Search

Calling is a key behavior in anuran ecology, associated with individual reproductive success and territory maintenance. Sites that allow better sound propagation, with higher intensity and less energy consumption, are a resource that males will compete for. We used body condition (BC) as a proxy for competitive performance to test the hypothesis that Dendropsophus jimi males with superior BC occupied better perches for calling in a pond with simple vegetative structure. Because grassy layer density and height are inversely correlated, presumably facilitating sound propagation, we expected a positive correlation between BC and perch height in open-field specialists. We also identified which morphological features were associated with higher perching. In addition, if calling males are depleting energy reserves during the breeding season, they should maintain BC through food consumption. To test this hypothesis, we performed a correlation between stomach volume and food item abundance with BC. We found perch height to be positively correlated with BC. Higher calling males were also characterized by having longer legs, shorter carpus and smaller heads. However, we found no correlation between BC and food intake. We suggest that calling males are depleting previously accumulated energy stocks. Higher calling perches are apparently actively disputed by D. jimi, as superior BC males are using mainly higher perches. We suggest that our findings on the small D. jimi are also expected for other open field Hylinae in the Cerrado. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-layer alternating sparse−dense framework for bird species identification. The framework takes audio recordings of bird vocalizations and produces compressed convex spectral embeddings (CCSE). Temporal and frequency modulations in bird vocalizations are ensnared by concatenating frames of the spectrogram, resulting in a high dimensional and highly sparse super-frame-based representation. Random projections are then used to compress these super-frames. Class-specific archetypal analysis is employed on the compressed super-frames for acoustic modeling, obtaining the convex-sparse CCSE representation. This representation efficiently captures species-specific discriminative information. However, many bird species exhibit high intra-species variations in their vocalizations, making it hard to appropriately model the whole repertoire of vocalizations using only one dictionary of archetypes. To overcome this, each class is clustered using Gaussian mixture models (GMM), and for each cluster, one dictionary of archetypes is learned. To calculate CCSE for any compressed super-frame, one dictionary from each class is chosen using the responsibilities of individual GMM components. The CCSE obtained using this GMM-archetypal analysis framework is referred to as local CCSE. Experimental results corroborate that local CCSE either outperforms or exhibits comparable performances to existing methods including support vector machine powered by dynamic kernels and deep neural networks. [ABSTRACT FROM AUTHOR]

The importance of perceived sound source distance has been noted in controlled exposure studies with free-ranging marine mammals. Different behavioral reactions have been observed for sonar exposures with a similar received level but differing source distances. This psychophysical study examined bottlenose dolphins' use of range-dependent acoustic features in classifying frequency-modulated tonal stimuli (∼10-kHz fundamental). Repetitive tones with simulated range-dependent high-frequency attenuation (HFA) and reverberation (REV) were presented with roving levels (levels varied ±10 dB). The dolphins were trained to produce a phonic response upon hearing tones simulating relatively distant 30-km sources and to withhold response for closer-range tones. Once this behavior was reliably performed, probe trials with intermediate ranges were used to examine stimulus classification based on HFA and REV. Dolphins responded to nearly all probe trials with ranges of 10 and 20 km, while responses were less frequent at 1 and 2 km. Probes with HFA and REV decoupled from simulated source distance indicated that the dolphins used HFA to a greater degree than REV in response decisions. These results suggest that dolphins can classify harmonic signals based on range-dependent HFA and REV independent of received level, making these cues potentially useful in deciding behavioral reactions to acoustic sources. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Zoology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Toadfishes (family Batrachoididae) are a well-studied family of soniferous fishes, yet only a fraction of species within the family have been recorded, and only few detailed descriptions of calls exist. Here, we present the first description of the acoustic ecology of Amphyichtys cryptocentrus, a new-world toadfish species, distributed across the southern Caribbean Sea. We recorded fourteen individuals in a seagrass habitat over six nights in the Bocas del Toro Archipelago. Like other toadfishes, A. cryptocentrus produces compound calls with broadband and tonal components; a typical call contains 1-2 grunts, followed by 1-2 boops (average fundamental frequency = 112 Hz, average source level = 138 dB re:1 μPa RMS). While we observed relatively low between-individual variation in frequency components, our results show that individuals can be readily identified based on their call composition and call rate. This suggests that each toadfish has an individual “voice,” which may transmit selection-linked information to females about body condition, status, or motivation to mate. We also observed that toadfish produced grunts during neighbors’ calls, a previously-described aggressive behavior called “acoustic tagging”, which can intercept a potential rival’s mating advertisement. Our findings suggest that A. cryptocentrus (and its population in Bocas del Toro, in particular) represents a useful system for the study of fish bioacoustics and behavioral ecology, and we demonstrate that acoustic communication represents a major aspect of social behavior in coral reef fishes. [ABSTRACT FROM AUTHOR]

