Animal Vocalizations Research Articles

Vocal Cues to Male Physical Formidability.

Animal vocalizations convey important information about the emitter, including sex, age, biological quality, and emotional state. Early on, Darwin proposed that sex differences in auditory signals and vocalizations were driven by sexual selection mechanisms. In humans, studies on the association between male voice attributes and physical formidability have thus far reported mixed results. Hence, with a view to furthering our understanding of the role of human voice in advertising physical formidability, we sought to identify acoustic attributes of male voices associated with physical formidability proxies. Mean fundamental frequency (F0), formant dispersion (Df), formant position (Pf), and vocal tract length (VTL) data from a sample of 101 male voices was analyzed for potential associations with height, weight, and maximal handgrip strength (HGS). F0 correlated negatively with HGS; Pf showed negative correlations with HGS, height and weight, whereas VTL positively correlated with HGS, height and weight. All zero-order correlations remained significant after controlling for false discovery rate (FDR) with the Benjamini–Hochberg method. After controlling for height and weight—and controlling for FDR—the correlation between F0 and HGS remained significant. In addition, to evaluate the ability of human male voices to advertise physical formidability to potential mates, 151 heterosexual female participants rated the voices of the 10 strongest and the 10 weakest males from the original sample for perceived physical strength, and given that physical strength is a desirable attribute in male partners, perceived attractiveness. Generalized linear mixed model analyses—which allow for generalization of inferences to other samples of both raters and targets—failed to support a significant association of perceived strength or attractiveness from voices alone and actual physical strength. These results add to the growing body of work on the role of human voices in conveying relevant biological information.

Experimental characterization and automatic identification of stridulatory sounds inside wood.

The propagation of animal vocalizations in water and in air is a well-studied phenomenon, but sound produced by bark and wood-boring insects, which feed and reproduce inside trees, is poorly understood. Often being confined to the dark and chemically saturated habitat of wood, many bark- and woodborers have developed stridulatory mechanisms to communicate acoustically. Despite their ecological and economic importance and the unusual medium used for acoustic communication, very little is known about sound production in these insects, or their acoustic interactions inside trees. Here, we use bark beetles (Scolytinae) as a model system to study the effects of wooden tissue on the propagation of insect stridulations and propose algorithms for their automatic identification. We characterize distance dependence of the spectral parameters of stridulatory sounds, propose data-based models for the power decay of the stridulations in both outer and inner bark, provide optimal spectral ranges for stridulation detectability and develop automatic methods for their detection and identification. We also discuss the acoustic discernibility of species cohabitating the same log. The species tested can be acoustically identified with 99% of accuracy at distances up to 20 cm and detected to the greatest extent in the 2–6 kHz frequency band. Phloem was a better medium for sound transmission than bark.

Shadows, wraiths, and amoebas:the distinctive flops of Anton Webern in the United States

On January 13, 1924, the music of Anton Webern was performed for the first time in the United States. It did not go well. Over the course of the next five years, performances of Webern’s works in the United States would become more frequent, but they just kept flopping. Some critics dismissed Webern’s compositions as “strange little things”; others went further, claiming that the music contained “neither melody, harmony, [n]or rhythm.” But if Webern’s music didn’t become better-liked during this period, it at least became better known. Webern developed a reputation distinct from that of his fellow modernists thanks to his incredibly quiet and remarkably brief compositions. Though critics did not respond positively to these qualities, they did take notice, with nearly every review from the period containing phrases such as “mere shadows of sound” or “scarcely perceptible tonal wraiths.” In one notable reception trend, Webern’s works were repeatedly likened to the sounds of animals, insects, skeletons, and even amoebas. Yet, far from presaging an eventual fading away, the initial flops endured by Webern’s music in the United States helped establish its staying power. The music may have failed, but in doing so it drew attention to Webern as an idiosyncratic composer unlike any other. As Nicolas Slonimsky once argued, “[n]ot every musical monstrosity is a potential musical masterpiece, but its chances of becoming one are measurably better than those of a respectable composition of mediocre quality.” Put another way, the story of Webern’s music in the United States proves that it matters how you flop.

