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The mechanoreceptors of land-dwelling juveniles of the family Coenobitidae were studied using scanning electron microscopy to determine how their morphology varied from the mechanoreceptors of the marine dwelling zoea stage. Archived specimens of Birgus latro Leach, 1816 and Coenobita clypeatus Latreille, 1829 from the collections maintained in the National Museum of Natural History, Smithsonian Institution were examined. The mechanoreceptors on the antennules of the planktonic marine larval stage, zoea, are potentially capable of detecting near field sound energy at frequencies two orders of magnitude lower than those of the antennules of the land-dwelling juveniles in both genera. This sensitivity to lower frequencies potentially enables the larval stages to detect sound energy sources at much greater distances.

Automated remote sensing has revolutionized the fields of wildlife ecology and environmental science. Yet, a cost-effective and flexible approach for large scale monitoring has not been fully developed, resulting in a limited collection of high-resolution data. Here, we describe BioSense, a low-cost and fully programmable automated sensing platform for applications in bioacoustics and environmental studies. Our design offers customization and flexibility to address a broad array of research goals and field conditions. Each BioSense is programmed through an integrated Raspberry Pi computer board and designed to collect and analyze avian vocalizations while simultaneously collecting temperature, humidity, and soil moisture data. We illustrate the different steps involved in manufacturing this sensor including hardware and software design and present the results of our laboratory and field testing in southwestern United States.

Identifying meaningful vocalizations in nonhuman animals can help explain the evolution of human communications. However, non-speech-like sounds, including laughter equivalents, are not well studied, although they may be meaningful. In this pilot study we investigate whether dogs perform a domain-specific pant during play by capturing vocalizations and behaviors during three interactions: training, play, and rest. Sixteen human and dog dyads participated in a session that included all three interactions in the same order: training, play, rest. During these sessions, each partner wore wireless microphones that transmitted to a receiver and digital recorder, while a standalone digital camera captured video of the interactions. A one-way ANOVA demonstrates that dogs do perform a domain-specific "play pant," which was almost completely absent during training and rest. These vocalizations mostly co-occurred with play behaviors (e.g., play bow) or tickling and cuddling. These preliminary findings suggest that a laugh-like play pant is used by dogs during play; future research should explore other interspecific acoustic signals as derived from conspecific signals and having communicative function.

The vocal activity and detectability of tropical birds are subject to high levels of temporal heterogeneity, but quantifying patterns of diel and day-to-day variation in complex systems is challenging with traditional point count methods. As a result, research concerning stochastic temporal effects on tropical bird assemblages is limited, typically offering only broad conclusions, such as that overall activity is highest in the first few hours of the morning and some species are active at different times of the day. Passive acoustic monitoring introduces several advantages for studying temporal variation, particularly by enabling simultaneous and continuous data collection across adjacent sites. Here, we employed autonomous recording units to quantify temporal variation in bird vocal activity and observed species richness at an Amazonian reserve in Madre de Dios, Peru, a region featuring some of Earth's richest, most complex bird assemblages. We manually annotated 18 dawn hour recordings, collected simultaneously from three separate days at the same six sites, which represent various microhabitats and bird community compositions. We documented significant and consistent temporal variation in avian vocal activity levels and observed species richness within the dawn hour and across days. We found that temporal effects were stronger for vocal activity than for observed species richness and that vocal activity patterns over the course of the dawn hour varied between species. Our results indicate that overlooked temporal variation in Amazonian soundscapes may obfuscate the results of surveys that do not sufficiently account for temporal variables with simultaneous monitoring. While manual analysis of large volumes of soundscape data remains challenging, such data should be collected to supplement traditional surveys whenever possible. Rapid advances in the automated processing of acoustic data could lead to more efficient methods for reducing temporal bias and improving the calibration and accuracy of tropical bird surveys.

Fin whale song is a ubiquitous low-frequency pulsing that has been recorded in every ocean basin. In recent years, the complexity of fin whale song has been realized. In the North Atlantic, this song is made up of two low-frequency note types (A and B notes) and one higher-frequency note type (upsweeps). The A and B notes are produced with both singlet and doublet inter-note intervals. These song patterns are interwoven throughout an individual's song and have been observed to shift over time, both gradually and suddenly. Like many baleen whales, the population size of fin whales is poorly defined. Passive acoustic monitoring has been suggested as a way to estimate abundance if a cue rate or calling rate can be determined. In this study, we used recordings from 119 fin whale tracks from 2013-2023 generated from passive acoustic recorders in the North Atlantic to define fin whale song patterns in this ocean basin, identify changes in these song patterns over time, and calculate cue rates. The fin whales recorded sang in 4 distinct patterns. Inter-note intervals were 25 s for A-A singlets, 13 s for B-B singlets, 12/20 s for B-B doublets, and 10/11 s for A-B doublets. B-B doublet inter-note intervals significantly increased from May 2019--April 2023 and A-B inter-note intervals showed an intra-annual increasing trend that reset each summer. Fin whale song in the North Atlantic also often includes higher frequency upsweep notes immediately prior to B notes. While A and B note peak frequency was steady over these years, upsweep peak frequency significantly decreased, continuing a similar trend that has been observed over 30 years. Despite these changes, the dominant song pattern remained consistent and cue rate for actively singing whales was relatively stable, which is in contrast to patterns observed in the North Pacific. Many of these nuances in fin whale singing behavior are newly described herein, and these findings are vital for monitoring baseline behavior, behavioral trends over time, and ultimately estimating abundance of a poorly understood species. [ABSTRACT FROM AUTHOR]

