Journal of Ecoacoustics

I recorded the ambient sounds at three locations in the wilderness of Aialik Bay in Kenai Fjords National Park, Alaska between 25 June and 21 September 2019. My aim was to capture an ecoacoustic snapshot of the coastal soundscape to provide a comparable baseline for evaluating wilderness characteristics defined by the Wilderness Act of 1964. I visually and empirically characterized the Aialik Bay wilderness soundscape using the acoustic metrics of soundscape power (normalized watts/kHz) and Normalized Difference Soundscape Index (NDSI) from 5373 five-minute recordings, combined with visual and aural spectral examination of 4386 recordings. Soundscape power exhibited similar patterns across frequency intervals with sound sources primarily occurring in the low-frequency (1–2 kHz) and mid-frequency (2–5 kHz) intervals. Significant differences within frequency intervals between sites suggested the presence of distinct sonotopes. Low-frequency sounds were dominant across all three sites with peak soundscape power values across study days and 24 h timeframes attributed to wind and occasional periods of technophony emitted from commercial tour boats and private boating activities. Low-frequency geophony from wave action was ever present. Technophony exhibited some predictable patterns consistent with the timing of sightseeing boat tours. Peak values of soundscape power at mid-frequencies were attributed to the geophony of rain. Although biophonies were less common than geophonies, the choruses of songbirds were prevalent in July and promptly occurred daily between 0300 and 0600. Biophonies generally declined over the course of the day. All sites displayed negative NDSI values over most study days and consistently negative values over 24 h time frames, indicating a soundscape primarily influenced by low-frequency geophony and periods of technophony. However, NDSI values showed patterns and peaks similar to biophonies at mid-frequency intervals indicating biophony was still a notable contribution to this geophony-dominant soundscape. Despite the acoustic footprint of motorboat noise detected at all sample sites, the soundscape of the Aialik Bay wilderness was dominated by the natural sounds of geophony, biophony, and occasional periods of natural quiet indicative of a wilderness only partially impacted by technophony. Full article

Auditory signals are often used by forest species to attract mates, define and defend territories, and locate prey, and thus these signals may be monitored and used to estimate species presence, richness and acoustic complexity of a patch of habitat. We analyzed recordings from a biodiversity hotspot in the rainforests of Batang Ai National Park in Sarawak, Malaysian Borneo. Three recording sites were established in the forest understory and continuous recordings were made for an acoustic snapshot of approximately 40 h. From these recordings, the bioacoustic index (BI) and acoustic complexity index (ACI) were computed. These acoustic indices exhibited clear periodicity with periods on the order of >6 h. The ACI and BI time series also showed oscillations, with peaks separated by 12 h corresponding to the alternation between bird and frog activity during the day and night, respectively. We quantified the relationships between the acoustic index values and anuran and avian richness, and environmental variables (rainfall intensity and time of day) using correlative and information theoretic techniques. ACI and BI were moderately positively and negatively correlated with rainfall intensity, respectively. ACI and BI were also weakly-to-moderately correlated to species richness, but with mixed directions between recording sites. However, the correlations and mutual information values, a model-free estimator of the relationship strength of random variables, were highest for the relationships between ACI and BI with respect to the rate of individual frog calls, rather than species richness alone. We conclude that acoustic indices are most useful for monitoring ecological dynamics on timescales longer than 6 h. We suggest that acoustic indices are best applied to studying changes in acoustic activity at the level of ecological populations rather than for estimating species richness, as they have been commonly applied in the past. Full article

The 2020 COVID-19 pandemic and the resulting national and international movement restrictions provide a unique opportunity to investigate the consequences of changing anthropogenic noise regimes on animal communities and soundscapes. Here, I used this lockdown period as a natural experiment to investigate changes to soundscape intensity, structure, and dynamics during restricted human activity (lockdown) in suburban Nottingham, UK. Using 11 common acoustic indices, I tested for differences in the richness and evenness of the soundscape during the COVID-19 lockdown, and I measured changes in soundscape dynamics by comparing the temporal variability of acoustic indices during versus after the lockdown. Regardless of how the soundscape was summarised, there were significant differences in the intensity, evenness, and temporal variability of the soundscape during the COVID-19 lockdown, principally driven by changes to anthropogenic noise. I recorded a shift away from a dominance of anthropophony towards more intense biological sounds during the lockdown, and the lockdown soundscape was generally more even, particularly because of changes to the magnitude of the diurnal cycle. These preliminary results from a mass human confinement experiment provide an early glimpse into how suburban soundscapes are impacted by noise pollution. In time, globally distributed longer-term monitoring efforts will reveal the generality of these findings, facilitating a mechanistic understanding of the impacts of anthropogenic noise on the world’s natural and human-dominated soundscapes. Full article

