Showing papers in "Bioacoustics-the International Journal of Animal Sound and Its Recording in 2012"

A toolbox for animal call recognition

Abstract: Monitoring the natural environment is increasingly important as habit degradation and climate change reduce the world's biodiversity. We have developed software tools and applications to assist ecologists with the collection and analysis of acoustic data at large spatial and temporal scales. One of our key objectives is automated animal call recognition, and our approach has three novel attributes. First, we work with raw environmental audio, contaminated by noise and artefacts and containing calls that vary greatly in volume depending on the animal's proximity to the microphone. Second, initial experimentation suggested that no single recognizer could deal with the enormous variety of calls. Therefore, we developed a toolbox of generic recognizers to extract invariant features for each call type. Third, many species are cryptic and offer little data with which to train a recognizer. Many popular machine learning methods require large volumes of training and validation data and considerable time and exper...

A comparative study in birds: call-type-independent species and individual recognition using four machine-learning methods and two acoustic features

Abstract: Species- and individual-specific animal calls can be used in identification as verified in playback experiments and analyses of features extracted from these signals. The use of machine-learning methods and acoustic features borrowed from human speech recognition to identify animals at the species and individual level has increased recently. To date there have been few studies comparing the performances of these methods and features used for call-type-independent species and individual identification. We compared the performance of four machine-learning classifiers in the identification of ten passerine species, and individual identification for three passerines using two acoustic features. The methods did not require us to pre-categorize the component syllables in call-type-independent species and individual identification systems. The results of our experiment indicated that support vector machines (SVM) performed best generally, regardless of which acoustic feature was used, linear predictive coefficie...

Vocal stereotypy in the rodent genera Peromyscus and Onychomys (Neotominae): taxonomic signature and call design

Abstract: Stereotypic behaviour, such as territorial calls and songs, is thought to be evolutionarily conserved, and therefore useful in discerning systematic relationships. We examined vocalizations of several species of Peromyscus and Onychomys, a monophyletic group of rodents (Peromyscini). We report stereotypic vocal signals occurring in both sexes of the deer mice Peromyscus californicus, P. eremicus, P. leucopus, P. melanophrys, P. polionotus, and the grasshopper mice Onychomys arenicola and O. leucogaster. The stereotypic vocalizations of P. eremicus, P. leucopus, and P. polionotus are confined to frequencies greater than 20 kHz, unlike those of Onychomys, which are clearly audible, or P. californicus and P. melanophrys, which generate lower frequency vocalizations than the other Peromyscus. We did not observe stereotypic vocalizations in P. aztecus. Intensity, context and consistency suggest that these vocalizations serve an announcement function. Distribution of spectral energy distinguishes genera and mos...

Swimbladder sound production: the forced response versus the resonant bubble

Abstract: Fish swimbladders can serve as sound-producing organs and accessory auditory organs that transfer vibrations to the ears. Since the 1960s swimbladders have been modelled acoustically as underwater bubbles: resonant monopoles that radiate sound omnidirectionally. Data inconsistent with this paradigm such as a low Q (a measure of sharpness of tuning) and rapid damping have been dismissed as damping by surrounding fish tissue. Despite its near universal acceptance, there are problems with the resonant-bubble paradigm. First, exciting a resonant structure such as a tuning fork does not require extreme speed, yet sonic swimbladder muscles are often considered the fastest in vertebrates. Additionally, resonant frequency will change with bladder size and depth, creating possible mismatches between communicating fish. Fish sounds have a wide frequency spectrum and are not tuned to a specific frequency. Further, a resonant bubble will continue to oscillate after muscle contraction ceases interfering with temporal coding of fish sounds and compromising the time fidelity of an auditory system. Finally, swimbladders have a number of interesting shapes, i.e. a heart shape in toadfish (Figure 1A), illogical for an omnidirectional radiator. We have proposed an alternate model, namely that swimbladder radiation does not depend on resonance but is driven as a forced response by the contraction of sonic muscles. Muscle contraction in the oyster toadfish drives the swimbladder in a quadrupole fashion – muscles push the sides of the bladder in, which then pushes the bottom of the bladder outward (Fine et al. 2001). Further, electrical stimulation of the sonic nerve generates sounds that damp rapidly, i.e. audible sound terminates before bladder motion indicating that only rapid bladder movements generate sound (Figure 1B). Bladder displacement is not sharply tuned and has high intrinsic damping (the damping coefficient z averages 0.37, equivalent to an automobile shock absorber). Stimulating the sonic muscles with a 100ms electrical train of pulses mimics the waveform of the courtship boatwhistle call, and evokes sound with a fundamental frequency equivalent to the stimulus frequency. The muscle can follow one-for-one to 400Hz indicating extreme resistance to tetany. Therefore the bladder is a low Q radiator with good time fidelity that will radiate the driving frequency regardless of the natural frequency of its internal cavity. Finally, sound spectra are broadly tuned and do not vary with fish size (Fine et al. 2009). We tested the directional radiation of the heart-shaped swimbladder by recording boatwhistles with paired hydrophones 1m from individual fish in the wild (Barimo and Fine 1998). One hydrophone was fixed in front of the fish and the other roved to various

