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Underwater noise pollution is becoming a pressing environmental issue that could affect aquatic wildlife, but very little research has been done on this topic. The effect can be even more dramatic for species actively using acoustic signals for communication and assessment of quality of opponents during agonistic encounters. We examined the effects of underwater noise on auditory sensitivity and aggressive behaviour in the vocalising skunk loach Botia morleti. Fish were exposed to white noise (142 do re: 1 µPa) for 12 hours and shifts of auditory threshold were measured with the auditory brainstem response protocol. Noise exposure resulted in elevated auditory thresholds throughout the entire auditory range. It was also found that significant recovery occurred in approximately 9 hours. The effects of noise-exposure on behaviour during aggressive contests were investigated by comparing contest dynamics between noise-exposed fish and a resident (non-exposed fish). The results showed that noise-exposure could influence behaviour in two ways: 1) contest durations with noise-exposed fish were significantly shorter; and 2) noise-exposed fish tended to engage in more re-escalation of contests than those with control fish. Two mechanisms (direct, indirect) were proposed to explain the findings. In the direct effect, noise exposure causes direct stress on the fish which results in decreased contest duration. In the indirect effect, the noise exposure cause a temporary hearing loss which results in a misperception of the acoustic signal emitted by the opponents. The sound perception and production feedback loop is compromised due to noise exposure (i.e., elevation of hearing threshold) and as a result, contests are repeatedly re-escalated because the information content of the signal can not be accurately perceived by the noise-exposed fish. The present study demonstrates that noise pollution could have dire physiological impacts as well as behavioural consequences (supported by National Organization for Hearing Research, N1MH-58198, Institute of Museum and Library Service-LL90187).

The underwater acoustic environment is inherently loud as a result of ambient sounds. In addition, there is an increasing amount of sound from anthropogenic sources, which produce noise within the hearing range of most fish (less than 1.0 kHz). For fish, the auditory system is one of the most important sensory systems because it provides information about ambient sounds, prey items, predators and potential mates. Since a fish's ability to accurately interpret its acoustic environment is essential for its survival, it is important to understand how noise affects sound perception ability of fish. This study examines the question: does noise exposure affect auditory sensitivity differently in hearing specialists (fish with coupling devices between the gasbladder or ancillary structures and inner ear, enhancing overall hearing with wider frequency range and lower threshold) and hearing generalists (fish without coupling devices, with narrow frequency range and higher threshold)? For this study, a hearing specialist species, the fathead minnow Pimephales promelas, and a hearing generalist species, the bluegill sunfish Lepomis macrochirus, were used to examine: (1) the immediate effects on auditory threshold of white noise exposure at various exposure durations (1-24 h at 0.3-4.0 kHz, 142 dB re: 1µPa); and (2) recovery time after noise exposure (1-14 days). Audiograms for noise-exposed fish were measured using the auditory brainstem response protocol, which records acoustically evoked brainwaves, and compared to control fish (no noise exposure). The results for specialists showed that their best hearing frequency range (0.8-2.0 kHz) was affected significantly more than other frequencies. In addition, recovery of hearing ability after noise exposure was found to be both frequency- and exposure-dependent. The results for hearing generalist fish will be presented and discussed (work supported by the Kentucky Academy of Science, National Organization for Hearing Research, NIMH-58198, Institute of Museum and Library Service-LL90187).

Sciaena umbra (Linneaus, 1758) is one of the four species of Sciaenidae that are present in the Mediterranean Sea. It lives in rocky reefs or in Posidonia grass meadows; it is a nocturnal predator, sexes are separated and eggs are buoyant. It has been known to produce sounds since 1947 at least, when Dijkgraaf described sounds of Sciaena umbra observed in the Zoological Station A. Dohrn of Naples. In the UNEP Asp-protocol of 1995 it was included in the list of species whose fishery needs regulating. In the Miramare Marine Reserve (north-eastern Adriatic Sea, Trieste, Italy), S. umbra is very abundant from May to September along the artificial rocky reefs under the pier of Miramare castle. Sounds were recorded digitally at 44.1 kHz sampling rate with a Reson TC 4032 hydrophone from the pier. Recording 10 minutes each hour for a whole day (24h) confirmed that sounds are present only from late afternoon until 1 a.m. Therefore all subsequent recordings of 10 minutes each hour were carried out from 19.00 to 24.00 only. Sounds are repetitive knocks composed of 1-11 pulses, more or less regularly spaced (131.6ms ± 33.8 SD), with the main frequency components within each pulse ranging between ca. 100 and 1,200 Hz. Based on time interval between sounds, there are at least three different acoustic patterns, named irregular, regular and chorus. Sounds are emitted from May till September with irregular patterns usually followed by regular ones during a daily session. Chorus patterns were recorded only in June and July and not consistently. If S. umbra is a serial spawner like most other Sciaenidae, chorus pattern might indicate spawning bouts.

