Acoustic monitoring for conservation in tropical forests: examples from forest elephants

Abstract

Summary The accelerating loss of biodiversity worldwide demands effective tools for monitoring animal populations and informing conservation action. In habitats where direct observation is difficult (rain forests, oceans), or for cryptic species (shy, nocturnal), passive acoustic monitoring (PAM) provides cost‐effective, unbiased data collection. PAM has broad applicability in terrestrial environments, particularly tropical rain forests. Using examples from studies of forest elephants in Central African rain forest, we show how PAM can be used to investigate cryptic behaviour, mechanisms of communication, estimate population size, quantify threats, and assess the efficacy of conservation strategies. We discuss the methodologies, requirements, and challenges of obtaining these data using acoustics. Where applicable, we compare these methods to more traditional approaches. While PAM methods and associated analysis are maturing rapidly, mechanisms are needed for processing the dense raw data efficiently with standard computer hardware, speeding development of detection algorithms, and harnessing communication networks to move data from the field to research facilities. Passive acoustic monitoring is a viable and cost‐effective tool for conservation and should be incorporated in monitoring schemes much more broadly. The capability to quickly assess changes in behaviour, population size, and landscape use, simultaneously over large geographical areas, makes this approach attractive for detecting human‐induced impacts and for assessing the success of conservation strategies.

Automated identification of avian vocalizations with deep convolutional neural networks

“…), elephants (Wrege et al. ), primates (Heinicke et al. ), and various avian species (Figueira et al.…”

Bioacoustic monitoring of animal vocal behavior for conservation

“…Distinct from the related discipline ecoacoustics, bioacoustics is behavior-centric and focuses on the acoustic signals of individuals and species, rather than broader ecological processes or environments (Sueur & Farina, 2015;Towsey, Parsons, & Sueur, 2014). Potentially suited to any soundproducing species, especially those that are rare, cryptic or otherwise difficult to observe (Williams, O'Donnell, & Armstrong, 2018;Wrege, Rowland, Keen, & Shiu, 2017;Zwart, Baker, McGowan, & Whittingham, 2014), bioacoustic monitoring via autonomous recording units is becoming increasingly popular for measuring metrics such as species presence-absence (Sebastián-González, Pang-Ching, Barbosa, & Hart, 2015;Zwart et al, 2014), species richness (Celis-Murillo, Deppe, & Ward, 2012;Wimmer, Towsey, Roe, & Williamson, 2013), abundance (Borker et al, 2014;Jaramillo-Legorreta et al, 2017), and density (Efford, 2011;Efford & Fewster, 2013;Lambert & McDonald, 2014;Marques et al, 2013;Rogers, Ciaglia, Klinck, & Southwell, 2013;Stevenson et al, 2015).…”

Emerging opportunities and challenges for passive acoustics in ecological assessment and monitoring

“…These are noninvasive, autonomous, usually omni‐directional (sampling a three‐dimensional sphere around the sensor), and offer the advantage of a larger detection area and fewer taxonomic restrictions than camera traps (which are usually limited to detecting larger birds and mammals at close range) (Lucas, Moorcroft, Freeman, Rowcliffe, & Jones, ). As such, they can simultaneously survey entire vocalising animal communities and their acoustic environments (Wrege, Rowland, Keen, & Shiu, ).…”

“…Currently, we are seeing the arrival of massive acoustic datasets collected across research networks and citizen science programmes (Table ). As auto‐ID tools and wireless data transmission improve, the increasing scope of these datasets could facilitate, for example, the tracking of range shifts under climate change (Davis et al., ), long‐term studies of population ecology and habitat use (Wrege et al., ), year‐on‐year tracking of population trends (Jaramillo‐Legorreta et al., ), conservation planning and efficacy assessment (Astaras et al., ; Border et al., ), behaviour and phenology studies in taxa beyond birds and cetaceans (Nedelec et al., ), as well as monitoring of species of concern as ecosystem services providers (e.g., pollinators), pests, invasive species or public health threats (Mukundarajan, Hol, Castillo, Newby, & Prakash, ).…”