Echolocation behaviour of vespertilionid bats (<i>Lasiurus cinereus</i> and <i>Lasiurus borealis</i>) attacking airborne targets including arctiid moths

Acharya, Lalita; Fenton, M. Brock

doi:10.1139/z92-180

Cited by 85 publications

(89 citation statements)

References 22 publications

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Section: The Journal Of Experimental Biologymentioning

confidence: 99%

“…There are many records of bats attacking airborne, insect-sized targets, from small pebbles to dry flies used in fishing (Acharya and Fenton, 1992;Barclay and Brigham, 1994). This raises the question: do HDC echolocators sometimes behave as if they were LDC echolocators?…”

Section: Advantages Of Hdc Echolocationmentioning

confidence: 99%

“…Hipposideros commersoni (Vaughan, 1977), Rhinolophus rouxi (Neuweiler et al, 1987), R. ferrumequinum and R. hipposideros (Jones and Rayner, 1989)]. This in contrast to LDC species, some of which attack inanimate objects in the wild (Acharya and Fenton, 1992;Barclay and Brigham, 1994).Relative to LDC echolocators, HDC bats dramatically increase call duty cycle during prey capture attempts (Vogler and Neuweiler, 1983;Schnitzler et al, 1985; Jacobs et al, 2008), suggesting the increase in duty cycle indicates that a bat has detected a fluttering target and is locking onto the target and/or confirming its identity. Multiple time-and frequency-smeared background clutter echoes may make the amplitude and frequency glints of fluttering insects more conspicuous in a manner analogous to stochastic resonance processing in the auditory system (e.g.…”

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confidence: 99%

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Evolution of high duty cycle echolocation in bats

Fenton

Faure

Ratcliffe

2012

Journal of Experimental Biology

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SummaryDuty cycle describes the relative ʻon timeʼ of a periodic signal. In bats, we argue that high duty cycle (HDC) echolocation was selected for and evolved from low duty cycle (LDC) echolocation because increasing call duty cycle enhanced the ability of echolocating bats to detect, lock onto and track fluttering insects. Most echolocators (most bats and all birds and odontocete cetaceans) use LDC echolocation, separating pulse and echo in time to avoid forward masking. They emit short duration, broadband, downward frequency modulated (FM) signals separated by relatively long periods of silence. In contrast, bats using HDC echolocation emit long duration, narrowband calls dominated by a single constant frequency (CF) separated by relatively short periods of silence. HDC bats separate pulse and echo in frequency by exploiting information contained in Doppler-shifted echoes arising from their movements relative to background objects and their prey. HDC echolocators are particularly sensitive to amplitude and frequency glints generated by the wings of fluttering insects. We hypothesize that narrowband/CF calls produced at high duty cycle, and combined with neurobiological specializations for processing Doppler-shifted echoes, were essential to the evolution of HDC echolocation because they allowed bats to detect, lock onto and track fluttering targets. This advantage was especially important in habitats with dense vegetation that produce overlapping, time-smeared echoes (i.e. background acoustic clutter). We make four specific, testable predictions arising from this hypothesis.Key words: Chiroptera, calling behaviour, signal design, Yinpterochiroptera, Yangochiroptera, flutter detection, Doppler shift compensation. Fig.1A-C). For the purpose of this paper, we define LDC bats as those producing signals with a duration <25% of their signal period during the search phase of echolocation. Most LDC bats produce echolocation calls with their larynx, although a handful of species in the family Pteropodidae use tongue clicks (Griffin et al., 1958;Yovel et al., 2010).HDC bats avoid auditory masking by separating pulse and echo in frequency, allowing them to broadcast calls and receive echoes at the same time (Schuller, 1974;Schuller, 1977). HDC bats take advantage of information contained in Doppler-shifted echoes generated by the relative movements of bat and target, including acoustic glints generated by the wingbeats of fluttering insects. Echolocation calls of HDC bats consist of a long CF component followed by a brief, downward FM sweep. In some species, the initial portion of the call also contains a short, upward FM sweep (Henson et al., 1987; Jones and Rayner, 1989). Narrowband calls of HDC bats are typically multi-harmonic with the highest signal energy in the second acoustic element (Pye and Roberts, 1970;Schnitzler and Denzinger, 2011). HDC bats emit long duration calls (e.g. 10 to >50ms) relative to their call period ( Fig.1D-F). We operationally define HDC bats as those whose signal durations are ≥25% of...