Passive acoustic monitoring can be used to assess the presence of vocal species. Automatic estimation of such information is critical for allowing diversity monitoring over long time spans. Among the existing tools, α-acoustic indices were originally designed to assess the richness/complexity of terrestrial soundscapes. However, their use in marine environments is impacted by fundamental differences between terrestrial and marine soundscapes. The aim of this study was to determine how they vary depending on the abundance and sound type richness of fish sounds. Fourteen indices used in terrestrial environments were tested. The indices were calculated for files from three sources: a controlled environment (playback of artificial tracks in a pool), in situ playbacks (playback of natural soundscapes), and a natural environment (only natural sounds). The controlled experiment showed that some indices were correlated with the sound abundance but not with the sound type richness, implying that they are not capable of distinguishing the different types of fish sounds. In the in situ playbacks, the indices were not able to capture differences, both in terms of the sound abundance and sound type diversity. In the natural environment, there was no correlation between most of the indices and the abundance of sounds. They were impacted by mass phenomena of biological sounds (e.g., the Pomacentridae sounds in shallow reefs) that cannot inform on fish acoustic diversity. Indices are appropriate when soundscapes are divided into bands. In contrast to terrestrial environments, frequency bands in coastal marine soundscapes do not provide ecologically relevant information on diversity. Overall, indices do not appear to be suitable for inferring marine fish sound diversity. Full article

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. Full article

High background noise can interfere with signal detection and perception. Bornean foot-flagging frogs,Staurois parvus, live along noisy streams and use both acoustic and visual signals to communicate. It remains unclear why acoustic signalling is retained given that visual signalling appears to have clear advantages under these noisy conditions. We hypothesized that temporal dynamics in stream noise have shaped the multimodal communication system inS. parvuswith acoustic signalling at an advantage under more quiet conditions, whereas visual signals will prevail when the noise of rushing water is high after rains. We found that as predicted, maleS. parvusincreased foot flagging and decreased advertisement calling when presented with playbacks of stream noise compared to less noisy pre-playback conditions. Such context-dependent dynamic-selection regimes are recently gaining wider attention and enhance our understanding of the flexibility seen in the use of multimodal signals inS. parvus. Full article

The Journal of Ecoacoustics (JEA) is online again after one year of forced interruption due to changing our Publisher... Full article

Biodiversity monitoring and assessment across a variety of gradients, could be achieved with the aid of the ecoacoustics discipline. Acoustic monitoring approaches can provide results regarding the species richness of birds, bats, frogs and insects including cicadas (Cicadoidea) and katydids (Tettigoniidae) with results similar to the ones provided by classical ecological methods (e.g. visual point count methods). The risk of extinction of several species has led to the creation of the Natura 2000 Network in the European Union’s territory. Greece provides a number of 202 Special Protection Areas (SPA’s) and 241 Sites of Community Importance (SCI), 239 of which are considered as Special Areas of Conservation (SAC). The specific areas provide both, an opportunity for ecoacoustics practice and an opportunity for ecoacoustic research. Even though the specific field of ecology has proven to be a valuable biodiversity assessment tool, areas that provide a variety of ecoacoustic events are yet to be documented. The goal of the specific article is to highlight these special conservation areas and propose a monitoring network using the non-invasive approach of ecoacoustics. For the specific research, the Greek protected areas were visualized in order to highlight sonotopes and soundtopes worthy of future research. Finally, in order to highlight the neglected issue of background noise regarding conservation efforts, the Kalloni’s salt pans were selected as a case study area. Noise measurements and sound recordings were conducted. Furthermore, noise and sound maps were created, in order to visualize the effects of noise. Full article

