Toward Passive Acoustic Monitoring of Lemurs: Using an Affordable Open-Source System to Monitor Phaner Vocal Activity and Density

Abstract

Developing new cost-effective methods for monitoring the distribution and abundance of species is essential for conservation biology. Passive acoustic monitoring (PAM) has long been used in marine mammals and has recently been postulated to be a promising method to improve monitoring of terrestrial wildlife as well. Because Madagascar’s lemurs are among the globally most threatened taxa, this study was designed to assess the applicability of an affordable and open-source PAM device to estimate the density of pale fork-marked lemurs (Phaner pallescens). Using 12 playback experiments and one fixed transect of four automated acoustic recorders during one night of the dry season in Kirindy Forest, we experimentally estimated the detection space for Phaner and other lemur vocalizations. Furthermore, we manually annotated more than 10,000 vocalizations of Phaner from a single location and used bout rates from previous studies to estimate density within the detection space. To truncate detections beyond 150 m, we applied a sound pressure level (SPL) threshold filtering out vocalizations below SPL 50 (dB re 20 μPa). During the dry season, vocalizations of Phaner can be detected with confidence beyond 150 m by a human listener. Within our fixed truncated detection area corresponding to an area of 0.07 km2 (detection radius of 150 m), we estimated 10.5 bouts per hour corresponding to a density of Phaner of 38.6 individuals/km2. Our density estimates are in line with previous estimates based on individually marked animals conducted in the same area. Our findings suggest that PAM also could be combined with distance sampling methods to estimate densities. We conclude that PAM is a promising method to improve the monitoring and conservation of Phaner and many other vocally active primates.

ecoSound-web: an open-source, online platform for ecoacoustics

“…Furthermore, phonies can be quantified in time, space, and frequency, and alpha acoustic diversity indices can be computed. ecoSound-web has already been used successfully to analyse bird communities 75 , to measure bat activities 76 and to host reference recordings 68 . Regionand taxon-specific reference collections can be created, like the anuran and primate call collection that we host 68,77 .…”

“…For primates, acoustic communication has been studied in detail 63 . However, the potential of passive acoustic monitoring has only recently been acknowledged 64 and applied to analyze, e.g., individual caller identity in orangutans 65 , occupancy in chimps and gibbons 66,67 or density in fork-marked lemurs 68 , and reference calls have yet to be openly published.…”

Are trapping data suited for home‐range estimation?

“…Moreover, the psychophysiological welfare of animals should not be neglected, and the time spent in the trap minimized. A promising alternative to live trapping could be the use of camera traps (Harmsen et al 2010, Chavel et al 2017, Distiller et al 2020b, Chandler et al 2021) or sound recorders (March et al 2010, Markolf et al 2022).…”

Application, progress, and future perspective of passive acoustic monitoring in terrestrial mammal research

“…地和食物资源造成严重威胁 (Evers et al, 2018), 导 致 很 多 物 种 处 于 濒 临 灭 绝 的 状 态 (Hui, 2022;Johnson et al, 2017)。为了更好地、有针对性地保护 野生动物, 亟需采用高效的方式开展野生动物的种 群动态、栖息地利用和行为等方面的监测和保护管 理工作 (Grooten & Almond, 2018)。声音信号可以向 多个方向传播, 还可以穿过物理障碍进行远距离传 播 (Ma et al, 2020), 因此基于动物叫声特征开发的 被动声学监测(passive acoustic monitoring, PAM)技 术 已 成 为 生 物 多 样 性 评 估 的 一 项 重 要 手 段 (Rosenstock et al, 2002;Weir & Mossman, 2005)。该 技术指将声音传感器(以下称自动录音机)安装在野 外环境中收集野生动物及其所在环境的声音信号 的监测方法 (Parker, 1991;)。自 动录音机的数量可以是单一的, 也可以是多个的, 录音机矩阵能同步收集声音信号数据 (Blumstein et al, 2011)。PAM技术在野外应用时能够根据需求选 择特定时间段进行声音数据的收集 (Dufourq et al, 2021)。与耗费大量的人力、物力和财力并且会侵扰 动物的传统的距离抽样法 (Buckland et al, 2010; 李 月辉, 2021)和标志重捕法 (Markolf et al, 2022) (Nordeide & Kjellsby, 1999;Hawkins & Amorim, 2000;Lobel, 2002)。20世纪80年代, 随着成本更低、操作更简单 的水下自动录音机的出现, PAM技术开始被用于水 生哺乳动物的定位和研究 (Clark, 1980;Fripp et al, 2005;Mellinger & Heimlich, 2013) (Parker, 1991;Vielliard, 1993) (Charlton et al, 2010;Wyman et al, 2012), 叫声可以传播发声者物种、位置、数量、性别、个 体等信息 (McGregor, 2005;Wilkins et al, 2013;Fan et al, 2019), 能够实现警报危险 (Blumstein & Daniel, 2004)、 防御领域 (Ma et al, 2020)、 吸引配偶 (Milich et al, 2014)…”