Early literacy with augmented reality

Augmented reality is currently one of the most rapidly emerging technologies, with applications in the field of education. AR technology, according to a review of numerous publications, provides new options for teachers and makes learning more appealing to pupils of all ages. Students can use mobile AR apps to observe a real-world environment with virtual things layered or composited on top of it. This is especially true for young children. The article highlights the activities that allow a child to have a unique AR experience. There is a comparison of available augmented reality (AR) applications for learning the alphabet. The author describes a novel augmented reality application that was created with Unity, C#, and Vuforia. The developed mobile AR application allows students to learn the Ukrainian alphabet, number names, and animal sounds. The learning process is enhanced by three-dimensional visualization and sounding of each letter and number thanks to this program. An analysis of a survey of teachers and parents found that utilizing an AR application greatly boosted children's motivation and self-efficacy in learning letters and numbers. The AR application aided in the retention of the child's attention while learning new content by speeding up the process of memorization.

A practical guide for generating unsupervised, spectrogram-based latent space representations of animal vocalizations.

The manual detection, analysis and classification of animal vocalizations in acoustic recordings is laborious and requires expert knowledge. Hence, there is a need for objective, generalizable methods that detect underlying patterns in these data, categorize sounds into distinct groups and quantify similarities between them. Among all computational methods that have been proposed to accomplish this, neighbourhood-based dimensionality reduction of spectrograms to produce a latent space representation of calls stands out for its conceptual simplicity and effectiveness. Goal of the study/what was done: Using a dataset of manually annotated meerkat Suricata suricatta vocalizations, we demonstrate how this method can be used to obtain meaningful latent space representations that reflect the established taxonomy of call types. We analyse strengths and weaknesses of the proposed approach, give recommendations for its usage and show application examples, such as the classification of ambiguous calls and the detection of mislabelled calls. What this means: All analyses are accompanied by example code to help researchers realize the potential of this method for the study of animal vocalizations.

Wolves Like to Wander Around: Nomadic, Distal, and Unfurling Forces in Maclear and Arsenault's Virginia Wolf

Perhaps where it is least expected in the literary arts – within a book for children about Virginia Woolf and her sister – the linguistic and visual narrative highlights a therapeutic, bioaesthetic power that is fundamentally nonhuman and trans-species. Virginia and Vanessa, the ‘Bloomsberry’ sisters in this text, undertake a shared creative practice and enlivenment that is creatural, intimate, wolfy, and filled with eco-aesthetic intensities. The story’s theme of a re-vitalizing capacity to become artistic highlights the nomadic and distalic, and the sisters engage with shared cosmic, earth, and animal shapes, sounds, colours and forces. The recuperative efforts imagined for these famous modernist sisters dwell in female relationality, but the text also acknowledges the vulnerability of living ‘on the cracks of life’, an acknowledgment Braidotti insists must remain part of the healthy life that recognizes and connects to pain, even as it works toward an affirmative ethics of biopower.

Microgeographical variation in birdsong: Savannah sparrows exhibit microdialects in an island population

Social communication often involves vocal learning, whereby young animals learn their vocalizations early in life by imitating the sounds of adults. In animals that learn their vocalizations, it is common to find patterns of geographical variation known as ‘vocal dialects’, acoustic features shared within a cluster of animals that differ from the vocalizations of animals in nearby clusters. Dialects may form when animals learn their vocalizations early in life and then disperse short distances, or when they modify their vocalizations to match local vocal patterns after dispersal. Dialects are typically studied at a regional or continental scale, but they may also persist at smaller scales in so-called ‘microgeographical song dialects’ or ‘microdialects’. Microdialects have received little research attention. In this study, we investigate microdialects and dispersal distance in song-learning Savannah sparrows, Passerculus sandwichensis, through a 4-year study of birds living on three islands in the Bay of Fundy, Canada. Our analyses yield evidence of microgeographical variation: birds showed higher acoustic similarity to their neighbours than to faraway individuals in the same population. When we classified songs on the basis of their highly variable middle sections, we found that particular song types formed spatial clusters of similar-sounding individuals. Therefore, acoustic variation in Savannah sparrow song appears to show dialects across small geographical distances. In an analysis of dispersal from natal sites to breeding sites, we found a median distance of 189 m, consistent with previous findings. Our results suggest that limited dispersal distances, combined with the social processes of vocal learning (overproduction and selective attrition), likely contribute to the presence of microdialects.

