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Abstract

Echolocation calls of four species of insectivorous bats of central Chile were recorded and characterized to determine vocal signatures that allow their identification in the field. Pulses of Tadarida brasiliensis were characterized by the highest duration and the lowest values for all frequencies, which do not overlap those of the remaining species. Tadarida emits narrowband, shallow frequency-modulated search calls. All three vespertilionid species studied (Histiotus montanus, Lasiurus varius and Myotis chiloensis) showed similar echolocation design to one another, consisting of a downward frequency modulation at the beginning of the signal followed by a narrowband quasi-constant frequency component; however, their calls differ by their spectral characteristics. Discriminant function analysis of six acoustic parameters (duration, initial frequency, slope frequency modulation, peak frequency, minimal and maximal frequencies) gave an overall classification of 87.4%, suggesting species could be correctly classified based on echolocation calls. Call duration and minimal frequency were the variables most important for species identification.

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... The Atacama Myotis is endemic to the central portion of the pacific coast of South America, where it is known from western Peru to north-central Chile (Wilson 2008;Rodríguez-San Pedro et al. 2015). The distribution ranges of both species overlap in the Coquimbo and Valparaiso regions (Galaz & Yañez 2006;Rodríguez-San Pedro & Simonetti 2013; however, they can be easily differentiated from each other based on external morphological characters and bioacoustics parameters. Myotis atacamensis differs from M. chiloensis because of the tiny skull and lighter fur color with dark bases and light tips (Díaz et al. 2016). ...
... Although previous data have been reported by Mann (1978), and Galaz and Yañez (2006), this information is still insufficient. The known geographic distribution of Myotis atacamensis in Chile is supported on very few records, mostly from the extreme north and the Atacama Desert (Mann 1978;Rodríguez-San Pedro & Simonetti 2013Ossa et al. , 2017. In this study, we present new records of M. atacamensis, obtained from a bat inventory carried out in northern Chile and the first record of the species in Santiago Metropolitan region. ...
... Ranges of forearm length in our study(34-35.8) are consistent with those reported in previous studies(Galaz & Yañez 2006;Rodríguez-San Pedro & Simonetti 2013;Pari et al. 2015) supporting the identity of our captured individuals. ...
Article
The Atacama Myotis is an endangered and poorly studied bat species, endemic from Peru and Chile. Using mist nets and ultrasonic recordings we release new information on activity patterns and roost use by M. atacamensis in Chile. We also report new records for the species, extending its distribution range to Santiago Metropolitan region. Our results suggest a wide distribution and relative abundance of M. atacamensis in northern Chile, in addition to remarkable habitat diversity for populations of this species. Bats were active in both natural and anthropogenic habitats. Abandoned mines and buildings in rural villages were the roosts most used by the species. These data provide additional information on the distribution, ecology, and natural history of M. atacamensis and can be useful in the design of conservation action plans for populations in the country.
... In fragmented landscapes, L. varius is able to use a variety of habitats that differ in structural clutter; therefore, we might expect differences in their echolocation call structure according to habitat structure. In spite of the descriptions of echolocation calls for L. varius (Rodríguez-San Pedro and Simonetti 2013a), changes in its echolocation behavior in concert with changes in habitat structure are known. Within this framework, we tested the general hypothesis that L. varius adjusts its echolocation calls to different foraging habitats according to their degree of structural clutter. ...
... Species identification was achieved by visual observation at dusk and sound analyses. In the area, L. varius is the only bat species broadcasting downward frequency-modulated calls with final frequency between 35 and 37 kHz (Rodríguez-San Pedro and Simonetti 2013a). Spectral and temporal parameters of calls of L. varius recorded from hand-released bats (Rodríguez-San Pedro and Simonetti 2013a) matched well with the recordings from free-flying bats and serve as additional confirmation of our species identification in the field. ...
... In the area, L. varius is the only bat species broadcasting downward frequency-modulated calls with final frequency between 35 and 37 kHz (Rodríguez-San Pedro and Simonetti 2013a). Spectral and temporal parameters of calls of L. varius recorded from hand-released bats (Rodríguez-San Pedro and Simonetti 2013a) matched well with the recordings from free-flying bats and serve as additional confirmation of our species identification in the field. ...
Article
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Intraspecific variability in echolocation calls could be an important factor hampering the accurate acoustic identification species in the field. We studied variations in the echolocation behavior of Lasiurus varius in relation to habitat structure. Echolocation calls of L. varius reflected the degree of clutter present in their foraging areas. Bats foraging in an uncluttered habitat emitted longer and lower bandwidth calls, with the lowest frequency values, while bats foraging in a cluttered habitat broadcast shorter and broadband signals showing an increase in frequency content of its calls. Discriminant function analysis gave an overall classification of 76% of the calls emitted in the different flight situations. Our results highlight the need for independent recordings at each study area or habitat type to circumvent potential echolocation call variations, particularly in fragmented landscapes.
... La implementación a nivel nacional del método bioacústico, el uso de detectores de ultrasonido y la identificación de especies a partir del registro de vocalizaciones (Ossa, 2010;Rodríguez-San Pedro & Simonetti, 2013a, 2014Ossa et al., 2015a;; Rodríguez-San Pedro & Allendes 2016a) ha generado un avance en las investigaciones, particularmente durante el último quinquenio, permitiendo que se conozcan aspectos adicionales de la ecología del grupo como sus patrones de actividad en paisajes fragmentados, distribución, uso de hábitat y otros (Ossa, 2010;Meynard et al., 2014;Rodríguez-San Pedro, 2014;Rodríguez-San Pedro et al., 2014a;Ossa & Rodríguez-San Pedro, 2015). Esto, sumado al desarrollo de estudios de línea de base de quirópteros para la elaboración de Estudios de Impacto Ambiental (EIA) a lo largo del país, ha permitido generar nueva información sobre rangos de distribución de algunas especies. ...
... Ecolocación-Pulsos contienen un único armónico, con un componente FM al inicio seguido por un componente QCF. La frecuencia de máxima energía se encuentra en promedio a 36.4 kHz, y sus pulsos tienen una duración promedio de 7.6 ms (Ossa, 2010;Rodríguez-San Pedro & Simonetti, 2013a, 2014 (Fig. 2J). ...
... Ecolocación-Llamadas contienen un único armónico, de tipo FM, adaptado para la captura de insectos en ambientes de vegetación densa. La frecuencia de máxima energía se encuentra entre 42 y 47 kHz, y sus pulsos tienen una duración entre 2 y 4 ms Rodríguez-San Pedro & Simonetti, 2013a) (Fig. 2M). ...
Article
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Bats are one of the least studied groups of vertebrates in Chile; however, in recent years the knowledge about them has advanced significantly due to the implementation of bioacoustics methods as well as by the recent inclusion of bats in environmental impact studies. Here we update the list of Chilean bats, raising to 13 the number of previously known species. In addition to updating the taxonomic status, incorporating a new species record for the country, also some ecological and behavioral information ispresented, including significant extensions of the geographic ranges of several species. Finally, we identify and propose some directions for future research to be developed in the country that will allow deepening the knowledge of this group of mammals.
... mist nets) do not provide a full representation of assemblages (see MacSwiney et al. 2008). However, in most areas there is a poor knowledge of the species acoustic rep- ertoires and, furthermore, of the consequences of intraspecific variation ( Rodríguez-San Pedro and Simonetti 2013). ...
... We selected the harmonic with most energy because it contains the appropriate intensity for adequate measure of acoustic parameters (Vaughan et al. Parsons and Jones 2000), and echolocation pulses with good signal-to-noise ratio with peak intensity more than 20 dB above noise level in the power spectrum ( Rodríguez and Mora 2006;Rodríguez-San Pedro and Simonetti 2013). We chose a single sequence of echolocation pulses per individual in order to avoid pseudo-replication ( Vaughan et al. 1997;Russo and Jones 2002;Biscardi et al. 2004). ...