This review discusses how welfare scientists can examine vocalizations to gain insight into the affective states of individual animals. In recent years, researchers working in professionally managed settings have recognized the value of monitoring the types, rates, and acoustic structures of calls, which may reflect various aspects of welfare. Fortunately, recent technological advances in the field of bioacoustics allow for vocal activity to be recorded with microphones, hydrophones, and animal-attached devices (e.g., collars), as well as automated call recognition. We consider how vocal behavior can be used as an indicator of affective state, with particular interest in the valence of emotions. While most studies have investigated vocal activity produced in negative contexts (e.g., experiencing pain, social isolation, environmental disturbances), we highlight vocalizations that express positive affective states. For instance, some species produce vocalizations while foraging, playing, engaging in grooming, or interacting affiliatively with conspecifics. This review provides an overview of the evidence that exists for the construct validity of vocal indicators of affective state in non-human mammals. Furthermore, we discuss non-invasive methods that can be utilized to investigate vocal behavior, as well as potential limitations to this line of research. In the future, welfare scientists should attempt to identify reliable, valid species-specific calls that reflect emotional valence, which may be possible by adopting a dimensional approach. The dimensional approach considers both arousal and valence by comparing vocalizations emitted in negative and positive contexts. Ultimately, acoustic activity can be tracked continuously to detect shifts in welfare status or to evaluate the impact of animal transfers, introductions, and changes to the husbandry routine or environment. We encourage welfare scientists to expand their welfare monitoring toolkits by combining vocal activity with other behavioral measures and physiological biomarkers. [ABSTRACT FROM AUTHOR]

Passive acoustic monitoring (PAM) studies generate thousands of hours of audio, which may be used to monitor specific animal populations, conduct broad biodiversity surveys, detect threats such as poachers, and more. Machine learning classifiers for species identification are increasingly being used to process the vast amount of audio generated by bioacoustic surveys, expediting analysis and increasing the utility of PAM as a management tool. In common practice, a threshold is applied to classifier output scores, and scores above the threshold are aggregated into a detection count. The choice of threshold produces biased counts of vocalizations, which are subject to false positive/ negative rates that may vary across subsets of the dataset. In this work, we advocate for directly estimating call density: The proportion of detection windows containing the target vocalization, regardless of classifier score. We propose a validation scheme for estimating call density in a body of data and obtain, through Bayesian reasoning, probability distributions of confidence scores for both the positive and negative classes. We use these distributions to predict site-level call densities, which may be subject to distribution shifts (when the defining characteristics of the data distribution change). These methods may be applied to the outputs of any binary detection classifier operating on fixedsize audio input windows. We test our proposed methods on a real-world study of Hawaiian birds and provide simulation results leveraging existing fully annotated datasets, demonstrating robustness to variations in call density and classifier model quality. [ABSTRACT FROM AUTHOR]

Bats play a pivotal role in maintaining ecological balance, and studying their behaviors offers vital insights into environmental health and aids in conservation efforts. Determining the presence of various bat species in an environment is essential for many bat studies. Specialized audio sensors can be used to record bat echolocation calls that can then be used to identify bat species. However, the complexity of bat calls presents a significant challenge, necessitating expert analysis and extensive time for accurate interpretation. Recent advances in neural networks can help identify bat species automatically from their echolocation calls. Such neural networks can be integrated into a complete end-to-end system that leverages recent internet of things (IoT) technologies with long-range, low-powered communication protocols to implement automated acoustical monitoring. This paper presents the design and implementation of such a system that uses a tiny neural network for interpreting sensor data derived from bat echolocation signals. A highly compact convolutional neural network (CNN) model was developed that demonstrated excellent performance in bat species identification, achieving an F1-score of 0.9578 and an accuracy rate of 97.5%. The neural network was deployed, and its performance was evaluated on various alternative edge devices, including the NVIDIA Jetson Nano and Google Coral. [ABSTRACT FROM AUTHOR]

We present a high-resolution, densely sampled data set of wild bird songs collected over multiple years from a single population of great tits, Parus major , in the U.K. The data set includes over 1 100 000 individual acoustic units from 109 963 richly annotated songs, sung by more than 400 individual birds, and provides unprecedented detail on the vocal behaviour of wild birds. Here, we describe the data collection and processing procedures and provide a summary of the data. We also discuss potential research questions that can be addressed using this data set, including behavioural repeatability and stability, links between vocal performance and reproductive success, the timing of song production, syntactic organization of song production and song learning in the wild. We have made the data set and associated software tools publicly available with the aim that other researchers can benefit from this resource and use it to further our understanding of bird vocal behaviour in the wild. • We present a large data set of songs from a wild population of great tits. • It contains 1.1 M acoustic units from 109 K songs recorded over several years. • It includes extensive metadata and annotations. • The data set and associated software tools are publicly available. [ABSTRACT FROM AUTHOR]