Antiphonal vocal bouts associated with departures in free-ranging African elephant family groups (Loxodonta africana)

Abstract: We describe the interactive nature of vocalizations emitted by African elephant (Loxodonta africana) family groups while visiting waterholes. Despite being in close visual contact with each other, individuals called interactively within a series of overlapping or antiphonal vocal bouts that increased significantly while departing from the waterhole. After initiating departure from the waterhole, elephants in this study increased their calling rate and their production of overlapping vocal bouts. The majority of calls either overlapped or occurred within 1.5 seconds of another call as part of an antiphonal bout, rather than as isolated calls. The departure of larger herds was accompanied by a greater number of calling bouts. The increase in interactive antiphonal bouts during departure might serve to facilitate group coordination and cohesion, as well as possibly reinforce social bonds. The longer repeated bouts could also facilitate eavesdropping by distant elephants by boosting signal detection since the...

Identification of individual Eastern Screech-Owls Megascops asio via vocalization analysis

Abstract: To more easily and non-invasively monitor urban Eastern Screech-Owl populations, we developed a method of distinguishing individual owls using their calls. A set of seven variables derived from recordings of ‘bounce’ calls taken from 10 known (either free-ranging birds recorded at a single site on a single night or identifiable captive owls) owls was tested using a model-based clustering analysis (Mclust) as a method of discriminating individual owls. The cluster analysis correctly classified these calls with 98% accuracy. A second set of calls from nine owls was used to further test the method and correctly classified 84% of the calls using the same variables. Four owls were recorded repeatedly from 2008 to 2010 to determine the extent to which calls changed over time; the cluster analysis correctly assigned 89% of the calls to the correct owl regardless of the year the recordings were made. Based on these results, we are confident that the Mclust analysis can be used to reliably and safely estimate abun...

Song characterization in the spectacled warbler (Sylvia conspicillata): a circum-Mediterranean species with a complex song structure

Abstract: The spectacled warbler (Sylvia conspicillata) is a small passerine with a patchy distribution throughout the circum-Mediterranean region, including the North Atlantic archipelagos of Madeira, Canary Islands and Cape Verde. Here we characterize the species song structure on the island of Fuerteventura, quantifying repertoire size, inter- and intra-individual spectrographic variation, to determine whether acoustic variation occurred within an island population. Male song display was organized in song bouts of a variable number of song phrases, which in turn were made up of 4–69 syllables. We classified syllable types to derive a measure of repertoire size (number of different syllables) per song bout, and then used rarefaction methods to calculate the estimated repertoire size for our population of males. Three categories of song bout length were considered in analyses: short song bouts of 10 phrases, average bouts of 19 phrases and long bouts of ≥ 29 phrases. The observed and estimated repertoire size per ...

