BIOACOUSTICSTable of Contents: Volume 11
BIOACOUSTICS
T. Kingston, G. Jones, Z. Akbar & T. Kunz (2000). Social calls in clear-winged woolly bats Kerivoula pellucida from Malaysia. Bioacoustics 11(1): 1-16
Abstract
Kerivoula pellucida is a small (4.5 g) vespertilionid bat, which forages in the understorey of tropical rainforests in Southeast Asia. Most echolocation signals are characteristic for the subfamily (very high-frequency, broadband FM calls (sweeping down from 178 kHz to 58 kHz) of low intensity and short duration (< 3.0 ms)), but this species also produces stereotypical calls of a markedly different structure. The arrangement of signal elements in these calls is unusual, and we present here a detailed analysis of calls from thirteen adult individuals (nine males and four females). These multiharmonic calls are of much lower frequency (fundamental peak frequency of 36 kHz), higher intensity and longer duration (12.0 ms) than the orientation calls, and are composites comprising a long quasi-constant frequency (QCF) syllable followed by an upward frequency modulated sweep (UFM). From considerations of signal design and preliminary field observations, we consider possible functions of these calls.
Keywords: Chiroptera, communication, echolocation.
T.J.S Balsby (2000). The function of song in Lesser Whitethroats Sylvia communis. Bioacoustics 11(1): 17-30
Abstract
To test the mate attraction hypothesis and the territory defence (establishment) hypothesis in the Whitethroat Sylvia communis, I studied the pattern of vocal activity in the different phases of the breeding cycle in 1995 and 1996. Furthermore the response of unmated and mated males to playback was studied in 1997. The 1ow “perch song” activity and “flight song” activity of mated males compared to unmated males suggest that song was used in mate attraction. The perch and flight song activity in the morning tended to increase during the season but only significantly in 1996. The perch song was also used in territorial defence as suggested by unmated males responding to the playback with increased song activity. The diving song was apparently used in courtship of the female, since most diving songs were directed towards females. In mated males the dscharp-call was the most frequent vocal behaviour and mated males primarily used this call in response to playback. The more discreet vocal behaviour of mated males suggests that males use a silent strategy.
Keywords: song function, silent strategy.
P.L. Edds-Walton (2000). Vocalisations of Minke Whales Balaenoptera acutorostrata in the St. Lawrence Estuary. Bioacoustics 11(1): 31-50
Abstract
Recordings of vocalizations in the presence of minke whales Balaenoptera acutorostrata were made from a bottom-mounted hydrophone in the St. Lawrence Estuary, a feeding area for some members of the Northwest Atlantic population. Minke whale activity was observed from a hillside hut and notes were taken with regard to position and swimming direction throughout each recording. The vocalizations were correlated consistently with the occurrence of minkes and sequential sound levels were commensurate with the whale's relative proximity to the hydrophone. Minke calls were heard in 51% of the recordings examined in detail; calling rates were low (0.1 sounds/min-3.6 sounds/min with multiple individuals). The predominant call was a 0.4 sec downsweep in frequency, beginning at 100-200 Hz (median = 118 Hz) and ending below 90 Hz (median = 80 Hz). The change in frequency was variable, between 20 and 70 Hz (median = 42 Hz). Frequency and temporal characteristics of the vocalizations were similar to those recorded from Antarctic minkes by Schevill and Watkins (1972). Comparisons of the minke downsweep with those from the closely related finback whale B. physalus, which is also common in the area, indicated that minke whale calls had higher initial frequencies, greater changes in frequency, and shorter call durations.
Keywords: Acoustic censusing, bioacoustics, baleen whale
T. Aubin, F. Rybak & B. Moulin (2000). A simple method for recording low-amplitude sounds: application to the study of the courtship song of the fruit fly Drosophila melanogaster. Bioacoustics 11(1): 51-67
Abstract
Some acoustic signals produced by small insects are very low in amplitude and attenuate rapidly with distance. To achieve high quality recordings with such signals, the use of specialized microphones or of sound insulation chambers is necessary. This paper presents a simple and efficient method for the recording of acoustic signals emitted by small sources. Its principle is based upon the use of two simultaneous digital recordings from two microphones: one records the ambient noise while the other records the ambient noise plus the signal to analyse. Both these recordings are converted into digital files and then a simple subtraction between the two isolates the signal with a good signal-to-noise ratio. With this method of background noise removal, the recording of low amplitude sounds in an uninsulated room with common microphones becomes possible. We have applied this method to the study of 12 complete courtships of Drosophila melanogaster and particularly to the analysis of pulse sounds produced by the male in presence of a female. The study focuses mainly on the rhythm of production of pulse trains over the course of the courtship.
