Acta Chiropterologica, 2(2): 127-144, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

The efficacy of Anabat ultrasonic detectors and harp traps for surveying microchiropterans in south-eastern Australia

ANGELA M. DUFFY, LINDA F. LUMSDEN¹, CATHERINE R. CADDLE, RYAN R. CHICK, and GRAEME R. NEWELL

Arthur Rylah Institute, Department of Natural Resources and Environment, P.O. Box 137, Heidelberg, Victoria 3084, Australia 1 Corresponding author: E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Insectivorous bats were surveyed using harp traps and ultrasonic bat detectors at 284 sites in three regions of Victoria, south-eastern Australia. Ten species were recorded in the Box-Ironbark region, 16 species in North-east Victoria, and 14 species in Gippsland. Detectors yielded more species records per site in the Box-Ironbark region (where forests are dry, open and fragmented), whereas harp traps were more successful in the North-east and Gippsland (where forests are generally denser and taller). Results suggest that detectors are likely to be most effective where there are fewer potential species to be considered in call identification, and that harp traps are likely to be most effective in areas of relatively dense vegetation with discrete flyways. Overall the two techniques were complementary, as they were subject to different biases in the suite of species most likely to be recorded. A library of over 250 ultrasonic reference calls was compiled as the basis for the identification of unknown calls. There was a high level of variation in the search-phase calls produced by each species, and between 15 and 40 reference calls were considered necessary to gain an adequate representation of this variation within the study area. This high level of intra-specific variability, combined with a considerable inter-specific overlap in call characteristics, resulted in a conservative approach to call identification. The development of an identification key was useful in alleviating problems of subjectivity and lack of repeatability associated with qualitative methods of call identification. Investigation of optimal sampling periods revealed that between three and five hours of recording after sunset was required to obtain records of approximately 70% of the species identified from a complete night of detector data. Suggestions are provided for the design of future surveys using harp traps and detectors.

Key words: Microchiroptera, survey methods, ultrasonic detectors, Anabat, harp traps, Victoria, Australia

Acta Chiropterologica, 2(2): 145-153, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

The efficacy of acoustic techniques to infer differential use of habitat by bats

RICHARD E. SHERWIN¹, WILLIAM L. GANNNON², and SHAUNA R. HAYMOND³

1 Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. 2 Division of Mammals, Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131, USA 3 Holistic Wildlife Services Biological Consulting, 104 Spring Drive SE, Rio Rancho, NM 87124, USA

The use of acoustic detectors to investigate differential use of habitat by bats has become increasingly common. However, in many of these studies, authors failed to clearly articulate assumptions a priori. For example, spatial and temporal scales were rarely defined. True replication is rarely reported, suggesting that authors assume that these systems are both spatially and temporally static. In this study, we attempted to clearly identify underlying assumptions of this technique, thereby limiting level of inference to a clearly defined and repeatable degree. We followed strict assumptions beforehand and were able to classify bat calls into guilds based on acoustic data. Lack of experience in acoustic identification by technicians did not affect the outcome, as guilds were based on bat call sequences following strict rules of classification. Individuals in guilds were not randomly distributed across sample locations. However, distribution of guild members did not suggest differential use of habitat, as within habitat variation was often greater than that observed among types of habitat. Explicitly stating assumptions before surveys were conducted 'protected' us from making incorrect inferences. We suggest that care be taken when attempting to infer differential use of habitat by bats using acoustic techniques.

Key words: Microchiroptera, acoustic monitoring, community ecology, detector, guild

Acta Chiropterologica, 2(2): 155-170, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

We review how time-expanded recordings and direct sampling of sound can be used to identify some bat species from their vocalizations, and how such methods may be applied to field surveys of bat activity. Some species emit distinctive social calls that permit identification, and social calls may be individually distinctive within species. Analysis of echolocation calls can identify cryptic species that are very similar in appearance, but differ in echolocation calls. Echolocation calls vary according to ecology and morphology both across and within species. Although some species emit distinctive echolocation calls, great care must be used in the acoustic identification of other species, especially in cluttered habitats. Species identification from echolocation calls is best approached by quantitative analysis, such as discriminant function analysis (DFA) based on several measurements taken from calls. DFA gives an objective measure of confidence in species identification, and can be applied to surveys of habitat use providing that certain limitations are recognised. Discrimination of species from their echolocation calls may be improved by quantifying the shape of calls from their frequency-time course, and by using artificial neural networks. Feeding rates can be estimated in bat detector surveys, though not all terminal buzzes emitted prior to prey capture are associated with successful capture of prey. Time expansion and direct sampling methods retain more detail of individual echolocation calls than do other methods. Not only can these methods be used to a certain extent for species identification and habitat use studies, they remain the only suitable methods for describing call design in bats from a detailed bioacoustics perspective.