For many rare or endangered anurans, monitoring is achieved via auditory cues alone. Human-performed audio surveys are inherently biased, and may fail to detect animals when they are present. Automated audio recognition tools offer an alternative mode of observer-free monitoring. Few commercially available platforms for developing these tools exist, and little research has investigated whether these tools are effective at detecting rare vocalization events. We generated a recognizer for detecting the vocalization of the endangered Houston toad Anaxyrus houstonensis using SongScope& bioacoustics software. We developed our recognizer using a large sample of training data that included only the highest quality of recorded audio (i.e., low noise, no interfering vocalizations) divided into small, manageable batches. To track recognizer performance, we generated an independent set of test data through randomly sampling a large population of audio known to possess Houston toad vocalizations. We analyzed training data and test data recursively, using a criterion of zero tolerance for false-negative detections. For each step, we incorporated a new batch of training data into the recognizer. Once we included all training data, we manually verified recognizer performance against one full month (March 2014) of audio taken from a known breeding locality. The recognizer successfully identified 100% of all training data and 97.2% of all test data. However, there is a trade-off between reducing false-negative and increasing false-positive detections, which limited the usefulness of some features of SongScope. Methods of automated detection represent a means by which we may test the efficacy of the manual monitoring techniques currently in use. The ability to search any collection of audio recordings for Houston toad vocalizations has the potential to challenge the paradigms presently placed on monitoring for this species of conservation concern. [ABSTRACT FROM AUTHOR]

Although many fish are soniferous, few of their sounds have been identified, making passive acoustic monitoring (PAM) ineffective. To start addressing this issue, a portable 6-hydrophone array combined with a video camera was assembled to catalog fish sounds in the wild. Sounds are detected automatically in the acoustic recordings and localized in three dimensions using time-difference of arrivals and linearized inversion. Localizations are then combined with the video to identify the species producing the sounds. Uncertainty analyses show that fish are localized near the array with uncertainties < 50 cm. The proposed system was deployed off Cape Cod, MA and used to identify sounds produced by tautog (Tautoga onitis), demonstrating that the methodology can be used to build up a catalog of fish sounds that could be used for PAM and fisheries management. [ABSTRACT FROM AUTHOR]

Sounds produced by Arctic cod were recorded for the first time and suggest passive acoustic monitoring (PAM) can be an effective additional tool for the study and management of the species. Each of the 38 calls detected in three different aquatic facilities consisted of a single grunt with 6 to 12 pulses and a mean duration of 289 ms. Call frequency ranged between 59 and 234 Hz, with a mean peak frequency of 107 Hz. These preliminary data suggest Arctic cod can be distinguished from other gadids, but additional studies of sympatric species are needed before PAM can be confidently adopted. [ABSTRACT FROM AUTHOR]

A fundamental hypothesis about vocal learning is that young animals learn vocalizations in their natal areas and, following postnatal dispersal, they may introduce new types of vocalizations into their breeding areas. We tested this hypothesis in a tropical bird, the Rufous-and-white Wren (Thryophilus rufalbus), a species in which both sexes produce learned songs. We collected blood samples and acoustic recordings from 146 adult wrens from 3 populations in northwestern Costa Rica. We genotyped individuals at 10 polymorphic microsatellite loci and identified first-generation migrants using partial Bayesian genotype assignment. We quantified acoustic variation by comparing fine-scale acoustic structure, song sharing, and repertoire novelty between residents and first-generation migrants. We found significant population-level differences in acoustic structure of songs among the 3 populations. Of the 146 individuals genotyped, 9 individuals were identified as first-generation migrants. In contrast to our predictions, however, we found that these first-generation migrants did not exhibit differences in the acoustic structure of their songs from resident individuals in their breeding population, either for males or females. We conclude that song learning in first-generation migrants must be behaviorally influenced by birds in their breeding populations, following postnatal dispersal. We observed population-level acoustic differences among the 3 study sites, which implies sustained divergent selection pressures at each site, possibly reflecting acoustic adaptation to different environments or social pressure to sing local songs. Understanding and quantifying patterns of cultural evolution at multiple scales provides insight into how behavioral barriers, such as acoustic signals, contribute to population differentiation and even speciation. [ABSTRACT FROM AUTHOR]