... For comparative purposes, we manually measured the following basic acoustic param- eters grouped in two types of display (Obrist 1995; Biscardi et al. 2004): (1) in the power spectrum (Figure 1(b)), frequency with most energy (FMAXE) in kHz measured at the peak of the echolocation pulse (Fenton 2002;Biscardi et al. 2004), lowest frequency (LF) and highest frequency (HF) in kHz taking −50 dB as threshold for avoiding background noise and isolating LF and HF (Fenton 2002;Biscardi et al. 2004) and (2) in the oscillogram ( Figure 1(c)), duration (DUR) in ms as the time between the start and end of an echolocation pulse (Fenton 2002;Rodríguez-San Pedro and Simonetti 2013), and interpulse interval (IPI) in ms from the beginning of one echolocation pulse to the beginning of the next echolocation pulse ( Rodríguez-San Pedro and Simonetti 2013). ...
Article
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Bats may exhibit plasticity in echolocation pulses as response to intrinsic and extrinsic factors, and the estimation of the magnitude of such variation can provide confidence in acoustic monitoring. Myotis nigricans (Schinz, 1821) is a widely distributed but relatively understudied Neotropical species for which, during fieldwork, we found maternity colonies in the Lagunas de Montebello National Park, in Chiapas, South-east Mexico, and no previous information in the area. Therefore, we aimed to provide an acoustic characterization on the basis of intraspecific variability for its recognition using bat detectors. For this purpose, we examined the moulding of shape, frequency-based and time-based acoustic parameters, specifically by the effect of age group (sub-adults vs. adults) and acoustic environment (open space vs. background vegetation). By graphic comparison of echolocation pulses between acoustic environments, we observed changes in shape by an increase in bandwidth and steeper modulation along background vegetation. Statistically, on univariate basis, we did not find a significant effect of age group, but we did of acoustic environment, specifically on highest frequency (higher average), duration (shorter average) and interpulse interval (shorter average) along background vegetation. On multivariate basis, we confirmed shorter average interpulse interval along background vegetation. The overall classification accuracy was relatively high (82.22%): 80% in open space and 84% along background vegetation. Our work reinforces previous knowledge about sound constraints imposed by vegetation clutter, and provides a reliable framework for acoustic monitoring of this species across structurally variable, and hence acoustically variable, environments in the area.
... The RF model was the best model showing good classification performance for the identification of bats in Uruguay from their acoustic calls. The results are comparable to those of other published studies which considered different type of methods (Armitage and Ober, 2010;Basil et al., 2014;Britzke et al., 2011;Rodríguez-San Pedro and Simonetti, 2013;Walters et al., 2012). For example, Britzke et al. (2011) compared several discriminant functions with Neural Networks, finding that Neural Networks outperformed all discriminant functions. ...
... SonoBat provides 76 quantitative variables), stressing the relevance of the variable selection issue in this kind of problems. Previous studies have used different strategies for variable selection ranging from a priori selection based on expert knowledge (Parsons and Jones, 2000, Britzke et al., 2011, Russo and Jones 2002, Rodríguez-San Pedro and Simonetti, 2013 to comparison of intragroup variances and F ratios among potential predictor variables (Walters et al., 2012). In one of the works where a priori selection was performed, PCA was used to reduce the correlation of the variables (Britzke et al., 2011) while other studies dismissed the correlation's negative impact (Walters et al., 2012). ...
Article
Acoustic bat identification is a complementary method to traditional mist-netting for chiropteran surveys. In this work, an algorithm based on artificial intelligence techniques was developed for bat species identification in Uruguay. An acoustic library of 662 search phase pulses of the 10 most common bat species in Uruguay was obtained. Random Forests, Support Vector Machines and Artificial Neural Networks algorithms were trained to predict bat species from acoustic variables. Variable selection was performed in an independent subset (one third) of the dataset, using the function varImpPlot of randomForest R package. Model performance was evaluated by means of the test error with the remaining two thirds of the data. To do this, data were split randomly into a training and a test set, then the model was trained with the training sample and its performance was assessed using the test sample. The procedure was performed 100 times and the test errors were averaged to have an unbiased measure of the performance of the models. The best predictor was a Random Forests classifier that considered 12 predictor variables. The achieved accuracy was comparable to other international published products. Additionally, a threshold value for classification probability was optimized to define an “unclassified” class that allows using this algorithm even when the training sample does not represent an exhaustive sample of local richness. A web application returning the predicted class and a confidence measure for a given observation was developed permitting the use of this tool by a broad spectrum of users, from biologist to technicians.
... Bat recordings were displayed simultaneously as spectrograms and oscillograms using BatSound 2.1 software (Pettersson Elektronik AB), and each species was manually identified by comparing the parameters of our recorded calls to a library of validated reference calls from Chilean bats (Rodríguez-San Pedro and Simonetti, 2013;Rodríguez-San Pedro et al., 2016). The following parameters were used in the classification analysis: duration (time between start and end of a pulse), start and end frequencies (frequencies at the start and the end of the pulse, respectively), and peak frequency (frequency of maximum energy of the pulse). ...
... Our finding that T. brasiliensis was unnaffected by the type of adjacent habitat in vineyards agree with an opportunistic and generalist foraging mode for this species, which is also consistent with previous observation of higher activity in vineyards immersed in more diversified landscapes (Rodrí guez-San Pedro et al., 2019). The wing morphology and echolocation characteristics of T. brasiliensis (e.g., high wing loading and high aspect ratio, and low frequency and narrow-banded echolocation calls) (Norberg and Rayner, 1987;Canals et al., 2005;Denzinger and Schnitzler, 2013;Rodríguez-San Pedro and Simonetti, 2013) confer high speed flight in open spaces which facilitates the movement of bats between isolated patches across the fragmented landscape, making them less sensible to habitat disturbances (Rodríguez-San Pedro and Simonetti, 2015). As expected, bat activity (overall and by species) and feeding buzzes in our study were influenced by the location within the farm, being significantly higher along the edges of vineyards as compared to the interior, regardless of the type of adjacent habitat. ...
Article
Conversion of natural land covers to agriculture is a major cause of the global biodiversity decline. Bats are an important component of biodiversity in agricultural landscapes because they provide pest control services. Although management recommendations towards the enhancement of insectivorous bat populations in agro-ecosystems have previously been highlighted, little information is available for promoting bat conservation within viticultural landscapes. In the present study, we examined the role of the adjacent habitat on bat activity in vineyards of central Chile. We also evaluated differences in bat activity between the edges and the interiors of the vineyards in relation to the type of adjacent habitat. To accomplish this, we conducted acoustic surveys along edge and the interior of 16 vineyards bordering different adjacent habitats. Overall bat activity in vineyards was not influenced by the adjacent habitat type, but it was by the location within the vineyard; edges showed significant higher activity than the interior of the vineyards. Vineyards adjacent to native vegetation showed the highest levels of activity for Lasiurus varius, Lasiurus villosissimus and Myotis chiloensis compared to those adjacent to monoculture or urban areas. All bat species were most active at the edges of the vineyards as compared to the interior, which increase the probability of this group providing ecosystem services in vineyards. Therefore, vineyard edges, in particular those adjacent to native vegetation, should be considered as part of agricultural management in order to promote bat diversity and abundance in this crop.
... Alas largas y angostas que le permiten un vuelo rápido, pero poco maniobrable. Tamaño corporal mediano (longitud total: 106-113 mm; longitud antebrazo: 36-42 mm; peso: 7-13 g) 1 Las llamadas de ecolocalización de esta especie presentan un único armónico de frecuencia modulada descendente seguido por un componente de frecuencia cuasi-constante, emitido entre los 65 y 35 kHz con una duración promedio de 5 ms 109,113 . ...
... Las llamadas de ecolocalización de esta especie presentan un sólo armónico de frecuencia modulada descendente, con una duración promedio de 4 ms y son emitidas entre los 89 y los 39 kHz 109,117 . ...
