Can an acoustic observatory contribute to the conservation of threatened species?

Observatories are designed to collect data for a range of uses. The Australian Acoustic Observatory (A2O) was established to collect environmental sound, including audible species calls, from 344 recorders at 86 sites around Australia. We examine the potential of the A2O to monitor near threatened, threatened, endangered and critically endangered species, based on their vocal behaviour, geographic distributions in relation to the sites of the A2O and on some knowledge of habitat use. Using IUCN and EPBC lists of threatened and endangered species, we extracted species that vocalized in the audible range, and using conservative estimates of their geographic ranges, determined whether there was a possibility of hearing them at these sites. We found that it may be possible to detect up to 171 threatened species at sites established for the A2O, and that individual sites have the potential to detect up to 40 threatened species. All 86 sites occurred in locations where threatened species could possibly be detected, and the list of detectable species included birds, amphibians, and mammals. We have incidentally detected one mammal and four bird species in the data during other work. Threatening processes to which potentially detectable species were exposed included all but two IUCN threat categories. We concluded that with applications of technology to search the audio data from the A2O, it could serve as an important tool for monitoring threatened species.     

Pond Acoustic Sampling Scheme: A draft protocol for rapid acoustic data collection in small waterbodies

1. Freshwater conservation is vital to the maintenance of global biodiversity. Ponds are a critical, yet often under‐recognized, part of this, contributing to overall ecosystem functioning and diversity. They provide habitats for a range of aquatic, terrestrial, and amphibious life, often including rare and declining species.
2. Effective, rapid, and accessible survey methods are needed to enable evidence‐based conservation action, but freshwater taxa are often viewed as “difficult”—and few specialist surveyors are available. Datasets on ponds are therefore limited in their spatiotemporal coverage.
3. With the advent of new recording technologies, acoustic survey methods are becoming increasingly available to researchers, citizen scientists, and conservation practitioners. They can be an effective and noninvasive approach for gathering data on target species, assemblages, and environmental variables. However, freshwater applications are lagging behind those in terrestrial and marine spheres, and as an emergent method, research studies have employed a multitude of different sampling protocols.
4. We propose the Pond Acoustic Sampling Scheme (PASS), a simple protocol to allow a standardized minimal sample to be collected rapidly from small waterbodies, alongside environmental and methodological metadata. This sampling scheme can be incorporated into a variety of survey designs and is intended to allow access to a wide range of participants, without requiring complicated or prohibitively expensive equipment.
5. Adoption of this sampling protocol would enable consistent sound recordings to be gathered by researchers and conservation organizations, and allow the development of landscape‐scale surveys, data sharing, and collaboration within an expanding freshwater ecoacoustic community—rather than individual approaches that produce incompatible datasets. The compilation of standardized data would improve the prospects for effective research into the soundscapes of small waterbodies and aid freshwater conservation efforts.

     

It's time to listen: there is much to be learned from the sounds of tropical ecosystems

Knowledge that can be gained from acoustic data collection in tropical ecosystems is low‐hanging fruit. There is every reason to record and with every day, there are fewer excuses not to do it. In recent years, the cost of acoustic recorders has decreased substantially (some can be purchased for under US$50, e.g., Hill et al. 2018) and the technology needed to store and analyze acoustic data is continuously improving (e.g., Corrada Bravo et al. 2017, Xie et al. 2017). Soundscape recordings provide a permanent record of a site at a given time and contain a wealth of invaluable and irreplaceable information. Although challenges remain, failure to collect acoustic data now in tropical ecosystems would represent a failure to future generations of tropical researchers and the citizens that benefit from ecological research. In this commentary, we (1) argue for the need to increase acoustic monitoring in tropical systems; (2) describe the types of research questions and conservation issues that can be addressed with passive acoustic monitoring (PAM) using both short‐ and long‐term data in terrestrial and freshwater habitats; and (3) present an initial plan for establishing a global repository of tropical recordings.     

