Bat Echolocation Researc h - Bat Conservation International

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Despite the uniformity of call design in phyllostomid bats, certain trends occur, which, if confirmed, could improve the use of acoustic information in this group. For instance, as in aerial insectivorous bats (see summary in Jones 1999; Schnitzler and Kalko 1998), there is a trend for higher frequencies in smaller leaf-nosed bats than in larger species (e.g., Thies et al. 1998). Furthermore, there is a trend towards longer pulse intervals with increasing body size. In addition to body size, habitat parameters such as the distance to clutter also play important roles in shaping pulse design and pattern of emissions. As for aerial insectivores, leaf-nosed bats flying in the open emit longer calls at longer inter-pulse intervals than in more closed habitats (e.g., Jones 1999; Schnitzler and Kalko 1998). This relationship holds true across a variety of feeding guilds including frugivorous and insectivorous bats. There are currently only a few data from a few species available and because of this, most results are limited to preliminary, qualitative assessments. Thus the true extent of intra- and interspecific variability in call design and pulse pattern has yet to be determined. We need quantitative, in-depth studies of a range of different-sized species with different ecologies. It is likely that for many phyllostomid bats, assessment of best or peak frequency of search calls, number of harmonics, sweep rate, and pulse interval will allow further classification. The results of those studies can then be integrated into modern analysis tools such as discriminant function analysis or multivariate statistics and neural networks to search for characteristic, species-specific patterns (e.g., Jones and Parsons, this volume; Parsons 2001) and probably also to link strongest frequency with body size. The prerequisites for quality recordings of phyllostomid echolocation calls are highly sensitive microphones with an excellent signal-to-noise ratio and a good frequency response in the higher-frequency range (> 50 kHz). Good-quality, on-axis sound recordings reduce the ambiguities inherent in incomplete recordings. Low signal-to-noise ratios and limited frequency range quickly lead to the loss of harmonics and of other characteristic call parameters, such as the energy distribution within a call. Furthermore, because of the importance of call structure for species identification, recording and analysis of phyllostomid echolocation calls require the preservation of harmonics. With an extended database, it is likely that acoustic monitoring of leaf-nosed bats will contribute more to acoustic surveys and monitoring programs. Already it is clear that some species such as P. hastatus are well suited for acoustic surveys because of their loud, low-frequency calls. Phyllostomid echolocation could also be used for acoustic surveillance of nectarivorous and frugivorous bats visiting flowers and fruits. By placing microphones close to potential food items, the frequency and duration of the visits and probably also the size classes of the visiting bats could be measured. a b c Figure 9: Search sequence of a: Lophostoma silvicolum flying close to clutter (vegetation), b: Artibeus jamaicensis flying in open space near a fig tree, and c: Phyllostomus hastatus flying in open space above the canopy. ACKNOWLEDGMENTS I thank the Smithsonian Tropical Research Institute in Panama for excellent working conditions and the many bat people who have joined me in my endeavors over the years. In particular, I wish to thank Hans-Ulrich Schnitzler for his continuous support, Charles Handley for introducing me to the fascinating world of Neotropical bats, and Marco Tschapka for his valuable comments on the manuscript. 68 Bat Echolocation Research: tools, techniques & analysis
LITERATURE CITED BARCLAY, R. M. R., M. B. FENTON, M. D. TUTTLE, and M. J. RYAN. 1981. Echolocation calls produced by Trachops cirrhosus (Chiroptera: Phyllostomidae) when hunting for frogs. Canadian Journal of Zoology 59:750-753. BELWOOD, J. J. 1988. Foraging behavior, prey selection and echolocation in phyllostomine bats (Phyllostomidae). Pp. 601-605 in Animal sonar systems (P. E. Nachtigall and P. W. B. Moore, eds.). Plenum Press, New York, Volume 156. BROSSET, A., P. CHARLES-DOMINIQUE, A. COCKLE, J. F. COS- SON, and D. MASSON. 