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Bioacoustics Volume 14 issue 1 (2003)

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Bioacoustics Volume 14 issue 3 (2004)

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T. J. Hammond, W. J. Bailey & G. R. Hammond. (2003). An automatic acoustic response system for behavioural studies of duetting insects. Bioacoustics 14(1): 3-14

Abstract

We present a novel technique for interactive playback of response calls in duetting insects. Many insects, in particular the subfamily Phaneropterinae (Tettigoniidae: Orthoptera) achieve mate pairing through a duet, whereby the female produces a short reply following the male call. Our technique allows the researcher to mimic the female acoustic behaviour, by recognising the male call and producing a female reply within a relevant time frame. Once the generic temporal structure of the male call is known, the researcher may define one or more parts of the male call to be used as triggers for the production of the synthetic response. Sufficient flexibility exists in the system to be used for any species with temporally-structured duet calls.

Keywords: acoustic behaviour, insect, duet, playback

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B. K. Branstetter, S. J. Mevissena, L. M. Herman, A. A. Pack & S. P. Roberts. (2003). Horizontal angular discrimination by an echolocating bottlenose dolphin Tursiops truncatus. Bioacoustics 14(1): 15-34

Abstract

A bottlenose dolphin was tested on its ability to echoically discriminate horizontal angular differences between two arrays of vertical, air-filled, PVC rods. The blindfolded dolphin was required to station in a submerged, vertically-oriented hoop, 2 radial metres from the stimuli, and indicate whether an array with four rods (S+) was to the left or the right of an array with two rods (S–), by pressing a corresponding paddle. The angular separation between the rods within each array (θw) was maintained at 2 degrees but the angular separation between the two arrays (θb) was varied to produce angular differences (Δθ = θb– θw) ranging from 0.25 degrees to 4 degrees. A modified method of constant stimuli was used to test for angular discrimination ability, and yielded a psychometric function having a 75% correct threshold of 1.6 degrees. This threshold fell between the passive listening minimum audible angle thresholds of 0.9 degrees for click signals and 2.1 degrees for a pure tone signal (Renaud & Popper 1975). Analyses of response times, number of clicks and inter-click intervals failed to detect any significant adaptive behaviour occurring as the task became more difficult. These results help to define angular resolution capabilities of dolphin sonar that may play an important role in representing spatial information in the dolphin’s environment.

Keywords: dolphin, echolocation, localisation, spatial resolution

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M. A. Q. Sulehrie, P. Golob, B. M. D. Tran & G. Farrell. (2003). Use of a biomonitor to assess the effect of seed hardness on larval feeding of Callosobruchus maculatus in Vigna varieties. Bioacoustics 14(1): 35-46

Abstract

Exploitation of seed hardness, as a mechanism of host plant resistance, could be a useful component of the integrated control of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae). However, traditional methods of measuring larval development period using bioassays do not provide any information on larval feeding activity within seeds. To overcome this difficulty, a biomonitor was used to investigate feeding in seeds of Vigna spp. of different hardness. Larval weight and activity counts were lower in the hard seeded types. Larvae feeding in soft seeds increased their activity with each stadium, with each stadium separated by periods of inactivity. Conversely, for larvae in hard seeds, activity in the second stadium was prolonged and almost indistinguishable from the third and fourth stadia. It is suggested that associations between seed hardness and bruchid development be investigated as contributors to a better understanding of the mechanisms of host plant resistance.

Keywords: biomonitor, Callosobruchus maculatus, Vigna, seed hardness, host plant resistance

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S. Sanvito & F. Galimberti. (2003). Source level of male vocalisations in the genus Mirounga: repeatability and correlates. Bioacoustics 14(1): 47-59

Abstract

Male vocalisations have an important role in mating tactics, breeding strategies and sexual selection. Most studies of vocalisations are concentrated on the time and frequency domains, while the intensity of sound, an important acoustic parameter that should be related to body size, is almost completely ignored as a possible honest signal of resource holding potential (RHP) and cue for mate choice. In this paper, we analyse the repeatability, the correlations with age and size, and the relationship with breeding status of source level (SL) of male vocalisations in the two species of elephant seals (Mirounga leonina and M. angustirostris). We found a high repeatability of SL, equal or higher than the repeatability of frequency domain parameters estimated in a previous study. Southern elephant seal males were significantly larger and produce significantly more powerful vocalisations than northern males. Moreover, in each species SL was related to age, body size, and breeding status of males, but relationships were weak and accounted for just a small proportion of SL variance. We conclude that, although SL may be an honest signal of gross differences of RHP, it is not, by itself, a good candidate for the transmission of high-resolution information on individual phenotype. A combination of SL and frequency components could be, on the contrary, an effective way to communicate RHP.

