Method For Ecoacoustics Research Articles

Visualization and Quantification of the Activities of Animal Vocalizations in Forest Species Using Robot Audition Techniques

Ecoacoustics is a recent ecological discipline focusing on the ecological role of sounds. This study applies robot audition techniques and ecoacoustic methods in the visualization and quantification of forest animal vocalization, focusing mainly on inter-specific interactions between birds and cicadas. We adopt HARK, an open-source robot audition software, which enables us to estimate the direction of arrival of sound sources and their separated sounds using a microphone array unit. We focus on recordings in an experimental forest in Japan, where birds and cicadas dominate the soundscape. Cicada songs were further replayed at a regular interval repeatedly. We create a false-colour spectrogram based on the directions of arrival of sounds to grasp the individual-level dynamics of the soundscape of birds and cicadas in the recording. We further describe a method to classify their vocalizations using three ecoacoustic indices, then illustrate their temporal vocalization dynamics, measured as the total song duration in each time segment. We also conducted a quantitative analysis of their vocal activities to determine if there exist interactions among birds and cicadas, and the effects of replayed vocalizations of cicadas on them. The preliminary analysis implied that there might exist temporal overlap avoidance behaviours between birds and cicadas, and replayed songs of cicadas may reduce the activity of birds. We believe that this proof-of-concept observation and analysis can contribute to the further development of the fine-scale measurement of the biodiversity or habitat quality of environments based on the vocal activities of multiple species, while further detailed analysis is necessary.

Exploring Ecoacoustic Trajectories in a Giant Sequoia Forest After Wildfire

Forest management strategies that create spatially diverse fire-caused disturbance outcomes, consistent with historic fire regimes, are a desired condition for fire adapted western United States forests. In this context, the temporal dynamics of forest response to fire can inform the tempo and scale of forest management, including prescribed burning. Here, we investigated the use of ecoacoustic methods to assess ecological condition in a four-year period (2016–2019) after wildfire in a giant sequoia forest landscape within Kings Canyon National Park, California, United States. Audio recorders at nine sites were deployed soon after the 2015 Rough Fire subsided. The monitoring sites were located in regions with different fire histories, representing five fire history categories. We used the Acoustic Complexity Index (ACI) to document biotic chorus complexity. This previously tested ecoacoustic index provided a daily indicator of biotic sound activity in frequencies dominated by avian calls. Patterns in ACI were evaluated using generalized additive mixed models to understand the relationship with time-since-fire and covariates that accounted for season, fire history category, and weather conditions. We showed that time-since fire and fire-history influenced patterns in ACI after accounting for season and air temperature effects. Monitoring sites where prescribed fire preceded the Rough Fire showed the highest predicted ACI and evidence for a relatively consistent seasonal pattern in ecoacoustic activity across subsequent seasons. Sites without prescribed fire and burned by the Rough Fire exhibited the most pronounced successive decreases in ACI in the first and second years after the fire. The daily temporal resolution of the ecoacoustic index also revealed phenological shifts related to time-since-fire and fire history. Sites unburned by the Rough Fire offered some context for how fire changed ecoacoustic activity post-wildfire, however evidence suggested they were also impacted by the presence of the nearby Rough Fire. The patterns in the ecoacoustic index when combined with vegetation surveys offered complementary insights into ecological dynamics of regeneration after fire. Our exploratory analysis showed that using ecoacoustic methods in wildfire monitoring offers a scalable approach to remote sensing of ecological trends. Archived recordings from the monitoring effort afford future opportunities for new or more detailed insights.

