BIOACOUSTICS
Table of Contents: Volume 19
Bioacoustics Volume 19 No 3 (2010)
Alexander N. G. Kirschel, Dent A. Earl, Yuan Yao, Ivan A. Escobar, Erika Vilches, Edgar E. Vallejo & Charles E. Taylor. (2009). Using Songs To Identify Individual Mexican Antthrush Formicarius moniliger: Comparison of Four Classification Methods. Bioacoustics 19(1-2): 1-20
Abstract
This study compares the ability of four classification methods to distinguish between songs of individual Mexican Antthrush Formicarius moniliger: self-organizing maps (SOMs), discriminant function analysis, fuzzy logic and hidden Markov models. Recordings were made under field conditions in a Mexican rainforest. Two types of data were analysed - recordings from birds that had been ringed and identified to sex, and recordings from birds that had been identified based on their recording location and song timing. An event detector extracted song features and SOMs were used to confirm the number of individuals recorded. The SOM separated all five ringed birds successfully, and also differentiated two other birds that were not identified while vocalising. The three supervised learning methods correctly classified over 97% of songs to individual from the set of identified recordings. Tests with songs for predicted, rather than known, individuals yielded more variable results across methods, with results ranging from 77.8% to 93.9% correctly identified. The respective merits of the three supervised classification procedures are discussed for automated recording, detection and classification.
Keywords: bioacoustics, Formicarius, self-organizing maps, hidden Markov models, vocal individuality
E. Ey & J. Fischer. (2009). The “acoustic adaptation hypothesis” - a review of the evidence from birds, anurans and mammals. Bioacoustics 19(1-2): 21-48
Abstract
The acoustic properties of the environment influence sound propagation. Many previous studies examined whether various species of anurans, birds and mammals adjust usage and / or structure of their vocal signals to limit degradation during propagation in this environment (“acoustic adaptation hypothesis”). The present review examines how widespread such adaptations actually are across taxa. First, evidence or environment-related adjustments in usage of vocal signals is collected from studies in birds and other vertebrates (i.e., anurans and mammals). Second, a meta-analysis conducted by Boncoraglio & Saino (2007) on the influences of the environment on the acoustic structure of avian vocalisations is taken as a reference, and results from additional studies in birds are reviewed and compared to its conclusions. Finally, evidence from similar studies conducted in anurans and mammals is collected and discussed. Concerning the usage of vocal signals, evidence of environment-related adaptations in the few studies found was more widespread in anurans and mammals than in birds. Regarding structure of vocal signals, evidence from additional studies in birds did not completely confirm results of the meta-analysis of Boncoraglio & Saino (2007). Pooling all bird studies together presented minimum frequency, frequency modulations and frequency range as acoustic variables most often adjusted to the environment, in contrast to temporal features, repetition rate and maximum frequency. The few studies conducted in anurans and mammals did not allow the identification of specific acoustic variables that typically show environment-related variations. Overall, evidence for the acoustic adaptation hypothesis was not as widespread as expected across taxa. The different aspects of vocal behaviour adapted to environmental conditions varied according to the species and local habitats. Environment-related adjustments in structure of vocal signals seem to be constrained by call function in anurans and mammals. This effect was not examined in birds, but vocal learning does not appear to be a pre-requisite to environment-related adjustment in this group.
Keywords: adaptation, anurans, birds, environment, mammals, vocal communication
Ana Carolina G. Atem, Marianne H. Rasmussen, Magnus Wahlberg, Hans C. Petersen & Lee A. Miller. (2009). Changes in Click Source Levels with Distance to Targets: Studies of Free-ranging White-beaked Dolphins Lagenorhynchus albirostris and Captive Harbor Porpoises Phocoena phocoena. Bioacoustics 19(1-2): 49-65
Abstract
Probably all odontocetes use echolocation for spatial orientation and detection of prey. We used a four hydrophone “Y'' array to record the high frequency clicks from free-ranging White-beaked Dolphins Lagenorhynchus albirostris and captive Harbour Porpoises Phocoena phocoena. From the recordings we calculated distances to the animals and source levels of the clicks. The recordings from White-beaked Dolphins were made in Iceland and those from Harbour Porpoises at Fjord & Bælt, Kerteminde, Denmark during prey capture. We used stringent criteria to determine which clicks could be defined as being on the acoustic axis. Two dolphin and nine porpoise click series could be used to track individual animals, which presumably focused on the array hydrophones or a fish right in front of the array. The apparent source levels of clicks in the individual tracks increased with range. One individual White-beaked Dolphin and three Harbour Porpoises regulate their output signal level to nearly compensate for one-way transmission loss while approaching a target. The other dolphin regulated the output differently. For most of the recordings the sound level at the target remains nearly constant and the echo level at the animal increases as it closes on the target.
