@article {58229, title = {Harmonic-hopping in Wallacea{\textquoteright}s bats}, year = {2004}, abstract = {

Evolutionary divergence between species is facilitated by ecological shifts, and divergence is particularly rapid when such shifts also promote assortative mating1,2,3. Horseshoe bats are a diverse Old World family (Rhinolophidae) that have undergone a rapid radiation in the past 5 million years4. These insectivorous bats use a predominantly pure-tone echolocation call matched to an auditory fovea (an over-representation of the pure-tone frequency in the cochlea and inferior colliculus5,6) to detect the minute changes in echo amplitude and frequency generated when an insect flutters its wings7. The emitted signal is the accentuated second harmonic of a series in which the fundamental and remaining harmonics are filtered out8. Here we show that three distinct, sympatric size morphs of the large-eared horseshoe bat (Rhinolophus philippinensis) echolocate at different harmonics of the same fundamental frequency. These morphs have undergone recent genetic divergence, and this process has occurred in parallel more than once9. We suggest that switching harmonics creates a discontinuity in the bats\&$\#$39; perception of available prey that can initiate disruptive selection1. Moreover, because call frequency in horseshoe bats has a dual function in resource acquisition and communication, ecological selection on frequency might lead to assortative mating and ultimately reproductive isolation and speciation, regardless of external barriers to gene flow1,2,3.

}, doi = {10.1038/nature02487}, url = {http://www.nature.com/articles/nature02487}, author = {Kingston, Tigga and Rossiter, Stephen J.} } @article {57918, title = {Automatic standardized processing and identification of tropical bat calls using deep learning approaches}, year = {2019}, abstract = {

Consistent and comparable metrics to automatically monitor biodiversity across the landscape remain a gold-standard for biodiversity research, yet such approaches have frequently been limited to a very small selection of species for which visual approaches (e.g., camera traps) make continuous monitoring possible. Acoustic-based methods have been widely applied in the monitoring of bats and some other taxa across extended spatial scales, but are have yet to be applied to diverse tropical communities.

In this study, we developed a software program \“Waveman\” and prepared a reference library using over 880 audio-files from 36 Asian bat species. The software incorporated a novel network \“BatNet\” and a re-checking strategy (ReChk) to maximize accuracy. In Waveman, BatNet outperforms three other published networks: CNNFULL, VggNet and ResNet_v2, with over 90\% overall accuracy and 0.94 AUC on the ROC plot. The classification accuracy rates for all 36 species are at least 86\% when analysed in combination. Moreover, our library preparation and ReChk greatly improved the sensitivity and reduced the false positive rate, when tested with 15 species for which more detailed and situationally diverse records were available. Finally, BatNet was successfully used to identify Hipposideros larvatus and Rhinolophus siamensis from three different environments. We hope this pipeline is useful tool to process bioacoustic data accurately, effectively and automatically, therefore allowing for greater standardization and comparability for researchers to understand bat activities across space and time and therefore provide a consistent tool for monitoring biodiversity for management and conservation.

}, keywords = {Algorithms, Automated monitoring, Automatic processing, bats, bioacoustics, Biodiversity metrics, Calls, Deep learning, echolocation, machine learning, Monitoring protocol, Neural network}, doi = {10.1016/j.biocon.2019.108269}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0006320719308961}, author = {Chen, Xing and Zhao, Jun and Chen, Yan-hua and Zhou, Wei and Hughes, Alice C.} } @article {57884, title = {Performance of Doppler shift compensation in bats varies with species rather than with environmental clutter}, journal = {Animal Behaviour}, volume = {158}, year = {2019}, month = {Jan-12-2019}, pages = {109 - 120}, abstract = {