Ecoacoustics: acoustic sensing for biodiversity monitoring at scale

Ecoacoustics: acoustic sensing for biodiversity monitoring at scale

Interdisciplinary approaches to freshwater ecoacoustics

Freshwater ecoacoustics is an emerging field that involves underwater audio recordings to detect the presence, location, and density of species in noninvasive and unbiased ways. Conducted long-term, ecoacoustics provides information on biophysical changes and environmental patterns that can advance freshwater conservation. River Listening is an interdisciplinary research project exploring the possibilities of freshwater ecoacoustics in the conservation and management of global river systems. The project works at the intersection of art and science by investigating the cultural and biological diversity of freshwater ecosystems through real-time listening and underwater recording used for biodiversity monitoring and public engagement. We use noninvasive recording techniques with accessible hydrophone kits and participatory workshops to engage local communities in the process and outcomes. The resulting database of hydrophone recordings is used for ongoing scientific research and diverse creative projects disseminated worldwide. The artistic outcomes from River Listening are central to our public engagement efforts, which include mobile phone applications with soundscapes triggered by GPS along rivers as well as live-streaming hydrophone arrays. These artistic projects have assisted in the advancement of scientific recording techniques and ecoacoustic methods. In this article, we introduce the foundations of River Listening and acknowledge a series of artists who have pioneered the use of hydrophone recording for both scientific and artistic purposes. The integration of art and science is further explored through a case study of our workshops and sound walks that have become the core public engagement tool for River Listening. We argue that interdisciplinary approaches are critical to the emerging field of freshwater ecoacoustics and call for further collaborations between artists, scientists, and communities to record and share the soundscapes of freshwater ecosystems.

Monitoring canopy bird activity in disturbed landscapes with automatic recorders: A case study in the tropics

Tropical forests are facing threats that may affect the dynamics of seed dispersers which participate in the forest regeneration. To implement appropriate conservation programs, it appears necessary to monitor seed dispersers and to estimate their response to local changes. Here, we used non-invasive ecoacoustic methods to monitor the activity of a canopy bird, the White-throated toucan, Ramphastos tucanus, a major seed disperser and flagship species of the Amazonian forest. We deployed nine acoustic recorders over 29 days along a road that connects French Guiana to Brazil. We used template matching to automatically detect the vocalizations of R. tucanus. This method, which can easily be repeated with limited human expertise, detected 1748 recordings with R. tucanus vocalizations. A GLMM analysis was applied to test for a possible effect of habitat type and human activity, while accounting for time of the day and rainfall. The number of vocalizations varied according to time of the day with peaks at dawn and dusk. The number of vocalizations did not differ significantly among sites, they were not affected by habitat type, and they were only marginally influenced by human activity. These results indicate that the vocal activity of a key conservation species can be monitored automatically in a non-invasive way. The species targeted, R. tucanus, does not seem to be significantly impacted by the road and local human activity. This might be related to the mobility of the species, which can easily cross the road, as well as low local forestry pressure.

The call of the wild: Investigating the potential for ecoacoustic methods in mapping wilderness areas

The critical importance of wilderness areas (WAs) for biodiversity conservation and human well-being is well established yet mapping criteria on which WA management policies are based take neither into account. Current WA mapping methods are framed in terms of absence of anthropogenic influence, and created using visual satellite data, obviating consideration of the ecological or anthropogenic value of WAs. In this paper we suggest that taking the acoustic environment into account could address this lacuna. We report the first investigation into the potential for ecoacoustic methods to complement existing geophysical approaches. Participatory walks, including in situ questionnaires and ecoacoustic surveys were carried out at points along transects traversing urban-wilderness gradients at four study sites in the Scottish Highlands and French Pyrenees. The relationships between a suite of six acoustic indices (AIs), wilderness classifications and human subjective ratings were examined. We observed significant differences between five out of six AIs tested across wilderness classes, demonstrating significant differences in the soundscape across urban-wild gradients. Strong, significant correlations between AIs, wilderness classes and human perceptions of wildness were observed, although magnitude and direction of correlations varied across sites. Finally, a compound acoustic index is shown to strongly predict mapped wildness classes (up to 95% variance explained MSE 0.22); perceived wilderness and biodiversity are even more strongly predicted. Together these results demonstrate that the acoustic environment varies significantly along urban-wild gradients; AIs reveal details of environmental variation excluded under current methods, and capture key facets of the human experience of wildness. An important next step is to ascertain the ecological and anthropogenic relevance of these differences, and develop new automated acoustic analysis methods suited to mapping the environmental characteristics of WAs. Taken together, our results suggest that future management of WAs could benefit from ecoacoustic methods to take the biosphere and anthroposphere into account.