... Los quirópteros están ampliamente distribuidos en el mundo, pero ausentes en las regiones polares y porciones del territorio de Oceanía (Hill & Smith 1984;Vaughan et al. 2000). La mayor cantidad de especies está concentrada en los trópicos (Findley 1993) y su diversidad disminuye a latitudes altas (Patterson et al. 2003). Sudamérica es rica en murciélagos. ...
... En general existe una mayor diversidad de mamíferos en el altiplano del extremo norte y la Patagonia del sur, mientras que la zona de menor diversidad es el Desierto de Atacama (Mella et al. 2005). Este patrón es totalmente contrastante con la diversidad de murciélagos encontrada, que decrece de Norte a Sur, siendo coincidente con lo documentado para el resto de los murciélagos del nuevo mundo (Patterson et al. 2003), pero con un máximo de diversidad en el bioma del Desierto de Atacama (Fig. 2). ...
Article
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Bats are the second most diverse order of mammals. South America is rich in bats, however Chile has low species diversity (12 especies) and absence of endemism. Scientific publications that have addressed the biological diversity and taxonomy of these Chilean mammals are also scarce. This review assessed the state of knowledge of bats in Chile and its main results. We critically characterize those knowledge areas more developed and those that require further work. Additionally, we propose an explanation regarding this low diversity. Finally, we make a map that organizes bat diversity according to natural biomes of Chile. As results, we find 27 publications in the last two decades. These works are mainly focused on Infectology and Ecophysiology. The Chilean biome concentrating the highest bat diversity is the Atacama Desert, and the diversity is decreasing latitudinally. In spite of long periods of stasis, the taxonomy of Chilean bats abruptly changed in the last century. We propose a biogeographical and ecophysiological interaction for the observed patter of diversity. Finally, we stressed the importance of further micro and macroevolutionary research, as well as conservation and bioacustic studies, for better understanding of important issues still unsolved.
... To obtain a graphical representation of the separation of groups based on their discriminant functions, we plotted the group centroids with 95% confidence limits for separate functions and the canonical discriminant functions. For each species, descriptive statistics (mean ± SE) were calculated (Rodríguez-San Pedro & Simonetti, 2013). All of these analyses were performed using the software SPSS 17.0. ...
... Overall, the level of accurate classification of calls into species group by DFA was reasonably high. However, classification rates at species level were comparatively lower when compared to similar studies (Hughes et al., 2011;Kofoky et al., 2009;Rodríguez-San Pedro & Simonetti, 2013). The relative poor performance of the DFA may be attributed to the use of fewer individual of each species. ...
Article
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Background: Despite their abundance and ecological importance, bats are under significant threat worldwide. There is little information about their distribution, roosting, and habitat requirement for most species, making assessing which species is threatened or in need of special conservation measures difficult. The knowledge gap may partly be due to limitations of the old methods of studying bats which mainly involved capture/or observational techniques. Material and methods: In order to evaluate the potential of identifying insectivorous bats by their echolocation calls in the Sahelian zone of northern Cameroon, 65 bats belonging to five species were captured using standard mist netting:Mops condylurus, Chaerephon major, Mops niveiventer, Scotophilus dinganii, and Scotophilus leucogaster. The bats were identified by using morphometric measurements. An Anabat SD1 detector was later used to record echolocation calls of each individual bat in flight after it was hand-released. The sonogram of each individual bat was analyzed using Analook and categorized into two call types (frequency modulation and frequency modulation/ quasi constant frequency) in order to develop a library of bat reference calls that could be used for a qualitative acoustic survey and species identification. Discriminant function analysis (DFA) was applied to search phase calls of the 65 individual bats in order to evaluate the potential for classifying calls into five species groups. Seven parameters calculated from each search phase call were used to classify calls. Results: Bats where place into two groups according to the structure of calls: FM bats (Mops condylurus, Chaerephon major, Mops niveiventer) and FM/QCF bats (Scotophilus dinganiiandScotophilus leucogaster). The DFA resulted in a correct overall classification of 69.7%. Conclusion: This preliminary study showed that DFA of call parameters is a feasible method that can be used to identify insectivorous bats in the region by their echolocation calls. Keywords:Echolocation, Maroua, Bats, Cameroon, Anabat SD1 detector, Sonogram
... A Student's t-test (square root transformation for normality) was used to test the similarity in echolocation calls of N. aurispinosus from Peru and Chile. Two Discriminant Function Analyses (DFA) were also used for species classification (Parsons and Jones 2000;Rodríguez-San Pedro and Simonetti 2013). A first DFA was performed including only echolocation calls of N. aurispinosus from Chile and southern Peru to evaluate the probability of assigning them to the same group and validate the classification of the species. ...
Article
The bat fauna from the extreme north of Chile is poorly known, principally due to a lack of dedicated surveys. To better assess the diversity of bats there, we conducted acoustic surveys at Arica city and three coastal valleys (Azapa, Lluta and Camarones) in the Arica and Parinacota region, Chile. We obtained 82 acoustic records of the Peale’s free-tailed bat (Nyctinomops aurispinosus) in nine sites within the region. This species had not been previously documented in Chile but was known from adjacent Tacna province, Peru. Echolocation calls of N. aurispinosus can be distinguished from other molossid bat species occurring in the area by its lower frequency range. Our data suggest a wide distribution of N. aurispinosus across the coastal valleys of the Arica and Parinacota region, where they were active in both natural and anthropized habitats. This southernmost record of N. aurispinosus for the Pacific coast, extends its known range ca. 150 km southward, and increases up to 15 the number of bat species in Chile.
... Echolocation calls of M. chiloensis contain a single harmonic and are characterized by a downward frequency modulation at the beginning of the signal followed by a narrowband quasi-constant frequency component (Ossa et al. 2010a(Ossa et al. , 2010bRodríguez-San Pedro and Simonetti 2013b). Search calls consist of short (< 4 ms) broadband signals sweeping down between 89 and 39 kHz with most energy at 47 kHz. ...
Article
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Myotis chiloensis (Waterhouse, 1838), the Chilean myotis, is found only in Argentina and Chile, where it is the most common bat species in the southern part of Chile. It is a small insectivorous bat and differs from other members of the genus because of its darker pelage. It uses human buildings and caves to establish colonies, and forages in dense forests of Nothofagus to capture insects, thereby providing ecosystem services to agriculture and forestry. M. chiloensis is considered of " Least Concern " by the International Union for Conservation of Nature and Natural Resources.
... As for other species of Myotis bats, calls of M. atacamensis are characterized by single downward frequency modulated pulses. This call design is regarded as an adaptation for foraging in cluttered forest habitats (Schnitzler & Kalko 2001;Broders et al. 2004;Rodríguez-San Pedro & Simonetti 2013). Similarity in call design with other congeneric species might lead to its misidentification in field due to signal overlap between species; however, echolocation calls of M. atacamensis seem to differ from its congener M. chiloensis by its higher final, minimal and peak frequencies (U = 233.50; ...
Article
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Myotis atacamensis is a vespertilionid bat known from western Peru to northern and central Chile, where it is usually associated with coastal deserts. Here, we report the southernmost record of the species, extending its geographical distribution by 160 km. This represents the first observation of M. atacamensis in the temperate sclerophyllous forest of central Chile, a pluviseasonal Mediterranean-climate ecosystem, suggesting it might not be restricted to arid and semiarid environments, as previously thought. We also present the first description of echolocation calls of this understudied species.
... Some time-frequency features tested include different combinations of descriptive measurements such as central frequency, highest frequency, lowest frequency, initial frequency, loudest frequency, average or maximum bandwidth, duration, type of blur filter used, average frequency slope, maximum power, frequency of maximum power in eight portions of the segment, component shape, and specific narrow-band energy with accumulation in time (e.g., Acevedo et al., 2009;Bardeli et al., 2010;Brandes et al., 2006;Duan et al., 2012;Pedro and Simonetti, 2013;Schrama et al., 2008). Besides these descriptive measurements, many other event-level features have also been studied including amplitude and frequency trajectory (Harma, 2003), harmonic structure (Harma and Somervuo, 2004), spectral peak tracks (e.g., Chen and Maher;Köküer, 2011, 2015), and the MPEG-7 angular radial transform (ART) descriptor (Lee et al., 2012). ...