The performance of vocal motor control is crucial for vocal communication; however, its evolution and ecological drivers are largely unknown. Doppler shift compensation (DSC), which has been found only in bats, represents an excellent model for studying the mechanisms and evolution of vocal control. We tested whether species that are more dependent on DSC for pulse\–echo separation have a more precise DSC and whether changes in environmental clutter would result in adjustments in DSC performance. We recorded the echolocation and flight behaviour of the greater horseshoe bat, Rhinolophus ferrumequinum, and the great leaf-nosed bat, Hipposideros armiger, flying through a corridor and a window in turn. The DSC precision in H. armiger was significantly lower than that of R. ferrumequinum; the offset between the reference frequency and resting frequency, however, was not significantly different between the two species. We also studied the DSC of H. armiger flying through windows of different sizes. Their flight speed decreased significantly with reduced window size. However, DSC precision and the offset did not vary significantly with window size. Our results suggest that DSC is more precise in rhinolophids, which have a higher demand for pulse\–echo separation by DSC, than in hipposiderids. Changes in environmental clutter do not necessarily result in adjustments of DSC performance. Functional importance associated with high-performance vocal control may be critical in shaping the precision of vocal control in the course of evolution. Instead, habitat clutter encountered by vocalizing animals may not play an important role.

}, issn = {00033472}, doi = {10.1016/j.anbehav.2019.10.008}, author = {Zhang, Yu and Lin, Aiqing and Ding, Jianan and Yang, Xinyao and Jiang, Tinglei and Liu, Ying and Feng, Jiang} } @article {53578, title = {The Behaviour and Vocalisations of Captive Geoffroy{\textquoteright}s Horseshoe Bats, Rhinolophus clivosus (Chiroptera: Rhinolophidae)}, journal = {Acta Chiropterologica}, volume = {20}, year = {2018}, month = {Jan-12-2018}, pages = {439}, abstract = {

Acoustic signals are important to the biology of animals, mediating crucial activities such as social interactions (communication) as well as orientation and foraging (echolocation). Many signals used in communication are vocal, which are especially important in nocturnal animals such as bats where social interactions occur in darkness. Despite this, little is known about the social calls and behaviours of echolocating bats. To better understand their social and acoustic behaviour, we compiled an ethogram and list of vocalisations for Geoffroy\&$\#$39;s horseshoe bat (Rhinolophus clivosus). We kept three non-contemporaneous and short-term captive groups to capture interactions and social calls using simultaneous video and audio recordings. The resultant ethogram was comprised of 40 unique types of behaviour, both social and non-social. Social calls (n = 255) were assigned to different call types by their frequency-time contour and categorised by their behaviours, situational categories and functional contexts (affiliative or agonistic). From the calls observed, four acoustically distinct call types were identified: (i) cascading/rising frequency-modulated (FM) calls (n = 26), (ii) oscillatory FM calls (n = 140), (iii) noisy screech calls (n = 68), and (iv) whistle calls (n = 21) (GLM: F30, 711 = 24.28, P \< 0.001). Call types showed only weak associations with certain behaviours, situational categories or functional contexts. However, calls with specific acoustic attributes accompanied the behaviour of wing swat [discriminant function analysis (DFA) classification success: 76\%; GLM: F20, 108 = 4.12, P \< 0.001] and situational category of flight (DFA classification success: 82\%; GLM: F20, 136 = 2.97, P \< 0.001). An analysis of acoustic attributes across all call types showed weak associations with functional context (Affiliative DFA classification success: 6\%). Only one acoustic parameter (peak frequency) had a slight significant difference between calls emitted during agonistic and affiliative interactions (GLM: F10, 73 = 2.30, P \< 0.05; post-hoc unequal n: P = 0.044). In addition to the description of distinct call types, we provide evidence of transitional calls in this bat species in which a social call transitions seamlessly into an echolocation pulse. This study gives a first glimpse into the behaviours and social vocalisations produced by R. clivosus. Basic behavioural data such as these may facilitate the design of experiments that allow greater insight into the social organisation of bats.