Two new genera of East African Acrometopini are erected: the monotypic Peronurella n. gen. with P. centralis n. sp. from Miombo woodlands in central Tanzania, and Tenerasphaga n. gen. for a morphological uniform group of species formerly included in Horatosphaga, T. chyuluensis n. sp., T. mbulu n. sp. T. nanyuki, T. nuda n. comb, T. meruensis n. comb, T. tenera n. comb and T. bazeletae n. comb. Additional species are described in the genera Altihoratosphaga, Lamecosoma and Peronura. Keys to African genera of Acrometopini and species of the genus Tenerasphaga are provided. We review the male calling songs and the morphology of the acoustical apparatus and discuss how the morphology of the stridulatory files explains the complicated song patterns and elements. All Acrometopini species showed a plesiomorphic karyotype with a diploid chromosome number of 2n = 31 and a X0 sex chromosome system in males. [ABSTRACT FROM AUTHOR]

Humpback whales (Megaptera novaeangliae) are well known for their complex song which is culturally transmitted and produced by males. However, the function of singing behavior remains poorly understood. Song was observed from 57 min of acoustic recording in the presence of feeding humpback whales aggregated in the near-shore waters on the west coast of South Africa. The structural organization of the song components, lack of overlap between song units, and consistency in relative received level suggest the song was produced by one “singer.” The unusual timing and location of song production adds further evidence of plasticity in song production. [ABSTRACT FROM AUTHOR]

The echolocation signals of most beaked whale species are still unknown. In fact, out of the 22 species comprising the family Ziphiidae, only the echolocation pulses for 7 species have been clearly described. This study describes two distinct beaked whale echolocation signals recorded in the Cook Strait region using passive acoustic technology. These signals differ from previously described Ziphiid species clicks. A description of the time-frequency characteristics of the two signals is provided. Understanding the characteristics of these signals is necessary to correctly identify species from their echolocation signals and enables future monitoring of beaked whales using passive acoustics techniques. [ABSTRACT FROM AUTHOR]

Unlike terrestrial mammals that have unambiguous aerial sound transmission pathways via the outer ear and tympanum, sound reception pathways in most odontocetes are not well understood. Recent studies have used auditory brainstem response (ABR) measurements to examine sound reception pathways. This study sought to determine how sound source placements, recording electrode arrangements, and ABR peak analyses affect interpretations of sound reception in the harbor porpoise (Phocoena phocoena). Click stimuli were delivered in air from a contact transducer (“jawphone”). Early ABR peaks (representing auditory nerve responses), and later peaks reflecting higher brainstem activity, were analyzed across jawphone and recording electrode positions. Auditory nerve responses were similar for jawphone placements from the ipsilateral posterior mandible to the tip of the rostrum. Later peaks, however, suggested a possible region of highest sensitivity midway between the posterior mandible and the rostrum tip. These findings are generally similar to previous data for porpoises. In contrast to auditory nerve responses that were largest when recorded near the ipsilateral meatus, later ABR peaks were largest when recorded with a contralateral (opposing) electrode. These results provide information on the processes underlying peaks of the ABR, and inform stimulus delivery and ABR recording parameters in odontocete sound reception studies. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Zoology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Zoology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to several factors such as ecological conditions, group size, and social organization, primates frequently spend time out of visual contact with individuals of their own group. Through the use of long‐distance vocalizations, often termed “contact calls,” primates are able to maintain contact with out‐of‐sight individuals. Contact calls have been shown to be individually distinct, and reverberation and attenuation provide information about caller distance. It is less clear, however, whether callers actively change the structure of contact calls depending on the distance to the presumed listeners. We studied this question in spider monkeys (Ateles geoffroyi), a species with complex spatial dynamics (fission‐fusion society) that produces highly frequency modulated contact calls, denominated “whinnies.” We determined the acoustic characteristics of 566 whinnies recorded from 35 free‐ranging spider monkeys that belong to a community located in Mexico, and used cluster analyses, discriminant function analyses, and generalized linear mixed models to assess if they varied in relation to the presumed distance to the listener. Whinnies could be grouped into five subtypes. Since the lowest frequency subtype was mainly produced by spider monkeys that exchanged whinnies at longer distances, and lower frequency calls propagate across longer distances, our results suggest that whinnies vary in order to enhance vocal contact between individuals separated by different distances. Our results also revealed that whinnies convey potential information about caller immediate behaviors and corroborated that these calls are individually distinct. Overall, our results suggest that whinny acoustic variation facilitates the maintenance of vocal contact between individuals living in a society with complex spatial dynamics. [ABSTRACT FROM AUTHOR]