Article
Non-invasive bioacoustic monitoring is becoming increasingly popular for biodiversity conservation. Two automated methods for acoustic classification of bird species currently used are frame-based methods, a model that uses Hidden Markov Models (HMMs), and event-based methods, a model consisting of descriptive measurements or restricted to tonal or harmonic vocalizations. In this work, we propose a new method for automated field recording analysis with improved automated segmentation and robust bird species classification. We used a Gaussian Mixture Model (GMM)-based frame selection with an event-energy-based sifting procedure that selected representative acoustic events. We employed a Mel, band-pass filter bank on each event's spectrogram. The output in each subband was parameterized by an autoregressive (AR) model, which resulted in a feature consisting of all model coefficients. Finally, a support vector machine (SVM) algorithm was used for classification. The significance of the proposed method lies in the parameterized features depicting the species-specific spectral pattern. This experiment used a control audio dataset and real-world audio dataset comprised of field recordings of eleven bird species from the Xeno-canto Archive, consisting of 2762 bird acoustic events with 339 detected “unknown” events (corresponding to noise or unknown species vocalizations). Compared with other recent approaches, our proposed method provides comparable identification performance with respect to the eleven species of interest. Meanwhile, superior robustness in real-world scenarios is achieved, which is expressed as the considerable improvement from 0.632 to 0.928 for the F-score metric regarding the “unknown” events. The advantage makes the proposed method more suitable for automated field recording analysis.
... Recent studies of the echolocation calls of the Myotis species in Chile differentiate the species easily because of the higher frequency range of M. atacamensis with respect to M. chiloensis (Ossa et al., 2010a;b, 2015;Rodríguez-San Pedro & Simonetti, 2013;Rodriguez-San Pedro et al., 2015). We present here the highest records of M. atacamensis, exceeding by 1075 and 1056 meters the previous records of the species. ...
Article
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Myotis atacamensis is a bat species with severely fragmented populations along the coast of Peru and Chile, recently considered as Endangered by the IUCN because of habitat fragmentation. Here we report for the first time records of the species via echolo-cation call analysis at localities above 3000 melevation, increasing the distribution of the species by more than 1000 min altitude.
... In our library, we found that the overall accuracy of species identification from the different methods used ranged from 62 to 81% (Table 3). These percentages may seem to be low compared with those that have been shown by other studies (e.g., MacSwiney G et al. 2008;Walters et al. 2012;Rodríguez-San Pedro and Simonetti 2013). Nevertheless, in our study, we included calls from bats of different sexes, gender, and locations. ...
Article
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Bats are nocturnal animals that can be identified by recording and analyzing quantitatively their echolocation calls. For this task, many studies have used both parametric and non-parametric approximations with a variety of results. This urges the necessity of developing more call libraries, that should be analyzed using the different statistical approaches to test their performance. This could be relevant in countries holding high biodiversity where the knowledge of the variation in the call structure among species is still scarce. We constructed and validated a call library from bats inhabiting a mountain ecosystem of central Mexico using the Linear Discriminant Function, Artificial Neural Network and Random Forest approaches. We recorded and analyzed 2,325 pulses from 114 individuals and 16 bat species of the families Vespertilionidae, Mormoopidae, Molossidae, and Natalidae. The Random forest model (81.3%) was the better species predictor over the artificial neural network and the discriminant function analysis (69 % and 62.1% respectively). Our work is one of the few attempts to do this exercise that has been conducted in Mexico. The library can be useful as a starting point of research in other regions of the highlands in central Mexico where the information is still scarce.
... These groupings with evident taxonomic imprint result from a combination of interspecific differences in external (including wing), as well as craniodental, traits (Giménez and Giannini 2017). In addition, these species present also important differences in their echolocation calls (see Rodríguez-San Pedro and Simonetti 2013;Rodríguez-San Pedro et al. 2016), which could influence directly their foraging habits and contribute to the expected resource partitioning (Aldridge and Rautenbach 1987;Bogdanowicz et al. 1999;Schnitzler and Kalko 2001) among these bats. ...
Article
Partitioning of food resources is one of the main drivers of bat community organization. We investigated the trophic structure of the Patagonian bat ensemble which comprises eight insectivorous species classified in the families Vespertilionidae and Molossidae. Natural history studies, particularly those of diet and resource use, are scarce for these species and for bats of harsh environments generally. Here, we report the analysis of 140 dietary records from the eight Patagonian species sampled in 23 Western Central Patagonian localities in Chubut Province, Argentina. We estimated the dietary composition, both as percentage volume and as frequency of occurrence, of each dietary item, which was identified to the level of order. Trophic-niche breadth and average prey hardness were calculated for each bat species. We applied a principal components analysis for volume dietary data and correspondence analysis for frequency data. We recorded six insect orders (Coleoptera, Lepidoptera, Trichoptera, Diptera, Neuroptera, and Hemiptera) in different proportions across species. The latter also diverged in average prey hardness and trophic-niche breadth. This study provides the first quantitative picture of trophic organization in bats from Patagonian habitats. While Myotis species mainly consumed Coleoptera, followed by Lepidoptera and Diptera, Lasiurus species took chiefly Lepidoptera; Histiotus predominantly hunted for Coleoptera, and T. brasiliensis captured chiefly Lepidoptera, Coleoptera, and Diptera. These different dietary combinations indicate resource partitioning among three vespertilionid and one molossid genera, as well as a degree of niche organization in Patagonian bats, which help to understand their ecosystem role as insect predators.
... The recorded audio files were analyzed manually to obtain frequency values, using Avisoft SAS Lab Pro (Avisoft Bioacoustics, Berlin, Germany). Each species was classified using the features of echolocation calls, according to the values of frequency at the end of the call and frequency at the highest energy and duration CONTACT Alejandra E. Muñoz aemunoz@uc.cl of the calls; those values are the most representative parameters to differentiate bats in central Chile [8,9]. The hourly activity of different species was plotted for a 10-min period throughout the night, to observe how the activity of bat species fluctuate throughout the night ( Figure 2). ...
Article
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Bats are one of the least-studied vertebrate groups in Chile. We sampled six fruit farms in theMediterranean-climate zone and three in a semiarid zone during 2015 and 2016, respectively.We assessed if activity (passes) and foraging (feeding buzzes) of bat species differed betweencultivated and uncultivated intra-farm habitats. We found six bat species, all threatened andinsectivorous.Tadarida brasiliensiswas the most frequently recorded species. We found moreactivity and foraging in uncultivated than cultivated habitats in total, although the oppositetrend was observed during springtime in semiarid region. More than a third of the bat passeswere feeding buzzes in both habitats, suggesting the potential service to agriculture. Furtherinvestigation is needed to promote conservation of bats and their integration as biocontrolsin agroecosystems in Chile.
... No significant difference in call duration was observed between Miniopterus magnater and Miniopterus fuliginosus contrary to several previously studied species Jones 2002, Rodríguez-San Pedro andSimonetti 2013). ...
Article
Bats play important roles in ecosystems, and are thus considered bioindicators. Libraries of echolocation calls provide huge potential resources for bat species identifications, ecological studies and conservation surveys. Here, the echolocation calls of two morphologically similar bat species ( Miniopterus magnater and Miniopterus fuliginosus ) were recorded and described in order to characterize vocal signatures for field identification in China. Both M. magnater and M. fuliginosus emitted short frequency modulated echolocation calls with narrow bandwidths. Each call of the former species included two harmonics, with the first harmonic being the strongest, whereas calls of the latter species normally contained one harmonic. Although call durations were similar between the two species, there were significant differences in start, end and peak frequencies between M. magnater and M. fuliginous . The results showed that 92.3% of all calls recorded in China were attributed to the correct species based on spectral features of echolocation calls. We concluded that echolocation calls are valuable characters for the identification of morphologically similar bat species.
