Echolocation by Insect-Eating Bats

[ "Hans-Ulrich Schnitzler () is professor and head of the Lehrstuhl Tierphysiologie of the University of Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany."]
BioScience (Impact Factor: 5.38). 09/2009; 51(Jul 2001):557-569. DOI: 10.1641/0006-3568(2001)051[0557:EBIEB]2.0.CO;2
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Available from: Hans Ulrich Schnitzler, Nov 26, 2014
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    • "In contrast, the dense vegetation within which these bats forage at De Hoop probably selects for higher frequencies (Odendaal et al., 2014) whereas advantages that accrue through more effective communication as a result of nonoverlapping call frequencies with R. clivosus would select for lower frequencies. Avoiding call overlap with R. clivosus by using higher frequency calls would probably also require a reduction in body size for increased flight manoeuvrability (Norberg & Rayner, 1987) to deal with the decreased detection range resulting from increased atmospheric attenuation of higher frequency calls (Lawrence & Simmons, 1982; Schnitzler & Kalko, 2001). All rhinolophids echolocating at higher frequencies than R. clivosus (e.g. "
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    ABSTRACT: Communication is a fundamental component of evolutionary change because of its role in mate choice and sexual selection. Acoustic signals are a vital element of animal communication and sympatric species may use private frequency bands to facilitate intraspecific communication and identification of con-specifics (acoustic communication hypothesis, ACH). If so, animals should show increasing rates of misclassification with increasing overlap in frequency between their own calls and those used by sympatric heterospecifics. We tested this on the echolocation of the horseshoe bat, Rhinolophus capensis, using a classical habituationedishabituation experiment in which we exposed R. capensis from two phonetic populations to echolocation calls of sympatric and allopatric horseshoe bat species (Rhinolophus clivosus and Rhinolophus damarensis) and different phonetic populations of R. capensis. As predicted by the ACH, R. capensis from both test populations were able to discriminate between their own calls and calls of the respective sympatric horseshoe bat species. However, only bats from one test population were able to discriminate between calls of allopatric heterospecifics and their own population when both were using the same frequency. The local acoustic signalling assemblages (ensemble of signals from sympatric conspecifics and heterospecifics) of the two populations differed in complexity as a result of contact with other phonetic populations and sympatric heterospecifics. We therefore propose that a hierarchy of discrimination ability has evolved within the same species. Frequency alone may be sufficient to assess species membership in relatively simple acoustic assemblages but the ability to use additional acoustic cues may have evolved in more complex acoustic assemblages to circumvent mis-identifications as a result of the use of overlapping signals. When the acoustic signal design is under strong constraints as a result of dual functions and the available acoustic space is limited because of co-occurring species, species discrimination is mediated through improved sensory acuity in the receiver.
    Full-text · Article · Mar 2015 · Animal Behaviour
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    • "2004 ; Chiu et al . 2009 ) , absolute differences in call period ( Obrist 1995 ) , perhaps to aid in self - recognition , and shorter call durations to reduce the incidence signal masking ( Schnitzler and Kalko 2001 ) between individuals ( Obrist 1995 ) . Assuming bats track other bats , we predicted that paired bats would call more often than bats flying alone . "
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    ABSTRACT: We compared the influence of conspecifics and clutter on echolocation and flight speed in the bat Myotis daubentonii. In a large room, actual pairs of bats exhibited greater disparity in peak frequency (PF), minimum frequency (F MIN) and call period compared to virtual pairs of bats, each flying alone. Greater inter-individual disparity in PF and F MIN may reduce acoustic interference and/or increase signal self-recognition in the presence of conspecifics. Bats flying alone in a smaller flight room, to simulate a more cluttered habitat as compared to the large flight room, produced calls of shorter duration and call period, lower intensity, and flew at lower speeds. In cluttered space, shorter call duration should reduce masking, while shorter call period equals more updates to the bat’s auditory scene. Lower intensity likely reflects reduced range detection requirements, reduced speed the demands of flying in clutter. Our results show that some changes (e.g. PF separation) are associated with conspecifics, others with closed habitat (e.g. reduced call intensity). However, we demonstrate that call duration, period, and flight speed appear similarly influenced by conspecifics and clutter. We suggest that some changes reduce conspecific interference and/or improve self-recognition, while others demonstrate that bats experience each other like clutter.
    Full-text · Article · Mar 2015 · Journal of Comparative Physiology
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    • "Thus, our definition of manoeuvrability includes agility. Chiroptera encompasses over 1230 species distributed worldwide (Schipper et al. 2008; Kunz et al. 2011) exhibiting diverse wing morphologies and, in the case of species using echolocation for orientation, differentiation in echo-acoustic characteristics (Neuweiler 1984; Schnitzler and Kalko 2001). While we can predict that morphologically and echo-acoustically different species will use and perceive the world in different ways, there are examples of species that coexist in the same environment despite showing little or no measurable morphological or echo-acoustical difference. "
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    ABSTRACT: Two sympatrically occurring bat species, the greater mouse-eared bat (Myotis myotis (Borkhausen, 1797)) and the lesser mouse-eared bat (Myotis blythii (Tomes, 1857)) (Chiroptera, Vespertillionidae), share numerous similarities in morphology, roosting behaviour, and echolocation and are often difficult to distinguish. However, despite these similarities, their foraging behaviour is noticeably different. Our aim was to examine the extent to which these different foraging strategies reflect morphological adaptation. We assessed whether the morphology of the wing, body, and tail differed between M. myotis and M. blythii. In addition, in a laboratory experiment involving an obstacle course, we compared differences in manoeuvrability by relating them to our morphological measurements. The two species differed in their overall size, wing-tip shape, and tail-to-body length ratio. The generally smaller sized M. blythii performed better in the obstacle course and was therefore considered to be more manoeuvrable. Although differences in wing-tip shape were observed, we found the most important characteristic affecting manoeuvrability in both species to be the tail-to-body length ratio. Additionally, when we compared two bats with injured wing membranes with unharmed bats of the same species, we found no difference in manoeuvrability, even when the wing shape was asymmetric. We therefore postulate that morphometric differences between the two species in their overall size and, more importantly, in their tail-to-body length ratio are the main physical characteristics providing proof of adaptation to different foraging and feeding strategies.
    Full-text · Article · Sep 2014 · Canadian Journal of Zoology
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