Keywords: Echolocation, biosonar, source level, apparent source level, prey capture, hydrophone array, White-beaked Dolphin, Lagenorhynchus albirostris, Harbour Porpoise, Phocoena phocoena
Leah Nemiroff & Hal Whitehead. (2009). Structural Characteristics of Pulsed Calls of Long-Finned Pilot Whales Globicephala melas. Bioacoustics 19(1-2): 67-92
Abstract
The pulsed calls of Long-finned Pilot Whales Globicephala melas have received little study, and their structure and function remain unclear. We examined the pulsed calls of Pilot Whales off Nova Scotia by taking multiple measures of 419 spectrograms from recordings made over a span of eight years. The results offer a quantitative description of pulsed call structure necessary for subsequent analysis of signal functionality and social relevance. Pilot Whale pulsed calls were found to be physically complex, with multiple, independently modulated components that are likely rich in information and difficult for eavesdroppers to imitate. The production of such structurally complicated signals suggests they play an important role in Pilot Whale communication. The pulsed calls appear to form two main call types: those with a maximum visible sideband above 18 kHz and those with a maximum visible sideband below 15 kHz. However, there is no indication of further discrete categories despite a large amount of variation between calls within those two broad categories. The high variation in call structures may indicate communicative plasticity, allowing the whales to communicate state, such as level of arousal, and to compensate or variable background noise levels. The structural similarity of Pilot Whale and Killer Whale Orcinus orca pulsed calls raises the question of whether the distantly related whale species, with a shared but rare social structure, have evolved similar call structures to solve similar communication challenges.
Keywords: Globicephala melas, Long-finned Pilot Whales, pulsed calls, vocalizations, communication
Kirill M. Orci & Gábor Szőcs. (2009). Ultrasonic and Sonic Emission During the Courtship Behaviour in Males of Z- and E-Pheromone Strains of the European Corn Borer Ostrinia nubilalis Hübner (Lepidoptera, Pyraustidae). Bioacoustics 19(1-2): 93-107
Abstract
This study presents the first detailed description of the oscillographic structure and spectrographic features of sound emission produced by Z- and E-strain males of Ostrinia nubilalis during their courtship behaviour. Males simultaneously produce ultrasonic and low-frequency sonic sound emissions during their courtship, vibrating their wings at a distance of 1-2 cm from the female. The sound emission shows two characteristic types: a long courtship song is followed by a short precopulation song after a few seconds of silence. The ultrasonic courtship song is composed of pulses repeated in pairs or more typically in long series with an even repetition rate (which showed to be temperature dependent) or in irregular sequences. The precopulation song is a short crescending pulse-series. In both song types the ultrasonic carrier-wave has constant frequency spectrum containing components from 20 kHz to 80 kHz. The low-frequency sound emission has a harmonic frequency spectrum (fundamental frequency between 40-70 Hz). During the precopulation song the low-frequency component shows a characteristic frequency sweep from 80-100 Hz to 70-80 Hz. No significant difference has been noticed comparing the songs of Z- and E-strain males of O. nubilalis. However sound emission is clearly different from that described recently in the closely related O. furnacalis, where pulses are performed in groups forming chirps and no different courtship song and precopulation song has been described. The possible signal function of low-frequency near field sound emission is discussed.
Keywords: acoustic communication, near field sound, silent signalling, signal species specificity
Shereena Griffiths, Sue Dow & Oliver Burman (2010). Ultrasonic Vocalizations and Their Associations With the Non-vocalization Behaviour of the Endangered Turkish Spiny Mouse Acomys cilicius Spitzenberger in a Captive Population. Bioacoustics 19(3): 143-157
Abstract
Although ultrasonic vocalizations (USVs) have been recorded in many species of rodent and in various contexts, e.g. sexual behaviour and aggression, it has not been demonstrated for the endangered Turkish Spiny Mouse Acomys cilicius Spitzenberger. This study investigated whether A. cilicius emits USVs and, if so, how these USVs associated with non-vocalization behaviour. Ultrasonic recording equipment was set up for 12 days in an off-exhibit enclosure of A. cilicius at Bristol Zoo. At least seven different types of USV were recorded. For eight of the 12 study days, ultrasonic and video recording equipment were run concurrently. From these observations it was found that emission of USVs were associated with sexual behaviour, aggression and social investigation. The results of this study show for the first time that captive A. cilicius produce USVs that resemble those produced by other rodent species, including its close relative the Egyptian Spiny Mouse A. cahirinus Desmarest. As these findings apply only to a captive Turkish Spiny Mouse population, additional work should be carried out to investigate the behaviour and USV production in the wild in addition to further research on captive populations investigating the apparent communicative function of these vocalizations.Keywords: Turkish Spiny Mouse, ultrasonic vocalization, communication, behaviour, conservation
Passilongo D., A. Buccianti, F. Dessi-Fulgheri, A. Gazzola, M. Zaccaroni & M. Apollonio (2010). The Acoustic Structure Of Wolf Howls In Some Eastern Tuscany (Central Italy) Free Ranging Packs. Bioacoustics 19(3): 159-175
Abstract
Italian wolf howls are described for the first time from observations between 2003–2008 of a population living in eastern Tuscany, central Italy. A sample of 37 howls selected among single responses and 128 howls included in the choruses of 7 free ranging packs was recorded and analysed. The mean fundamental frequency of the howls ranged between 274–908 Hz. Two main structures recognised by means of multivariate explorative analysis, in particular Principal Component and Cluster Analysis, were ascribed to breaking and flat howls. Discriminant Function Analysis was applied to the recognised groups with the aim to find a general rule for classification. Howls with different features were correctly assigned to the groups obtained by explorative analysis in 95.8% of cases. The analysis of the variables characterising the structure of the howls suggests that maximum frequency and range of fundamental frequency are the most important parameters for classification, while duration does not appear to play any significant role.Keywords: Canis lupus, acoustic structure, mammal communication, sonogram, fundamental frequency.