... The development of bat identification at the species level was tested mainly in Europe Lucas, 2000;Obrist et al., 2004;Papadatou et al., 2008;Parsons and Jones, 2000;Preatoni et al., 2005;Redgwell et al., 2009;Russo and Jones, 2002;Skowronski and Harris, 2006;Walters et al., 2012) and the Americas (Agranat, 2013;Armitage and Ober, 2010;Biscardi et al., 2004;Botto Nuñez et al., 2018;Corcoran, 2007;Pedro and Simonetti, 2013;Stathopoulos et al., 2018), as listed in Appendix. Recently, bat identification studies started to develop a localized and species-scale identifier in East and Southeast Asia (Chen et al., 2020;Fukui et al., 2004;Funakoshi, 2010;Masuda et al., 2017). ...
Article
Bats inhabit all continents except Antarctica, and they have enormous potential as bioindicators. Therefore, monitoring bats helps us to understand the surrounding environmental changes. However, bats are nocturnal, which makes it difficult to visually monitor their behavior. This paper proposes a bat species identifier method based on the analysis of ultrasound called echolocation calls, which is a promising method to monitor bats’ activity levels effectively. We develop a robust method to identify the bat species with improved accuracy by analyzing their echolocation calls. First, 1,400 sound files with four families, 13 genera, and 30 species were recorded in Japan and the Jincheon-gun in South Korea from 1999 to 2019. Bat echolocation calls were detected from the sound files and used to generate 54,525 spectrograms by applying short-time Fourier transform. We developed a deep learning–based bat species identifier using convolutional neural networks with MobileNetV1 used as the model’s architecture. Furthermore, we applied nested cross-validation with the Bayesian optimization algorithm to search for the optimal combination of hyperparameters and evaluate the expected performance. We achieved 98.1% accuracy, which outperformed previous studies that treated more than 30 bat species. We visualized important regions of the spectrograms which correspond to prediction using the Guided Grad-CAM. Moreover, we discussed how to treat the noise class and minimize the model training time. Then, we proposed potential solutions to boost the identifier’s performance, the generalization of the echolocation call recording protocols, and applicable techniques to improve the identification accuracy. Future perspectives are 1) to change the deep learning algorithm from image classification to object detection and 2) to apply the proposed identifier to unknown bat echolocation calls to evaluate the feasibility of estimating bat fauna and spatial activity distribution.
... Study of echolocation calls in microchiropteran bat has much effectiveness in studies of the ecology, behavior, taxonomy, and conservation of bats. Many studies indicated that different species of bats use different echolocation calls, thus suggesting that bat species in many cases could be identified based on their calls (Russo and Jones 2002;Obrist et al. 2004;Macias et al. 2006;Rodrı'guez-San and Simonetti 2013). All members of the genus Rhinolophus are the high duty cycle (HDC) which use calls that are of longer duration than the inter-call interval (Jones 1996). ...
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There is a high level of morphological similarity among rhinolophid species leading to problematic taxonomic identifications. We undertook analyses of mitochondrial DNA gene sequences (D-loop), along with morphologic and acoustic examinations in order to evaluate taxonomic status and phylogenetic relationships of the horseshoe bat species in Iran. All analyses based on molecular, morphological, and sonar characteristics revealed five rhinolophid species including Rhinolophus mehelyi, R. euryale, R. ferrumequinum, R. blasii, and R. hipposideros in Iran. Genetic study revealed one lineage in R. mehelyi, two lineages in each of species R. euryale, R. ferrumequinum, and R. blasii, and three lineages in R. hipposideros. Our results showed high haplotype diversity (Hd) in the Iranian rhinolophid species. Compared with other studies of bat D-loop sequences, the genetic mean nucleotide diversity obtained for R. blasii in the current study (π = 0.0569) was the highest value and for R. euryale was found to be the lowest value (π = 0.0126) among nucleotide diversity values for other bat species. The average dominant frequency (peak frequency ± standard deviation) for R. euryale, R. ferrumequinum, R. mehelyi, R. blasii, and R. hipposideros was 106.57 ± 0.32, 82.02 ± 0.19, 105.57 ± 0.45, 92.85 ± 0.95, and 110.74 ± 1.93 respectively. As a conclusion, based on the present genetic study, there are one to three lineages including at least one southern and one northern in every rhinolophid species in Iran.
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Agricultural intensification is one of the major causes for the global loss of biodiversity and associated ecosystem services. As an alternative to conventional farming, organic management is considered a way to mitigate some of the negative impacts on biodiversity in agricultural landscapes; however, their benefits for bats are not very conclusive. We investigated the hypothesis that organic farming benefits bats in vineyards by improving conditions for foraging through increased availability of prey. We also hypothesized that bat activity would vary between edges and the interior of vineyards in response to prey availability that in turn would be influenced by agricultural management. Bat activity was quantified along edge and the interior of each vineyard type by using acoustic surveys. In addition, we sampled nocturnal flying insects at each site using light traps. Species richness and overall bat activity were significantly higher in organic than conventional vineyards, with organic edges concentrating the highest bat activity. Our results suggest negative effects of agricultural intensification on insectivorous bats. The high bat activity along edges compared to the interior of vineyards suggest that these structural features of the landscape are important components for bat populations in vineyards, and therefore should be considered within agricultural management in order to promote bat abundance and their role as pest suppressors.
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Nowadays the task of monitoring bat species is a very difficult task because of several factors. The main ones are the difficulty of creating databases automatically and the particularities of the vocalizations of bats. For this reason, it is common to extract bat calls manually from a recording and treat them individually. We propose a new form of identification and labeling process based on adapting bat calls to the audible spectrum and significantly reducing the noise of its spectrogram. This process can be performed automatically from a recording made in a natural area. Our database consists of 189 h of recordings obtained in various natural areas in Costa Rica. 50 bats calls of 7 different classes are extracted from this database. We have obtained an average error of 2.7% and 3 of the 7 classes have an error below 1%.
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Forestry plantations represent about 4 % of the global land cover and demand for wood is steadily increasing worldwide. Impacts of forest plantations on biodiversity are controversial; forest plantations could positively influence biodiversity by producing a buffer zone between native forests and agriculture, while replacement of native forests with plantations could reduce biodiversity. Chile is one of the main producers of wood worldwide, and production is largely based on intensively managed monocultures of exotic tree species. Only a few studies have looked at the effects of forestry plantations on biodiversity in Chile, mainly focusing on pine plantations. The aim of this study was to characterize habitat use and richness of bats between native forests, eucalyptus plantations and grasslands in a biodiversity hotspot in southern Chile to determine how land use affects an important mammalian taxa. We found no difference in use or richness of bats in eucalyptus plantations versus native forests. Regional context within the larger Valdivian watershed (Andes, central valley, coastal range) had a stronger influence on bat activityand richness than land use type (native forest, plantation, grassland), with the Andean region being the most diverse and where most bat activity is concentrated. Our results suggest that the composition and structure of the surrounding landscape mosaic may be fundamental to determine the impacts of forestry and human land use on biodiversity.
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We report new distributional records for Histiotus montanus and first records of Histiotus laephotis for Chile. Morphological measurements and analyses of echolocation calls confirm the differences between the species. Histiotus montanus has a smaller forearm (49.7±0.8 vs. 51.7±0.4 mm) and darker and shorter ears than H. laephotis; the latter has a yellowish fur in contrast to other Histiotus species. Acoustic analyses showed significant differences between the species: H. laephotis have shorter pulses (1.3±0.4 vs. 3.6±2.6 ms), with lower start and peak frequencies (start frequency 38.2±2.6 vs. 46.4±4.6 kHz; peak frequency 30.4±3.7 vs. 32.1±2.2 kHz) than H. montanus. These findings place the Tarapacá region of northern Chile as the most diverse in terms of bat species in the country. Furthermore, these results increase the total number of bat species known to occur in the country to 13.