The boreal forest of Alberta, Canada is important breeding habitat for North American songbirds. Thousands of oil and gas wellsites exist in this region that have been actively reclaimed since the 1960s. Limited information exists on how songbirds respond to regeneration of wellsites following reclamation. Methods that provide spatially accurate data are required to determine impacts of these small disturbances characteristic of energy sector on songbirds. Acoustic localization can be used to determine singing locations, based on time of arrival differences of songs to an array of microphones. We used acoustic localization to determine the assemblage of songbirds on 12 reclaimed wellsites ranging from 7 to 49 years since reclamation, and how the similarity of this assemblage to 12 control mature forest sites (greater than 80 years old) changed with increasing canopy cover on the wellsite. Songbird community composition became more similar to mature forest as canopy cover increased on reclaimed wellsites. Results from this study suggest that wellsite reclamation practices are allowing for initial suitable vegetation recovery, however more research on the effectiveness of different strategies at promoting regeneration of wellsites and subsequent impact on songbird communities is required. Full article

Soundscape analysis is a potentially powerful tool in ecosystem monitoring. Ecoacoustic metrics, including the Acoustic Complexity Index (ACI) and Acoustic Entropy (H), were originally developed for terrestrial ecosystems and are now increasingly being applied to investigate the biodiversity, habitat complexity and health of marine systems, with mixed results. To elucidate the efficacy of applying these metrics to marine soundscapes, their sensitivity to variations in call rate and call type were evaluated using a combination of field data and synthetic recordings. In soundscapes dominated by impulsive broadband snapping shrimp sounds, ACI increased non-linearly with increased snapping rate (∼100–3500 snaps/min), with a percent range of variation (∼40–50%) that exceeds that reported in most studies. H, however, decreased only slightly (∼0.04 units) in response to these same snap rate changes. The response of these metrics to changes in the rate of broadband snapping was not strongly influenced by the spectral resolution of the analysis. For soundscapes dominated by harmonic fish calls, increased rates of calling (∼5–120 calls/min) led to decreased ACI (∼20–40% range of variation) when coarse spectral resolutions (Δf = 94 or 47 Hz) were used in the analysis, but ACI increased (∼20% range of variation) when a finer resolution (Δf = 23 Hz) was employed. Regardless of spectral resolution used in the analysis, H decreased (∼0.20 units) in response to increased rates of harmonic calling. These results show that ACI and H can be modulated strongly by variations in the activity of a single sound-producing species, with additional sensitivity to call type and the resolution of the analysis. Variations in ACI and H, therefore, cannot be assumed to track call diversity, and the utility of these metrics as ecological indicators in marine environments may be limited. Full article

In response to anthropogenic noise, many bird species adjust their song frequency, presumably to optimize song transmission and overcome noise masking. But the costs of song adjustments may outweigh the benefits during different stages of breeding, depending on the locations of potential receivers. Selection might favor unpaired males to alter their songs because they sing to attract females that may be widely dispersed, whereas paired males might not if mates and neighbors are primary receivers of their song. We hypothesized male house wrens (Troglodytes aedon) respond differently to noise depending on their pairing status. To test our hypothesis we synthesized pink noise, which mimics anthropogenic noise, and played it at three intensities in territories of paired and unpaired focal males. We recorded their songs and analyzed whether song structure varied with pairing status and noise treatment. To validate our study design, we tested whether noise playback affected measurement of spectral song traits and changed noise levels within territories of focal males. Consistent with our predictions, unpaired males sang differently than paired males, giving longer songs at higher rates. Contrary to predictions, paired males changed their songs by increasing peak frequency during high intensity noise playback, whereas unpaired males did not. If adjusting song frequency in noise is beneficial for long-distance communication we would have expected unpaired males to change their songs in response to noise. By adjusting song frequency, paired males reduce masking and produce a song that is easier to hear. However, if females prefer low frequency song, then unpaired males may be constrained by female preference. Alternatively, if noise adjustments are learned and vary with experience or quality, unpaired males in our study population may be younger, less experienced, or lower quality males. Full article