}, doi = {10.3161/15081109ACC2018.20.2.014}, url = {https://bioone.org/journals/acta-chiropterologica/volume-20/issue-2/15081109ACC2018.20.2.014/The-Behaviour-and-Vocalisations-of-Captive-Geoffroys-Horseshoe-Bats-Rhinolophus/10.3161/15081109ACC2018.20.2.014.full}, author = {Hana Petersen and Nikita M. Finger} } @article {53350, title = {Acoustic similarity elicits responses to heterospecific distress calls in bats (Mammalia: Chiroptera)}, journal = {Animal Behaviour}, volume = {146}, year = {2018}, month = {Jan-12-2018}, pages = {143 - 154}, abstract = {

Frequently, individuals of one species respond to alarm calls produced by another species. This form of interspecies communication can be critical for survival. How animals recognize and respond to heterospecific alarm calls is, however, still poorly understood. This is especially true for bats, which are highly vocal and possess a specialized auditory system. We hypothesized that, among bat species, acoustic similarity between heterospecific and conspecific alarm calls is a key factor that underlies call recognition. However, this ability could also be acquired via associative learning from prior exposure or result from phylogenetic relatedness among caller and receiver species, as shown by others. Here we focused on distress calls of bats as representing a certain type of alarm call. To test our hypothesis, we recorded distress calls of 11 bat species from four families at five different sites. We broadcast the recorded calls to three of these species (Rhinolophus sinicus, Myotis badius and Myotis laniger). For all three species, neither prior exposure (familiarity) nor phylogenetic relatedness explained the variation in the response strength, as measured by echolocation vocalizations of receiver species in response to playback of heterospecific distress calls. In contrast, acoustic similarity, especially in peak frequency, between conspecific and heterospecific distress calls, was positively correlated with response strength in the receiver species. Thus, our findings emphasize that, at least among bats, acoustic similarity is a key factor allowing recognition of heterospecific alarm calls. It remains unclear whether evolutionary, genetic and/or neurophysiological mechanisms entrain an individual to respond selectively to a specific acoustic feature.

}, keywords = {acoustic similarity, bat, distress call, interspecific eavesdropping, learning, peak frequency, phylogenetic relatedness}, issn = {00033472}, doi = {10.1016/j.anbehav.2018.10.018}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0003347218303191https://api.elsevier.com/content/article/PII:S0003347218303191?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0003347218303191?httpAccept=text/plain}, author = {Huang, Xiaobin and Metzner, Walter and Zhang, Kangkang and Wang, Yujuan and Luo, Bo and Sun, Congnan and Jiang, Tinglei and Feng, Jiang} } @article {53289, title = {Resource Ephemerality Drives Social Foraging in Bats}, journal = {Current Biology}, year = {2018}, month = {Jan-11-2018}, abstract = {

Observations of animals feeding in aggregations are often interpreted as events of social foraging, but it can be difficult to determine whether the animals arrived at the foraging sites after collective search [1, 2, 3, 4] or whether they found the sites by following a leader [5, 6] or even independently, aggregating as an artifact of food availability [7, 8]. Distinguishing between these explanations is important, because functionally, they might have very different consequences. In the first case, the animals could benefit from the presence of conspecifics, whereas in the second and third, they often suffer from increased competition [3, 9, 10, 11, 12, 13]. Using novel miniature sensors, we recorded GPS tracks and audio of five species of bats, monitoring their movement and interactions with conspecifics, which could be inferred from the audio recordings. We examined the hypothesis that food distribution plays a key role in determining social foraging patterns [14, 15, 16]. Specifically, this hypothesis predicts that searching for an ephemeral resource (whose distribution in time or space is hard to predict) is more likely to favor social foraging [10, 13, 14, 15] than searching for a predictable resource. The movement and social interactions differed between bats foraging on ephemeral versus predictable resources. Ephemeral species changed foraging sites and showed large temporal variation nightly. They aggregated with conspecifics as was supported by playback experiments and computer simulations. In contrast, predictable species were never observed near conspecifics and showed high spatial fidelity to the same foraging sites over multiple nights. Our results suggest that resource (un)predictability influences the costs and benefits of social foraging.