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Forestry plantations supporting native species exhibit a dense understory, which might reduce bat activity within plantations. We compared bat activity in Monterrey pine plantations with and without an under-story in central Chile. Total activity did not differ be-tween plantations with a developed understory and those without it, being higher on-track than off-tracks sites. Trails provide commuting areas for bats within planta-tions allowing its use regardless of their degree of structural clutter. Promoting understory in plantations provides habitats for bats and might enhance their con-servation in human-modified landscapes.
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Aim Our understanding of the biological strategies employed by species to cope with challenges posed by aridity is still limited. Despite being sensitive to water loss, bats successfully inhabit a wide range of arid lands. We here investigated how functional traits of bat assemblages vary along the global aridity gradient to identify traits that favour their persistence in arid environments. Location Global. Time period Contemporary. Major taxa studied Bats. Methods We mapped the assemblage‐level averages of four key bat traits describing wing morphology, echolocation and body size, based on a grid of 100‐km resolution and a pool of 915 bat species, and modelled them against aridity values. To support our results, we conducted analyses also at the species level to control for phylogenetic autocorrelation. Results At the assemblage level, we detected a rise in values of aspect ratio, wing loading and forearm length, and a decrease in echolocation frequency with increasing aridity. These patterns were consistent with trends detected at the species level for all traits. Main conclusions Our findings show that trait variation in bats is associated with the aridity gradient and suggest that greater mobility and larger body size are advantageous features in arid environments. Greater mobility favours bats’ ability to track patchy and temporary resources, while the reduced surface‐to‐volume ratio associated with a larger body size is likely to reduce water stress by limiting cutaneous evaporation. These findings highlight the importance of extending attention from species‐specific adaptations to broad scale and multispecies variation in traits when investigating the ability of species to withstand arid conditions.
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Context Disentangling the relative effects of forest loss versus fragmentation on species distribution and abundance is crucial for adopting efficient biodiversity conservation actions, which could change with the nature of the landscape matrix. Objectives We tested the moderating effect of landscape matrix on insectivorous bats response to forest loss and fragmentation. Methods We conducted acoustic surveys at forest patches surrounded by either an agricultural-dominated matrix or a pine-dominated matrix. We related bat activity to forest amount and the number of forest patches at multiple spatial scales, and compared their effects between landscape matrices. Results Bat activity was associated with both predictors, however their effects varied with the matrix type. In agricultural landscapes, as the amount of forest increased, the activity of Histiotus montanus, Lasiurus cinereus and Tadarida brasiliensis increased, while activity of Myotis chiloensis decreased. Similarly, as fragmentation increased, the activity of Lasiurus varius and M. chiloensis increased, while activity of H. montanus decreased. In production-forest landscapes, only H. montanus decreased its activity with increasing forest amount. In contrast, activity of L. cinereus, M. chiloensis and T. brasiliensis increased with increasing fragmentation. Forest amount was a stronger predictor for agricultural landscapes than for production-forest landscapes, suggesting that low contrast matrices can mitigate the effects of forest loss. Conclusions Fragmented landscapes with native forest patches surrounded by a low contrast matrix may support a higher activity of insectivorous bats. Management efforts in fragmented landscapes should aim to decrease the patch-matrix contrast, which will mitigate the effects of forest loss on bats.
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Bats are the second most diverse order of mammals. South America is rich in bats, however Chile has low species diversity (12 especies) and absence of endemism. Scientifi c publications that have addressed the biological diversity and taxonomy of these Chilean mammals are also scarce. This review assessed the state of knowledge of bats in Chile and its main results. We critically characterize those knowledge areas more developed and those that require further work. Additionally, we propose an explanation regarding this low diversity. Finally, we make a map that organizes bat diversity according to natural biomes of Chile. As results, we find 27 publications in the last two decades. These works are mainly focused on Infectology and Ecophysiology. The Chilean biome concentrating the highest bat diversity is the Atacama Desert, and the diversity is decreasing latitudinally. In spite of long periods of stasis, the taxonomy of Chilean bats abruptly changed in the last century. We propose a biogeographical and ecophysiological interaction for the observed patter of diversity. Finally, we stressed the importance of further micro and macroevolutionary research, as well as conservation and bioacustic studies, for better understanding of important issues still unsolved.
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Frequential and time lineal parameters have shown a good performance in the recognition of bat species and nowadays there are many works which obtain those characteristics very accurately. However, it is necessary to move forward and test the capabilities of other characterizations on bioacoustics successfully used in other fields. In this work the chaos theory, which is an area of nonlinear dynamics systems, is applied to bat acoustic identification. The database used in the evaluation consists of 50 bat calls of seven different classes extracted from a previous work. The combinations of linear and nonlinear parameters have resulted in an average error of 1.8%, improving the accuracy in 0.42%. The differences to identify between the most difficult species and the easiest ones have been reduced.
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MSc Thesis. BAT BIOACOUSTIC STUDIES IN BUENOS AIRES PROVINCE, ARGENTINA. Italian language.
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Moonlight intensity influences the activity patterns of bats. Some bat species reduce their activity levels during brighter nights, a phenomenon known as “lunar phobia.” While lunar phobia of bats has been extensively studied in tropical regions, the same is not the case of bats in temperate regions. By using acoustic detectors, we examined differences in the activity of insectivorous bats on nights with different moonlight intensity in an agricultural landscape of central Chile. We also examined the hourly activity patterns throughout the night and how these varied between full and new moon nights. All bat species modified their activity based on the moonlight intensity; however, their effects were species-specific. The activity of Lasiurus varius, L. villosissimus, Myotis chiloensis, and Histiotus montanus was lower during bright nights, while Tadarida brasiliensis was the only species whose activity was higher during bright nights. Hourly activity throughout the night differed between full moon nights and new moon nights in most bat species. During full moon, bats concentrated their activities in the early hours of the nights; a more homogeneous activity pattern was exhibited during new moon night. Our study demonstrates that moonlight affects the activity of bats in Chile, a factor that should be considered when studying bats.
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PREFACE This book is designed as a guide aimed at satisfying the needs of those conducting field work on bats in the Amazon. It is largely based on Lim et al. (2001), with modifications derived from both personal observations and three years of field experience in the Brazilian Amazon at the Biological Dynamics of Forest Fragments Project (BDFFP), as well as a thorough revision of available bat keys and scientific papers describing new species. Our aim was to write a straightforward, easy-to-use guide that would be both practical and very visual, and would facilitate bat species identification in the field. We tried to avoid as much as possible confusing features such as fur colour, as well as certain skull and teeth characteristics that cannot be easily measured under field conditions. We decided to group together many of the cryptic species that are still indistinguishable in the field and that can only reliably be identified using molecular methods such as DNA barcoding. Taxonomic nomenclature throughout this key follows Nogueira et al. (2014). This is an interactive field-guide that we hope will be continuously improved and updated. We will be delighted to receive readers’ comments and suggestions! Please send them to: adria.baucells@gmail.com Thank you! The Authors
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We recorded and characterized the echolocation calls emitted by the common vampire bat Desmodus rotundus during foraging in natural habitats in Chile. Signal design typically shows multiple harmonics consisting of a brief quasi-constant frequency (QCF) component at the beginning of the pulse followed by a downward frequency modulated component. Calls are characterized by long durations (5.5 ms) and emitted as single pulses or in groups of 2–3 pulses at a repetition rate of 29 Hz. The higher frequency ranges (85–35 kHz) and the unusual QCF component that characterized multiharmonic signals of free-flying D. rotundus in Chile is a remarkable feature for acoustic identification with other Chilean bats.
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Lasiurus varius (Poeppig, 1835) is a vespertilionid bat commonly known as Chilean red bat or cinnamon red bat. L. varius is characterized by its deep reddish coloration without frosted appearance, and by the uropatagium covered with long hairs that extend beyond the trailing edge, which clearly distinguishes it from the other species in the genus. The distribution of this rare species is restricted to the southern parts of Argentina and Chile.