Abstract: Acoustic communication is taxonomically widespread in bark beetles and is proposed to play an important role in a variety of social and defensive behavioural contexts. Yet our understanding of how signals vary between contexts is currently limited. The present study tests the hypothesis that acoustic signals vary between behavioural contexts in the female pine engraver beetle Ips pini (Say) (Coleoptera: Curculionidae: Scolytinae). Female Ips pini produce acoustic chirps using a vertex‐pronotal stridulatory organ. Randomly sampled chirps generated under three contexts (i.e. distress, predation and premating) are compared for their duration, number of pulses, interpulse intervals, pulse rate and amplitude envelope shapes. The results obtained show that, during premating events, chirps are significantly longer in duration and tend to have a higher proportion of descending amplitude envelopes than chirps occurring during distress and predation events. Chirps produced during distress and predation conditions are indistinguishable from one another. By contrast to the results from previous bark beetle studies, no support is found for categorizing chirps as ‘interrupted’ or ‘uninterrupted’ types based on temporal patterns. The functional significance of context‐dependent variation in chirp characteristics is discussed. Previous studies on acoustic communication in bark beetles are limited as a result of a general lack of objective sampling and measurement criteria for characterizing signals. Recommendations are outlined for future studies on the functions and evolution of acoustic communication in bark beetles. [ABSTRACT FROM AUTHOR]

Bioacoustics is an interdisciplinary field bridging biological and acoustic sciences, which uses sound technologies to record, preserve, and analyse large datasets of animal communications. But it is also a world, made of the meanings created through inter- and intra-species communication. This article empirically explores a variety of bioacoustics research, including interviews with researchers, as part of a broader qualitative study, in order to theorize the expanding sense and sensation of a global biosphere and sonic data. By giving a sustained and detailed account of the science of bioacoustics, particularly how its modes of measurement allow for a new way of understanding what is involved in the de-centred modes of hearing that re-centre acts of listening and, by extension, the nature of the relation between researcher and researched, the article contributes to methodological discussions regarding the longstanding questions of how researchers and scientists are implicated in the knowledge and objects they collectively produce. [ABSTRACT FROM AUTHOR]

The sounds of early modern Paris are first explored through poetic and satirical depictions of urban noise, with emphasis placed on the disruption that they present. The attempt by Louis XIV to assert his absolute power becomes manifest in the means employed to control and contain those sounds deemed to be potentially subversive and seditious, especially in the threat posed by performers of songs on the Pont-Neuf, which was one of the few public spaces where people of all classes rubbed shoulders. The example of the blind singer Philippot le Savoyard shows how the Pont-Neuf became the prime locus of difference and marginality. [ABSTRACT FROM AUTHOR]

