Acoustic Habitat Research Articles

Group size and mating system predict sex differences in vocal fundamental frequency in anthropoid primates

Vocalizations differ substantially between the sexes in many primates, and low-frequency male vocalizations may be favored by sexual selection because they intimidate rivals and/or attract mates. Sexual dimorphism in fundamental frequency may be more pronounced in species with more intense male mating competition and in those with large group size, where social knowledge is limited and efficient judgment of potential mates and competitors is crucial. These non-mutually exclusive explanations have not been tested simultaneously across primate species. In a sample of vocalizations (n = 1914 recordings) across 37 anthropoid species, we investigated whether fundamental frequency dimorphism evolved in association with increased intensity of mating competition (H1), large group size (H2), multilevel social organization (H3), a trade-off against the intensity of sperm competition (H4), and/or poor acoustic habitats (H5), controlling for phylogeny and body size dimorphism. We show that fundamental frequency dimorphism increased in evolutionary transitions towards larger group size and polygyny. Findings suggest that low-frequency male vocalizations in primates may have been driven by selection to win mating opportunities by avoiding costly fights and may be more important in larger groups, where limited social knowledge affords advantages to rapid assessment of status and threat potential via conspicuous secondary sexual characteristics.

Rapid assessment of vessel noise events and quiet periods in Glacier Bay National Park and Preserve using a convolutional neural net

Abstract Patterns of underwater human-generated noise events and durations of noise-free intervals (NFIs) are soundscape metrics that can potentially affect animal communication and behavior. Due to the arduous task of manual analysis, these metrics have not been described in Glacier Bay National Park and Preserve (GBNP). To surmount this challenge, we created a machine-learning (ML) model trained on 18 hr of labeled audio samples from a hydrophone operating in GBNP since 2000. The validated convolutional neural net transfer-learning model (GBNP-CNN) was used to classify several categories of sound sources in nearly 9,000 hours of data from the same hydrophone, enabling our study of vessel noise between 2017 and 2020. We focused on the occurrence and duration of NFI and the hourly proportion (HP) of vessel noise. As expected, shorter NFI and higher HP were found during daytime hours. The GBNP-CNN F1 score was 75%, largely due to the model’s confusion of vessel noise with harbor seal roars. Therefore, NFI lengths should be considered minimum estimates, but the errors do not qualitatively affect diurnal or seasonal patterns. In 2018, mean daytime NFI during peak tourism months (June–August) was less than half the duration compared to May and September (1.3 min vs. 2.9 min). In 2020, when large-vessel tourism was substantially reduced but small-craft activity continued, we found that HP decreased in June–August. In conjunction with other soundscape metrics, monitoring NFI trends using ML models such as GBNP-CNN will provide crucial information for management and conservation of acoustic habitats and sensitive species in GBNP.

Sharing the waters: Application of a marine spatial planning approach to conserve and restore the acoustic habitat of endangered beluga whales (Delphinapterus leucas) in and around the Saguenay–St. Lawrence Marine Park

Anthropogenic underwater noise degrades the quality of whale habitats, affecting vital functions which may compromise the recovery of species at risk exposed to chronic vessel-based activities. The endangered St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) lives downstream from industrial activities in a highly accessible coastal environment. Many approaches were deployed in the Saguenay–St. Lawrence Marine Park to address the issue of cohabitation between whales and vessels. Place-based conservation measures aimed at protecting and restoring the tranquility of key areas of SLE beluga critical habitat by managing vessel-based activities were implemented through a marine spatial planning approach. They involved protecting the quietness of the South Channel by avoiding rerouting shipping, establishing of a regulatory area closure in Baie Sainte-Marguerite and of a beluga conservation area without commercial whale-watching in the Upper SLE. Compliance monitoring show that these efforts are effective to enhance the protection and restoration of the acoustic habitat.

