BIOACOUSTICS
Table of Contents: Volume 16
G. Peters (2006). Terrestrial Carnivore Sounds with Repeated Rapid Alternation of Two Structurally Different Components: an Indication of Complex Sound Production Mechanisms in Mammals? Bioacoustics 16(1): 1-25
Abstract
Acoustic signals of several species from different families of the terrestrial Carnivora (Mammalia) are described and discussed in detail. All show a rapid and regular repetitive alternation between two structurally different component sound elements. It is argued that this general structural feature is indicative of different morphological structures or mechanisms in the larynx or supralaryngeal vocal tract, contributing to sound production or modification in a temporally coordinated way. A few examples are listed of acoustic signals in the aquatic Carnivora and mammalian orders other than the Carnivora showing a similar general structural pattern. Several of the relevant acoustic signals mentioned include sound production by the laryngeal source but morphological structures in the supralaryngeal vocal tract are likely to generate additional components in some of these. Sounds also exist with two different structural components alternating without contribution of the laryngeal source to sound generation. In nearly all the examples given, knowledge as to the definite nature and mode of action of these structures and as to their temporal coordination is only fragmentary at best. It is important to clarify the respective share of each morphological structure and physiological mechanism contributing to sound production and modification in order to characterize and classify an animal acoustic signal and when studying specific signals in a comparative phylogenetic context.
Keywords: mammalian vocalization, acoustic signal, terrestrial Carnivora, sound production, articulation
Joshua J. Schwartz & Vincent T. Marshall (2006). Forms of Call Overlap and Their Impact on Advertisement Call Attractiveness to Females of the Gray Treefrog Hyla versicolor. Bioacoustics 16(1): 39-56
Abstract
Male gray treefrogs, Hyla versicolor, advertise for females in choruses in which calls often overlap. Previous research has demonstrated that such acoustic interference among conspecifics can impair the ability of a male to attract a mate. However, the stimulus set used in those studies was quite limited. Here we performed single-speaker and two-speaker tests of phonotaxis with female Hyla versicolor to explore the impact of different degrees and forms of call overlap on the relative attractiveness of male signals. We found that: (1) overlapped calls are recognized as acceptable signals by females, although they are less attractive than calls that are not overlapped; (2) the relative phase of the overlapping calls matters. When calls were time-shifted by 50% of their pulse-period (180 degree offset), attractiveness of overlapped calls was reduced relative to non-overlapped calls as much as it would be by a reduction in intensity of about 12 dB SPL or a drop in call duration of between one third to one half. A 90 degree phase offset was equivalent to a 3 dB drop in SPL; (3) partial call overlap may not impair call attractiveness if one third or less of the call is overlapped; (4) if the ending portion of a call is overlapped it may impair attractiveness less than if previous segments of a call are obscured; (5) if most (three fourths or more) of a male’s calls are free of interference, overlap of his remaining calls does not significantly impair his attractiveness.
Keywords: communication, treefrogs, chorusing, acoustic interference, female choice
Malene Simon, Fernando Ugarte, Magnus Wahlberg & Lee A. Miller. (2006). Icelandic killer whales Orcinus orca use a pulsed call suitable for manipulating the schooling behaviour of herring Clupea harengus. Bioacoustics 16(1): 57-74
Abstract
Icelandic and Norwegian killer whales feed on herring, after debilitating them with underwater tail slaps. We analysed sound recordings of Icelandic and Norwegian killer whales engaged in feeding and other behaviour. We describe a pulsed call made by Icelandic killer whales shortly before underwater tail slaps, which had an atypical low frequency (average peak frequency: 683 ±131 Hz), long duration (3.0 ±1.1 s) and high intensity (source level 169-192 dB pp re 1 μPa @ 1 m). The low-frequency emphasis of this call was below the most sensitive hearing range of killer whales, suggesting that the call may not be optimal for interspecific communication. However, herring could easily perceive the killer whale call since the frequency content is similar to the resonant frequency of their swim bladder as well as to the most sensitive frequency band of hearing in this species. Previous studies have shown that sound may cause schooling herring to cluster. A high density of herring in a school would increase the effectiveness of the underwater tail slaps. We suggest that some Icelandic killer whales use this low-frequency call to herd herring into dense schools immediately before delivering an underwater tail slap, thereby increasing their foraging success.
Keywords: Killer Whale, Orcinus orca, vocalisations, tail slaps, Atlantic Herring, Clupea harengus.
Swati Diwakar & Rohini Balakrishnan. (2006). Male and Female Stridulation in an Indian Weta (Orthoptera: Anostostomatidae). Bioacoustics 16(1): 75-85
Abstract
We present the first description of the calls and stridulatory structures of males and females of an Indian weta species from the Western Ghats of Southern India. Calls of males and females produced by femoro-abdominal stridulation were recorded and call features such as chirp duration, chirp period, syllable period and syllable duration were characterised. The calls of males were highly stereotyped with regular chirp periods and durations whereas chirp rates in the female calls were more variable. The number of syllables per chirp was constant for males and females and the fine temporal features such as syllable periods and syllable durations showed low inter-individual variation in both males and females. The arrangement of femoral stridulatory structures was different from the previously described anostostomatid species. The high stereotypy of calls of males and females indicates that the signal could serve for identification of species and sex.