Long-duration recordings of the natural environment have many advantages in passive monitoring of animal diversity. Technological advances now enable the collection of far more audio than can be listened to, necessitating the development of scalable approaches for distinguishing signal from noise. Computational methods, using automated species recognisers, have improved in accuracy but require considerable coding expertise. The content of environmental recordings is unconstrained, and the creation of labelled datasets required for machine learning purposes is a time-consuming, expensive enterprise. Here, we describe a visual approach to the analysis of environmental recordings using long-duration false-colour (LDFC) spectrograms, prepared from combinations of spectral indices. The technique was originally developed to visualize 24-hour “soundscapes.” A soundscape is an ecoacoustics concept that encompasses the totality of sound in an ecosystem. We describe three case studies to demonstrate how LDFC spectrograms can be used, not only to study soundscapes, but also to monitor individual species within them. In the first case, LDFC spectrograms help to solve a “needle in the haystack” problem—to locate vocalisations of the furtive Lewin’s Rail (Tasmanian), Lewinia pectoralis brachipus. We extend the technique by using a machine learning method to scan multiple days of LDFC spectrograms. In the second case study, we demonstrate that frog choruses are easily identified in LDFC spectrograms because of their extended time-scale. Although calls of individual frogs are lost in the cacophony of sound, spectral indices can distinguish different chorus characteristics. Third, we demonstrate that the method can be extended to the detection of bat echolocation calls. By converting complex acoustic data into readily interpretable images, our practical approach bridges the gap between bioacoustics and ecoacoustics, encompassing temporal scales across three orders of magnitude. Using the one methodology, it is possible to monitor entire soundscapes and individual species within those soundscapes. Full article

Background noise can have a substantial effect on communication signals, however far less is known about how natural soundscapes may influence hearing sensitivity. Here we compare the audiograms of 26 wild beluga whales measured in their natural environment to a series of ecoacoustic measurements within a primary portion of their Bristol Bay summer habitat, the Nushagak Estuary in Bristol Bay, AK, USA. Environmental acoustic measurements were made during 2012 and 2016 using two different methods: a moored recorder and drifter buoys. Environmental noise curves varied substantially. Drifter recordings from the middle of Nushgak Estuary had the highest spectrum levels during ebb tides with acoustic energy from sediment transport extending well into higher frequencies (ca. 60 kHz), likely due to rapidly moving tidal flow and shifting sediment in that location. Drifter recordings near the estuary mouth and shallow tidal flats were lower amplitude. Noise levels generally varied during drifts (in one case up to ca. 6 dB) reflecting acoustic cues available to the local belugas. The moored recorder showed a substantially different spectral profile, especially at lower frequencies, perhaps due to its attachment to a pier piling and subsequent pier noise. Hearing sensitivity varied by individual and thresholds often fell above 1/3 octave-band noise levels, but not overall noise spectral density. Audiograms of the most sensitive animals closely paralleled the lowest ambient noise power spectral density curves, suggesting that an animal’s auditory dynamic range may extend to include its habitat’s quietest conditions. These data suggest a cautious approach is necessary when estimating the sound-sensitivity of odontocetes found in quiet environments as they may have sensitive auditory abilities that allow for hearing within the lowest noise-level conditions. Further, lower level ambient noise conditions could provide a conservative estimate of the maximal sensitivity of some cetacean populations within specific environments. Full article

Ecoacoustics is a new discipline that investigates the ecological role of sounds. Ecoacoustics is a relevant field of research related to long-term monitoring, habitat health, biodiversity assessment, soundscape conservation and ecosystem management. Several life traits of the species, populations, communities, and landscapes/waterscapes may be described by ecoacoustics. Non-invasive programmable recording devices with on-board ecoacoustic metric calculations are efficient and powerful tools to investigate ecological systems. A set of processes in four [adaptive, behavioural, geographical, ecosemiotic] domains supports and guides the development of ecoacoustics. The first domain includes evolutionary mechanisms that join sound typology with the physical and biological characteristics of the environment and create frequency partitioning among species to reduce competition. The second domain addresses interspecific signals associated with geophysical and anthropogenic sounds that operate to shape temporary acoustic communities and orient species to select suitable acoustic habitats. The third domain pertains to the geography of sound, an entity composed of three subordinate acoustic objects: sonotopes, soundtopes, and sonotones, which are operationally delimited in a geographical and temporal space by the distribution of the ecoacoustic events. The ecoacoustic events allow the classification of complex configurations of acoustic signals and represent the grain of a soundscape mosaic. The fourth domain operates by ecosemiotic mechanisms within the species level according to a function-specific perception of the acoustic information facilitated by encoding processes. Full article