Perspectives on the Ecological Role of Geophysical Sounds

Humans categorize unwanted sounds in the environment as noise. Consequently, noise is associated with negative human and ecological values, especially when it is derived from an anthropogenic source. Although evidence confirms that many machine-generated anthropogenic sounds have negative impacts on animal behavior and communication, natural sources of non-biological sound, such as wind, rain, running water, and sea waves (geophonies) have also been categorized as noise and are frequently dismissed or mischaracterized in acoustic studies as an outside factor of acoustic habitats rather than an integrated sonic component of ecological processes and species adaptations. While the proliferation of machine-generated sound in the Biosphere has become an intrusive phenomenon in recent history, geophony has shaped the Earth’s sonic landscapes for billions of years. Therefore, geophonies have very important sonic implications to the evolution and adaptation of soniferous species, forming essential ecological and semiotical relationships. This creates a need to distinguish geophonies from machine-generated sounds and how species respond to each accordingly, especially given their acoustic similarities in the frequency spectrum. Here, we introduce concepts and terminology that address these differences in the context of ecoacoustics. We also discuss how Acoustic Complexity Indices (ACIs) can offer new possibilities to quantifiably evaluate geophony in relation to their sonic contest.

The effect of COVID-19 on underwater sound

The sounds of the turning machinery and propulsion systems from commercial ships are ubiquitous in the temperate deep ocean basins. The vertical structure of seawater temperature, salinity, and pressure conspire to create nearly lossless underwater propagation conditions at 10’s and 100’s of Hz, the frequency band where diesel engines and generators, cavitating propellers, and turning gearboxes produce their peak acoustic energy. In the shallow waters of the continental margins, the human use of the ocean for transport, fishing, recreation, and construction has led to increasing levels of anthropogenic noise over the last century. As the COVID-19 pandemic spread across the globe, the reduction of economic activity and marine traffic resulted in a decrease in underwater noise, with observations made at a number of underwater listening stations and autonomous recording devices across the ocean basins. These measurements, along with ship track data provided by the automated identification system (AIS) and trade and shipping statistics, improve our knowledge of the relationship between acoustic energy, the marine acoustic habitat, and the various human uses of the ocean.

Broad-Scale Responses of Harbor Porpoises to Pile-Driving and Vessel Activities During Offshore Windfarm Construction

Offshore windfarm developments are expanding, requiring assessment and mitigation of impacts on protected species. Typically, assessments of impacts on marine mammals have focused on pile-driving, as intense impulsive noise elicits adverse behavioral responses. However, other construction activities such as jacket and turbine installation also change acoustic habitats through increased vessel activity. To date, the contribution of construction-related vessel activity in shaping marine mammal behavioral responses at windfarm construction sites has been overlooked and no guidelines or mitigation measures have been implemented. We compared broad-scale spatio-temporal variation in harbor porpoise occurrence and foraging activity between baseline periods and different construction phases at two Scottish offshore windfarms. Following a Before-After Control-Impact design, arrays of echolocation click detectors (CPODs) were deployed in 25 km by 25 km impact and reference blocks throughout the 2017–2019 construction. Echolocation clicks and buzzes were used to investigate porpoise occurrence and foraging activity, respectively. In parallel, we characterized broadband noise levels using calibrated noise recorders (SoundTraps and SM2Ms) and vessel activities using AIS data integrated with engineering records. Following an impact gradient design, we then quantified the magnitude of porpoise responses in relation to changes in the acoustic environment and vessel activity. Compared to baseline, an 8–17% decline in porpoise occurrence was observed in the impact block during pile-driving and other construction activities. The probability of detecting porpoises and buzzing activity was positively related to the distance from vessel and construction activities, and negatively related to levels of vessel intensity and background noise. Porpoise displacement was observed at up to 12 km from pile-driving activities and up to 4 km from construction vessels. This evidence of broad-scale behavioral responses of harbor porpoises to these different construction activities highlights the importance of assessing and managing all vessel activities at offshore windfarm sites to minimize potential impacts of anthropogenic noise.