1996. Bat communities and deforestation in French Guiana. Canadian Journal of Zoology 74: 1975-1982. FENTON, M. B., ET AL. 1992. Phyllostomid bats (Chiroptera: Phyllostomidae) as indicators of habitat disruption in the Neotropics. Biotropica 24:440-446. FENTON, M. B. 1995. Natural history and biosonar signals. Pp. 17-86 in Hearing by bats (R. R. Fay and A. N. Popper, eds.). Springer, Heidelberg, Germany. FINDLEY, J. S. 1993. Bats: a community perspective. Cambridge University Press, Cambridge, United Kingdom. Gannon, W. L., and W. Bogdanowicz, eds. 2000. Contributions to the study of bats: field use of acoustic detectors. Acta Chiropterologica, Volume 2). HOWELL, D. J. 1974. Acoustic behavior and feeding in glossophagines bats. Journal of Mammalogy 55:293-308. JONES, G. 1999. Scaling of echolocation parameters in bats. Journal of Experimental Biology 202:3359-3367. KALKO, E. K. V. 1998. Organisation and diversity of tropical bat communities through space and time. Zoology: analysis of complex systems 101:281-297. KALKO, E. K. V., and M. CONDON. 1998. Echolocation, olfaction, and fruit display: how bats find fruit of flagellichorous cucurbits. Functional Ecology 12:364-372. KALKO, E. K. V., C. O. HANDLEY JR., and D. HANDLEY. 1996. Organization, diversity, and long-term dynamics of a Neotropical bat community. Pp. 503-553 in Longterm studies in vertebrate communites (M. Cody and J. Smallwood, eds.). Academic Press, Los Angeles, California. KALKO, E. K. V., and H.-U. SCHNITZLER. 1998. How echolocating bats approach and acquire food. Pp. 197-204 in Bats: phylogeny, morphology, echolocation, and conservation biology (T. H. Kunz and P. A. Racey, eds.). Smithsonian Institution Press, Washington, D.C. KOOPMAN, K. F. 1993. Order Chiroptera. Pp. 137-241 in Mammal species of the world, a taxonomic and geographic reference (D. E. Wilson and D. M. Reeder, eds.). 2nd ed. Smithsonian Institution Press, Washington, D.C. LEIGH, E. G. 1999. Tropical forest ecology. Oxford University Press, Oxford, United Kingdom. O’FARRELL ,M., and B. W. MILLER. 1997. A new examination of echolocation calls of some Neotropical bats (Emballonuridae and Mormoopidae). Journal of Mammalogy 78:954-963. O’FARRELL, M., and B. W. MILLER. 1999. Use of vocal signatures of inventory of free-flying Neotropical bats. Biotropica 31:507-516. PARSONS, S. 2001. Identification of New Zealand bats (Chalinolobus tuberculatus and Mystacina tuberculata) in flight from analysis of echolocation calls by artificial neural networks. Journal of Zoology, London 253:447-456. SCHNITZLER, H.-U., and E. K. V. KALKO. 1998. How echolocating bats search for food. Pp. 181-196 in Bats: phylogeny, morphology, echolocation, and conservation biology (T. H. Kunz and P. A. Racey, eds.). Smithsonian Institution Press, Washington, D.C. SCHNITZLER, H.-U., and E. K. V. KALKO. 2001. Echolocation behavior of insect-eating bats. BioScience 51:557- 569. SIMMONS, J. A., and R. A. STEIN. 1980. Acoustic imaging in bat sonar: echolocation signals and the evolution of echolocation. Journal of Comparative Physiology 135:61-84. SIMMONS, N. B., and R. S. VOSS. 1998. The mammals of Paracou, French Guiana: a Neotropical rainforest fauna. part I: bats. Bulletin of the American Museum of Natural History 237:1-219. THIES, W., E. K. V. KALKO, and H.-U. SCHNITZLER. 1998. The roles of echolocation and olfaction in two Neotropical fruit-eating bats, Carollia perspicillata and C. castanea, feeding on Piper. Behavioral Ecology and Sociobiology 42:397-409. Section 2: Acoustic Inventories 69
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Bat Echolocation R esearc h tools,
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TABLE OF CONTENTS CO N T R I B U T
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CONTRIBUTING AUTHORS Ingemar Ahlén
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I N T R O D U C T I O N Bat Echoloc
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BAT NATURAL HISTORY AND ECHOLOCATIO
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species (Thies et al. 1998). Before
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y the African bat Cardioderma cor (
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participants in this symposium. Sin
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INTRODUCTION Bat detectors convert
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less sensitive than a heterodyne de
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14 advanced computer software made
Page 23 and 24: COMMUTING AND FORAGING BEHAVIOR Fig
Page 25 and 26: NIGHTLY ACTIVITY BASED ON CAPTURE W
Page 27 and 28: 20 Recordings of echolocation calls
Page 29 and 30: 22 and analyzing echolocation calls
Page 31 and 32: 24 Resource partitioning in rhinolo
Page 33 and 34: Section 2 ACOUSTIC INVENTORIES ULTR
Page 35 and 36: f tuned = f bat . As an example, wi
Page 37 and 38: The chance of detection also depend
Page 39 and 40: ent species. But in the field, it i
Page 41 and 42: Section 2: Acoustic Inventories Fig
Page 43 and 44: Suchflug und Richtungskarakteristik
Page 45 and 46: Journal N Percentage of total (%) A
Page 47 and 48: ential power of data. Hayes (1997)
Page 49 and 50: For instance, we recorded a single
Page 51 and 52: KALCOUNIS, M. C., K. A. HOBSON, R.