Repertoire composition and singing behaviour in two eastern populations of the Hermit Thrush (Catharus guttatus)

Abstract: Although it is highly recognisable, relatively little is known about the repertoire composition and singing behaviour of the Hermit Thrush (Catharus guttatus). To address this, we recorded spontaneously singing males in two eastern populations (Halifax, NS (n = 11) and Hancock County, ME (n = 7)) and analysed the recordings with respect to repertoire size, basic song type characteristics and song syntax. Males had song type repertoires of 7–12 song types, and no song type sharing between individuals was observed within or between populations. While frequency-related structural characteristics of the song types were the same between the populations, song type duration (especially that of the introductory note) differed significantly. The song types within each repertoire could be categorised into high and low song types based on introductory note frequency, and these song type categories also differed with respect to the amount and distribution of spectral energy. In both populations, males sang with immed...

Hierarchical and rhythmic organization in the songs of humpback whales (Megaptera novaeangliae)

Abstract: Since the groundbreaking work of Payne and McVay (1971), humpback songs have been conceptualized in terms of the upward hierarchical organization of sound units within phrases, and phrases within themes. Songs change within each season and all whales in a geographical region detect and sing the reshaped song. Here we propose two properties that act to make relearning the evolving song possible. First, each level of the hierarchical structure constrains the others. We estimated the degree of constraint using information theory and found that the theme, phrase, and prior sound unit reduced the source entropy of the current sound unit equally. Different sound units are found in each theme and phrase; each theme and phrase ‘uses up’ some of the sound units. Second, the rhythm of the sound units acts to simplify the phrase structure. The timing between sound units often separates adjacent phrases by longer silent durations, and in spite of huge differences in the number of sound units within phrases, the overa...

Evolution of acoustic communication: a multi-level analysis of signal variation

Abstract: Evolutionary change in signals may occur within and between populations. A pre-requisite of signal evolution is that heritable traits vary sufficiently between individuals for selection to operate....

Huge memory in a tiny brain: unique organization in the advertising song of Pallas's Warbler Phylloscopus proregulus

Abstract: The song structure of Pallas's Warblers – one of the smallest birds in the Palaearctic fauna – was investigated in central-southern Siberia (Russia). The endless song of this species consists mainly of various trills replacing each other in rapid succession. The individual repertoires include up to 270 types of trills and other vocal components grouped into packages – specific vocal structures repeating on a regular basis during the course of singing. Duration of the packages ranges from 9.9 up to 68.6 s (on average 30.5 ± 12.6 s). Each package contains a unique set of mutually associated vocal components. All components are typical for the given package and are usually not found in the other packages from a particular male. All packages are of a highly combinatory nature. The succession order of the different components within a given package varies over the course of its performance. The individual repertoire includes up to 20 different packages, which are organized serially in accordance with several (...

Bio-acoustic analyses to assess emotion in animals: Acoustic patterns are linked to behavioural, cardiac and hormonal responses of ewes to the separation from their lambs (abstract)

Abstract: Needs for objective and automatic assessment of animal welfare are increasing in livestock production. The strong dam-offspring relationship is a good model to investigate the vocal expression of emotions in animals since removing the lamb induces behavioural distress in ewes (e.g. agitation and vocalisations). We analysed acoustic characteristics in bleats of ewes following an unpredictable separation from their lambs, in addition to their behavioural and physiological responses. Twenty four ewes of INRA 401 breed were individually exposed to 3 successive 3 min phases: 1) in contact with their lamb placed behind a grid, 2) at 6m away from the lamb and 3) again in contact. Behaviour, vocalisations and cardiac activity (via adhesive external electrodes and a telemetric remote system) were recorded and blood was collected just after the test by venipuncture for cortisol assay. After the lamb was moved away, the ewes were more active and more vigilant, they also bleated more, and their heart rate and cortisol levels dramatically increased. These results confirm that the separation induced behavioural and physiological responses of distress in ewes which reflect negative emotional states. Beside, acoustic analyses show that lamb withdrawal induced changes in the voice characteristics of mothers in correlation with their physiological and behavioural responses. Temporal parameters (e.g. total duration) increased, as did amplitude parameters (e.g. energy, RMS). Concerning the frequency parameters, fundamental frequency increased but frequency Bandwidth, Quartiles (Q25%), (Q50%), (Q75%) decreased. Therefore some bleat characteristics can be used as acoustic markers of emotional distress. Acoustic sensory modality could thus provide an objective basis of negative emotions in sheep, which measure could be easier to automate than other behavioural and physiological correlates of emotional reactions.