Key words: echolocation, social calls, discriminant analysis, neural networks, habitat use, feeding rates

Acta Chiropterologica, 2(2): 171-183, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

Contribution of acoustic methods to the study of insectivorous bat diversity in protected areas from northern Venezuela

JOSE OCHOA G.¹, MICHAEL J. O'FARRELL², and BRUCE W. MILLER³

1 Asociacion Venezolana para la Conservacion de Areas Naturales (ACOANA) / Wildlife Conservation Society, Apartado 69520, Caracas 1063-A, Venezuela; E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. 2 O'Farrell Biological Consulting, 2912 North Jones Boulevard, Las Vegas, NV89108, USA 3 Wildlife Conservation Society, 185th and Southern Boulevard, Bronx, NY 10460, USA

We present the results of an acoustic survey of aerial insectivorous bats conducted in four protected areas in northern Venezuela. These areas represent localities where the taxonomic composition of the bat communities was relatively well known. We conducted field surveys using the Anabat II detector and analysis system. We compared acoustic inventories with previous lists obtained with conventional sampling methods (principally mist nets). We identified 30 species acoustically (representing 15 genera of the families Emballonuridae, Noctilionidae, Mormoopidae, Vespertilionidae, and Molossidae) on the basis of vocal signatures. Nineteen of these were verified by capture and subsequent recording of released animals; the remainder were identified by comparison with verified vocalizations from other localities. An additional 11 unidentified but distinct taxa were recorded and are referred to here as 'sonotypes' (based on similarities in call structure to known species) representing eight genera of the families Emballonuridae, Vespertilionidae, and Molossidae. The short-term acoustic surveys nearly equaled or exceeded the known species richness at three of the four localities, and added two to nine species to previous lists from all locations; many of these bats correspond to taxa difficult to detect with conventional capture methods.

Key words: insectivorous bats, acoustic survey, Anabat, community inventory, technique comparison, Neotropics, protected areas, Venezuela

Acta Chiropterologica, 2(2): 185-196, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

Geographic variation in the echolocation calls of the hoary bat (Lasiurus cinereus)

MICHAEL J. O'FARRELL¹, CHRIS CORBEN², and WILLIAM L. GANNON³

1 0'Farrell Biological Consulting, 2912 North Jones Boulevard, Las Vegas, NV 89108, USA E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. 2 333 Enterprise Drive #16, Rohnert Park, CA 94928, USA 3 Division of Mammals, Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131, USA

Use of bat detectors to perform inventories, determine activity, and assess differential use of habitats has become a generally accepted method. However, there has been vigorous disagreement as to the level of efficacy, primarily relating to the ability to distinguish certain species and groups of species. The primary explanation suggested for the inability to identify certain species is due to the magnitude of intraspecific variation resulting in overlap among species, presumably compounded by geographic variation. Lasiurus cinereus has been identified as exhibiting the greatest degree of geographic variation including recent findings of distinct variation between populations in Hawaii and Manitoba. We find that claims of geographic variation have not been proven because of small sample size and lack of adequate description of method, including the behavior of the bat and the context during which bats were recorded. Previous geographical comparisons of species have relied on standard statistical methods that do not allow a comprehensive examination of the range in variation of diagnostic call parameters. We present data from a broad range of sites throughout mainland United States and Hawaii, and compare a multivariate statistical approach with repertoire plots of characteristic frequency versus call duration. Although we demonstrated a statistical finding of geographic variation in L. cinereus, small sample size, context, and behavior could not be discounted as the proximal cause of observed variation. The perceived variation across the geographic range that we sampled did not affect our ability to identify the species by call structure. We suggest methods for future studies of geographic variation.