Keywords: Drosophila melanogaster, low-amplitude sound recording, background noise removal, courtship song.
D.J. Mennill & L.M. Ratcliffe (2000). A field test of Syrinx sound analysis software in interactive playback. Bioacoustics 11(1): 77-86
Abstract
Syrinx is a newly developed PC-based software package designed for interactive playback of animal vocalizations and for digital sound recording and analysis in the lab or in the field. Syrinx permits flexible modeling of complex vocal interactions in an interactive playback setting. Large numbers of sounds can be stored on disk as digital wave files for instant recall in the field. The playback trial timer and real-time scrolling spectrographic display of microphone input facilitate the tailoring of playback responses to subtle changes in the vocalizations of playback subjects. Based on our field test of this software in an interactive playback experiment with Black- capped Chickadees Poecile atricapillus, we conclude that Syrinx is a versatile and user-friendly tool for performing interactive playback with a minimum of equipment.
K.A. Cortopassi & J.W. Bradbury (2000). The comparison of harmonically related rich sounds using spectrographic cross-correlation and principal components analysis. Bioacoustics 11(2): 89-127
Abstract
We explore the effectiveness of spectrographic cross-correlation (SPCC) combined with principal coordinates (PC0) analysis as a method for sound comparison. We do this using synthetic sounds modeled after the individually-distinctive, harmonically-rich contact calls of wild orange-fronted conures Aratinga canicularis. Calls with acoustic properties similar to Aratinga contact calls are common in other taxa including non-oscine birds, primates and cetaceans. We generated signals with known variations in time-frequency pattern, duration, noise level, harmonic content and harmonic weighting, and applied SPCC-PCO analysis to obtain an ordering of sounds in n-dimensional space. We find that shared time-frequency patterns dominate the positioning of sounds in PCO space. This was true despite high variability in signal-to-noise ratio (from -60 to +40 dB) and duration (150-275 ms). Furthermore, inclusion of naturally-weighted harmonics (versus fundamentals only) enhances, rather than obscures, the separation of call types. We conclude that SPCC-PCO is an effective method for sorting sounds based on overall time-frequency pattern. In addition, the resulting PCO measures can be used in statistical tests of association with extrinsic variables. The method is thus an effective starting point for examining most bioacoustic hypotheses.
Keywords: spectrographic cross-correlation, principal coordinates analysis, sound comparison, parrot vocalizations, sound synthesis
S. Veitl, S. Begall & H. Burda (2000). Ecological determinants of vocalization parameters: The case of the coruro (Spalacopus cyanus, Octodontidae), a fossorial social rodent. Bioacoustics 11(2): 129-148
Abstract
Coruros Spalacopus cyanus, social fossorial rodents from Chile, use a complex acoustic repertoire with eleven different true vocalisations and one mechanical sound in various behavioural contexts. The complex of contact calls is particularly well differentiated. Juvenile coruros produced six true vocalisations of which four were structurally identical to adult calls. One vocalization had components of two adult sounds and one occurred only in juvenile animals. Certain calls from the adult repertoire were lacking. The frequencies of sounds of juveniles were considerably higher than those of adults, with many sounds reaching the ultrasonic range. Nevertheless, pure ultrasonic sounds were not recorded. The frequencies of the analysed sounds of coruros extended from 0.17 to 20.33 kHz with dominant frequency components between 0.17 and 10 kHz. The acoustic properties of calls are suitable for transmission above and below ground, thus providing further indirect evidence that coruros are not strictly confined to an underground way of life. Indeed, the great variability of frequency ranges, with lower frequencies always being included, reflects a specialization for communication in variable acoustic environments. The most distinctive and unique vocalization of coruros is the long duration musical trilling (lasting up to two minutes), which is a long-distance call emitted in alarm and arousal contexts. Recordings of this call from natural burrows in the field in Chile showed similar structural features to vocalisations from captive colonies in the laboratory. Our findings provide a further example of matching physical properties of vocalisations to the acoustic conditions of the habitat. However, vocalisations in subterranean rodents consist almost exclusively of short-distance calls, the trilling of coruros being the notable exception. Since the selective pressure of the acoustic environment upon the evolution of short-distance vocalisations is probably minimal, we suggest that during their evolution, subterranean mammals have matched their vocalisations primarily to their hearing range and not directly to the acoustics underground. Hearing probably has been the primary target of natural selection, serving not only for communication but also for detection of predators (and, in carnivores, of prey).