Ecoacoustics can detect ecosystem responses to environmental water allocations

Abstract Globally, water abstraction for human consumption and irrigated agriculture leads to significant changes in aquatic ecosystems. To counter these detrimental effects, water releases—often termed environmental water allocations—restore overbank flow or are delivered to artificially disconnected wetlands. While a suite of monitoring methods is available, few programmes track continuous change in biota, mainly because repeated remote site visits can be prohibitively expensive. In this paper, we propose a new approach to environmental flow monitoring, using ecoacoustic methods. We test acoustic monitoring of frog and waterbird responses to environmental water deliveries in the Goulburn Broken, a valley in the southern Murray–Darling river system. Response to three major environmental water deliveries within 2 years was monitored at four sites along Reedy swamp. Every 2 weeks, 30 s were recorded every 30 min, for a total of 24 hr. We used two analysis strategies—manual counts of bird calls, as well as ecoacoustic indices, which describe the sonic properties of the acoustic spectrum at a site. Manual counts demonstrated that water‐dependent birds were clearly responding to environmental water deliveries, whereas non‐water‐dependent species did not show any increases in activity. After restricting the analysis to the dawn chorus of birds and frogs, two acoustic indices (the median amplitude and the acoustic complexity index) showed responses to watering events. Ecoacoustic methods show promise for continuous response monitoring to environmental water allocations. However, the first strategy—manual annotation of calls—might be too labour intensive for standard monitoring programmes. The second strategy—index‐based approaches—can also detect ecological responses, although further investigation using control sites is needed. Automated call classifiers are an alternative that is currently being developed for endangered species. We also encourage simultaneous monitoring of the soundscape above and under water.

A new method for ecoacoustics? Toward the extraction and evaluation of ecologically-meaningful soundscape components using sparse coding methods.

Passive acoustic monitoring is emerging as a promising non-invasive proxy for ecological complexity with potential as a tool for remote assessment and monitoring (Sueur & Farina, 2015). Rather than attempting to recognise species-specific calls, either manually or automatically, there is a growing interest in evaluating the global acoustic environment. Positioned within the conceptual framework of ecoacoustics, a growing number of indices have been proposed which aim to capture community-level dynamics by (e.g., Pieretti, Farina & Morri, 2011; Farina, 2014; Sueur et al., 2008b) by providing statistical summaries of the frequency or time domain signal. Although promising, the ecological relevance and efficacy as a monitoring tool of these indices is still unclear. In this paper we suggest that by virtue of operating in the time or frequency domain, existing indices are limited in their ability to access key structural information in the spectro-temporal domain. Alternative methods in which time-frequency dynamics are preserved are considered. Sparse-coding and source separation algorithms (specifically, shift-invariant probabilistic latent component analysis in 2D) are proposed as a means to access and summarise time-frequency dynamics which may be more ecologically-meaningful.

Using ecoacoustic methods to survey the impacts of climate change on biodiversity

Climate change is an important cause of the irreversible transformation of habitats, of the rapid extinction of species, and of the dramatic changes in entire communities, especially for tropical assemblages and for habitat- and range-restricted species, such as mountaintop and polar species.In particular, climate change effects several aspects of animal sounds (e.g., song amplitude and frequency, song post, and sound phenology). Animal sounds, which are life traits characterized by high plasticity, are able to cope with even modest variations of environmental fundamentals like vegetation cover, land mosaic structure, temperature, humidity, and pH (for aquatic medium). Moreover, the climatic effects on these biophonies can be observed earlier than change in vegetation patterns and visible landscape structures.Ecoacoustics, the discipline that investigates the role of sound on animal ecology from species to landscapes, offers robust models, such as acoustic adaptation, acoustic niche, acoustic active space, acoustic community, and acoustic phenology to investigate the effect of climate change on species, populations, communities, and landscapes.From an operational perspective, ecoacoustics procedures can be applied in different contexts, such as locations, weather, species, populations, behavior, physiology, and phenology. In addition, thematic priorities can be selected, such as latitudinal and altitudinal gradients, restricted habitats, stopover areas, extreme environments, weather conditions, short distance migrants, species at high vocal plasticity, sink-source status, active space, social attraction, physiological modifications, dawn and dusk choruses, sound from stressed plants, and time series analysis.The noninvasiveness of passive acoustic recording, the simultaneous collection of important data, such as community richness and diversity, immigration and extinction events, and singing dynamics as well as the availability of innovative noninvasive technologies operating over a long-term period, establish ecoacoustics as a new and important tool with which it is possible to analyze massive acoustic data sets and quickly predict and/or evaluate the effects of climate change on the environment.Moreover, passive recording is supported by cheap, user-friendly field sensors and robust data processing and may be part of the citizen science research agenda on climate change.