The Duration of an Auditory Icon Can Affect How the Listener Interprets Its Meaning

Initially introduced in the field of informatics, an auditory icon consists of a short sound that is present in everyday life, used to represent a specific event, object, function, or action. Auditory icons have been studied in various fields, and overall, compared to other types of auditory alarms, they can be very efficient in informing the listener about a situation or event. So far, auditory icons have been used with a wide range of durations, ranging from a few hundreds of milliseconds up to several seconds. Still little is known, however, about whether and how icon duration influences its interpretation. In the present study, we therefore asked listeners to rate 12 auditory icons, divided into four different sound categories (nonverbal human sounds, machine sounds, human activities, and animal vocalizations), in five different durations (200, 400, 800, 1,600, and 3,200 ms). They rated (1) how appropriately the icon sound itself represented the icon's referent and (2) how appropriately each duration of the icon sound represented the icon's referent. Overall, results demonstrate that the duration of the auditory icons in this stimulus set can directly affect how the icon represents the referent. Auditory icons in the test set characterized by human activities represented their referent most appropriately in a relatively shorter duration (400 or 800 ms). The majority of the auditory icons in the set consisting of machine sounds, nonverbal human sounds , and animal vocalizations , however, were considered as more appropriately representing their referent in longer durations (800 ms and 1,600 ms). Further systematic research is necessary to determine whether the duration effects shown here may generalize to other stimulus sets.

Nonlinear vocal phenomena affect human perceptions of distress, size and dominance in puppy whines.

While nonlinear phenomena (NLP) are widely reported in animal vocalizations, often causing perceptual harshness and roughness, their communicative function remains debated. Several hypotheses have been put forward: attention-grabbing, communication of distress, exaggeration of body size and dominance. Here, we use state-of-the-art sound synthesis to investigate how NLP affect the perception of puppy whines by human listeners. Listeners assessed the distress, size or dominance conveyed by synthetic puppy whines with manipulated NLP, including frequency jumps and varying proportions of subharmonics, sidebands and deterministic chaos. We found that the presence of chaos increased the puppy's perceived level of distress and that this effect held across a range of representative fundamental frequency (fo) levels. Adding sidebands and subharmonics also increased perceived distress among listeners who have extensive caregiving experience with pre-weaned puppies (e.g. breeders, veterinarians). Finally, we found that whines with added chaos, subharmonics or sidebands were associated with larger and more dominant puppies, although these biases were attenuated in experienced caregivers. Together, our results show that nonlinear phenomena in puppy whines can convey rich information to human listeners and therefore may be crucial for offspring survival during breeding of a domesticated species.

Developing a novel bioacoustic monitoring for Garden Dormice using passive sound recorders and machine learning

One of the challenges of small mammal conservation is to be able to find the target species in the field. This is especially true for small nocturnal hibernators like dormice. Passive bioacoustic monitoring, as a non-invasive method, can be a useful tool to more efficiently find vocalizing animals in the field. However, bioacoustic methods produce a large amount of data, of which the manual analysis is highly time consuming. Therefore, there is need for an automatized process for identifying animal vocalization in acoustic data. Two types of recorders, audiomoths and BAR-LT recorders, were installed at a total of 10 locations of known Garden Dormouse (Eliomys quercinus) activity in Germany and were left recording in the field from June to September, producing a total of 3.54 TB of data. Based on our own and volunteers’ observations, Garden Dormouse vocalizations were manually identified in a subset of the sound files produced. These vocalizations, as well as ambient sound samples, were labelled and extracted to train a TensorFlow model, which was then tested on new subsets of the complete dataset. Comparing sound quality and acquisition costs of the two recorder types shows the potential for large-scale monitoring applications using the less expensive and open source audiomoth. Next steps include a time analysis of Garden Dormouse calls to find out when they are vocally more active during the study period. Such knowledge can help narrow the temporal scale of future bioacoustic studies on this species.

Vocal tract allometry in a mammalian vocal learner.