We describe a new frog species that is the sibling of Pristimantis reichlei. These two sister species inhabit the Amazonian lowlands and adjacent foothills of the Andes, from central Bolivia to central Peru. Pristimantis reichlei occurs from central Bolivia to southern Peru (Alto Purús National Park), while the new species occurs from northern Bolivia (Departamento Pando) to Panguana in central Peru (Departamento Huánuco), at elevations between 220 and 470 m a.s.l. In spite of their morphological crypsis, these siblings occur in syntopy without evidence of interbreeding (in the Alto Purús area) and are recovered as reciprocally monophyletic. Their uncorrected pairwise genetic distances in the 16S rRNA gene range from 9.5–13.5%, and their advertisement calls differ in both qualitative and quantitative traits. Moreover, our study found uncorrected pairwise distances within the new species of up to 5.0% and up to 9.3% within P. reichlei. We therefore cannot rule out the possible existence of hybrids or additional species-level lineages hidden in this complex. Furthermore, we found another potential pair of sibling species composed of P. danae and an unnamed lineage, with divergences of 9.4% in the 16S gene, whose in-depth analysis and taxonomic treatment are pending future revision. With the new nominal species, the Pristimantis danae species group now includes 20 species, distributed across the upper Amazon basin and in the eastern Andes, from western Brazil to Bolivia and Peru. Our study, together with an increasing number of other studies, indicates that sibling species are far from being rare among Amazonian amphibians and that species resolution remains low even for groups that have received considerable attention in recent years. [ABSTRACT FROM AUTHOR]

Monitoring biodiversity changes associated with ecological restoration is crucial in the current UN Decade on Restoration. Although several studies highlight the impacts of restoration on ecosystems, it is also important to understand how restoration alters species' behavior, including vocalization. Advances in conservation technology, such as passive acoustic monitoring, facilitate rapid and noninvasive monitoring. In this study, we quantified changes in the vocal behavior of a bird species in response to small‐scale restoration carried out by removing the invasive shrub, Lantana camara (lantana), in a Central Indian tropical dry forest. We examined associations between sites of varying lantana densities and the vocalization of one of its primary dispersers, red‐vented bulbul (RVBU). We found statistically significant differences in note‐length and bandwidth of RVBU vocalizations across sites. A random forest classification model showed that Lantana density was not an important predictor of RVBU vocalizations. Apart from the percentage of forest area and farms in our sites, total human population was the most important predictor for RVBU vocalizations suggesting RVBU's use of human habitations as possible resource hubs. Our findings suggest that lantana removal is not associated with significant changes in RVBU vocalization. This study provides empirical evidence that ecological restoration may not alter species' vocalization in the short term and highlights the importance of moving beyond species presence and understanding the impact of restoration on species behavior. [ABSTRACT FROM AUTHOR]

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Navigation through dense foliage presents a fundamental challenge to autonomous systems, and achieving a performance level similar to echolocating bats could have important applications in areas such as forestry and farming. However, the clutter echoes originating from such environments have been difficult to analyze. To study the problem of sonar‐based navigation in dense foliage in simulation, an artificial generation system for leaf impulse responses (IRs) based on variational auto‐encoders is proposed. The system is to aid the construction of artificial foliage echo environments. A dataset of leaf echoes was collected in an anechoic chamber and convolved with the original signal to estimate the IR of each leaf. A modified version of the conditional variational autoencoder ‐ generative adversarial network (cVAE‐GAN) architecture was trained successfully on this dataset to produce a generative model that was conditional on leaf viewing angles, size, and species. The IRs generated by the model capture quantitative and qualitative similarity to the measured IRs. It surpasses the previous state of the art foliage echo model based on reflecting disks. The model's computational efficiency and its success suggest its potential use for simulating large environments of foliage to study bat biosonar and aid in engineering biomimetic sonar devices. [ABSTRACT FROM AUTHOR]

Female advertisement of reproductive state and receptivity has the potential to play a large role in the mating systems of many taxa, but investigations of this phenomenon are underrepresented in the literature. North American red squirrels (Tamiasciurus hudsonicus) are highly territorial and engage in scramble competition mating, with males converging from spatially disparate territories to engage in mating chases. Given the narrow estrus window exhibited in this species, the ubiquitous use of vocalizations to advertise territory ownership, and the high synchronicity of males arriving from distant territories, we hypothesized that female vocalizations contain cues relating to their estrous state. To test this hypothesis, we examined the spectral and temporal properties of female territorial rattle vocalizations collected from females of known reproductive condition over 3 years. While we found no distinct changes associated with estrus specifically, we did identify significant changes in the spectral characteristics of rattles relating to both female body mass and reproductive state relative to parturition. To the best of our knowledge, this is the first evidence of changes in vocal characteristics associated with late pregnancy in a nonhuman mammal. [ABSTRACT FROM AUTHOR]

Machine learning tools are widely used in support of bioacoustics studies, and there are numerous publications on the applicability of convolutional neural networks (CNNs) to the automated presenceabsence detection of species. However, the relation between the merit of acoustic background modelling and the recognition performance needs to be better understood. In this study, we investigated the influence of acoustic background substance on the performance of the acoustic detector of the White-lored Spinetail (Synallaxis albilora). Two detector designs were evaluated: the 152- layer ResNet with transfer learning and a purposely created CNN. We experimented with acoustic background representations trained with season-specific (dry, wet, and all-season) data and without explicit modelling to evaluate its influence on the detection performance. The detector permits monitoring of the diel behaviour and breeding time of White-lored Spinetail solely based on the changes in the vocal activity patterns. We report an advantageous performance when background modelling is used, precisely when trained with all-season data. The highest classification accuracy (84.5%) was observed for the purposely created CNN model. Our findings contribute to an improved understanding of the importance of acoustic background modelling, which is essential for increasing the performance of CNN-based species detectors. [ABSTRACT FROM AUTHOR]