Keywords: Acoustic signals, anostostomatid, femoro-abdominal stridulation, India, weta
J.N. Oswald, S. Rankin, & J. Barlow (2006). First Description of Whistles of Pacific Fraser's Dolphins Lagenodelphis hosei. Bioacoustics 16(2): 99-111
Abstract
Acoustic recordings were made in the presence of four single-species schools of Fraser’s Dolphin Lagenodelphis hosei during combined acoustic and visual shipboard line-transect cetacean abundance surveys. Recordings were made using a towed hydrophone array and sonobuoys. Echolocation clicks were detected during only one recording session and no burst pulses were detected. Whistles were present in all four recording sessions. Fourteen variables were measured from the fundamental frequencies of 60 whistles. The whistles were generally simple, with few inflection points or steps. Whistles ranged from 6.6 kHz to 23.5 kHz, with durations ranging from 0.06 to 0.93 sec. Whistle characteristics closely match those reported for L. hosei recorded in the Gulf of Mexico (Leatherwood et al. 1993) and the Caribbean (Watkins et al. 1994), although, in general, the Pacific dolphins were less vocally active than the Caribbean dolphins described by Watkins et al. (1994). This difference may be related to the orientation of the hydrophone array relative to the dolphins. It may also be due to behaviour, as the Caribbean dolphins were engaged in feeding activities and the Pacific dolphins were fast travelling to evade the approaching vessel.
Keywords: whistles, Lagenodelphis hosei, tropical Pacific
Swati Diwakar & Rohini Balakrishnan. (2006). The Assemblage of Acoustically Communicating Crickets of a Tropical Evergreen Forest in Southern India: Call Diversity and Diel Calling Patterns. Bioacoustics 16(2): 113-135
Abstract
This study provides the first description of the call structures of twenty ensiferan species constituting the nocturnal acoustic community of an evergreen forest in Southern India. Of the twenty species, ten belonged to the superfamily Grylloidea, nine to the superfamily Tettigonioidea and one to the superfamily Gryllacridoidea. The calls of the gryllid species were narrow-band with dominant frequencies ranging from 3 – 7 kiloHertz. The calls of the tettigoniids covered a wide spectral range, reaching far into the ultrasound in some species. Four of the nine tettigoniid species had narrow-band, relatively low frequency calls centred at 3, 9, 11 and 15 kiloHertz respectively. The temporal patterns of the species were diverse, with syllable durations ranging from eight to 63 milliseconds and syllable periods from 17 milliseconds to two seconds. The calls of the species showed considerable overlap in both spectral and temporal features. Calling activity peaked between six o’clock in the evening and midnight and died down subsequently. We found no diel partitioning of calling time between acoustically communicating ensiferan species. Species accumulation curves suggest that the acoustic community has been almost completely sampled.
Keywords: acoustic community, diel calling patterns, Ensifera, India, tropical forests
S. Rankin & J. Barlow (2006). Vocalisations of the Sei Whale Balaenoptera acutorostrata off the Hawaiian Islands. Bioacoustics 16(2): 137-145
Abstract
Little is known about the sounds produced by the Sei Whale Balaenoptera borealis and no recordings have been made in their presence in the Pacific Ocean. This research presents sounds recorded in the presence of Sei whales near the Hawaiian Islands in November, 2002. A total of 107 vocalizations, including two variations of low-frequency downswept calls, were measured. Two of these calls were sweeps from100 Hz to 44 Hz, over 1.0 seconds. The second call type (n=105) consisted of low frequency calls which swept from 39 Hz to 21 Hz over 1.3 seconds. These calls are different from sounds attributed to Sei whales in the Atlantic and Southern Oceans, where recordings were made only in the summer months. These sounds are similar, however, to sounds attributed to fin whales in Hawaiian waters. Additional studies are needed in order to understand the spatial and temporal variation in the vocal repertoire of Sei and Fin whales in the Pacific Ocean.
Marco Dragonetti (2006). Individuality in Scops owl Otus scops vocalizations. Bioacoustics 16(2): 147-172
Abstract
The focus of this study was to determine whether individual vocal identification of Scops Owls Otus scops was possible and if there was a stability of the hoot-calls over a short time period in the same individuals. Spontaneous vocalizations of 13 owls were recorded in 2004 in Southern Tuscany, Italy. Visual analysis of spectrograms and quantitative multivariate analysis of six vocal features showed marked individual differences. In some owls a repertoire of two different hoot types was found. In 2005, 10 Scops owls were recorded three times in the same breeding season (2 hours and 10 days after the first session). Statistical analysis of data showed that 60% of owls did not change call features over time. However a slight but significant variability between successive vocal performances of the same owl was found in 40% of cases. This variability may decrease the recognition power by acoustic analysis. To overcome this obstacle I suggest a multi step qualitative/quantitative approach. A Difference Index (DI) was calculated to set a threshold between the slight intra-individual and the very high inter-individual variability. This method allowed the recognition of calls of each owl recorded over time in 2005.