Both marine mammals and hydroacoustic instruments employ underwater sound to communicate, navigate or infer information about the marine environment. Concurrent timing of acoustic activities using similar frequency regimes may result in (potentially mutual) interference of acoustic signals when both sources are within audible range of the recipient. While marine mammal fitness might be negatively impacted upon, both on individual and population level, hydroacoustic studies may generate low quality data or suffer data loss as a result of bioacoustic interference. This article pursues, in analogy to landscape planning, the concept of marine soundscape planning to reconcile potentially competing uses of acoustic space by managing the anthropogenic sound sources. We here present a conceptual framework exploring the potential of soundscape planning in reducing (mutual) acoustic interference between hydroacoustic instrumentation and marine mammals. The basis of this framework is formed by the various mechanisms by which acoustic niche formation (i.e., the partitioning of the acoustic space) occurs in species-rich communities that acoustically coexist while maintaining high fidelity (hi-fi) soundscapes, i.e., by acoustically partitioning the environment on the basis of time, space, frequency and signal structure. Hydroacoustic measurements often exhibit certain flexibility in their timing, and even instrument positioning, potentially offering the opportunity to minimize the ecological imprint of their operation. This study explores how the principle of acoustic niches could contribute to reduce potential (mutual) acoustic interference based on actual acoustic data from three recording locations in polar oceans. By employing marine soundscape planning strategies, entailing shifting the timing or position of hydroacoustic experiments, or adapting signal structure or frequency, we exemplify the potential efficacy of smart planning for four different hydroacoustic instrumentation types: multibeam echosounders, air guns, RAFOS (Ranging and Fixing of Sound) and tomographic sound sources. Full article

The ambient acoustic environment, or soundscape, is of broad interest in the study of marine ecosystems as both a source of rich sensory information to marine organisms and, more broadly, as a driver of the structure and function of marine communities. Increasing our understanding of how soundscapes affect and reflect ecological processes first requires appropriate characterization of the acoustic stimuli, and their patterns in space and time. Here, we present a novel method developed for measuring soundscape variation, using drifting acoustic recorders to quantify acoustic dynamics related to benthic habitat composition. Selected examples of drifter results from sub-tidal oyster-reef habitats in Pamlico Sound, North Carolina, USA, and from coral reef habitats in St. John, US Virgin Islands, highlight the efficacy and utility of this approach in quantifying soundscape variation in diverse habitats. The platform introduces minimal noise into the acoustic recordings, and allows sampling at spatial scales that might typically be overlooked using stationary hydrophone methods. We demonstrate that mobile hydrophone recording methods offer new insight into soundscape variation and provide a complementary approach to conventional passive acoustic monitoring techniques. Full article

We report on a simple and practical application of HARK, an easily available and portable system for bird song localization using an open-source software for robot audition HARK, to a deeper understanding of ecoacoustic dynamics of bird songs, focusing on a fine-scaled temporal analysis of song movement — song type dynamics in playback experiments. We extended HARKBird and constructed a system that enables us to conduct automatic playback and interactive experiments with different conditions, with a real-time recording and localization of sound sources. We investigate how playback of conspecific songs and playback patterns can affect vocalization of two types of songs and spatial movement of an individual of Japanese bush-warbler, showing quantitatively that there exist strong relationships between song type and spatial movement. We also simulated the ecoacoustic dynamics of the singing behavior of the focal individual using a software, termed Bird song explorer, which provides users a virtual experience of acoustic dynamics of bird songs using a 3D game platform Unity. Based on experimental results, we discuss how our approach can contribute to ecoacoustics in terms of two different roles of sounds: sounds as tools and subjects. Full article