Page 53 and 54: and McCracken (this volume) discuss
Page 55 and 56: using other methods (Fig. 4). Ident
Page 57 and 58: Figure 6: Schematic diagram of diff
Page 59 and 60: AMPLITUDE-RELATED PARAMETERS Loudne
Page 61 and 62: tereri. Hand netting on the followi
Page 63 and 64: flight in bats. Pp. 93-108 in Bat b
Page 65 and 66: difficult to understand why the aut
Page 67 and 68: Figure 5: Call sequence showing the
Page 69 and 70: function analysis and artificial ne
Page 71 and 72: species identifications. Echolocati
Page 73: tially from calls emitted in the op
Page 77 and 78: HETERODYNE AND TIME-EXPANSION METHO
Page 79 and 80: 74 QUANTIFYING SOUND FEATURES To qu
Page 81 and 82: Figure 14: Pulse rhythm diagrams fo
Page 83 and 84: A FINAL WORD Figure 21: Heterodyne
Page 85 and 86: 80 INTRODUCTION Ultrasonic detector
Page 87 and 88: 82 munity was uncovered when ultras
Page 89 and 90: 84 INTRODUCTION Being nocturnal, ba
Page 91 and 92: A Figure 2: Surveys of bat activity
Page 93 and 94: LITERATURE CITED Figure 5A: Pipistr
Page 95 and 96: 90 In order to set a foundation for
Page 97 and 98: 92 diagram, e.g., a spectrogram, fo
Page 99 and 100: ecording time of the cassette. When
Page 101 and 102: 96 detail is not helpful for specie
Page 103 and 104: tification, providing the immediate
Page 105 and 106: spectrum, which is a graph of the e
Page 107 and 108: since there is no evidence that the
Page 109 and 110: 104 Figure 5: Different modes in se
Page 111 and 112: currently the case. Even at the sim
Page 113 and 114: 108 INTRODUCTION Much of our knowle
Page 115 and 116: Figure 1: On-axis search call recor
Page 117 and 118: 112 SUMMARY To summarize, flight-ca
Page 119 and 120: 114 SIGNAL PROCESSING TECHNIQUES FO
Page 121 and 122: al a situation as possible. Ideally
Page 123 and 124: For all networks, correct identific
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ety of London 69:111-128. JONES, G.
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eveal species-specific vocal signat
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Figure 6: Comparison of Myotis cili
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ity of the two Myotis spp. calls (F
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Section 4 RESOURCES, RESEARCH, AND
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A The data extracted from the diffe
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used. This theoretically makes it p
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ple, will not show individual calls
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Figure 10: Fast Fourier transform p
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ACKNOWLEDGEMENTS I thank the organi
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munity (now called the European Uni
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staff to collect all of the require
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and van Parijs 1993). Early studies
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Figure 5: Variation in the echoloca
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47:60-69. JONES, G., and R. D. RANS
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RECORDING TECHNIQUES Section 4: Res
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monly observed with such broadband
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ple sonograms and power spectra can
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ences between Myotis californicus a
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intensity). Our ability to detect m
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• The detector is kept stationary
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the number of bat passes in real ti
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SHERWIN, R. E., W. L. GANNON, and S
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tion trends, while they also raise
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