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BatScope is a free application for processing acoustic high-frequency recordings of bats. It can import data, including meta-data information, from recorders such as Batlogger. The resulting content can be filtered visually as spectrograms or according to data fields and can be displayed. Automated processing includes detecting and extracting of echolocation calls, filtering noise, and measuring statistical parameters. Calls are classified to species by statistically matching to a reference database. A weighted list of classifiers helps to assign the most likely species per call. Classifiers were trained on 19 636 echolocation calls of 27 European bat species. When classifiers all agree on a species (76.4% of all cases), the mean correct classification rate reaches 95.7%. A sequence’s summary statistic indicates the most likely species occurring therein. Classifications can be verified visually, by filtering, and by acoustic comparison with reference calls. Procedures are available for, e.g., excluding dubious cutouts from the statistics and for accepting or overriding the proposed species assignment. Acoustic recordings can be exported and exchanged with other users. Finally, the verified results can be exported to spreadsheets for further analyses and reporting. We currently reprogram BatScope using Java, PostgreSQL, and R to reach a unified and portable software architecture.
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Brazil is a megadiverse country with more than 180 bat species. However, most inventories have been mostly made using mist-net sampling and roost search and due to the lack of bioacoustics studies, the bat fauna is certainly subrepresented and biased. The knowledge on distribution and ecology of Brazilian bats is mainly within the Phyllostomidae. Reliable data on bat echolocation calls is the key to improve the knowledge on the distribution patterns and foraging ecology of the remaining eight bat families present in the country. Our work aims to (i) integrate information on echolocation calls of non-phyllostomids occurring in Brazil; (ii) detect regional changes in the acoustic profile of those species; (iii) identify gaps in knowledge both in terms of species and regions sampled; and (iv) to point out which species are acoustically recognizable in a reliable way. Finally, we present a key to supporting the acoustic identification of non-phyllostomids in Brazil. We compiled publications on echolocation calls of Neotropical bat species occurring in Brazil and summarized qualitative and quantitative information of acoustic parameters used in call descriptions. We considered 93 non-phyllostomid bat species to occur in Brazil of which 65 have been acoustically described but for 28 we found no published information. Information on echolocation calls was retrieved from 47 publications and acquired in 17 countries. The use of bioacoustics can be a fundamental tool to expand the knowledge on Brazilian bats and improve their conservation.
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Landscape composition and heterogeneity are considered important factors for enhancing biodiversity and their associated ecosystem services in human-modified landscapes. Despite their roles in pest suppression in agricultural areas, insectivorous bats have been poorly represented in studies assessing the effects of landscape structural changes, particularly in the Neotropics. We evaluated how the composition and heterogeneity of the landscape, at several spatial scales, influenced the diversity and activity of aerial insectivorous bats in organic vineyards. Bat activity was quantified using acoustic surveys at 16 vineyards distributed across the central zone of Chile, where landscape composition and heterogeneity were determined by spatial analysis (GIS). Data were analyzed using partial least square regressions (PLS). The diversity and activity of aerial insectivorous bats in vineyards increased with the compositional and configurational heterogeneity of the landscape. Bat diversity and species richness in vineyards increased as the area covered by native vegetation increased, and urban areas decreased. Total bat activity, feeding activity and the activity of the dominant species T. brasiliensis increased with the diversity of cover types in the landscape, and also as the area covered by annual crops and rural areas increased. This study highlights the importance of agricultural landscape composition and heterogeneity for aerial insectivorous bats in organic vineyards. Effective conservation efforts and management strategies in this crop should aim to increase cover diversification at the landscape scale. In addition, retaining native forest remnants around or within vineyards may promote bat conservation and their role as suppressors of crop pests in these production landscapes.
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We assessed foraging activity of insectivorous bats in a fragmented landscape of central Chile including native temperate forest, forest fragments, commercial pine plantations and local human settlements. Overall bat activity was noticeably greater along adult pine plantation edges, local human settlement and the edge of continuous forest than over interior habitats and unplanted forest plantation clear-cuts. Tadarida brasiliensis foraged mostly above human settlements and edges of adult pine plantations but avoided interior habitats. Lasiurus cinereus was more active along edges of both adult pine plantations and continuous forest than in clear-cuts and interior habitats of forest fragments. In contrast, Lasiurus varius, Histiotus montanus and Myotis chiloensis occurred not only along vegetation edges but also within the interior habitats of adult pine plantations. The high activity levels suggest that bats not only pass through exotic pine plantations, but that they are active in these habitats commuting and feeding, thus enhancing their capacity to persist in landscapes modified by humans in which exotic forestry plantations are an important component.
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Segunda Edición actualizada de los Murciélagos de Chile
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Spectral and temporal features of echolocation calls emitted by 22 bat species from Italy (three rhinolophids, 18 vespertilionids and the molossid Tadarida teniotis) are described. Time-expanded recordings of calls from 950 bats of known identity were examined. Rhinolophus ferrumequinum, R. hipposideros, R. euryale and T. teniotis could be identified by measuring the call frequency of highest energy (FMAXE). Quadratic discriminant function analysis with cross-validation was applied to calls from the remaining 18 species. A function based on start frequency (SF), end frequency (EF), FMAXE and duration (D) provided a correct overall classification of approximately 82%. A classification model at genus level that also comprised middle frequency (MF) and inter-pulse interval (IPI) reached 94% correct classification. Two separate discriminant functions were devised for species emitting FM (frequency modulated) and FM/QCF calls (i.e. calls consisting of a frequency-modulated component followed by a terminal part whose frequency is almost constant) respectively. The former function included SF, EF, FMAXE and D and provided an overall classification rate of 71%; the latter comprised EF, MF, D and IPI, and reached 96%. The functions may be applied to bat habitat surveys in southern Italy since they cover most of the species occurring in the area.
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To evaluate the efficacy of the Anabat II ultrasonic detector and analysis system for use as a tool for conducting inventories, we compared results of acoustic versus capture techniques in the southwestern United States. We sampled 57 locations using standard methods (mist nets and double-frame harp traps) and simultaneously with an ultrasonic detector (Anabat II). Assuming total number of species obtained by both methods equaled a complete inventory, captures accounted for 63.5% and acoustic sampling 86.9% of the combined species present. Acoustic sampling was capable of sampling bats that routinely flew outside the sampling capabilities of nets and traps. We found no statistical difference between capture and acoustic sampling with respect to species that use low-intensity echolocation. Acoustic sampling of bat communities is a powerful tool but should be used with various capture techniques to perform the most accurate inventory.
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The Brazilian free-tailed bat, Tadarida brasiliensis (Saint-Hilaire, 1824), uses calls that represent a broad continuum of design variation which is dependent upon habitat and situation, and exhibits characteristic changes in call design as bats close in on airborne targets. Here we demonstrate the influence of conspecifics on call design. We found that the peak frequency used in calls varies more as the number of bats flying in the same space increases (measured from single bats and pairs of bats). We investigated this phenomenon through comparing call-parameter differences found between two bats recorded flying together (actual pairs) with call-parameter differences between two bats each recorded flying alone at different locations that were randomly assigned to one another (virtual pairs). We found that actual pairs of bats used calls which differed in peak frequency more so than did virtual pairs. This result is particularly striking given that these frequency differences were greater between bats in the same space than between bats in two different habitats. We argue that these differences indicate that this species is practicing jamming avoidance, air traffic control, or both.
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Although echolocation calls of most bats exhibit species-specific characteristics, intraspecific variation can obscure differences among species and make reliable acoustic identification difficult. We examined levels of intraspecific variation in search-phase calls of 7 species of vespertilionid bats from several locations in the eastern and central United States. Echolocation calls were recorded from light-tagged bats using the Anabat II detector and associated software. Analook software was used to calculate values for 5 parameters of calls: duration, maximum frequency, minimum frequency, frequency of the body, and slope of the body. Analysis of our results indicates that most intraspecific variability in calls was attributable to differences among individuals and within individual call sequences. Observed levels of geographic variation, although significant in all species examined, were comparatively small and showed no trends among areas. We include a preliminary description of variability in echolocation calls of Nyticeius humeralis and Myotis leibii.