Key words: acoustic identification, Anabat, echolocation, call structure, geographic variation, Lasiurus cinereus

Acta Chiropterologica, 2(2): 197-207, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

Community level support for the allotonic frequency hypothesis

DAVID S. JACOBS

Department of Zoology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

The allotonic frequency hypothesis proposes that some insectivorous bats increase their access to moths that can hear echolocation calls by using frequencies to which the ears of the moths are less sensitive. The hypothesis predicts that the frequencies of bat echolocation calls are positively correlated with the incidence of moths in the diet of these bats. Studies that have provided evidence in support of the allotonic frequency hypothesis have relied on data collected by a number of researchers, in a number of different ways and at different times. The aim of this study was to test the allotonic frequency hypothesis on a single African bat community so that data for the different species could be collected at more or less the same time and in the same way. This community consisted of three high duty cycle species, Cloeotis percivali, Hipposideros caffer, and Rhinolophus simulator, and two low duty cycle species, Miniopterus schreibersii and Scotophilus borbonicus. As predicted by the hypothesis, echolocation frequency was positively correlated with the proportion of moths in the diet of these bats. Echolocation frequency was also a better predictor of diet than wing morphology suggesting that the selection pressure exerted by moth hearing might have acted directly on call frequency and secondarily on wing morphology, as part of the same adaptive complex. These results suggest that structure of bat communities might be determined by prey defenses rather than by competition.

Key words: echolocation, diet, moths, wing loading, Hipposideridae, Rhinolophidae, Vespertilionidae

Acta Chiropterologica, 2(2): 209-213, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

Variability in sensitivity of Anabat II bat detectors and a method of calibration

DAVID J. LARSON and JOHN P. HAYES

Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Use of bat detectors can be an effective method of comparing relative amounts of activity of bats among areas. If multiple detectors are used, differences in sensitivity of detectors could bias results. We investigated the variability in sensitivity and field of detection of 14 Anabat II bat detectors. Levels of sensitivity varied among detectors, greatly affecting relative sizes of the fields of detection. Calibration using an ultrasonic signal source can minimize variability in sensitivity among detectors.

Key words: Anabat II, bat detectors, calibration, echolocation calls

Acta Chiropterologica, 2(2): 215-224, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

Choosing the 'correct' bat detector

M. BROCK FENTON

CBCB, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Direct field comparisons revealed that in any time period, a bat detecting system using zero-crossing period meter analysis (the Anabat II Bat Detector with Anabat ZCAIM and Anabat 6 software) detected significantly fewer bat echolocation calls than a time-expansion bat detecting system (Pettersson D980 detector with BatSoundPro software). Furthermore, the features of 81 echolocation calls (highest frequency, in kHz; lowest frequency, in kHz; duration, in ms) recorded and analyzed on both systems differed significantly. Regression analyses indicated no consistent, frequently unpredictable differences between Anabat and Pettersson values for the lowest frequencies in echolocation calls, but a significant correlation for their highest frequencies and durations. In a variety of field settings in Israel and in southern Ontario, Canada involving both foraging bats and bats emerging from a cave roost, the Pettersson system recorded echolocation calls not detected by the Anabat system. When many Myotis bats were emerging from a cave roost in Israel, the Anabat system did not detect the calls of a Rhinolophus species or those of another vespertilionid which were detected by the Pettersson system. The differences in performance between the two kinds of systems reflect differences in sensitivity and operation between zero-crossing period meters and time-expansion systems. Data on bat activity or echolocation calls detected and analyzed by a zero-crossing period meter system like Anabat are not as consistent or as reliable as those obtained by a time-expansion system like the Pettersson. Differences in performance of bat detectors coincide with considerable difference in costs, from about US$ 650 for an Anabat system, to over US$ 2,000 for a Pettersson system, which involves digital time-expansion. A time-expansion system involving a high speed tape recorder will cost over US$ 30,000. When it comes to bat detectors and analysis systems, the quality of data that will be obtained is a direct reflection of cost - buyers get what they pay for.

Key words: bat activity, echolocation calls, time-expansion, zero-crossing period meters

Acta Chiropterologica, 2(2): 225-236, 2000

PL ISSN 1508-1109 copyright Museum and Institute of Zoology PAS

Assumptions and practical considerations in the design and interpretation of echolocation-monitoring studies

JOHN P. HAYES

Department of Forest Science, 321D Richardson Hall, Oregon State University, Corvallis, OR 97331, USA E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Bat detectors increasingly are used in studies of the ecology and behavior of bats. A number of assumptions are implicit to these studies, although these assumptions rarely are stated explicitly and sometimes are not recognized by researchers. The strength of inference resulting from echolocation-monitoring studies is, in part, a function of the extent to which underlying assumptions are met. Recognition of underlying assumptions is thus an important facet of the design and interpretation of echolocation-monitoring studies. In this paper, I outline and discuss six key assumptions underlying most echolocation-monitoring studies. Accounting for sources of temporal, spatial, and sampling variation is key for designing robust studies and for meeting the assumptions underlying echolocation-monitoring studies.

Key words: echolocation, bat detectors, experimental design, inference, monitoring