Walid Barakat Hussein, Mohamed Ahmed Hussein & Thomas Becker (2010). Detection of the Red Palm Weevil Rhynchophorus ferrugineus Using Its Bioacoustics Features. Bioacoustics 19(3): 177-194
Abstract
The Red Palm Weevil (RPW) is the most destructive pest of the date palm in the world and a serious pest of coconuts. The insect has caused up to 20% loss of these plantations in Asia and the Middle East. The economic damage to palm crops due to RPW could be mitigated significantly by bioacoustics recognition in an earlier phase of infestation and by applying the appropriate treatment. This study is conducted under the hypothesis that distinctive spectral and temporal features in RPW larval sounds can be combined to construct improved indicators for automated detection of infestations. In this paper, a signal processing system is developed with available acoustic technology to detect the existence of RPW in a tree through its feeding sounds. A large set of features are extracted, including unconventional features such as temporal roll-off, temporal slope and temporal spread. Additionally, an analysis is provided of the criteria for the choice of the optimum frame length, as well as the selection of the suitable window function. The results confirm the efficiency of the developed system with the selected representative features, window functions and frame length to detect the existence of the RPW.Keywords: Red Palm Weevil, bioacoustics detection, signal processing, feature extraction, feature selection.
Klaus-Gerhard Heller, Tim Daniel Ostrowski & Claudia Hemp (2010). Singing and hearing in Aerotegmina kilimandjarica (Tettigoniidae: Hexacentrinae), a species with unusual low carrier frequency of the calling song. Bioacoustics 19(3): 195-210
Abstract
The carrier frequency of the calling songs of bush-crickets (Tettigonioidea) is generally negatively correlated with body size; the smaller the species, the higher the frequency. However, in the correlation between body size and frequency there is a large variation. Some species do not seem to follow the main trend, but the reason(s) for the deviations from the negative correlation are largely unknown. Especially interesting are species which produce sounds “too” low for their size because this requires special and – judging from the other species – probably expensive modifications of the tegmina. Here we present data on the signal and the acoustic behaviour of Aerotegmina kilimandjarica, a small species with extraordinarily enlarged and inflated tegmina. The calling song has its peak frequency at 5 kHz (bandwidth 10 dB below peak 4-10 kHz). The species has a typical tettigoniid hearing curve, being most sensitive at 10 kHz (threshold 45 dB SPL). Taking into account the atmospheric attenuation, the song (loudness 100 dB SPL at 1 m) has a greater range at 5 kHz than at 10 kHz, so that maximising the range may have been one reason for the use of this unusually low frequency.Keywords: Tettigoniidae, calling song, frequency, acoustic communication, sexual selection
C.R Weir (2010). First Description of Atlantic Humpback Dolphin Sousa teuszii Whistles, Recorded Off Angola. Bioacoustics 19(3): 211-224
Abstract
The Atlantic humpback dolphin Sousa teuszii is endemic to the west coast of Africa and is poorly studied. During January 2008, 2.7 hr of acoustic recordings were made during 11 S. teuszii encounters in the Namibe province of Angola. Echolocation click trains were audible in most recordings. A total of 298 individual dolphin whistles were recorded, of which 86 were of sufficient signal to noise ratio for the measurement of 10 fundamental frequency variables. Sousa teuszii whistles occurred in the 2.5 to 23.4 kHz fundamental frequency range and were relatively simple in structure, with 85% having a single inflection point. The fundamental frequency was relatively low, with mean minimum and maximum frequencies of 4.8 and 8.2 kHz respectively. Harmonics occurred in 92% of whistles, sometimes extending beyond the 44 kHz recording range. The most frequently recorded contour categories were convex and concave, and very few whistles exhibited complex modulation. The whistles produced by S. teuszii are broadly comparable with those published for the Indo-Pacific humpback dolphin S. chinensis. Future studies should consider context-specific use of whistle types, and should include comparisons with S. teuszii groups in other geographic locations to ensure the full species’ whistle repertoire is adequately characterised.Keywords: Atlantic humpback dolphin, Sousa teuszii, Angola, vocalisations, whistles