Background: Mosquito-borne diseases are rapidly spreading to vast territories, putting at risk most of the world's population. A key player in this scenario is Aedes aegypti, a hematophagous species which hosts and transmits viruses causing dengue and other serious illnesses. Since vector control strategies relying only on insecticides have proven unsustainable, an alternative method involving the release of Wolbachia-harboring individuals has emerged. Its successful implementation vastly depends on how fit the released individuals are in the natural habitat, being able to mate with wild populations and to spread Wolbachia to subsequent generations. In mosquitoes, an important aspect of reproductive fitness is the acoustic communication between males and females, which translates to interactions between harmonic frequencies in close proximity flight. This study aimed to characterize the flight tone produced by individuals harboring Wolbachia, also evaluating their ability to establish stable acoustic interactions. Methods: Wild-type (WT) and Wolbachia-harboring specimens (wMelBr) were thorax-tethered to blunt copper wires and placed at close proximity to sensitive microphones. Wing-beat frequencies (WBFs) were characterized at fundamental and harmonic levels, for both single individuals and couples. Harmonic interactions in homogeneous and heterogeneous couples of WT and wMelBr variants were identified, categorized and quantified accordingly. Results: In tethered 'solo' flights, individuals harboring Wolbachia developed WBFs, differing slightly, in a sex-dependent way, from those of the WT strain. To test the ability to form harmonic 'duets', tethered couples of wMelBr and WT individuals were shuffled in different sex pairs and had their flight tones analyzed. All couple types, with WT and/or wMelBr individuals, were able to interact acoustically in the frequency range of 1300-1500 Hz, which translates to the convergence between male's second harmonic and female's third. No significant differences were found in the proportions of interacting couples between the pair types. Surprisingly, spectrograms also revealed the convergence between alternative harmonic frequencies, inside and outside the species putative hearing threshold. Conclusions: Wolbachia infection leads to small sex-dependent changes on the flight tones of Ae. aegypti, but it does not seem to prevent the stereotyped harmonic interaction between males and females. Therefore, when released in the natural habitat to breed with native individuals, Wolbachia-harboring individuals shall be fit enough to meet the criteria of acoustically-related mating behavior and promote bacteria dispersion effectively. [ABSTRACT FROM AUTHOR]

Humpback whales produce a wide range of low- to mid-frequency vocalizations throughout their migratory range. Non-song “calls” dominate this species' vocal repertoire while on high-latitude foraging grounds. The source levels of 426 humpback whale calls in four vocal classes were estimated using a four-element planar array deployed in Glacier Bay National Park and Preserve, Southeast Alaska. There was no significant difference in source levels between humpback whale vocal classes. The mean call source level was 137 dBRMS re 1 μPa @ 1 m in the bandwidth of the call (range 113–157 dBRMS re 1 μPa @ 1 m), where bandwidth is defined as the frequency range from the lowest to the highest frequency component of the call. These values represent a robust estimate of humpback whale source levels on foraging grounds and should append earlier estimates. [ABSTRACT FROM AUTHOR]

Male humpback whales produce a mating display called “song.” Behavioral studies indicate song has inter- and/or intra-sexual functionality, suggesting song may be a multi-message display. Multi-message displays often include stereotypic components that convey group membership for mate attraction and/or male-male interactions, and complex components that convey individual quality for courtship. Humpback whale song contains sounds (“units”) arranged into sequences (“phrases”). Repetitions of a specific phrase create a “theme.” Within a theme, imperfect phrase repetitions (“phrase variants”) create variability among phrases of the same type (“phrase type”). The hypothesis that song contains stereotypic and complex phrase types, structural characteristics consistent with a multi-message display, is investigated using recordings of 17 east Australian males (8:2004, 9:2011). Phrase types are categorized as stereotypic or complex using number of unit types, number of phrase variants, and the proportion of phrases that is unique to an individual versus shared amongst males. Unit types are determined using self-organizing maps. Phrase variants are determined by Levenshtein distances between phrases. Stereotypic phrase types have smaller numbers of unit types and shared phrase variants. Complex phrase types have larger numbers of unit types and unique phrase variants. This study supports the hypothesis that song could be a multi-message display. [ABSTRACT FROM AUTHOR]