}, keywords = {bat, behavioral ecology, echolocation, foraging, GPS, movement ecology, navigation, sociobiology}, issn = {09609822}, doi = {10.1016/j.cub.2018.09.064}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0960982218312909https://api.elsevier.com/content/article/PII:S0960982218312909?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0960982218312909?httpAccept=text/plain}, author = {Egert-Berg, Katya and Hurme, Edward R. and Greif, Stefan and Goldstein, Aya and Harten, Lee and Herrera M., Luis Gerardo and Flores-Mart{\'\i}nez, Jos{\'e} Juan and Vald{\'e}s, Andrea T. and Johnston, Dave S. and Eitan, Ofri and Borissov, Ivo and Shipley, Jeremy Ryan and Medellin, Rodrigo A. and Wilkinson, Gerald S. and Goerlitz, Holger R. and Yovel, Yossi} } @article {50498, title = {To seek or speak? Dual function of an acoustic signal limits its versatility in communication}, journal = {Animal Behaviour}, volume = {127}, year = {2017}, month = {Jan-05-2017}, pages = {135 - 152}, abstract = {

The perception of different attributes of conspecifics is an integral part of intraspecific communication. It can facilitate the recognition of interaction partners or the assessment of potential mates. Acoustic signals can encode fine-scaled information through the interplay of acoustic variability and specificity. A reliable vocal signature is both unique within a class and variable between classes. Therefore, acoustic complexity might be associated with the number of classes to be discriminated. We investigated the assumption that limitations to signal design may affect the communicative functionality of a signal. To do so, we chose a signal with potentially dual functionality which may therefore display such limitations. In bats, echolocation is used primarily for foraging and orientation but there is increasing support for its additional role in communication. An acoustic analysis of echolocation pulses of the bat Rhinolophus clivosus confirmed sex and individual vocal signatures in echolocation pulses. A habituation\–dishabituation playback experiment suggested that bats perceived these signatures because listening bats clearly discriminated between the sexes (two classes) and between individuals (representatives of a multiclass category), although to different degrees. The simple acoustic structure of these vocalizations provides sufficient specificity for sex discrimination but has limitations for individual discrimination because pulse parameters of individuals increasingly overlapped with increasing group size. We conclude that selection for the primary function of echolocation restricts the acoustic space available for communication. However, we frequently observed echolocation pulses with conspicuous structural modifications. Statistical analyses revealed that these vocalizations yielded increased individual distinctiveness. Such added systematic variation may indicate a communicative function and perhaps a signalling intent of the emitter, although the latter has yet to be tested. The findings suggest that the required specificity for effective communication could be obtained through modification of echolocation variants when adaptations for orientation and foraging constrain the evolution of complex communication signatures.

}, keywords = {acoustic communication, bats, co-option, constraints, eavesdropping, echolocation, habituation{\textendash}dishabituation playback, individual and sex discrimination, signal design, vocal signatures}, issn = {00033472}, doi = {10.1016/j.anbehav.2017.03.005}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217300775}, author = {Anna Bastian and David Steve Jacobs} } @article {50492, title = {The effects of cultural drift on geographic variation in echolocation calls of the Chinese rufous horseshoe bat ( Rhinolophus sinicus)}, journal = {Ethology}, volume = {123}, year = {2017}, month = {Jan-08-2017}, pages = {532 - 541}, abstract = {

Drift, selection, or their combined effects commonly drive geographic variation in traits. Clarifying the relative roles of each process is a long-standing research goal in evolutionary biology. Acoustic signals of bats are a phenotypic characteristic that plays an important role in social organization and species recognition. We extensively sampled the Chinese rufous horseshoe bat (Rhinolophus sinicus) throughout China and Vietnam and reconstructed a species phylogeny to better understand the patterns and causes of the geographic variation of acoustic signals. Our results showed that the resting frequency (RF) of calls varied with latitude, sex, and distance among different colony locations. RF differences were not correlated with genetic distance (based on only one nuclear locus and the mitochondrial locus), climatic factors (mean annual temperature and mean annual precipitable water), or body size, although differences in calls increased with distance among various populations. This suggests that cultural drift may play more important roles than genetic drift and acoustic adaptation in shaping acoustic differences within regions in R. sinicus.