The impact of the “Anthropause” on the communication and acoustic habitat of Southeast Alaskan humpback whales

The COVID-19 pandemic caused profound changes in global human behavior, including substantial decreases in marine transportation, a pervasive ocean noise source. The human tragedy of the pandemic provides an unprecedented opportunity to investigate how humpback whales communicate in the absence of chronic noise common to their acoustic habitats. The Alaskan tourism industry was impacted particularly strongly; Southeast Alaska experienced a near complete absence cruise ships during the 2020 tourism season (May—September). In summer 2019 and 2020, we deployed a SoundTrap hydrophone in Glacier Bay National Park to document vessel-generated ambient noise and vocal characteristics of humpback whales (Megaptera novaeangliae) which have been studied in this region since the 1980’s. In the absence of cruise ships, underwater noise from vessels was significantly lower in Glacier Bay compared to 2019. Median daily noise levels (dBRMS 100–1500 Hz) were three times quieter during 2020 than in 2019. Preliminary analyses of humpback whale calling behavior show an increased number of call types in 2020 compared to the same period in 2019. Documenting humpback whale communication in quiet conditions can help illuminate impacts of chronic vessel noise and aid the development of measures to reduce human impacts in this and other marine protected areas.

Sensing ecosystem dynamics via audio source separation: A case study of marine soundscapes off northeastern Taiwan.

Remote acquisition of information on ecosystem dynamics is essential for conservation management, especially for the deep ocean. Soundscape offers unique opportunities to study the behavior of soniferous marine animals and their interactions with various noise-generating activities at a fine temporal resolution. However, the retrieval of soundscape information remains challenging owing to limitations in audio analysis techniques that are effective in the face of highly variable interfering sources. This study investigated the application of a seafloor acoustic observatory as a long-term platform for observing marine ecosystem dynamics through audio source separation. A source separation model based on the assumption of source-specific periodicity was used to factorize time-frequency representations of long-duration underwater recordings. With minimal supervision, the model learned to discriminate source-specific spectral features and prove to be effective in the separation of sounds made by cetaceans, soniferous fish, and abiotic sources from the deep-water soundscapes off northeastern Taiwan. Results revealed phenological differences among the sound sources and identified diurnal and seasonal interactions between cetaceans and soniferous fish. The application of clustering to source separation results generated a database featuring the diversity of soundscapes and revealed a compositional shift in clusters of cetacean vocalizations and fish choruses during diurnal and seasonal cycles. The source separation model enables the transformation of single-channel audio into multiple channels encoding the dynamics of biophony, geophony, and anthropophony, which are essential for characterizing the community of soniferous animals, quality of acoustic habitat, and their interactions. Our results demonstrated the application of source separation could facilitate acoustic diversity assessment, which is a crucial task in soundscape-based ecosystem monitoring. Future implementation of soundscape information retrieval in long-term marine observation networks will lead to the use of soundscapes as a new tool for conservation management in an increasingly noisy ocean.

Ecoacoustics and Multispecies Semiosis: Naming, Semantics, Semiotic Characteristics, and Competencies

Biosemiotics to date has focused on the exchange of signals between organisms, in line with bioacoustics; consideration of the wider acoustic environment as a semiotic medium is under-developed. The nascent discipline of ecoacoustics, that investigates the role of environmental sound in ecological processes and dynamics, fills this gap. In this paper we introduce key ecoacoustic terminology and concepts in order to highlight the value of ecoacoustics as a discipline in which to conceptualise and study intra- and interspecies semiosis. We stress the inherently subjective nature of all sensory scapes (vivo-, land-, vibro- and soundscapes) and propose that they should always bear an organismic attribution. Key terms to describe the sources (geophony, biophony, anthropophony, technophony) and scales (sonotopes, soundtopes, sonotones) of soundscapes are described. We introduce epithets for soundscapes to point to the degree to which the global environment is implicated in semiosis (latent, sensed and interpreted soundscapes); terms for describing key ecological structures and processes (acoustic community, acoustic habitat, ecoacoustic events) and examples of ecoacoustic events (choruses and noise) are described. The acoustic eco-field is recognized as the semiotic model that enables soniferous species to intercept core resources like food, safety and roosting places. We note that whilst ecoacoustics to date has focused on the critical task of the development of metrics for application in conservation and biodiversity assessment, these can be enriched by advancing conceptual and theoretical foundations. Finally, the mutual value of integrating ecoacoustic and biosemiotics perspectives is considered.