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The echolocation behavior of Eptesicus fuscus was studied in the field in western Cuba. Bats leaving their roost produce short calls of around 2.3 ms showing two harmonics with a downward frequency modulation between 75 and 33 kHz in the first harmonic. During hunting, search calls typically show a single harmonic with a downward frequency modulation at the beginning of the signal, followed by a quasiconstant frequency component. Search calls are characterized by durations shorter than 8 ms and bandwidths of approximately 16 kHz. The minimal frequency is maintained rather constant around 33 kHz. Transitions from the search to the approach and terminal phases are characterized by an increase in duty cycle as a consequence of the increase in pulse repetition rate and the decrease in duration. Calls emitted in the laboratory are similar to those emitted in the wild. Compared with the echolocation repertoire of E. fuscus in North America, shorter calls with constant minimal frequencies are characteristic of this species in Cuba.
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1. A method for the identification of bat species from time-expanded broad-band recordings of their echolocation calls is presented. The method may be used for the assessment of habitat use by bats.2. Recordings were made of echolocation calls produced by 536 bats of known species identity, belonging to 15 species found in Great Britain. One call was analysed per individual, and sonograms and descriptive statistics of six time and frequency variables of calls are presented. British bats can be placed in three groups according to the structure of their calls: high duty cycle FM/CF/FM bats (Rhinolophus spp.), low duty cycle FM bats (Myotis spp. and Plecotus spp.) and intermediate duty cycle FM/CF bats (Pipistrellus and Nyctalus spp. and Eptesicus serotinus).3. FM/CF/FM bats could be identified from the peak frequency of their calls. Two separate quadratic multivariate discriminant analyses were carried out on the time and frequency parameters of calls produced by FM bats and FM/CF bats. For FM bats 67%, and for FM/CF bats 89%, of unknown calls were classified to species.
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Echolocation is characteristic of bats of the suborder Microchiroptera. Though recent studies of echolocation calls in Latin America have generated significant advances in knowledge about distribution, habitat use and ecology of bats, the recording and analysis of bat calls is barely known in Chile. As a first step in studies on the ecology of the endemic Chilean myotis bat (Myotis chiloensis), we carried out morphometric measures and analyzed echolocation calls in a rural site near Pucón (39°15'S 17°W) in the Araucanía Region of southern Chile. During January 2009, we obtained 22 records from captured and 75 records from flying individuals. The analysis of calls in searching phase showed that the terminal frequency for this species is 43.4 ± 1.2 kHz, with a mean duration of 2.1 ± 1.0 ms and an interval between pulses of 77.5 ± 16.9 ms. The calls are FM – QCF, as is characteristic for the family Vespertilionidae. The contribution of new morphometric data from captured and released individuals indicates differences from previous studies. The records and acoustic analysis establishes a baseline for more detailed future ecological investigation of this and other bat species in Chile.
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We studied the echolocation behaviour of Nycticeius cubanus in the field in western Cuba. During hunting, N. cubanus search for insects emitting cries that sweep from 80 to 40 kHz in 4 to 12 ms. Search call characteristics correlate with the clutter structure of the hunting areas. Bats hunting in an uncluttered space broadcast longer and narrower signals, while bats hunting in cluttered space broadcast shorter and broadband signals. Longer calls were emitted with longer intervals while the duty cycle was kept below 15 % during search and approach phases. The call's minimal frequency remained about 43 kHz showing variation coefficients of less than 3%. As a consequence, bandwidth correlates positively with the maximal frequency. Calls emitted by different sympatric individuals are accurately classified by sender using a discriminant function analysis, suggesting vocal signatures in N. cubanus. The statistical analysis of several passes of calls broadcast during the hunting activity of a single individual, demonstrates a high intra-individual plasticity in vocal signatures and points to a dynamic system.
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We used both field and flight cage observations to investigate the echolocation and foraging behavior of the seldom studied, small, aerial insectivorous bat Myotis nigricans (Vespertilionidae) in Panama. In contrast to its temperate congeners, M. nigricans foraged extensively in open space and showed an echolocation behavior well adapted to this foraging habitat. It broadcast narrowband echolocation signals of 7 ms duration that enhance the chance of prey detection in open space. Because of rhythmical alternations of signal amplitude from signal to signal in our sound recordings of search signals in open space, we conclude that the bats scanned their environment with head movements, thereby enlarging their search volume. In edge-and-gap situations, and in the flight cage, M. nigricans introduced an initial broadband component to its search calls. In the field and in the flight cage, M. nigricans hawked for prey in aerial catches; gleaning was never observed. M. nigricans demonstrates call structures, such as narrow bandwidth and rather long signals adapted to foraging predominantly in open space. Moreover, call structure is highly plastic, allowing M. nigricans to forage in edge-and-gap situations also. These adaptations in call structure and plasticity have evolved convergently at least twice within the genus Myotis. Finally, M. nigricans echolocation and foraging behavior parallels that of the small, aerial, insectivorous pipistrelle bats (Vespertilionidae), which are not closely related to M. nigricans but forage in similar habitats.
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Bat tolerance to neotropical forest fragmentation may be related to ability by bats to use available habitats in the modified environmental matrix. This paper presents data on general bat activity (for three hours starting at dusk) measured with an ultrasound detector in a fragmented landscape in the region of Los Tuxtlas, Mexico. Bat activity was measured in continuous forests, forests fragments, forest-pasture edges, forest corridors, linear strips of vegetation, citrus groves, pastures and the vegetation present in local villages. The highest bat activity rates were recorded in the villages, in the forest fragments and in linear strips of vegetation. The lowest activity rates were detected in pasture habitats. Data suggest that native and man-made arboreal vegetation may be important for sustaining bat activity in fragmented landscapes.
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We examined variation in the echolocation calls of Brazilian free-tailed bats, Tadarida brasiliensis, on a broad geographical scale and in response to local environmental variables. Significant differences in call structure were observed among populations throughout the species range in the United States, but this variation was not associated with geographical distance or local weather conditions. Observed variability between sites was primarily due to differences between bats, and the flexibility in call structure that can be achieved by individuals. During this study, we observed that bats recorded in the presence of high-frequency sounds from chorusing insects used higher call frequencies than bats recorded in silence. This led us to test the hypothesis that bats adjust echolocation call structure in response to local ambient noise. We broadcast experimentally manipulated ultrasonic insect sounds to free-flying Brazilian free-tailed bats and found a positive correlation between the frequency of the insect sound stimulus and the call frequencies used by bats. These results document that bats adjust echolocation call structure to avoid acoustic interference from ambient noise in their local environment.
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Ultrasonic detectors were used to compare bat activity and species richness at replicated continuous and isolated forests, large and small remnants, corridors and open areas on the south-west slopes of New South Wales, Australia. The habitat matrix in this area consists primarily of agricultural land interspersed with indigenous forest remnants and pine plantations. Ten taxa of bat were recorded, with the fewest in corridors. A multivariate analysis revealed that a gradient in forest area, habitat diversity and structural complexity was the most consistent predictor of activity for four taxa (C. morio, Nyctophilus spp., V. regulus and F. tasmaniensis), suggesting that these are sensitive to the effects of forest fragmentation. Six species (N. australis, M. planiceps l.p., C. gouldii, M. schreibersii, V. darlingtoni, V. vulturnus) appeared tolerant of fragmentation and were not sensitive to isolation effects. Most tolerant species were active over open areas and probably used resources in the agricultural mosaic. Typically they were fast flying, low manoeuvrability species which are predicted to forage in uncluttered habitats. Although total activity in small remnants and corridors was as great as that in large forests continuous with a 690 000 ha national park, feeding activity was greatest in continuous forests, suggesting that larger forests with high habitat diversity offered more foraging opportunities. Despite providing fewer feeding opportunities, remnants represent an important conservation resource for bats because activity is concentrated here and they provide potential roost sites. Activity of each species in open areas was not significantly lower than that in corridors (non-riparian), suggesting that corridors were not used regularly by bats to move through the landscape. More detailed studies of the movements of species identified as sensitive to fragmentation would help to explain how fragmentation affects these species and thus what measures are required to improve their conservation.
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