Keywords: subterranean rodent, acoustic communication, vocalisations, Spalacopus, alarm call
I. Hahn & H. Mattes (2000). Vocalisations of the Másafuera Rayadito Aphrastura masafuerae on Isla Alejandro Selkirk, Chile. Bioacoustics 11(2): 149-158
Abstract
Three vocalization types of the másafuera rayadito Aphrastura masafuerae are described using sonograms: common call, alarm call, and song. They are analysed according to their structure, kHz-frequency, duration and time of day. The common call can be uttered singly or in a series with regular pauses. This intensive call is heard even through fog and wind and seems to be used for contacting the partner as well as signalling the home range to neighbours. The alarm call is a continuous series of similar syllables without pauses. The song is given exclusively in the morning before sunrise by only one individual of the pair. It has one type of phrase only, which is repeated. Phrases are interrupted by regular pauses. These vocalization types are clearly different from each other, but also have features in common: the monotonous structure, repetition of units and temporal frequency of elements.
Keywords: Vocalization, Song description, Aphrastura masafuerae, Ovenbirds, Juan Fernandez Islands
A.M.R. Terry, P.K. McGregor & T.M. Peake (2001). A comparison of some techniques used to assess vocal individuality. Bioacoustics 11(3): 169-188
Abstract
In this paper we assess the applicability to the extraction of conservation information of three commonly used methods of examining the individuality of acoustic signals: qualitative assessment, spectrographic cross-correlation and discriminant function analysis. We tested the ability of human observers, with different levels of training, to sort and match spectrograms of bittern and fantail warbler vocalisations. This simulated a census and monitoring situation. We found that training had little effect on accuracy and high inter-individual variation made generalizations difficult. Cross- correlation provides an objective measure of similarity but was shown to be sensitive to background noise and the signal structure being compared. Discriminant function analysis is a powerful descriptor of individuality and functions well when developing predictive tools. However it should not be used to count a population and its use is constrained to re-identification in populations of known size.
Keywords: Individuality, cross-correlation, qualitative analysis, discriminant function, conservation.
S.C. Burnett, K.A. Kazial & W. Mitchell Masters (2001). Discriminating individual big brown bat (Eptesicus fuscus) sonar vocalizations in different recording situations. Bioacoustics 11(3): 189-210
Abstract
Previous studies have found variability and individual distinctiveness in the echolocation calls of bats. We consider two implications of individually distinct echolocation calls: 1) whether bats may be able to use such variation to recognise familiar conspecifics, and 2) whether investigators could use such variation to identify known individuals or to census populations. We compared the discriminability of the echolocation calls of big brown bats (Eptesicus fuscus) recorded in three situations: (a) while held in the hand, (b) while perched on a platform, and (c) while flying in an anechoic chamber. Using variables describing each sonar call, we employed discriminant function analysis (DFA) to assign calls to recording situation or to bat. Discrimination of calls by recording situation was largely unsuccessful, although flying calls could be distinguished from platform calls. Assignment of calls to individual bat across recording situations yielded 72% success, and, within a given recording situation, yielded 87% success. Stepwise DFA reduced the number of variables needed to discriminate between individuals with only a slight decrease in correct classification. These results suggest that bats (or researchers) may be able to use the information contained in the echolocation calls for individual recognition. Individual distinctiveness raises the possibility of censusing bats by sound. We used cluster analysis in an attempt to determine whether, given a sample of calls from an unknown number of bats, a reasonable estimate of the number of bats could be obtained. Results were unsatisfactory, suggesting that cluster analysis probably will not permit acoustic censusing of bats in the field.