The ongoing biodiversity crisis, driven by factors such as land-use change and global warming, emphasizes the need for effective ecological monitoring methods. Acoustic monitoring of biodiversity has emerged as an important monitoring tool. Detecting human voices in soundscape monitoring projects is useful both for analyzing human disturbance and for privacy filtering. Despite significant strides in deep learning in recent years, the deployment of large neural networks on compact devices poses challenges due to memory and latency constraints. Our approach focuses on leveraging knowledge distillation techniques to design efficient, lightweight student models for speech detection in bioacoustics. In particular, we employed the MobileNetV3-Small-Pi model to create compact yet effective student architectures to compare against the larger EcoVAD teacher model, a well-regarded voice detection architecture in eco-acoustic monitoring. The comparative analysis included examining various configurations of the MobileNetV3-Small-Pi-derived student models to identify optimal performance. Additionally, a thorough evaluation of different distillation techniques was conducted to ascertain the most effective method for model selection. Our findings revealed that the distilled models exhibited comparable performance to the EcoVAD teacher model, indicating a promising approach to overcoming computational barriers for real-time ecological monitoring. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated that there is extensive variation in the songs of White-crowned Sparrow (Zonotrichia leucophrys) throughout the species range, including between neighboring (and genetically distinct) subspecies Z. l. nuttalli and Z. l. pugetensis. Using a machine learning approach to bioacoustic analysis, we demonstrate that variation in song is correlated with year of recording (representing cultural drift), geographic distance, and climatic differences, but the response is subspecies- and season-specific. Automated machine learning methods of bird song annotation can process large datasets more efficiently, allowing us to examine 1,913 recordings across ~60 years. We utilize a recently published artificial neural network to automatically annotate White-crowned Sparrow vocalizations. By analyzing differences in syllable usage and composition, we recapitulate the known pattern where Z. l. nuttalli and Z. l. pugetensis have significantly different songs. Our results are consistent with the interpretation that these differences are caused by the changes in characteristics of syllables in the White-crowned Sparrow repertoire. This supports the hypothesis that the evolution of vocalization behavior is affected by the environment, in addition to population structure. [ABSTRACT FROM AUTHOR]

Fish bioacoustics, or the study of fish hearing, sound production, and acoustic communication, was discussed as early as Aristotle. However, questions about how fishes hear were not really addressed until the early 20th century. Work on fish bioacoustics grew after World War II and considerably in the 21st century since investigators, regulators, and others realized that anthropogenic (human-generated sounds), which had primarily been of interest to workers on marine mammals, was likely to have a major impact on fishes (as well as on aquatic invertebrates). Moreover, passive acoustic monitoring of fishes, recording fish sounds in the field, has blossomed as a noninvasive technique for sampling abundance, distribution, and reproduction of various sonic fishes. The field is vital since fishes and aquatic invertebrates make up a major portion of the protein eaten by a signification portion of humans. To help better understand fish bioacoustics and engage it with issues of anthropogenic sound, this special issue of The Journal of the Acoustical Society of America (JASA) brings together papers that explore the breadth of the topic, from a historical perspective to the latest findings on the impact of anthropogenic sounds on fishes. [ABSTRACT FROM AUTHOR]

Modification of ecosystems as a consequence of urbanisation alters natural habitat structures and soundscapes, creating constraints for vocal communication in animals. Birds are able to adjust their vocalisation to the prevailing acoustic features of their habitat. As such, their sounds have been shown to reflect the level of anthropogenic disturbances across landscapes. While the effect of a single anthropogenic disturbance like ambient noise on birds' vocal communication is widely investigated, the combined effects of various disturbances remain less explored. We tested single and combined effects of anthropogenic noise and urban physical structures on the vocalisations of two African passerines, the Common Bulbul Pycnonotus barbatus and Northern Grey-headed Sparrow Passer griseus. We predicted that (i) both species would increase the minimum frequency of their vocalisation to avoid masking by ambient noise, (ii) both species would decrease their maximum frequency to evade distortion by physical structures, (iii) the two urban components would have a significant combined effect on the vocalisations, and (iv) the change in minimum or maximum frequency will lead to a corresponding change in the vocalisation bandwidth. For the Common Bulbul, the minimum frequency increased significantly as the ambient noise level increased, but the maximum frequency did not change in response to urban physical structures. For the Northern Grey-headed Sparrow, the minimum frequency did not show a response to ambient noise, but the maximum frequency decreased significantly as physical structures and ambient noise increased. We did not find any evidence for a combined effect of urban physical structures and ambient noise on the vocal adjustment of either species. A change in either the minimum or maximum frequency resulted in a corresponding change in the vocalisation bandwidth of each species. Our findings highlight how the same vocalisation traits of different songbird species can be affected differently by novel selective pressures in acoustic communication that arise in urban environments. [ABSTRACT FROM AUTHOR]