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Section: The Journal Of Experimental Biologymentioning

confidence: 99%

Section: Advantages Of Hdc Echolocationmentioning

confidence: 99%

mentioning

confidence: 99%

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Evolution of high duty cycle echolocation in bats

Fenton

Faure

Ratcliffe

2012

Journal of Experimental Biology

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112

129

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“…Overall, these changes suggest increased time and effort spent searching for and attempting to capture each prey item, and increased occurrence of pauses. Post-capture pauses during echolocation may be used for prey-handling in some bat species (Acharya and Fenton, 1992;. If the same is true for sperm whales, the increased number of transitions into pause state during airgun exposure may indicate increased time spent manipulating and handling prey or possibly increased prey capture success rate.…”

Section: Discussionmentioning

confidence: 99%

“…After a buzz, bats generally pause echolocation click production for a period of several hundred milliseconds to several seconds (Griffin et al, 1960;Kalko and Schnitzler, 1989;Hartley, 1992b;Kalko, 1995;Moss and Surlykke, 2001;Hiryu et al, 2007). The mean duration of the post-buzz pause is often longer after successful captures than after unsuccessful ones (Acharya and Fenton, 1992;. This increase in pause duration may be related to time required for prey handling; however, found that pause duration did not increase as prey size (and thus inferred handling time required) increased.…”

Section: Introductionmentioning

confidence: 99%

Echolocation-based foraging by harbor porpoises and sperm whales, including effects of noise and acoustic propagation

DeRuiter¹

2008

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In this thesis, I provide quantitative descriptions of toothed whale echolocation and foraging behavior, including assessment of the effects of noise on foraging behavior and the potential influence of ocean acoustic propagation conditions on biosonar detection ranges and whale noise exposure. In addition to presenting some novel basic science findings, the case studies presented in this thesis have implications for future work and for management.In Chapter 2, I describe the application of a modified version of the Dtag to studies of harbor porpoise echolocation behavior. The study results indicate how porpoises vary the rate and level of their echolocation clicks during prey capture events; detail the differences in echolocation behavior between different animals and in response to differences in prey fish; and show that, unlike bats, porpoises continue their echolocation buzz after the moment of prey capture.Chapters 3-4 provide case studies that emphasize the importance of applying realistic models of ocean acoustic propagation in marine mammal studies. These chapters illustrate that, although using geometric spreading approximations to predict communication/target detection ranges or noise exposure levels is appropriate in some cases, it can result in large errors in other cases, particularly in situations where refraction in the water column or multi-path acoustic propagation are significant.Finally, in Chapter 5, I describe two methods for statistical analysis of whale behavior data, the rotation test and a semi-Markov chain model. I apply those methods to test for changes in sperm whale foraging behavior in response to airgun noise exposure. Test results indicate that, despite the low-level exposures experienced by the whales in the study, some (but not all) of them reduced their buzz production rates and altered other foraging behavior parameters in response to the airgun exposure. Sincere thanks also to the many other people who have helped with data collection and analysis over the course of my graduate work, and also to everyone who offered comments on drafts of this thesis. More detailed acknowledgments can be found at the end of each chapter, but here I would especially like to thank the following. Thesis Objectives and Chapter 1 OverviewThe goal of my thesis research has been to provide quantitative descriptions of toothed whale echolocation and foraging behavior (Chapters 2 and 5), including assessment of the effects of noise on foraging behavior (Chapter 5) and the potential influence of ocean acoustic propagation conditions on biosonar detection ranges (Chapter 3) and whale noise exposure (Chapter 4). I have focused on two study species, the harbor porpoise (Phocoena phocoena, Chapters 2-3) and the sperm whale (Physeter macrocephalus, Chapters 4-5).The following sections present background information relevant to the research presented in the rest of the thesis, beginning with a review of previous research on the use of echolocation by foraging animals. This review is followed by b...

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