Keywords: male vocalisations, source level, honest signals, elephant seals, Mirounga

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L. E. Rendell & H. Whitehead. (2003). Comparing repertoires of sperm whale codas: a multiple methods approach. Bioacoustics 14(1): 61-81

Abstract

A common task for researchers of animal vocalisations is statistically comparing repertoires, or sets of vocalisations. We evaluated five methods of comparing repertoires of ‘codas’, short repeated patterns of clicks, recorded from sperm whale (Physeter macrocephalus) groups. Three of the methods involved classification of codas – human observer classification, k-means cluster analysis using Calinski and Harabasz’s (1974) criterion to determine k, and a divisive k-means clustering procedure using Duda and Hart’s (1973) criterion to determine k. Two other methods used multivariate distances to calculate similarity measures between coda repertoires. When used on a sample coda dataset, observer classification failed to produce consistent results. Calinski and Harabasz’s criterion did not provide a clear signal for determining the number of coda classes (k). Divisive clustering using Duda and Hart’s criterion performed satisfactorily and, encouragingly, gave similar results to the multivariate similarity measures when used on our data. However, the relative performance of the k-means techniques is likely data dependent, so one method is not likely to perform best in all circumstances. Thus results should be checked to ensure they extract logical clusters. Using these techniques concurrently with multivariate measures allows the drawing of relatively robust conclusions about repertoire similarity while minimising uncertainties due to questionable validity of classifications.

Keywords: cluster analysis, classification, vocal repertoire, sperm whale, codas

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B. Lohr, A. Lauer, M. R. Newman & R. J. Dooling (2004). Hearing in the Red-billed Firefinch Lagonosticta senegala and the Spanish Timbrado Canary Serinus canaria: the influence of natural and artificial selection on auditory abilities and vocal structure. Bioacoustics 14(2): 83-98

Abstract

We tested the auditory sensitivity of red-billed firefinches Lagonosticta senegala and Spanish timbrado canaries Serinus canaria. Both these species produce songs and calls that are narrowband and relatively high in frequency, with spectral energy falling predominantly in the region of 3-6 kHz. Hearing thresholds were measured in these two species and compared to the auditory sensitivity of closely related species: the well studied zebra finch Taeniopygia guttata, and other strains of canary bred for song. Auditory thresholds were similar in both groups of birds, with firefinches having an audiogram typical for that of small birds. Timbrado canaries exhibited an audiogram with its greatest sensitivity in the relatively high region of 4-6 kHz, corresponding to the peak frequency of its calls. Critical ratios measured over a range of several octaves increased in a monotonic fashion at a rate of 2-3 dB per octave for both firefinches and timbrado canaries. Critical ratios in these two species are similar to what has been found in most other small passerine species, suggesting spectral resolving abilities similar to most small birds tested to date.

Keywords: behavioural audiogram, hearing, red-billed firefinch, Spanish timbrado canary, vocalisations.

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G. Peters, M. L. East, H. Herzel, J. R. Henschel, G. L. Mills, K. Wilhelm & H. Hofer (2004). Spotted hyaena whoops: frequent incidence of vocal instabilities in a mammalian loud call. Bioacoustics 14(2): 99-109

Abstract

Spotted hyaena Crocuta crocuta whoops are loud calls normally produced in a sequence termed a bout. Whoops are produced by hyaenas irrespective of age or sex to display identity and convey information about the location of the caller. The majority (91%, n=460) of whoops produced by spotted hyaenas, from two geographically separate populations in southern Africa and one population in eastern Africa, showed pronounced nonlinear phenomena, predominantly subharmonics. Whoops produced by males and females had a similarly high probability of subharmonics, and 91.5% of the 78 bouts examined contained calls with subharmonics.

These results provide evidence that nonlinear vocal phenomena are a common feature of hyaena whoops. The presence of subharmonics in whoops may be enhanced by vocal tract resonances when the fundamental frequency and first formant in the calls are close or coincide. Vocal membranes may also play a role. The high incidence of subharmonics in whoops may enhance individual recognition by adding structural complexity to calls. As 33 of 34 individually known spotted hyaenas examined in this study produced whoops containing subharmonics, it is unlikely that the production of subharmonics is confined to calls from individuals of a particular social status, sex, size, or level of developmental asymmetry, as proposed for nonlinear phenomena in the calls of other mammalian species, although variation in structural features of subharmonics may convey information about these characteristics.