RECENT BIOACOUSTIC PUBLICATIONS (2008 and earlier)

Abstract: (2009). RECENT BIOACOUSTIC PUBLICATIONS (2008 and earlier) Bioacoustics: Vol. 18, No. 3, pp. 291-318.

Effects of temperature on the song parameters of the Moroccan bushcricket Eugaster spinulosa (Orthoptera, Tettigoniidae)

Abstract: Acoustic signals are important for inter- and intraspecific interactions in many species. Their information potential depends largely on species characteristics. Here we describe quantitatively the song of Eugaster spinulosa (Johannson 1763), (Orthoptera, Tettigoniidae) and analyse the relationships of song parameters with temperature. To the best of our knowledge there are no previous descriptions available of the song of any species in the genus. Songs of seven males from the mountains of Jebilet, Marrakech (Morocco), were recorded in a semi-anechoic chamber for 105 days. Using automated thermal tables, individuals were exposed to a daily cycle of temperatures between 17.5 and 41.5°C. The calling song of Eugaster spinulosa is broader in frequency (2–28 kHz) than the song of other tettigoniids. It consists of extended series of separately audible echemes, which are polysyllabic and comprise a variable number of broadband syllables, usually between 5 and 10. The stridulatory activity of Eugaster spinulosa...

Applying bioacoustics: what can be learned from pure and applied aspects?

Abstract: Sounds produced by animals are often very apparent to humans, indeed in some instances these sounds are the only indication of the presence of the animal. Sound is also a key channel of communicati...

Adaptive auditory plasticity for social communication in the plainfin midshipman fish (Porichthys notatus)

Abstract: Acoustic communication plays an important role in the social behaviours of vocal teleost fishes in the family Batrachoididae (midshipman and toad fishes). The midshipman and toadfishes have become good models for investigating the neural and endocrine mechanisms of auditory perception and vocal production shared by all vertebrates (Bass and Lu 2006), in part, because the reproductive success of these batrachoidid fishes is highly dependent on acoustic communication. Recent neuroethological studies of acoustic communication in the plainfin midshipman fish (Porichthys notatus) have provided strong evidence for the related reproductive-state and steroid-dependent modulation of hearing sensitivity in this species that leads to enhanced coupling of sender and receiver in this communication system (Sisneros and Bass 2003; Sisneros et al. 2004a). The plainfin midshipman fish is a vocal marine teleost fish found along the west coast of the USA. During the late spring and summer, midshipman fish migrate from deep water into the rocky intertidal zone to court and spawn. Midshipman fish are known to have three adult reproductive morphs that include female and two male morphs known as type I and II. Type I or ‘singing’ males acoustically court females with their seasonal advertisement calls or ‘hums’, which is a multiharmonic acoustic signal with a fundamental frequency (F0) that ranges from 90 to 100Hz (Brantley and Bass 1994). The dominant harmonics of the hum range up to 400Hz and can contain as much or more spectral energy than the F0. These harmonics have been hypothesized to be important for the detection and localization of the advertisement signal during the reproductive season (Sisneros and Bass 2003). Type II males or ‘sneaker’ males use an alternative reproductive tactic that does not require them to build nests or acoustically court females. Instead type II males satellite and/or ‘sneak’ spawn in the nests of type I males to steal fertilizations from ‘singing’ males when they are actively courting females. Females rely heavily on their auditory sense to detect and locate advertising males that produce the multiharmonic hums during the breeding season and will often exhibit robust phonotaxis to a synthesized hum (and even to a low frequency tone near the F0 of the male’s advertisement call). Previous work showed that the frequency sensitivity of the auditory afferents that innervated the saccule, the main organ of hearing in the midshipman, changed seasonally with reproductive state such that reproductive females were better suited than nonreproductive females to encode the dominant harmonics of the male’s advertisement call (Sisneros and Bass 2003). An investigation of the seasonal periodicity of reproduction

Directional hearing and strategies for sound communication

Abstract: Successful sound communication between animals located in vegetation requires that the sound signals retain sufficient amplitude and structure to allow the receiving animals to extract the message....