The source-filter theory suggests that animal traits, such as body size, are reliably encoded in vocalizations. These vocal signals, with a likely precopulatory function, are thought to be costly; given energetic constraints, they are expected to be in a trade-off with postcopulatory traits, such as testicular volume. Although this trade-off has been generally tested through comparative studies across species, it remains understudied whether it holds within a single species. Using parallel-laser photogrammetry, we conducted a 9-month study at Palenque National Park, Mexico, to investigate whether fundamental frequency (F0) or formant dispersion (ΔF) of roars and barks from 14 male black howler monkeys encode cues of body size, and whether they are in a trade-off with testicular volume. We found that only roar ΔF was associated with body size, with larger males producing roars with lower ΔF, suggesting a likely use of roars in male–male competition or female mate choice in black howlers. In contrast, after accounting for the positive effect of body size on testicular volume, no association was found between these vocal features and testicular volume. Our results show the presence of acoustic allometry within roars of male black howlers and suggest the absence of a trade-off within a single species, despite its presence at the genus level. • Roar formant dispersion was an honest signal of body size in adult male black howlers. • Formant dispersion, not fundamental frequency, correlated negatively with body size. • Barks did not contain information about adult male body size. • Testicular volume was not correlated with acoustic features of roars or barks. • Vocal–testicular trade-off reported across howler species was absent in black howlers. [ABSTRACT FROM AUTHOR]

Despite a relatively broad distribution in Africa, the Spotted Rubber Frog, Phrynomantis affinis, is extremely rarely encountered. Only 18 specimens from 12 localities have been collected with a few additional observations recorded. Virtually nothing of the species' natural history is known. We report or summarise new localities and range extensions of P. affinis in Namibia and Zambia and describe the call for the first time. We also compare its call to that of the sister species, P. bifasciatus, describing this call for the first time and noting a considerable range extension. The calls show several key differences, with P. affinis calls generally having a lower dominant frequency, pulse repetition rate, and number of pulses than P. bifasciatus. The calls of Namibian and Zambian P. affinis also show marked differences. These descriptions add valuable natural history information for both species and will considerably improve the field detection of the enigmatic P. affinis. [ABSTRACT FROM AUTHOR]

thebeat is a Python package for working with temporal sequences and rhythms in the behavioral and cognitive sciences, as well as in bioacoustics. It provides functionality for creating experimental stimuli, and for visualizing and analyzing temporal data. Sequences, sounds, and experimental trials can be generated using single lines of code. thebeat contains functions for calculating common rhythmic measures, such as interval ratios, and for producing plots, such as circular histograms. thebeat saves researchers time when creating experiments, and provides the first steps in collecting widely accepted methods for use in timing research. thebeat is an open-source, on-going, and collaborative project, and can be extended for use in specialized subfields. thebeat integrates easily with the existing Python ecosystem, allowing one to combine our tested code with custom-made scripts. The package was specifically designed to be useful for both skilled and novice programmers. thebeat provides a foundation for working with temporal sequences onto which additional functionality can be built. This combination of specificity and plasticity should facilitate research in multiple research contexts and fields of study. [ABSTRACT FROM AUTHOR]

Anuran communication is largely based on acoustic signals, but different sensory modes are also widespread, including visual communication using body color traits as a way of signaling. The Brazilian treefrog, Boana albomarginata, has a complex behavioral repertoire presenting several call types and performing gestures as visual signals. This species has a greenish body color with orange patches on the flanks and thighs. These patches become visible when males are in a calling posture or performing visual signals such as leg kicking and limb lifting, suggesting that they might use the patches as visual cues. We sampled seven populations, using call recordings and photographs to access males call and color traits. We demonstrate that there is variation in color and call properties across populations. Additionally, we observe variation in the relationship between color traits and call properties in different populations, revealing that only two populations exhibit a significant correlation between color and call traits. Further, while call properties and color traits were not related with individual body size, they were associated with body condition. The results indicate a universal pattern across populations for call properties, wherein males in better condition consistently displayed lower-pitched calls, longer calls, and shorter intervals between calls. Regarding color traits, males in better condition in four out of the seven evaluated populations exhibited larger orange patch sizes, lower orange hue values, and higher hue contrasts. Although we observed some level of relation among color, call, and body traits, there is not a universal pattern across all populations. Significance statement: Animal social interactions are mediated by signals transmitted through different sensory modes (i.e., acoustic, chemical, tactile, and visual), and more than one of these modalities can compose the behavioral repertoire of one species. Using photographs and acoustic recordings of Boana albomarginata males in natural environments, we documented geographic variation in both signals, call and color, and investigated their potential to convey individual body size and condition. Our findings reveal that both signals were correlated with individual body condition. In addition, color traits were associated with call properties in some populations. [ABSTRACT FROM AUTHOR]