Keywords: Scops Owl, Otus, vocal identification, vocal individuality, vocal variability
C.V. Long (2007). Vocalisations of the degu Octodon degus, a social caviomorph rodent . Bioacoustics 16(3): 223-244
Abstract
Caviomorph species are well known for their social nature and variety of vocal sounds used in intra-species communication, making them ideal candidates for the study of vocalisations. Here, I provide a much needed categorisation for one such species, the Degu Octodon degus. By analysing 3535 vocal sounds, I demonstrate that there are 15 distinct categories for degu vocalisations, showing that degus have a wider and more complex vocal repertoire than was previously assumed. I find that the use of vocal sounds varies widely with season and behavioural context, consistent with interaction in a complex social hierarchy. I identify that certain categories are not used by pups and that others may be gender-specific. In addition, I find that vocalisations used by lactating females may have an alternative function to that previously assumed. By examining the frequency range of the vocalisations identified, I predict that the hearing range of the degu lies between 71 Hz to 21.7 kHz. Finally, I describe the structure, causation and likely function of each vocal type.
Keywords: Octodon degus, vocalisation, communication, caviomorph species, vocal behaviour.
M. Penna and R. Marquez (2007). Amplification and spectral modification of incoming vocalizations inside burrows of the frog Eupsophus roseus (Leptodactylidae). Bioacoustics 16(3): 245-259
Abstract
In previous studies, calling sites of two species of burrowing frogs Eupsophus in southern Chile have been shown to amplify conspecific vocalizations generated externally, thus providing a means to enhance the reception of neighbour’s vocalizations in breeding aggregations. In the current study the amplification of vocalizations of Eusophus roseus was investigated to explore the extent of sound enhancement reported previously for two congeneric species. Advertisement calls broadcast through a loudspeaker placed in the vicinity of a burrow, monitored with small microphones, are amplified by up to 14 dB inside cavities relative to outside. The fundamental resonant frequency of burrows, measured with broadcast noise and pure tones, ranges from 345-1335 Hz; however it is not correlated with burrow length. The spectra of incoming calls are altered inside burrows by predominantly increasing the amplitude of lower relative to higher harmonics. The call amplification effect inside burrows of E. roseus parallels the effect reported previously for two congeneric species and reinforces the suggestion that sound enhancement inside calling sites has a widespread effect on signal reception by burrowing animals.
Keywords: Anura, burrow acoustics, temperate forest, tube resonance, sound reception
O. A. Filatova, I. D. Fedutin, A. M. Burdin & E. Hoyt (2007). The structure of the discrete call repertoire of killer whales Orcinus orca from Southeast Kamchatka. Bioacoustics 16(3): 261-280
Abstract
The problem of categorization arises in any classification system because classes should be discrete while the characteristics of most natural objects and aspects of nature are more or less gradual. In systematics, this problem usually is solved by creating several levels of categories, such as class, order, family, genus and species. In the existing killer whale discrete call classification, only two levels occur – call type and call subtype. In this paper we describe structural categories at a broader level than call type in the discrete sounds of killer whales and compare these categories between and within vocal clans in a community of resident killer whales from Southeast Kamchatka, Russian Far East, and also with killer whales outside this community. We found four main classes of discrete calls in the repertoire of resident killer whales from Southeast Kamchatka. The calls of Southeast Kamchatka transient killer whales and Sakhalin killer whales do not fall into these classes. This suggests that the resident killer whale community from Southeast Kamchatka has some rules defining the structure of calls which are typical for this community. Consequently, all resident killer whales from Southeast Kamchatka can be said to share the same vocal tradition.
Keywords: Killer Whale, Orcinus orca, calls, classification, Kamchatka
T. Ganchev & I. Potamitis (2007). Automatic Acoustic Identification of Insects: the case of crickets and cicadas. Bioacoustics 16(3): 281-328
Abstract
We report on our research efforts towards developing efficient equipment for the automatic recognition of insects using only the acoustic modality. Specifically, we deal with three groups of insects, namely the crickets, cicadas and katydids. Inspired by well-documented tactics of speech processing, the signal processing employed in the present work is elaborated further with respect to the sound production mechanisms of insects. In order to improve the practical efficacy of our equipment, we adopt a score-level fusion of classifiers with non-parametric (probabilistic neural network) and parametric (Gaussian mixture models) estimation of the probability density function. An efficient hierarchic classification scheme is introduced, where the identification of unlabelled input takes place at various levels of hierarchy, such as suborder, family, subfamily, genus and species. We evaluate the practical significance of our approach on a large and well-documented catalogue of recordings of crickets, cicadas and katydids. For the hierarchic classification scheme, we report identification accuracy that exceeds 99% at suborder and family levels. In the straight classification scheme, we report accuracy of 90% for 307 species.
Keywords: bioacoustics, automated identification, computer-assisted taxonomy, biodiversity, insects, crickets, cicadas, katydids