Keywords: Eptesicus fuscus, big brown bat, echolocation, individual discrimination
J.M. Terhune, S.R. Healey & H.R. Burton (2001). Easily measured call attributes can detect vocal differences between Weddell seals from two areas. Bioacoustics 11(3): 211-222
Abstract
Underwater vocalisations of Weddell seals Leptonychotes weddellii were recorded approximately 1400 km apart at Casey and Davis, Antarctica. Recordings were made during the 1992 and 1997 breeding seasons at Davis and during the 1997 season at Casey. Two observers independently analysed four attributes (start and end frequency, duration and number of elements) of narrow bandwidth calls from each location and time. There were few observer differences when the calls were grouped into four broad types (Trills, Descending Whistles, Ascending Whistles and Mews). Amending Whistles and Mews were rare at Casey but common at Davis. Descending Whistles occurred significantly more often at Davis. Except for Trills, discriminant function analyses indicated less variation between the call attributes at Davis in 1992 and 1997 than between either of the Davis data sets and that from Casey. Vocalization differences between Weddell seals from different areas can be detected by measuring common attributes of narrow bandwidth calls.
Keywords: Leptonychotes weddellii, vocalisations, geographic variation
H.-H. Bergmann & H. Düttmann (2001). Can testosterone induce the male whistle-shake call in female shelducks Tadorna tadorna? Bioacoustics 11(4): 265-276
Abstract
We investigated by application of testosterone-proprionate whether females of the dimorphic Shelduck Tadorna tadorna are capable of producing vocalisations typical of the male sex. We found that hormone-treated females generated the whistle-shake call, an epigamic vocalization pattern of male Shelducks. Although the female whistle- shake call was male-like in its syntactic form, we observed significant differences in both the phonetic and temporal characteristics of male and female whistle-shake calls. None of the testosterone-treated females was found to produce real male-typical elements. All whistle-shake calls of these females consisted of elements which are also used in calls of untreated females, e.g. the agagak-call. The present endings indicate that the sexual dimorphism in Shelduck vocalisations is not due to early organising actions of sex hormones influencing the differentiation of the brain. It results mainly from adult sex differences in the endogenous testosterone production. Only males produce testosterone in considerable amounts. The inability of testosterone-treated female Shelducks to generate male-typical element might be caused by limitations in the sound-producing organ, the syrinx. Male Shelducks have associated with the syrinx a large resonating chamber, the bulla ossea, which is lacking in females.
Keywords: Tadorna tadorna, testosterone, female vocalisations, syrinx, hormonal control
S. Cerchio & M. Dahlheim (2001). Variation in feeding vocalizations of humpback whales (Megaptera novaeangliae) from southeast Alaska. Bioacoustics 11(4): 277-295
Abstract
Vocalizations of feeding humpback whales from southeast Alaska were analyzed to characterize quantitatively the predominant vocalization associated with feeding and assess variation among vocalizations. Whales uttered series of cries similar in acoustic structure to those described previously as stereotyped, rhythmic 'feeding calls'. Individual cries ranged in duration from 0.4 to 8.2 sec. (median = 2.6 sec). Cries typically had a short, strongly frequency modulated (FM) introductory and ending component (labeled Section A and C, respectively). Cries had relatively little FM over the main body of the call (labeled Section B) which ranged in fundamental frequency from 360 to 988 Hz (median = 553 Hz) and sometimes exhibited a frequency oscillation over a bandwidth of approximately 16 to 65 Hz. Principle components analysis indicated that most variation in the data-set (over 35%) could be attributed to measures of absolute frequency, however a substantial amount of variation was also due to other acoustic parameters such as duration, frequency oscillation and average slope of cry sections A and C. Within series, cries were stereotyped and varied little, whereas there was statistically significant variation in cries between series. Furthermore, overlapping cries, which are considered to represent the vocalizations of different individuals, varied significantly. These results suggest that whales may produce individually specific cries, and we propose two alternative hypotheses to account for our observations: 1) cries may carry individual signature information, and 2) simultaneously vocalizing animals may actively mismatch cries to maximize a herding elect on prey.
Keywords: humpback whale, foraging, feeding vocalization, individual variation, multivariate