Bottom trawling noise: Are fishing vessels polluting to deeper acoustic habitats?

The impact of bottom trawling noise was quantified on two surrounding marine acoustic habitats using fixed mooring acoustic recorders. Noise during trawling activity is shown to be considerably louder than ambient noise and a nearby underway research vessel. Estimated source levels were above cetacean damage thresholds. Measurements at a submarine canyon indicated potential noise focussing, inferring a role for such features to enhance down slope noise propagation at continental margin sites. Modelled sound propagates more efficiently when sourced from trawling gear dragging along the seabed relative to the vessel as a surface source. Results are contextualised with respect to marine mammal harm, to other anthropogenic ocean noise sources, topography and seasons. Noise energy emitted by bottom trawling activity is a source of pollution that requires further consideration, in line with other pervasive trawling pressures on marine species and seabed habitats, especially in areas of heightened ecological susceptibility.

No need to shout? Harbor porpoises (Phocoena phocoena) echolocate quietly in confined murky waters of the Wadden Sea.

Porpoise echolocation parameters may vary depending on their acoustic habitat and predominant behavior. Research was conducted in the Wadden Sea, an acoustically complex, tidally driven habitat with high particle resuspension. Source levels and echolocation parameters of wild harbor porpoises were estimated from time-of-arrival-differences of a six-element hydrophone array. The back-calculated peak-to-peak apparent source level of 169 ± 5 dB re 1 μPa was significantly lower than reported from Inner Danish Waters (-20 dB) and British Columbia (-9 dB) with narrower bandwidth. Porpoises therefore reduce their source level in the Wadden Sea under acoustically complex conditions suggesting an avoidance of cluttering.

Distribution of blue whale populations in the Southern Indian Ocean based on a decade of acoustic monitoring

Globally, the Indian Ocean appears to have the greatest blue whale (Balaenoptera musculus ssp) acoustic diversity, with at least four acoustic populations from three defined sub-species. To understand how these different populations use this region as habitat, we first need to characterize their spatial and seasonal distributions. Here, we build on previous passive acoustic monitoring studies and analyze a passive acoustic dataset spanning large temporal (9 years) and spatial (3–9 sites covering more than 12 million km2 of potential acoustic habitat in the southwest Indian Ocean) scales. A novel detection algorithm was employed to investigate the long-term presence of Antarctic blue whale and SEIO and SWIO pygmy blue whale calls. We found that Antarctic and pygmy blue whales have completely different spatial and seasonal distribution in the southern Indian Ocean. Antarctic blue whales are heard almost year-round on the whole array, with great inter-annual variability. The two pygmy blue whales share a highly stable seasonal acoustic presence, but their geographical distributions overlap at only a few central Indian Ocean sites. However, Antarctic and pygmy blue whale acoustic co-occurrence is common, especially in sub-tropical waters. These temporal and spatial distributions strengthen our understanding of seasonal occurrence and habitat use of distinct populations of blue whales in the southern Indian Ocean. A better comprehension of the ecology of Indian Ocean blue whales will require interdisciplinary studies to examine the drivers of the variability seen from passive acoustic studies.

A comparative study of avian middle ear mechanics

Sound and hearing play an important role in the lives of many birds, and studies have been published on the acoustic habitat of various species, as well as on various aspects of their hearing system. However the function of the middle ear remains largely unexplored, with existing studies focusing on either single species, or a very narrow range of species. In this article we report measurements of the middle ear transfer function in 39 taxonomically diverse avian species. We used laser vibrometry to measure the vibrations of the columellar footplate in response to tones played in each animal’s ear canal, and calculated the middle ear transfer functions.Transfer functions varied substantially across species, but appeared to follow common trends. Comparisons between the peak frequency in the transfer function and length/mass of the columella reveal a correlation between the three, however statistical analysis suggests that columellar length is a primary indicator of the peak frequency. These results provide a broad survey of avian middle ear function, and the observed trends provide a method with which to begin to predict the response of single ossicle middle ear systems.