The application of acoustic indices is incipient and still needs validation before it can reliably characterize soundscapes and monitor rapidly disappearing hot-spot areas as the Brazilian tropical savanna (Cerrado). Here we investigate which of six acoustic indices better correlate with the 24 h zoophony richness of insects, anurans, birds, and mammals. We sampled one minute every 30 minutes for seven days on three sites in Serra da Canastra National Park (Minas Gerais state, Brazil) and extracted the sonotype richness and six indices based on recordings with a bandwidth of up to 48 kHz. The Acoustic Diversity, Evenness, Entropy, and Normalized Difference Soundscape indices followed the temporal trends of the sonotype richness of insects and anurans. The Acoustic Complexity (ACI) and Bioacoustic (BIO) indices did not correlated with sonotype richness. ACI and BIO were influenced by sonic abundance and geophony. We emphasize the need to include insects and anurans on soundscape and acoustic ecology analyses and to avoid bias on avian fauna alone. We also suggest that future studies explore measures of sonic abundance and acoustic niche occupation of sonotypes to complement measures of zoophony richness and better understand what each faunal group is telling us about indices. Full article

Autonomous recording is commonly used to examine the structure of avian communities in a variety of landscapes. Many birds return to the breeding grounds in May yet acoustic surveys typically begin in June. In many species, singing activity declines through the breeding season and so detections may be lower later in the season. The aim of our study was to compare the species richness and the community composition measured early (mid-late May) and later (mid-late June) in the breeding season. We recorded the community of singing birds at 13 locations in York Region, Ontario, Canada woodlots over two days using autonomous recorders. We used spectrographic analysis to scan recordings and identify all vocalizing species. We found that species richness was significantly higher in early recordings compared to later recordings with detections of both migrants and residents displaying this trend. Most food and foraging guilds were also detected significantly less often later in the season. Despite changes in species richness, the proportion of the community represented by each foraging guild did not vary between early and late recordings. Our results suggest that acoustic recordings could be collected earlier in the breeding season, extending the survey period into May. If the primary goal of monitoring is to document species presence/absence then earlier recordings may be advantageous. Full article

Standardized methods for biodiversity monitoring are needed to evaluate conservation efforts. Acoustic indices are used in biodiversity assessments, but need to be compared to traditional wildlife methods. This work was conducted in the Santa Rosa National Park between June and November, 2015. We installed recorders and conducted bird point counts in twelve sampling sites. We compared acoustic indices (Acoustic Evenness Index [AEI], Acoustic Diversity Index [ADI], Acoustic Complexity Index [ACI], Bioacoustic Index [BIO], Normalized Difference Soundscape Index [NDSI], Total Entropy [TE], Median Amplitude Envelope [MAE], Number of peaks [NP]) with indices from bird point counts (Bird Abundance, Bird Richness, Bird Diversity and Bird Evenness), and discuss the utility of acoustic indices as indicators for biodiversity monitoring in tropical forests. ADI, ACI, BIO and TE presented a similar temporal pattern peaking between 5 am and 6 am; and an additional peak at 5 pm, except for ACI. These patterns were consistent with the daily biological rhythms. AEI, ACI, BIO and Bird Abundance were related to characteristics of younger forests (lower percentage of canopy cover) but NP, ADI, TE, Bird Diversity and Bird Evenness were related to characteristics of older forests (higher percentage of canopy cover and a lower number of patches). ACI was positively correlated to Bird Abundance and NP was positively correlated to Bird Diversity. ACI reflects biological activity, but not necessarily a more diverse bird community in this study area. This might be an indication of a strong acoustic competition, or several highly dominant bird species in younger forests. Furthermore, acoustic communities in tropical forests commonly include insects (cicadas) and frogs, which might affect resulting acoustic indices. A variety of methods are probably needed to thoroughly assess biodiversity. However, a combination of indices such as ACI and NP might be considered to monitor trends in abundance and diversity of birds in dry forests. Full article