ABSTRACTAcoustic allometry occurs when features of animal vocalisations can be predicted from body size measurements. Despite this being considered the norm, allometry sometimes breaks, resulting in species sounding smaller or larger than expected for their size. A recent hypothesis suggests that allometry-breaking mammals cluster into two groups: those with anatomical adaptations to their vocal tracts and those capable of learning new sounds (vocal learners). Here, we tested which mechanism is used to escape from acoustic allometry by probing vocal tract allometry in a proven mammalian vocal learner, the harbour seal (Phoca vitulina). We tested whether vocal tract structures and body size scale allometrically in 68 young individuals. We found that both body length and body mass accurately predict vocal tract length and one tracheal dimension. Independently, body length predicts vocal fold length while body mass predicts a second tracheal dimension. All vocal tract measures are larger in weaners than in pups and some structures are sexually dimorphic within age classes. We conclude that harbour seals do comply with anatomical allometric constraints. However, allometry between body size and vocal fold length seems to emerge after puppyhood, suggesting that ontogeny may modulate the anatomy–learning distinction previously hypothesised as clear cut. We suggest that seals, and perhaps other species producing signals that deviate from those expected from their vocal tract dimensions, may break allometry without morphological adaptations. In seals, and potentially other vocal learning mammals, advanced neural control over vocal organs may be the main mechanism for breaking acoustic allometry.

Parameterizing animal sounds and motion with animal-attached tags to study acoustic communication

Stemming from the traditional use of field observers to score states and events, the study of animal behaviour often relies on analyses of discrete behavioural categories. Many studies of acoustic communication record sequences of animal sounds, classify vocalizations, and then examine how call categories are used relative to behavioural states and events. However, acoustic parameters can also convey information independent of call type, offering complementary study approaches to call classifications. Animal-attached tags can continuously sample high-resolution behavioural data on sounds and movements, which enables testing how acoustic parameters of signals relate to parameters of animal motion. Here, we present this approach through case studies on wild common bottlenose dolphins (Tursiops truncatus). Using data from sound-and-movement recording tags deployed in Sarasota (FL), we parameterized dolphin vocalizations and motion to investigate how senders and receivers modified movement parameters (including vectorial dynamic body acceleration, “VeDBA”, a proxy for activity intensity) as a function of signal parameters. We show that (1) VeDBA of one female during consortships had a negative relationship with centroid frequency of male calls, matching predictions about agonistic interactions based on motivation-structural rules; (2) VeDBA of four males had a positive relationship with modulation rate of their pulsed vocalizations, confirming predictions that click-repetition rate of these calls increases with agonism intensity. Tags offer opportunities to study animal behaviour through analyses of continuously sampled quantitative parameters, which can complement traditional methods and facilitate research replication. Our case studies illustrate the value of this approach to investigate communicative roles of acoustic parameter changes.Significance statementStudies of animal behaviour have traditionally relied on classification of behavioural patterns and analyses of discrete behavioural categories. Today, technologies such as animal-attached tags enable novel approaches, facilitating the use of quantitative metrics to characterize behaviour. In the field of acoustic communication, researchers typically classify vocalizations and examine usage of call categories. Through case studies of bottlenose dolphin social interactions, we present here a novel tag-based complementary approach. We used high-resolution tag data to parameterize dolphin sounds and motion, and we applied continuously sampled parameters to examine how individual dolphins responded to conspecifics’ signals and moved while producing sounds. Activity intensity of senders and receivers changed with specific call parameters, matching our predictions and illustrating the value of our approach to test communicative roles of acoustic parameter changes. Parametric approaches can complement traditional methods for animal behaviour and facilitate research replication.

Vocal communication of magnitude across language, age, and auditory experience.

Like many other vocalizing vertebrates, humans convey information about their body size through the sound of their voice. Vocalizations of larger animals are typically longer in duration, louder in intensity, and lower in frequency. We investigated people's ability to use voice-size correspondences to communicate about the magnitude of external referents. First, we asked hearing children, as well as deaf children and adolescents, living in China to improvise nonlinguistic vocalizations to distinguish between paired items contrasting in magnitude (e.g., a long vs. short string, a big vs. small ball). Then we played these vocalizations back to adult listeners in the United States and China to assess their ability to correctly guess the intended referents. We find that hearing and deaf producers both signaled greater magnitude items with longer and louder vocalizations and with smaller formant spacing. Only hearing producers systematically used fundamental frequency, communicating greater magnitude with higher fo. The vocalizations of both groups were understandable to Chinese and American listeners, although accuracy was higher with vocalizations from older producers. American listeners relied on the same acoustic properties as Chinese listeners: both groups interpreted vocalizations with longer duration and greater intensity as referring to greater items; neither American nor Chinese listeners consistently used fo or formant spacing as a cue. These findings show that the human ability to use vocalizations to communicate about the magnitude of external referents is highly robust, extending across listeners of disparate linguistic and cultural backgrounds, as well as across age and auditory experience. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Topographical distribution of spectrotemporal receptive field properties in the bat primary auditory cortex