Influence of acoustic habitat variation on Indo-Pacific humpback dolphin (Sousa chinensis) in shallow waters of Hainan Island, China.

The Indo-Pacific humpback dolphin (IPHD, Sousa chinensis) is a coastal species inhabiting tropical and warm-temperate waters. The presence of this vulnerable dolphin was recently discovered in shallow waters southwest of Hainan Island, China. The influence of the acoustic habitat on the distribution and behavior of IPHD was investigated using an array of passive acoustic platforms (n = 6) that spanned more than 100 km of coastline during a 75-day monitoring period. Its presence was assessed within 19 215 five-min recordings by classifying echolocation clicks using machine learning techniques. Spectrogram analysis was applied to further investigate the acoustic behavior of IPHD and to identify other prominent sound sources. The variation in the ambient noise levels was also measured to describe the spatiotemporal patterns of the acoustic habitat among the different sampling sites. Social and feeding sounds of IPHD (whistles and click-series of pulsed sounds) were identified together with other biological sources (finless porpoise, soniferous fishes, and snapping shrimps) and anthropogenic activities (ship noise, explosions, and sonars). Distribution, acoustic behavior, and habitat use of this nearshore dolphin species were strongly influenced by the abundance of soniferous fishes, and under similar conditions, the species was more acoustically active in locations with lower noise levels.

Anthropogenic noise does not surpass land cover in explaining habitat selection of Greater Prairie-Chicken (Tympanuchus cupido)

AbstractOver the last century, increasing human populations and conversion of grassland to agriculture have had severe consequences for numbers of Greater Prairie-Chicken (Tympanuchus cupido). Understanding Greater Prairie-Chicken response to human disturbance, including the effects of anthropogenic noise and landscape modification, is vital for conserving remaining populations because these disturbances are becoming more common in grassland systems. Here, we evaluate the effect of low-frequency noise emitted from a wind energy facility on habitat selection. We used the Normalized Difference Soundscape Index, a ratio of human-generated and biological acoustic components, to determine the impact of the dominant acoustic characteristics of habitat relative to physical landscape features known to influence within–home range habitat selection. Female Greater Prairie-Chickens avoided wooded areas and row crops but showed no selection or avoidance of wind turbines based on the availability of these features across their home range. Although the acoustic environment near the wind energy facility was dominated by anthropogenic noise, our results show that acoustic habitat selection is not evident for this species. In contrast, our work highlights the need to reduce the presence of trees, which have been historically absent from the region, as well as decrease the conversion of grassland to row-crop agriculture. Our findings suggest physical landscape changes surpass altered acoustic environments in mediating Greater Prairie-Chicken habitat selection.

Feature identification using acoustic signature of Ocean Researcher III (ORIII) of Taiwan

Feature identification using acoustic signature of Ocean Researcher III (ORIII) of Taiwan

Acoustic codes from a rural sanctuary: How ecoacoustic events operate across a landscape scale

Sonotopes are the acoustic patches of a soundscape, composed by different occurrences of geophonies, biophonies, and technophonies. According an ecosemiotic perspective, ecoacoustic events (EEs) are the vehicles from the attribution of meaning to the emergent sonotopes and work as neural codes. The process of encoding is suggested to be active between the perception of sonotopes and EE detection. In Ortolano Rural Sanctuary, from a grid of 12 acoustic digital recorders (ADRs) at an average distance of 30 m each with a microphone set to receive sounds from a near acoustic field, 824,160 one-minute acoustic files were obtained from October 2017 to September 2018. From these files, using the combination of three acoustic complexity indices (ACIft, ACIft evenness, and ACItf evenness), through the ecoacoustic event detection and identification (EEDI) procedure, more than 200 EEs on average per ADR were extracted during this period. The EEs were seasonally aggregated with a significant separation between fall-winter and spring-summer periods. Rain and wind were important in EE composition according to location and seasonality. The number of EEs detected from just one month to three months was 57% of the total, and the first of the nine classes of ACIft belonged to 78% of all classes of abundance. The EEs and ACItf similarity were not correlated with the distance between ADRs, confirming the correctness of the near-field approach to detect sounds from landscapes and EE spatial independence. The ranging capacities to distinguish distance from sound sources and to discriminate the temporal and frequential patterns of acoustic signals are some of the mechanisms that species use to detect and encode environmental acoustic complexity. Species are supposed to use EE to explore and assess the acoustic habitat and probably to obtain mental maps of the surroundings they must move around using an acoustic exploration.