Passive acoustic monitoring is a potentially valuable tool in biodiversity hotspots, where surveying can occur at large scales across land conversion types. However, in order to extract meaningful biological information from resulting enormous acoustic datasets, rapid analytical techniques are required. Here we tested the ability of a suite of acoustic indices to predict avian bioacoustic activity in recordings collected from the Western Ghats, a biodiversity hotspot in southwestern India. Recordings were collected at 28 sites in a range of land-use types, from tea, coffee, and cardamom plantations to remnant forest stands. Using 36 acoustic indices we developed random forest models to predict the richness, diversity, and total number of avian vocalizations observed in recordings. We found limited evidence that acoustic indices predict the richness and total number of avian species vocalizations in recordings (R2 < 0.51). However, acoustic indices predicted the diversity of avian species vocalizations with high accuracy (R2 = 0.64, mean squared error = 0.17). Index models predicted low and high diversity best, with the highest residuals for medium diversity values and when continuous biological sounds were present (e.g., insect sounds >8 sec). The acoustic complexity index and roughness index were the most important for predicting avian vocal diversity. Avian species richness was generally higher among shade-grown crops than in the open tea plantation. Our results suggest that models incorporating acoustic indices can accurately predict low and high avian species diversity from acoustic recordings. Thus, ecoacoustics could be an important contributor to biodiversity monitoring across landscapes like the Western Ghats, which are a complex mosaic of different land-use types and face continued changes in the future. Full article

Elevational gradients influence the distribution and composition of animal species and can provide useful information for the development of conservation strategies in the context of climate change. Despite an increase in studies of species diversity along elevational gradients, there is still a lack of information about community responses to environmental gradients, in part because of the logistical limitations of sampling multiple taxa simultaneously. One solution is to use passive acoustic monitoring (PAM) to acquire and analyze information from different animal taxa simultaneously along an entire elevational gradient. To improve our understanding of how environmental gradients influence patterns of animal communities and to test the relationship between soundscapes and animal composition we investigated how variation in bird and anuran composition affect the acoustic structure and composition of the soundscapes along an elevation gradient. We used PAM deploying portable acoustic recorders along three elevational transects in the Luquillo Mountains (LM), Puerto Rico. We found that elevation plays a major role in structuring the acoustic community and that the soundscape composition reflected the same patterns of anuran and bird distribution and composition along the elevational gradient. This study shows how different animal taxa respond to environmental gradients and provide strong evidence for the use of soundscapes as a tool to describe and compare species distribution and composition across large spatial scales. Full article

Ctenomys are mainly solitary subterranean rodents. Life underground has advantages (protection against predators, environmental control and reduced competition) but also implies disadvantages (digging costs, coping with hypercapnia, physiological and sensory changes, and communication problems) that can affect the social structure. Reproduction is a critical moment in the use of the signal repertoire, because individuals should locate in space, travel to, contact and copulate with a suitable partner. Energy expenditure involved in digging (connecting) tunnels makes difficult to attain a partner burrow system, but predation risk involved in moving above ground can counterbalance it and coupled with the spatial structure of the population, can determine the best communicative strategy to contact and locate a potential partner. Vocalisations allow to communicate over longer distances an with a reduced risk, while chemical signals, mostly aimed at vomerolfaction involve proximity or direct contact with the sample odour thus making information gathering more risky. As Ctenomys can use different signal types to gather different types of information leading to copulation, we propose that the use of these signals would be flexible, depending mostly on population spatial structure and type of predators living in the zone. This is because differences among species and/or populations in the use and characteristics of long-range vocalisations could be induced by environmental and/or social factors. This variation could be considered as a case of phenotypic plasticity, determining communication strategies variability in reproductive context, mostly dependent on long-range communication signals and the behaviour of males. Full article