Spectrotemporal modulations are a prominent feature of natural sounds including animal vocalizations and human speech. Echolocating bats must process spectrotemporal cues such as echo delays and spectrum properties to navigate their environment; however, the neuronal networks in the primary auditory cortex (A1) that process features of natural sounds remain incompletely understood. Here, we investigated the topographical distribution of tuning properties throughout A1 of Mexican free-tailed bats. While the majority of the bats’ A1 neurons are tuned to downward FM sweeps, the entire cortex is required to capture and categorize patterns of spectral details embedded within each biosonar echo. We captured the neural responses of the A1 to complex acoustic stimuli using linear, 16-channel translaminar microelectrode arrays. We analyzed 145 spectrotemporal receptive fields (STRFs) across A1, as well as the spectral and temporal modulation transfer functions (sMTF and tMTF, respectively) to determine neural tuning preferences in the spectral and temporal dimensions. We found evidence of neuronal sub-categories that were classified as having simple or complex (multi-peaked) STRFs. For simple STRFs, sMTFs and tMTFs were evaluated as a function of best frequency, and spatial location and revealed tonotopic trends similar to those reported for non-specialized animals.

A remote lab exercise to introduce students to the fundamentals of bioacoustics using smartphones and R

Animals communicate through a variety of modalities including visual, auditory and chemical. Acoustic signals are particularly well suited for studying the evolution of animal communication due to the relative ease in which sounds can be recorded and analyzed. Therefore, a thorough overview of acoustic communication is a fundamental aspect of any animal behavior course. The purpose of this lab exercise is to introduce students to bioacoustics, or the study of animal sounds and their habitats. For the field component, students use their smartphones to collect focal recordings of target animals as well as collect acoustic data that will be used to investigate variation in soundscapes at different times (e.g. dawn and dusk) and/or different locations (e.g., urban versus rural). The computer lab component utilizes the R programming environment to import sound files and visualize differences in acoustic data using both spectrograms and principal component analysis biplots. The computer lab exercises are meant for undergraduate students with relatively little coding background but could be easily adapted for students of different skill levels. All materials needed to use and modify the course materials are openly available on GitHub, which should remove any financial barriers for students or instructors.

Comprehending Information in Acoustic Signals: AReview of Bioacoustic Studies

Development in bioacoustic studies have provided new opportunities to understand the information related with different types of vocalization produced by humans and other living organisms in different conditions. Bioacoustics not only help humans to understand the different types of hidden information present in the acoustic signals of living organisms but also assist in understanding how acoustic signals can be used in improving their health and diagnosing severe diseases easily. Bioacoustics benefit both humans and animals by decoding the relation of the acoustic signals with the behaviour of the animal and environment in which they live. Bioacoustic studies also aid in understanding the effects of anthropogenic activities on acoustic signals of other animals. Monitoring through acoustic tools is most convenient and a large number of precision tools are available in the recent times. This paper reviews the findings of bioacoustic studies published between 2000 to 2020 worldwide. Significant researches in the field of sound communication of different animal species have been cited in this review. Varied animal behaviours can be accounted for based on the sound produced by animals under different physiological state, environmental influences and human activities. Study of animal sounds may be of remarkable value from welfare and conservation perspective.

Real-time identification of marine mammal calls based on convolutional neural networks

Animal vocalization is one of the most important ways to identify the existence and occurrence of marine mammals. Accurately detecting and identifying marine mammal species in real time is significant in the field of marine mammal research. In this study, we developed a novel method based on convolutional neural networks (CNNs) to precisely identify the calls of bottlenose dolphins (Tursiops), dugongs (Dugong dugong), and the Indo-Pacific humpback dolphin (Sousa chinensis). Compared with traditional detection and classification techniques, the proposed method is a one-step algorithm that combines detection and classification. It can automatically learn the features of different marine mammal calls and position the target calls with bounding boxes in a spectrogram. Furthermore, the whole process can be conducted in real time. With this method, the raw data are cut into fixed lengths and spectrograms are created. Next, the annotated sound data are sent to the CNNs to train an identification model. Experimental results showed that the proposed method achieved >91% precision and >84% recall of test data with real-time speed. In the future, this method can be applied to passive acoustic observation equipment for quick, accurate pre-detection of marine mammal calls.