Despite the high diversity of bats in neotropics, traditional methods such as mist nets, harp traps and roost detection have limitations in capturing that diversity in a landscape, with most detected species restricted to those that forage in the undergrowth or enclosed spaces. Therefore, acoustic records become a tool that complements and enhances the efforts to get more complete bat inventories while avoiding alterations in usual foraging activities and disruption in their life cycles. This study describes the acoustic parameters (spectral and temporal variables) of the echolocation pulses of insectivorous bats to characterise different species of bats in Southwest Colombia acoustically. We recorded echolocation calls between December 2017 and May 2020 in the Andean and Pacific regions of the Department of Nariño. We analysed 81 sequences of echolocation calls from eight bat species belonging to three families: Vespertilionidae, Molossidae and Emballonuridae. We perform recordings on free-flying bats with identity corroboration by capture for recording in flight rooms and examination in the hand. Myotis riparius and Lasiurus blossevillii were recorded for the first time in the Nariño Department. M. albescens, M. keaysi, M. riparius and L. blossevillii (Vespertilionidae) had pulses of frequency modulated (FM) with a quasi-constant frequency (QCF) ending; Molossus molossus, Tadarida brasiliensis and Promops centralis (Molossidae) had pulses with constant frequency (CF) and QCF; and Saccopteryx bilineata (Emballonuridae) had pulses with QCF. This study contributes to the efforts to facilitate the identification of insectivorous bats of the Neotropics using the acoustic monitoring approaches, represents a reference to compare the acoustic studies in Southwestern Colombia and contributes to increasing our knowledge of the bat diversity in the region. [ABSTRACT FROM AUTHOR]

Biofinish is an innovative wood protection system inspired by biological processes. It enhances the hydrophobicity of wood through oil treatment, resulting in improved dimensional stability. Living cells of the fungus Aureobasidium pullulans effectively protect wood from deterioration caused by other decaying fungi. The melanin pigment produced by the fungus provides an appealing dark surface and additionally protects the wood substrate against UV radiation. The significant advantage of Biofinish is its remarkable self-healing ability, which distinguishes it from conventional wood protection methods. This research aimed to explore fungal species colonising surfaces exposed to natural weathering and assess the survival of A. pullulans on wood surfaces coated with Biofinish during its in-service period. This study was performed on a facade composed of European larch wood (Larix decidua) treated with linseed oil and coated with Biofinish at the InnoRenew CoE building in Izola, Slovenia, following a 9-month exposure period. The majority of the detected species belonged to the genera Aureobasidium. The results indicated the survival and effective antagonistic action of A. pullulans, the living and active ingredient of the coating, against other wood-decaying fungi. [ABSTRACT FROM AUTHOR]

The songs of seven grasshopper species of subfamily Gomphocerinae from Russia, Ukraine, Georgia, and Kazakhstan were studied. We analysed not only the sound, but also the stridulatory movements of the hind legs to more entirely describe the songs. In Mesasippus kozhevnikovi, Chorthippus macrocerus, and C. hammarstroemi, the legs are moved in a relatively simple pattern; four other species, Myrmeleotettix palpalis, Stenobothrus newskii, C. pullus, and Megaulacobothrus aethalinus demonstrate more complex leg movements. In six of the seven species studied, the courtship songs contain more sound elements than the calling songs. The highest number of courtship sound elements was found in M. palpalis and M. aethalinus. The different parts of a remarkably long stridulatory file in M. aethalinus are thought to participate in the production of different sound elements. The songs in S. newskii are shown for the first time. This species produces sound not only by common stridulation but also by wing beats. A relationship of S. newskii to some other species of the genus Stenobothrus, which are able to crepitate, is discussed. We also analyse the frequency spectra of the songs. A maximum energy of the song power spectra in six species studied lies in ultrasound range (higher than 20 kHz). In only M. aethalinus, the main peaks in the song power spectra lie lower than 20 kHz. The courtship behaviour in M. palpalis, C. macrocerus, and C. hammarstroemi was shown to include conspicuous visual display (movements of antennae, palps and the whole body). [ABSTRACT FROM AUTHOR]

Habitat loss, fragmentation, and land conversion for human use are currently the main drivers of biodiversity loss in the Neotropics. Agropastoral and silvicultural activities are especially important, as they have expanded in the last decades due to the increasing demand for global food and wood production. This presents a challenge in developing management strategies that balance biodiversity conservation with productivity, which can only be achieved through a better understanding of biodiversity responses to landscape changes. In this study, we investigated how landscape changes affect the species richness, relative abundance, and species composition of a bat community in a fragmented landscape in southeastern Brazil, using an approach that integrates data from mist-nets and bioacoustics. Forest cover at intermediate and large scales was the best predictor of bat richness and relative abundance, as well as the relative abundance of frugivorous bats. For open and edge space aerial insectivorous bats, landscape variables did not have a strong explanatory power, suggesting that other variables may better predict their relative abundance. Our study highlights the importance of using multiple sampling methods to study Neotropical bats, as well as the importance of the multiscale approach to evaluate landscape effects on biological communities. [ABSTRACT FROM AUTHOR]