Echolocating bats can rapidly modify frequency modulation (FM) curvatures of their calls when facing challenging echolocation tasks. Frequency parameters, such as start/end/peak frequency, have often been extracted from the time-frequency domain to study the call variation. Even though this kind of signal investigation method reveals important findings, these approaches to analyze bat echolocation calls use bulk parameters, which hide subtleties in the call structure that may be important to the bat. In some cases, calls can have the same start and end frequencies but have different FM curvatures, and subsequently may influence the sensory task performance. In the present study, the authors demonstrate an algorithm using a combination of digital filters, power limited time-frequency information, derivative dynamic time warping, and agglomerative hierarchical clustering to extract and categorize the time-frequency components (TFCs) of 21 calls from Brazilian free-tailed bat (Tadarida brasiliensis) to quantitatively compare FM curvatures. The detailed curvature analysis shows an alternative perspective to look into the TFCs and hence serves as the preliminary step to understand the adaptive call design of bats. [ABSTRACT FROM AUTHOR]

Vermilion flycatchers, a suboscine, sing songs with more elements in territories with higher urban noise levels. We tested the hypothesis that this pattern is achieved through vocal flexibility, by which individuals add elements to their songs when noise increases; we also tested whether males modulate other song attributes and song output with noise. To this end, we did a playback experiment with free-living males where we recorded their songs during three noise treatments: first ambient noise (FAN), high urban noise (HUN), and second ambient noise (SAN) treatments. We counted the number of song elements and measured acoustic attributes both in the whole song and in the song terminal element (T). Males did not modify the number of song elements, nor song minimum frequency, with noise. The T minimum frequency slightly increased during SAN when compared to the FAN and HUN treatments, but it did not differ between the HUN and FAN treatments. Thus, we interpret these results as a lack of reliable evidence of immediate noise-induced song flexibility in frequency parameters. Song entropy decayed during the trials, but this seemed to be an effect of time and not a noise-induced change. Vermilion flycatchers appear to be less capable of modulating spectral song attributes to cope with noise than many oscines. We discuss other potential strategies that this species may use to deal with noise and a possible mechanism by which males end up singing longer songs in noisier territories (natural selection). [ABSTRACT FROM AUTHOR]

Advertisement calls are often used as essential basic information in studies of animal behaviour, ecology, evolution, conservation, taxonomy or biodiversity inventories. Yet the description of this type of acoustic signals is far to be completed, especially in tropical regions, and is frequently non-standardized or limited in information, restricting the application of bioacoustics in science. Here we conducted a scientometric review of the described adverstisement calls of anuran species of Brazil, the world richest territory in anurans, to evaluate the amount, standard and trends of the knowledge on this key life-history trait and to identify gaps and directions for future research strategies. Based on our review, 607 studies have been published between 1960 to 2016 describing the calls of 719 Brazilian anuran species (68.8% of all species), a publication rate of 10.6 descriptions per year. From each of these studies, thirty-one variables were recorded and examined with descriptive and inferential statistics. In spite of an exponential rise over the last six decades in the number of studies, described calls, and quantity of published metadata, as revealed by regression models, clear shortfalls were identified with regard to anuran families, biomes, and categories of threat. More than 55% of these species belong to the two richest families, Hylidae or Leptodactylidae. The lowest percentage of species with described calls corresponds to the most diverse biomes, namely Atlantic Forest (65.1%) and Amazon (71.5%), and to the IUCN categories of threat (56.8%), relative to the less-than-threatened categories (74.3%). Moreover, only 52.3% of the species have some of its calls deposited in the main scientific sound collections. Our findings evidence remarkable knowledge gaps on advertisement calls of Brazilian anuran species, emphasizing the need of further efforts in standardizing and increasing the description of anuran calls for their application in studies of the behaviour, ecology, biogeography or taxonomy of the species. [ABSTRACT FROM AUTHOR]