Keywords: spotted hyaena, Crocuta crocuta, whooping, subharmonics, vocal instabilities, nonlinear vocal phenomena

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A. Lemasson, J-P. Richard & M. Hausberger. (2004). A new methodological approach to context analysis of call production. Bioacoustics 14(2): 111-125

Abstract

There is a need to improve the assessment of causes and consequences of vocal behaviour. The lack of descriptions of the context of call or song production comes from the complexity of its definition. The context is composed of numerous physical and social parameters and therefore its analysis should be multi-dimensional. Classical approaches involve a relatively subjective data reduction. This is due to a pre-selection of the parameters which may be potentially involved, as the analysis becomes rapidly complicated when the number of factors increases. This paper describes a helpful method that allows a much wider range of potential parameters to be explored and displayed visually. The parameters selected for subsequent analysis are those indicated by the display as most relevant and are therefore not arbitrary.

We applied this method to observations of events (external or internal to the group) or behaviours (including postures) preceding and following call production. Calls of Campbell’s monkeys Cercopithecus campbelli present call types composed of several stereotyped sub-types, raising the question of whether or not such variations have a functional meaning for animals. We present three examples of the application of this method to describe in detail the context of production of a given call type, to detect specific temporal sequences of production and to discriminate between structurally quite similar sub-types.

Keywords: context, call production, methodology, repertoire, campbell’s monkey

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M. I. Goretskaia (2004).  Song structure and singing behaviour of Willow Warbler Phylloscopus trochilus acredula in populations of low and high density. Bioacoustics 14(3): 183-195

Abstract

Song structure and singing behaviour in two nesting populations of Willow Warbler Phylloscopus trochilus acredula of different density were studied in Moscow and Kostroma Regions, Russia, from 1994-1997. In total 520 songs of 9 males from the low-density population and 566 songs of 12 males from the high density population were analysed. Singing periods in the high density Willow Warbler population (11 males, 758 min.) were longer (58% of the time) than in the low density population (13 males, 866 min.) (58%). In the high density population, 51% of singing time consisted of “singing duels” (singing in gaps between the songs of a neighbouring male, and singing during the singing of a neighbouring male), while in the low density population only 7% did. The initial phrases of Willow Warbler songs were significantly longer in the high density population, with up to 9-13 elements, while there were no occurrences of this length in the low density population. Songs as a whole were longer and more variable in the high density population. Thus changes in structure, singing activity and behaviour are linked to male-male interaction and density of the nesting community.

Keywords: song structure, population density, Phylloscopus trochilus, singing behaviour.

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R. S. Tokumaru, C. Ades & P. F. Monticelli (2004).  Individual differences in infant guinea pig pups isolation whistles. Bioacoustics 14(3): 197-208

Abstract

When separated from their mother and other group members, guinea pig Cavia porcellus pups emit distinctive high pitched whistles. To determine if these vocalisations are individually distinctive, we recorded the whistles of isolated guinea pig pups, 8 to 10 days old, and subjected their acoustical parameters to discriminant analysis. The results of the reclassification accuracy were higher than random assignment, indicating the existence of individual differences. Individual pup vocalisations did not differ from one another by any single acoustic parameter, but by a set of parameters. Individual recognition of such isolation calls by mothers could play an important role in facilitating reestablishment of contact.

Keywords: distress vocalisation, individual characteristics, pup recognition, guineapigs, Cavia porcellus.

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S. H. Blumenrath, T. Dabelsteen & S. B. Pedersen (2004).  Being inside nest boxes: does it complicate the receiving conditions for Great Tit Parus major females? Bioacoustics 14(3): 209-223

Abstract

Birdsong is degraded as it propagates through the habitat. This affects its use as a signal in communication networks, depending on song type as well as sender and receiver location. Nest holes constitute special receiver locations to females of many hole-nesting species. Although such locations are frequently used by females during their fertile period, for instance at dawn when information gathering from singing males may be essential, the conditions for receiving sounds inside nest holes are currently unknown. We investigated these conditions with a sound transmission experiment, in which great tit songs were broadcast in a deciduous forest and rerecorded from both outside and inside a nest box. Several aspects of sound degradation encompassing signal attenuation and distortion were quantified.

Attenuation was strongest inside the nest box for both song and background noise. However, the signal-to-noise ratio, which affects song detection and discrimination, was only slightly reduced inside the nest box. Signal distortion, which has implications for both information transfer and ranging, provided conflicting results for the two types of song notes, the highly modulated buzz notes and the less modulated pure notes. These results provide the first evidence that entering nest boxes complicates song reception conditions for female songbirds. We suggest that this may ultimately affect vocally mediated information gathering in the network.

Keywords: communication networks, sound degradation, nest boxes, communication range, ranging

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