Traffic noise impacts on urban forest soundscapes in south‐eastern Australia

While the negative impacts of road infrastructure on faunal diversity and abundance have been extensively studied, many traffic noise studies have been conducted in the presence of confounding factors. Therefore, the extent to which traffic noise alone is responsible for impacts is not well known and a better understanding is required to inform urban planning and management decisions. We examined the impact of traffic noise on soundscape patterns at road edges in urban forests. Acoustic sensors were deployed at road and powerline edges, as well as within interior habitat, at three sites in south‐east Queensland, Australia. Powerline edges were included to separate edge effects from traffic noise impacts. We used soundscape power (normalized watts per kHz) of technophony (traffic noise in the 1–2 kHz range) and biophony (animal sounds in the 3–11 kHz range) to investigate soundscape patterns. The results showed that biophony was consistently lower at road edges and was negatively correlated with traffic noise and positively correlated with distance to road edge. Technophony was higher at road edges and was found to correlate negatively with distance to road edge and positively with traffic noise. Technophony and biophony at powerline edges generally exhibited values comparable to interior habitat. These results indicate that traffic noise affects urban forest soundscape patterns at road edges in south‐eastern Australia.     

The impact of environmental factors in birdsong acquisition using automated recorders

The use of automatic acoustic recorders is becoming a principal method to survey birds in their natural habitats, as it is relatively noninvasive while still being informative. As with any other sound, birdsong degrades in amplitude, frequency, and temporal structure as it propagates to the recorder through the environment. Knowing how different birdsongs attenuate under different conditions is useful to, for example, develop protocols for deploying acoustic recorders and improve automated detection methods, an essential part of the research field that is becoming known as ecoacoustics. This article presents playback and recapture (record) experiments carried out under different environmental conditions using twenty bird calls from eleven New Zealand bird species in a native forest and an open area, answering five research questions: (1) How does birdsong attenuation differ between forest and open space? (2) What is the relationship between transmission height and birdsong attenuation? (3) How does frequency of birdsong impact the degradation of sound with distance? (4) Is birdsong attenuation different during the night compared to the day? and (5) what is the impact of wind on attenuation? Bird calls are complex sounds; therefore, we have chosen to use them rather than simple tones to ensure that this complexity is not missed in the analysis. The results demonstrate that birdsong transmission was significantly better in the forest than in the open site. During the night, the attenuation was at a minimum in both experimental sites. Transmission height affected the propagation of the songs of many species, particularly the flightless ones. The effect of wind was severe in the open site and attenuated lower frequencies. The reverberations due to reflective surfaces masked higher frequencies (8 kHz) in the forest even at moderate distances. The findings presented here can be applied to develop protocols for passive acoustic monitoring. Even though the attenuation can be generalized to frequency bands, the structure of the birdsong is also important. Selecting a reasonable sampling frequency avoids unnecessary data accumulation because higher frequencies attenuate more in the forest. Even at moderate distances, recorders capture significantly attenuated birdsong, and hence, automated analysis methods for field recordings need to be able to detect and recognize faint birdsong.     

Do soundscape indices predict landscape‐scale restoration outcomes? A comparative study of restored seabird island soundscapes

Measuring restoration outcomes is essential, but challenging and expensive, particularly on remote islands. Acoustic recording increases the scale of monitoring inexpensively; however, extracting biological information from large volumes of recordings remains challenging. Soundscape approaches, characterizing communities using acoustic indices, rapidly analyze large acoustic datasets and can be used to compare restoration sites against reference conditions. We tested this approach to measure nocturnal seabird recovery following invasive predator removal in the Aleutian Islands. We used recordings of nocturnal seabird soundscapes from six islands with varied histories of predators, from never invaded (one island) to 9–34 years post‐predator removal (four islands) and currently invaded (one island). We calculated 10 indices of acoustic intensity and complexity, and two pairwise indices of acoustic differences. Three indices reflected patterns of seabird recovery. Acoustic richness (measuring temporal entropy and amplitude) increased with time since predator removal and presence of historical predator refugia (r² = 0.44). These factors and moonlight accounted for 30% of variation in cumulative spectral difference from the reference island. Over 10% of acoustic richness and temporal entropy was explained by Leach's Storm‐petrel (Oceanodroma leucorhoa) calls. However, indices characterized the soundscape of rat‐invaded Kiska Island like a never invaded island, likely due to high abiotic noise and few seabird calls. Soundscape indices have potential to monitor outcomes of seabird restoration quickly and cheaply, if confounding factors are considered and controlled in experimental design. We suggest soundscape indices become part of the expanding acoustic monitoring toolbox to cost‐effectively measure restoration outcomes at scale and in remote areas.     