Background noise can interfere with and influence acoustic communication behavior. Signal interference is dependent on the amplitude and spectral characteristic of background noise, which varies over space and time. The likelihood of signal interference is greater when background noise is concentrated within the same frequency bands of an animal’s vocalization, but even a partial masking effect can elicit signaling behavior modification. Relative to a rural landscape, background noise in an urban landscape is disproportionately comprised by anthro- pogenic sound, which fluctuates in amplitude throughout the day and occurs primarily in low frequencies (0–2 kHz). In this study, we examined if urban-rural differences in vocal activity patterns exist in a species Zonotrichia leucophrys nuttalli that communicates above the frequency range of anthropogenic noise (2–8 kHz). We tested whether vocal activity patterns changed in relation to sound in the high or low frequency bands within and between urban and rural locations. Automated acoustic recording devices (ARDs) continuously recorded throughout the morning song chorus, 0500 to 1,100 h, during the 2014 breeding season in San Francisco (urban) and Marin (rural) Counties, CA. Supervised learning cluster analysis was used to quantify vocal activity by totaling the number of songs. In general, vocal activity was greater in urban locations com- pared to rural locations. However, within rural and urban study sites, we found vocal activity decreased where low frequency noise levels were higher. There was not a relationship between vocal activity and high frequency, biotic sound. In both urban and rural locations, low frequency noise levels increased through the morning, while vocal activity remained relatively consistent. Our results demonstrate how patterns of vocal activity can change with low frequency, abiotic noise, even when there is no direct spectral overlap with the acoustic signal. Full article

The launch of a journal is always an opportunity to advance scientific knowledge, because a journal consolidates ideas and facts in a field. With this in mind, Journal of Ecoacoustics (JEA) aims to open a new season of theoretical, empirical and applied studies in Ecoacoustics, a recent ecological discipline that represents the development of bioacoustics studies into the ecological realm. Full article

Mounting evidence suggests that anthropogenic noise neg-atively impacts many wildlife species, including songbirds. One mechanism by which noise affects songbirds may be through acoustic obstruction to their systems of vocal communication. However, many species increase the amplitude or pitch of their vocalizations, which may partially mitigate the impact of high noise levels. When the amplitude of anthropogenic noise varies over time, such as near a moderate-use highway, short gaps between noise events may also provide an important oppor- tunity for communication. But, whether songbirds adjust vocalization rates rapidly to avoid overlap with noise is unknown for most species. We used acoustic playback to expose song- birds to simulated road noise during the dawn chorus in oth- erwise quiet habitats. We measured vocalization rates under ambient conditions and during quiet gaps embedded within playback of road noise to assess whether a community of songbirds, and nineteen individual species, vocalize more reg- ularly during noise gaps. There were no significant differences in community-wide acoustic output. Species-specific analysis revealed that only four species altered their vocal rates during quiet gaps in noise, but that the direction of the effect varied by species. Point count results revealed that birds generally remained on site for the duration of the experiment, suggesting that abandonment of noisy locations was unlikely to confound our results. In sum, increasing vocal output during short gaps in noise occurred in only a handful of species, perhaps con- tributing to the limited number of species that are found within noisy habitats. Full article

In line with the development of socio-ecological perspectives in conservation science, there is increasing interest in the role of soundscape perception in understanding human-environment interactions; the impact of natural soundscapes on human wellbeing is also increasingly recognized. However, research to date has focused on preferences and attitudes to western, urban locations. This study investigated individual emotional associations with local soundscape for three social groups living in areas with distinct degrees of urbanization, from pristine forest and pre-urban landscapes in Ecuador, to urban environments in UK and USA. Participants described sounds that they associated with a range of emotions, both positive and negative, which were categorized according to an adapted version of Schafer’s sound classification scheme. Analyses included a description of the sound types occurring in each environment, an evaluation of the associations between sound types and emotions across social groups, and the elaboration of a soundscape perception map. Statistical analyses revealed that the distribution of sound types differed between groups, reflecting essential traits of each soundscape, and tracing the gradient of urbanization. However, some associations were universal: Natural Sounds were primarily associated with positive emotions, whereas Mechanical and Industrial Sounds were linked to negative emotions. Within non-urban environments, natural sounds were associated with a much wider range of emotions. Our analyses suggest that Natural Sounds could be considered as valuable natural resources that promotes human wellbeing. Special attention is required within these endangered forest locations, which should be classified as a “threatened soundscapes,” as well as “threatened ecosystems,” as we begin to understand the role of soundscape for the wellbeing of the local communities. The methodology presented in this article offers a fast, cheap tool for identifying reactions towards landscape modification and identifying sounds of social relevance. The potential contribution of soundscape perception within the current conservation approaches is discussed. Full article