7 km. VC 2019 Acoustical Society of America. https://doi.org/10.1121/1.5092973 [AMS] Pages: 1619–1628 I. INTRODUCTION trap and release, the very species that avoid human contact may be wary of approaching traps or react adversely to hav- The ability to locate and follow wild animals is essential ing a collar attached (Wilson and McMahon, 2006). The for the study of behavior of animals in their natural environ- process of capture, instrumentation, and release, as well as ment. However, many species are difficult to locate in the the presence of the device itself, may affect the behavior of wild or to follow as they go about their normal activities. the animal in the future (Wilson and McMahon, 2006). This may be because the animals themselves are cryptic or Also, while collaring animals can provide large amounts of avoid humans, active at night, or range over very large accurate position data, only those animals wearing collars distances (Boitani, 2003). Difficulties in locating these are recorded. Unless an entire group can be instrumented, animals can lead to a poor understanding of their social information on social behavior may be difficult to achieve. behavior, habitat use, and population dynamics, all of which Second, the device requires a power supply that almost are important for making conservation and management inevitably has a finite lifespan. While very high frequency decisions (Boitani, 2003). Technological solutions have been (VHF) beacons may last for years, GPS receivers, and partic- available for many years to follow wild animals based on ularly devices with wireless data download, may be limited various radio tagging technologies (Ropert-Coudert and to months of operation, or even weeks (Johnson et al., Wilson, 2005; Boitani and Powell, 2012). These include sim- 2002). Although larger animals are capable of carrying large ple low-power beacons for use with direction finding anten- batteries, those that range over longer distances may require nae, data-logging Global Positioning System (GPS) devices, more powerful transmitters, thereby reducing the battery life and data download via cellular telephone technology. even further (Cagnacci et al., 2010). However, all of these solutions require instrumenting the Third, the cost of the equipment and capture-release can animal with some kind of electronic device. This approach be considerable. Instrumenting a large number of animals has a number of drawbacks. may be prohibitive purely in terms of capital outlay, and First, the animal must be captured without injury, and a those animals that must be darted, rather than live-trapped, device suitably attached to the animal, such as a collar incur considerable extra cost simply for the procedure of (Schemnitz et al., 2009). While many species may be easy to instrumentation (Boitani, 2003). All of these considerations notably come together in the study of wild canids. Few large predators are the subject of a)Electronic mail: [email protected] b)Present address: Cooperative Predator Vocalization Consortium, Daytona such widespread conservation and management challenges Beach, FL 32174, USA. as the grey wolf Canis lupus (Fritts et al., 2003; Mech and J. Acoust. Soc. Am. 145 (3), March 2019 0001-4966/2019/145(3)/1619/10/$30.00 VC 2019 Acoustical Society of America 1619 Boitani, 2010). The most widespread terrestrial mammalian allow the tracking of animal movements, and also lead to predator in the world, the wolf was indigenous to the entire inferential conclusions about the use of vocal communication Holoarctic region until population numbers were severely to mediate social behavior in the wild (Campbell and Francis, reduced by human activity (Nowak, 2003). In many parts of 2012; Fitzsimmons et al., 2008; Blumstein et al., 2011). the world, notably North America and Europe, rising wolf Passive acoustic localization has been a well-established populations have frequently come into conflict with human technique in marine mammal research for many years (Clark activity, particularly ranching and the rearing of livestock et al., 1996; Zimmer, 2011), and the low attenuation of (Sillero-Zubiri and Laurenson, 2001). Thus, the conservation sound underwater allows for accurate measurements to be efforts to re-establish wolf populations as an essential ele- made over long distances. Many commercial and non- ment of the native ecosystems (Beschta and Ripple, 2009; commercial systems are available for tracking whales, in Fortin et al., 2005) is in conflict with the management efforts particular, using this technology (Gillespie et al., 2009). to minimize livestock losses and maintain a positive percep- However, terrestrial applications are much more challenging. tion of these wild animals among sympatric human popula- Few terrestrial animals make calls audible over long distan- tions (Fritts et al., 2003). For these reasons, the detailed and ces, and so existing work on acoustic localization in terres- quantitative study of wolf movement behavior, social behav- trial environments has focused on short-range calls and ior, and population dynamics is particularly challenging. In birdsong, in particular (Mennill et al., 2012b; Mennill et al., most locations, wild wolves avoid humans and can be diffi- 2012a; Frommolt and Tauchert, 2014). Accurate localization cult to survey (Boitani and Powell, 2012). In North America, at short ranges is complicated by the small time delays in particular, wolves range over very large and inaccessible involved, and so care must be taken to measure the locations areas, meaning that following the animals on foot or in of the recorders and the time differences very accurately, for vehicles is almost impossible. In the largest study of wild the latter, usually by means of spectrogram correlation wolves, in Yellowstone National Park (YNP), a small num- (Frommolt and Tauchert, 2014; Harlow et al., 2013). In ber of animals are darted from helicopters, collared with addition, synchronization between detectors must be particu- radio beacons, and used to find the approximate location of larly precise, and this, as well as cost considerations, may packs (Smith,
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