}, keywords = {drift, geographic variation, resting frequency, Rhinolophus sinicus, selection}, doi = {10.1111/eth.2017.123.issue-810.1111/eth.12627}, url = {http://doi.wiley.com/10.1111/eth.2017.123.issue-8}, author = {Xie, Lifen and Sun, Keping and Jiang, Tinglei and Liu, Sen and Lu, Guanjun and Jin, Longru and Feng, Jiang} } @article {47815, title = {Horseshoe bats and Old World leaf-nosed bats have two discrete types of pinna motions}, journal = {The Journal of the Acoustical Society of America}, volume = {141}, year = {2017}, month = {Jan-05-2017}, pages = {3011 - 3017}, abstract = {

Horseshoe bats (Rhinolophidae) and the related Old World leaf-nosed bats (Hipposideridae) both show conspicuous pinna motions as part of their biosonar behaviors. In the current work, the kinematics of these motions in one species from each family (Rhinolophus ferrumequinum and Hipposideros armiger) has been analyzed quantitatively using three-dimensional tracking of landmarks placed on the pinna. The pinna motions that were observed in both species fell into two categories: In \“rigid rotations\” motions the geometry of the pinna was preserved and only its orientation in space was altered. In \“open\–close motions\” the geometry of the pinna was changed which was evident in a change of the distances between the landmark points. A linear discriminant analysis showed that motions from both categories could be separated without any overlap in the analyzed data set. Hence, bats from both species have two separate types of pinna motions with apparently no transitions between them. The deformations associated with open\–close pinna motions in Hipposideros armiger were found to be substantially larger compared to the wavelength associated with the largest pulse energy than in Rhinolophus ferrumequinum (137\% vs 99\%). The role of the two different motions in the biosonar behaviors of the animals remains to be determined.

}, issn = {0001-4966}, doi = {10.1121/1.4982042}, url = {http://asa.scitation.org/doi/10.1121/1.4982042}, author = {Yin, Xiaoyan and Qiu, Peiwen and Yang, Lili and M{\"u}ller, Rolf} } @article {47320, title = {To seek or speak? Dual function of an acoustic signal limits its versatility in communication}, journal = {Animal Behaviour}, volume = {127}, year = {2017}, month = {Jan-05-2017}, pages = {135 - 152}, abstract = {

The perception of different attributes of conspecifics is an integral part of intraspecific communication. It can facilitate the recognition of interaction partners or the assessment of potential mates. Acoustic signals can encode fine-scaled information through the interplay of acoustic variability and specificity. A reliable vocal signature is both unique within a class and variable between classes. Therefore, acoustic complexity might be associated with the number of classes to be discriminated. We investigated the assumption that limitations to signal design may affect the communicative functionality of a signal. To do so, we chose a signal with potentially dual functionality which may therefore display such limitations. In bats, echolocation is used primarily for foraging and orientation but there is increasing support for its additional role in communication. An acoustic analysis of echolocation pulses of the bat Rhinolophus clivosus confirmed sex and individual vocal signatures in echolocation pulses. A habituation\–dishabituation playback experiment suggested that bats perceived these signatures because listening bats clearly discriminated between the sexes (two classes) and between individuals (representatives of a multiclass category), although to different degrees. The simple acoustic structure of these vocalizations provides sufficient specificity for sex discrimination but has limitations for individual discrimination because pulse parameters of individuals increasingly overlapped with increasing group size. We conclude that selection for the primary function of echolocation restricts the acoustic space available for communication. However, we frequently observed echolocation pulses with conspicuous structural modifications. Statistical analyses revealed that these vocalizations yielded increased individual distinctiveness. Such added systematic variation may indicate a communicative function and perhaps a signalling intent of the emitter, although the latter has yet to be tested. The findings suggest that the required specificity for effective communication could be obtained through modification of echolocation variants when adaptations for orientation and foraging constrain the evolution of complex communication signatures.

}, keywords = {acoustic communication, bats, co-option, constraints, eavesdropping, echolocation, habituation{\textendash}dishabituation playback, individual and sex discrimination, signal design, vocal signatures}, issn = {00033472}, doi = {10.1016/j.anbehav.2017.03.005}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217300775}, author = {Anna Bastian and David Steve Jacobs} }