The study of nocturnal bird migration brings observational challenges because of reduced visibility and observability of birds at night. Remote sensing tools, especially radars, have long been the preferred choice of scientists to study nocturnal migrations. A major downside of these remote sensing tools is the lack of species-level information. With technological advances in recent decades and with improved accessibility and affordability of acoustic tools, sound recordings have steeply increased in popularity. In Europe, there is no exhaustive qualitative and quantitative evaluation of the content of such acoustic databases and therefore the value for migration science and migration-related applications, such as bird collision hazard assessments, is mostly unknown. In the present work we compared migration schedules estimated from citizen science data with quantitative temporal occurrence of species in four years of acoustic recordings. Furthermore, we contrasted acoustic recordings with citizen science observations and weather radar data from one spring and one autumn season to assess the qualitative and quantitative yield of acoustic recordings for migration-related research and applications. Migration intensity estimated from weather radar data correlated best at low levels with acoustic records including all species in spring while in autumn passerine species showed stronger correlation than the entire species composition. Our findings identify a minor number of species whose call records may be eligible for applications derived from acoustics. Especially the highly vocal species Song thrush and Redwing showed relatively good correlations with radar and citizen science migration schedules. Most long-distance passerine migrants and many other migrants were not captured by acoustics and an estimated seasonal average of about 50% of nocturnally migrating passerine populations remained undetected. Overall, the ability of acoustic records to act as a proxy of overall migration dynamics is highly dependent on the migration period and species involved. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max (L.) Merr.) is an important agricultural crop around the world, and previous studies suggest that honey bees (Apis mellifera Linnaeus) can be a component for optimizing soybean production through pollination. Determining when bees are present in soybean fields is critical for assessing pollination activity and identifying periods when bees are absent so that bee-toxic pesticides may be applied. There are currently several methods for detecting pollinator activity, but these existing methods have substantial limitations, including the bias of pan trappings against large bees and the limited duration of observation possible using manual techniques. This study aimed to develop a new method for detecting honey bees in soybean fields using bioacoustics monitoring. Microphones were placed in soybean fields to record the audible wingbeats of foraging bees. Foraging activity was identified using the wingbeat frequency of honey bees (234 ± 14 Hz) through a combination of algorithmic and manual approaches. A total of 243 honey bees were detected over 10 days of recording in 4 soybean fields. Bee activity was significantly greater in blooming fields than in non-blooming fields. Temperature had no significant effect on bee activity, but bee activity differed significantly between soybean varieties, suggesting that soybean attractiveness to honey bees is heavily dependent on varietal characteristics. Refinement of bioacoustics methods, particularly through the incorporation of machine learning, could provide a practical tool for measuring the activity of honey bees and other flying insects in soybeans as well as other crops and ecosystems. [ABSTRACT FROM AUTHOR]

Taxonomic uncertainty at the species level compromises our knowledge of biodiversity, conservation, and systematics. The impact of such uncertainty is heightened in megadiverse regions such as Amazonia due to high levels of cryptic diversity. We used integrative taxonomy based on newly collected topotypical specimens to redescribe the Amazonian nurse frog Allobates gasconi and infer its phylogenetic relationships. This species was described in 2002 based solely on morphology, but several characters crucial for the reliable diagnosis of species in Allobates were not considered. Our results show that A. gasconi sensu stricto is not a member of the A. caeruleodactylus clade as previously claimed, but is a member of the A. trilineatus clade. Allobates gasconi is readily distinguished from congeners by a combination of morphological and bioacoustic characters; a revised diagnosis is provided. The type series of A. gasconi comprises more than one species, and we exclude a paratype from lower Juruá River. The species is restricted geographically to flooded environments in the middle and upper Juruá River in Brazil and in the Ucayali River in Peru. The initial misidentification, subsequent absence of topotypic molecular and acoustic data, and the poor preservation condition of the type series have contributed to taxonomic confusion since A. gasconi was first described. The descriptions of other species of Allobates published more than two decades ago were based mainly on gross morphology, and we recommend integrative taxonomic revisions to elucidate their systematics. [ABSTRACT FROM AUTHOR]

Passive forest restoration can buffer the effects of habitat loss on biodiversity. We acoustically surveyed aerial insectivorous bats in a whole‐ecosystem fragmentation experiment in the Brazilian Amazon over a 2‐year period, across 33 sites, comprising continuous old‐growth forest, remnant fragments, and regenerating secondary forest matrix. We analyzed the activity of 10 species/sonotypes to investigate occupancy across habitat types and responses to fragment size and interior‐edge‐matrix (IEM) disturbance gradients. Employing a multiscale approach, we investigated guild (edge foragers, forest specialists, flexible forest foragers, and open space specialists) and species‐level responses to vegetation structure and forest cover, edge, and patch density across six spatial scales (0.5–3 km). We found species‐specific habitat occupancy patterns and nuanced responses to fragment size and the IEM disturbance gradient. For example, Furipterus horrens had lower activity in secondary forest sites and the interior and edge of the smallest fragments (1 and 10 ha) compared to continuous forest, and only two species (Pteronotus spp.) showed no habitat preference and no significant responses across the IEM and fragment size gradients. Only the Molossus sonotype responded negatively to vegetation structure. We uncovered no negative influence of forest cover or edge density at guild or species‐level. Our results indicate that reforestation can buffer the negative effects of fragmentation and although these effects can still be detected in some species, generally aerial insectivorous bats appear to be in recovery after 30 years of passive forest restoration. Our findings reinforce the need to protect regenerating forests while conserving vast expanses of old‐growth forest. [ABSTRACT FROM AUTHOR]