Anthropogenic Landscape Changes and Their Impacts on Terrestrial and Freshwater Soundscapes

Quantifying the effects of anthropogenic sounds on wildlife at the landscape scale of observation has been notoriously difficult because these sounds are often confounded with the presence of infrastructure and loss of habitat through resource exploitation activities. In this paper, we review how anthropogenic landscape changes affect the power level and propagation of sounds in both terrestrial and freshwater ecosystems, as well as the behavioural response of organisms to novel acoustic habitats. Resource exploitation and other human activities change soundscapes both directly, by affecting sound production and propagation, and indirectly, by modifying landscape structure and species distribution patterns. Intermittent anthropogenic sounds are concentrated in the lower frequencies, tend to be louder than enduring sounds of the same origin and create more patchy soundscapes. We identified key sensorial traits that are related to the auditory acuity of species in different taxonomic groups, including fish, birds, anurans, stridulating insects and small mammals, and which may help us understand why certain species are more sensitive to anthropogenic changes to soundscapes. Prioritizing research in an increasingly noisy world requires a proper understanding of the auditory sensitivity of species, the characteristics of anthropogenic sounds (i.e. intermittent or enduring), and how sound production and propagation is affected by landscape structure. Further research on species’ sensorial traits would provide a framework with which to scale responses to anthropogenic sounds from individuals to communities and better predict the impact of human activities on terrestrial and freshwater ecosystems.

New Feature Classes for Acoustic Habitat Mapping—A Multibeam Echosounder Point Cloud Analysis for Mapping Submerged Aquatic Vegetation (SAV)

A new method for multibeam echosounder (MBES) data analysis is presented with the aim of improving habitat mapping, especially when considering submerged aquatic vegetation (SAV). MBES data were acquired with 400 kHz in 1–8 m water depth with a spatial resolution in the decimeter scale. The survey area was known to be populated with the seagrass Zostera marina and the bathymetric soundings were highly influenced by this habitat. The depth values often coincide with the canopy of the seagrass. Instead of classifying the data with a digital terrain model and the given derivatives, we derive predictive features from the native point cloud of the MBES soundings in a similar way to terrestrial LiDAR data analysis. We calculated the eigenvalues to derive nine characteristic features, which include linearity, planarity, and sphericity. The features were calculated for each sounding within a cylindrical neighborhood of 0.5 m radius and holding 88 neighboring soundings, on average, during our survey. The occurrence of seagrass was ground-truthed by divers and aerial photography. A data model was constructed and we applied a random forest machine learning supervised classification to predict between the two cases of “seafloor” and “vegetation”. Prediction by linearity, planarity, and sphericity resulted in 88.5% prediction accuracy. After constructing the higher-order eigenvalue derivatives and having the nine features available, the model resulted in 96% prediction accuracy. This study outlines for the first time that valuable feature classes can be derived from MBES point clouds—an approach that could substantially improve bathymetric measurements and habitat mapping.

Analysis of bioacoustics and noise pollution in the penguin exhibit at Newport Aquarium

The present study researches the acoustic habitat of the penguin exhibited at Newport Aquarium in Newport, KY by means of measuring environmental noise within their exhibit. Noise exposure has been well studied in humans by using a weighted decibel scale to provide safety guidelines for the level of noise and the maximum time one can be exposed to each level. Therefore, the same principle is being used to observe if these animals are experiencing noise pollution from their own environmental sounds. The absorption coefficients of the materials that make up the habitat were also taken into consideration during data collection. The aim of this research is to gather calculations for the time it takes for the sound pressure level to reduce by 60dB (RT60) after periods of vocalization by the colony of penguins and to determine if these reverberation values reach the peak sensitivity of hearing thresholds for them.