鸟类迁徙对图们江下游湿地声景时间格局的影响

声景生态学是一个相对较新和快速发展的研究领域,被动声学监测技术和声学指数已经成为研究湿地鸟类和声景多样性的重要方法。本研究评价了鸟类迁徙对中国东北图们江流域下游湿地声景日、月和季节变化的影响。我们从2020年11月至2021年12月在图们江下游敬信湿地设置10个采样点,获得91,988条时长5min的有效音频,计算了声音复杂度指数(acoustic complexity index,ACI)、生物声学指数(bioacoustic index,BIO)、声音均匀度指数(acoustic evenness index,AEI)和标准化声景差异指数(normalized difference soundscape index,NDSI)以及1–11 k Hz频段的功率谱密度(power spectral density,PSD)。结果表明,声学指数对鸟类迁徙活动敏感,其中2个迁徙期声景(2–4月和10–11月)都以1–2k Hz雁类白天的叫声为主,NDSI显著降低,1–2k Hz的PSD显著升高,但雁类向北迁徙时几个声学指数变化更为敏感,有效地捕获了迁徙峰值,表明不同季节鸟类迁徙模式存在差异...     

Singing streams: Describing freshwater soundscapes with the help of acoustic indices

1. Understanding soundscapes, that is, the totality of sounds within a location, helps to assess nature in a more holistic way, providing a novel approach to investigating ecosystems. To date, very few studies have investigated freshwater soundscapes in their entirety and none across a broad spatial scale.
2. In this study, we recorded 12 freshwater streams in South East Queensland continuously for three days and calculated three acoustic indices for each minute in each stream. We then used principal component analysis of summary statistics for all three acoustic indices to investigate acoustic properties of each stream and spatial variation in their soundscapes.
3. All streams had a unique soundscape with most exhibiting diurnal variation in acoustic patterns. Across these sites, we identified five distinct groups with similar acoustic characteristics. We found that we could use summary statistics of AIs to describe daytimes across streams as well. Most difference in stream soundscapes was observed during the daytime with significant variation in soundscapes both between hours and among sites.
4. Synthesis and Application. We demonstrate how to characterize stream soundscapes by using simple summary statistics of complex acoustic indices. This technique allows simple and rapid investigation of streams with similar acoustic properties and the capacity to characterize them in a holistic and universal way. While we developed this technique for freshwater streams, it is also applicable to terrestrial and marine soundscapes.

     

东北虎豹国家公园森林声景的昼夜和季节变化

被动声学监测技术和声学指数通过对音频数据的时频域特征进行定量分析,可以反映声景的复杂度、多样性和健康程度等,已经成为评估生物多样性变化的重要手段。本研究从2020年6月至2021年6月在东北虎豹国家公园采集了52个点的声学数据,计算了春、夏、秋、冬4个季节和黎明、白天、黄昏、夜晚4个昼夜时间段的声音复杂度指数(acoustic complexity index,ACI)、声音多样性指数(acoustic diversity index,ADI)、声音均匀度指数(acoustic evenness index,AEI)、生物声学指数(bioacoustic index,BIO)、标准化声景差异指数(normalized difference soundscape index,NDSI)、声音熵指数(acoustic entropy index,H)和1–21k Hz共20个频段的功率谱密度(power spectral density,PSD)等声学指数,评价了声景构成和多样性的昼夜和季节性差异。结果表明,东北虎豹国家公园的声景随季节变化具有显著的昼夜节律差异,尤其是夜晚的声景和声学成分...     

现代生物声学的学科发展趋势及中国机遇

随着数字录音技术、电子学和微电子学、人工智能、信息科学等跨学科领域的技术革新,现代生物声学逐渐与生物学、生态学等学科及关联学科之间形成了广泛的交叉前沿领域。现阶段,现代生物声学主要以生物学、生态学等基础学科的理论方法为指导,着重于揭示环境中各类声音在生物之间以及生物与人类、环境之间的相互作用及相关科学规律,为人类认识、保护和利用生物声学资源提供理论基础和解决方案。本文重点阐述了现代生物声学的学科内涵和学科特征,介绍了动物生物声学、生态声学、水下生物声学、环境生物声学、保护生物声学、计算生物声学以及现代生物声学研究的技术框架等前沿热点和发展趋势,评估了中国生物声学研究的学科现状与发展机遇,并对未来学科建设进行了展望。