In birds, pre-hatching calls are part of the communication behavior between parents and offspring, and may serve multiple functions. The Clark's Grebe (Aechmophorus clarkii) has a wide distribution in Mexico, and in 2015 we monitored a reproductive colony in the lagoon of Zumpango in central Mexico. We describe and measure the pre-hatching calls of two individuals from two different clutches. Eggs were about 22–25 days old. We obtained 5.16 minutes of recordings, with 81 calls made up by a frequency-modulated note and with an average call duration of 8.05 milliseconds and a peak dominant frequency of 828.20 Hertz (max 870.40; min 771.38). Calls were emitted at intervals of 1.38 seconds. This is the first description of pre-hatching calls in the Clark's Grebe, a poorly studied waterbird in Mexico. [ABSTRACT FROM AUTHOR]

Bottlenose dolphins (Tursiops truncatus) rely on frequency- and amplitude-modulated whistles to communicate, and noise exposure can inhibit the success of acoustic communication through masking or causing behavioral changes in the animal. At the US Navy Marine Mammal Program (MMP) in San Diego, CA, dolphins are housed in netted enclosures in the San Diego Bay and exposed to noise from vessels, unmanned underwater vehicles, and other remote sensing devices. The acoustic behavior of 20 dolphins was monitored and whistle rates during noise events were quantified. Whistle rates during the onset of the event (i.e., the first 5 min) did not significantly differ from the pre-onset (5 min immediately preceding). Whistle rates were also not significantly different for the entire duration of the event compared to a matched control period. The noise's frequency range (i.e., control, mid-frequency (0–20 kHz) or high-frequency (21–80 kHz)), signal-to-noise ratio, and sound pressure level were not significantly related to the dolphins' whistle rate. Considering this is a location of frequent and moderate noise output, these results lend support to established guidelines on anthropogenic noise exposure for cetaceans, suggesting that moderate noise exposure levels may not impact communication efforts in bottlenose dolphins. [ABSTRACT FROM AUTHOR]

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Machine learning provides researchers in speech processing and bioacoustics numerous advanced and non-invasive techniques to investigate animal vocalizations. Hidden Markov Models (HMMs) are machine learning techniques that were developed and implemented for the automatic gender recognition and speaker identification of Rhesus Macaques (Macaca mulatta) using traditional spectral and temporal features, namely Mel-Frequency Cepstral Coefficients (MFCCs) and delta (velocity) and delta-delta (acceleration) coefficients. By extracting the combined features from the frames of the vocalizations using 4 ms frame size and 2 ms step size and 4 state, left-to-right HMMs, the important tasks of gender recognition and speaker identification were performed on the database of 7285 coo call-types from 8 animals (4 males, 4 females). The task of gender recognition produced a 84.45% accuracy (1233/1460 correct recognitions), and the task of speaker identification of the 4 males and 4 males yielded 91.08% (633/695 correct identifications, males) and 83.27% (637/765 correct identifications, females) and 81.85% (119/1460 correct identifications) for all 8 animals. Based on the performance, the novel contributions of the framework—applying HMMs to the gender recognition and speaker identification of the Rhesus Macaques (M. mulatta) in an automated manner—could easily be extended to other mammals for automatic classification and recognition. [ABSTRACT FROM AUTHOR]

Organisms, such as fishes and invertebrates and including their larval stages, listen to underwater soundscapes to detect information about nearby habitats. Such soundscapes may be influenced by habitat degradation or enhancement, which can lead to acoustically mediated feedback loops affecting the overall ecosystem.Despite the importance of underwater sounds on ecological functioning, there have been limited studies documenting soundscapes of intertidal ecosystems and few, if any, of living shoreline soundscapes. Living shorelines would especially benefit from acoustically mediated effects for objectives like encouraging fish and invertebrate settlement.This case study used a Before‐After‐Control‐Impact design to sample soundscapes and nekton (i.e., fishes and mobile macroinvertebrates) at a living shoreline construction and a nearby hardened shoreline in Cedar Key, FL (USA). Diel soundscape patterns and acoustic attenuation at the two sites were also described a year following the living shoreline construction.In the acoustic sampling, the high frequency bands of both shorelines were dominated by invertebrate sounds that were influenced by season, site and time of day, while the low frequency band of the living shoreline was often dominated by a loud anthropogenic sound. About a year after the living shoreline installation—despite similar measured acoustic attenuation at both sites—the living shoreline featured louder sound pressure levels compared to the hardened shoreline, which may be particularly beneficial for promoting foundational species and other organism settlement.These results demonstrate that Gulf of Mexico intertidal habitats may have soundscape differences even within close proximity and that living shorelines may enhance acoustic characteristics in ways beneficial to continued shoreline development. This represents an important step in better understanding the relationships between habitat structures, nekton communities, and their associated soundscapes as well as the application of passive acoustic monitoring to improve coastal management and conservation. [ABSTRACT FROM AUTHOR]

Biotremology, officially coined in 2016, has rapidly emerged as a distinct scientific discipline, focusing on the study of substrate‐borne mechanical waves in animal communication, particularly among insects. Initially seen as a niche within bioacoustics, biotremology is now recognized for its broad significance, rivalling chemical communication in its prevalence. This special issue highlights the multidisciplinary nature of biotremology, with research spanning insect behaviour, ecology and pest management. Studies showcase advances in understanding vibrational communication across diverse insect taxa, the development of new tools for reliable playback experiments and the growing potential of biotremology in applied pest control. This collection provides a snapshot of a dynamic field in rapid expansion, pushing the boundaries of both fundamental research and practical applications. [ABSTRACT FROM AUTHOR]