Objectives: Vocalization as part of vigilance behaviour is widespread across animal taxa, including ruminants. Calls of wild-living giraffes have never been recorded and spectrographically investigated. This study reports the acoustic structure of vigilance-related hiss and snort calls of wild-living giraffes Giraffa camelopardalis. Results: The hiss and snort calls were emitted during five recording sessions produced by nine individual giraffes (8 adults and 1 subadult) in their natural environment in Namibia (3 individuals) and Kenya (6 individuals). These calls attended vigilance behaviour toward humans in hides or in vehicles and cheetahs as natural predators of giraffe young. This study provides spectrographic analyses of 22 hiss and 20 snort calls. The giraffe hisses were broadband vocalizations of an average duration of 0.72 s (from 0.24 to 1.04 s) and a peak frequency of 0.69 kHz. The giraffe snorts were broadband pulsed calls of an average duration of 0.28 s (from 0.13 to 0.55 s), a peak frequency at 0.20 kHz and comprised a prominent low-frequency pulsation of 23.7 pulses/s. The acoustic structure of giraffe hisses is reminiscent of vigilance-related hisses of musk deer Moschus moschiferus. Giraffe snorts differ from snorts of other ruminants by their prominent pulsed pattern. [ABSTRACT FROM AUTHOR]

Loud sound emitted during offshore industrial activities can impact marine mammals. Regulations typically prescribe marine mammal monitoring before and/or during these activities to implement mitigation measures that minimise potential acoustic impacts. Using seismic surveys under low visibility conditions as a case study, we review which monitoring methods are suitable and compare their relative strengths and weaknesses. Passive acoustic monitoring has been implemented as either a complementary or alternative method to visual monitoring in low visibility conditions. Other methods such as RADAR, active sonar and thermal infrared have also been tested, but are rarely recommended by regulatory bodies. The efficiency of the monitoring method(s) will depend on the animal behaviour and environmental conditions, however, using a combination of complementary systems generally improves the overall detection performance. We recommend that the performance of monitoring systems, over a range of conditions, is explored in a modelling framework for a variety of species. [ABSTRACT FROM AUTHOR]

American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, S3/SC 1, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, animal bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes a catalog of Acoustical American National Standards. To receive a copy of the latest Standards catalog, please contact Neil Stremmel. Comments are welcomed on all material in Acoustical Standards News. This Acoustical Standards News section in JASA and other information on the Standards Program of the Acoustical Society of America are available via the ASA home page: http://acousticalsociety.org. [ABSTRACT FROM AUTHOR]

Bat echolocation call identification methods are important in developing efficient cost-effective methods for large-scale bioacoustic surveys for global biodiversity monitoring and conservation planning. Such methods need to provide interpretable probabilistic predictions of species since they will be applied across many different taxa in a diverse set of applications and environments. We develop such a method using a multinomial probit likelihood with independent Gaussian process priors and study its feasibility on a data set from an on-going study of 21 species, five families and 1800 bat echolocation calls collected from Mexico, a hotspot of bat biodiversity. We propose an efficient approximate inference scheme based on the expectation propagation algorithm and observe that the overall methodology significantly improves on currently adopted approaches to bat call classification by providing an approach which can be easily generalized across different species and call types and is fully probabilistic. Implementation of this method has the potential to provide robust species identification tools for biodiversity acoustic bat monitoring programmes across a range of taxa and spatial scales. [ABSTRACT FROM AUTHOR]

Animals enhance sensory acquisition from a specific direction by movements of head, ears or eyes. As active sensing animals, echolocating bats also aim their directional sonar beam to selectively “illuminate” a confined volume of space, facilitating efficient information processing by reducing echo interference and clutter. Such sonar beam control is generally achieved by head movements or shape changes of the sound-emitting mouth or nose. However, lingual-echolocating Egyptian fruit bats, Rousettus aegyptiacus, which produce sound by clicking their tongue, can dramatically change beam direction at very short temporal intervals without visible morphological changes. The mechanism supporting this capability has remained a mystery. Here we measured signals from free-flying Egyptian fruit bats and discovered a systematic angular sweep of beam focus across increasing frequency. This unusual signal structure has not been observed in other animals, and cannot be explained by the conventional and widely used “piston model” that describes the emission pattern of other bat species. Through modeling we show that the observed beam features can be captured by an array of tongue-driven sound sources located along the side of the mouth, and that the sonar beam direction can be steered parsimoniously by inducing changes to the pattern of phase differences through moving tongue location. The effects are broadly similar to those found in a phased array–an engineering design widely found in human-made sonar systems that enables beam direction changes without changes in the physical transducer assembly. Our study reveals an intriguing parallel between biology and human engineering in solving problems in fundamentally similar ways. [ABSTRACT FROM AUTHOR]