A Fish and Dolphin Biophony in the Boat Noise-Dominated Soundscape of the Cres-Lošinj Archipelago (Croatia)

Spatio-temporal variability of marine soundscapes reflects environmental dynamics and local habitat health. This study characterizes the coastal soundscape of the Cres-Lošinj Natura 2000 Site of Community Importance, encompassing the non-tourist (11–15 March 2020) and the tourist (26–30 July 2020) season. A total of 240 h of continuous recordings was manually analyzed and the abundance of animal vocalizations and boat noise was obtained; sound pressure levels were calculated for the low (63–2000 Hz) and high (2000–20,000 Hz) frequency range. Two fish sound types were drivers of both seasonal and diel variability of the low-frequency soundscape. The first is emitted by the cryptic Roche’s snake blenny (Ophidion rochei), while the second, whose emitter remains unknown, was previously only described in canyons and coralligenous habitats of the Western Mediterranean Sea. The high-frequency bands were characterized by bottlenose dolphin (Tursiops truncatus) vocalizations, indicating dolphins’ use of area for various purposes. Boat noise, however, dominated the local soundscape along the whole considered periods and higher sound pressure levels were found during the Tourist season. Human-generated noise pollution, which has been previously found 10 years ago, is still present in the area and this urges management actions.

Evaluation of the main sensitivity drivers in relation to indoor comfort for individuals with autism spectrum disorder. Part 2: Influence of age, co-morbidities, gender and type of respondent on the stress caused by specific environmental stimuli

Variations of environmental parameters, like thermo-hygrometric, acoustic, visual and indoor air quality can influence the sensitivities of individuals on the spectrum. This paper presents research on this issue, studied by means of questionnaires administered to parents and professional caregivers taking care of people with Autism Spectrum Disorder (ASD).The study highlights that there are clear differences if the indirect evaluations are performed by parents or professional caregivers, in relation to the specific identification of stress sources. Additionally, acoustic domain is identified as the one causing the major stress, especially caused by strong noises and particular sounds such as voices, animal sounds and impacts, and its dependence on the severity of autism is evidenced. Furthermore, a lower impact of thermal, visual and IAQ factors is determined, with the exception of some specific stimuli like light contrast (glare), high illumination, particular light sources or stale air. Finally, this paper provides evidence of the influence of age, severity of autism and co-morbidities on perceived stress.

Contrasting Effects of Chronic Anthropogenic Disturbance on Activity and Species Richness of Insectivorous Bats in Neotropical Dry Forest

For prioritizing conservation actions, it is vital to understand how ecologically diverse species respond to environmental change caused by human activity. This is particularly necessary considering that chronic human disturbance is a threat to biodiversity worldwide. Depending on how species tolerate and adapt to such disturbance, ecological integrity and ecosystem services will be more or less affected. Bats are a species-rich and functionally diverse group, with important roles in ecosystems, and are therefore recognized as a good model group for assessing the impact of environmental change. Their populations have decreased in several regions, especially in the tropics, and are threatened by increasing human disturbance. Using passive acoustic monitoring, we assessed how the species-rich aerial insectivorous bats—essential for insect suppression services—respond to chronic human disturbance in the Caatinga dry forests of Brazil, an area potentially harboring ca. 100 bat species (nearly 50% are insectivorous), but with > 60% its area composed of anthropogenic ecosystems under chronic pressure. Acoustic data for bat activity was collected at research sites with varying amounts of chronic human disturbance (e.g., livestock grazing and firewood gathering). The intensity of the disturbance is indicated by the global multi-metric CAD index (GMDI). Using Animal Sound Identifier (ASI) software, we identified 18 different bat taxon units. Using Hierarchical Modeling of Species Communities (HMSC), we found trends in the association of the disturbance gradient with species richness and bat activity: species richness was higher at sites with higher human disturbance, whereas bat activity decreased with increasing human disturbance. Additionally, we observed taxon-specific responses to human disturbance. We conclude that the effects of chronic anthropogenic disturbance on the insectivorous bat fauna in the Caatinga are not homogeneous and a species-specific approach is necessary when assessing the responses of local bats to human disturbances in tropical dry forests, and in other biomes under human pressure.