Today, sounds produced by cetaceans are used for acoustic detection of individuals and groups in the wild. However, the detection probability ascertained by a concomitant visual survey has not been demonstrated extensively. We studied the finless porpoises Neophocaena phocaenoides in the Yangtze River from Wuhan to Poyang Lake in 1998 in China, using underwater sound monitoring with hydrophones (B&K 8103) placed along the sides of a research vessel, concurrent with visual observations. The peak to peak detection threshold was set at 133 dB re 1 µPa. With this threshold level, porpoises could be detected reliably within 300 m of the hydrophone. In a total of 774 km cruise, 588 finless porpoises were sighted by visual observation and 44,864 ultrasonic pulses were recorded by the acoustical observation system. The acoustic monitoring system could detect the presence of the finless porpoises 82% of the time. False alarms in the system occurred with a frequency of 0.9%. The performance of the acoustic detection system depends highly on the sound production rate and the directionality of the beam pattern. Echolocation click events of two finless porpoises were recorded with an acoustic data logger in an oxbow of the Yangtze River. They produced 3 to 4 click trains in a minute. A behavioural data logger attached to the identical animal provided the dive depth and the body angle simultaneously. Comparing the values of dive depth, the body angle and the level of water surface reflection, the 120 degrees off-axis sonar signals were found to have 160 dB peak-to-peak sound pressure level at one meter from the animal. The finless porpoises produced sonar signals frequently and the off-axis signal had sufficient level to be detected. High frequency acoustical observation is suggested as an effective method for field surveys of small cetaceans, which produce high frequency sonar signals.

Every winter, humpback whales Megaptera novaeangliae congregate in warm, low-latitude waters to mate and give birth. While in winter waters, male humpback whales produce long complex songs. Song content is dynamic and singers incorporate changes as they occur. Average source levels suggest that most sounds in the song would become masked by ambient noise levels at distances less than a few tens of kilometres. Thus, singers must be relatively close to one another, much closer than the distance separating wintering regions, in order to match the whole complex acoustic structure of the local song type. The tendency for singers to converge on current song themes, plus limited propagation distance, allows the potential for stable geographic variation to occur. The use of geographic variation in song to map population structure was evaluated by comparing songs recorded in winter migratory termini in Madagascar, Western Australia, Eastern Australia, New Caledonia, Tonga and Colombia in winter of 1996. Differences in regional variants were most pronounced between Madagascan, Australian and Colombian song. Eastern Australian, New Caledonian and Tongan song were most similar. Some evidence of song sharing between Western and Eastern Australian waters was present. Phenetic analysis was consistent with Discovery tag models of humpback stock .structure in the southern hemisphere. The results suggest some migratory exchange among wintering regions of Area V and slight exchange between Areas IV and V; but the time and location at which song sharing occurs remains speculative.

Voiced cries are described as cries where the fundamental frequency is well evident in the spectrogram, while voiceless and partially voiced cries partially or totally lack a well defined contour (Lieberman 1985: In Infant crying: Theoretical and research perspectives. (B. M. Lester & C. F. Z. Boukydis, eds.) Plenum Press; New York pp. 29-58). Some authors suggest that a greater percentage of the latter is pathognomonic of CNS damage, as happens in kernicterus due to hyperbilirubinemia (Koivisto 1987: Acta Paediatrica Scandinavia Suppl. 335, 1-73). In a study of the ontogeny of premature infant cries carried in our laboratory, we found a greater amount of voiceless and partially voiced cries in premature infants aged 34 and 40 weeks than in normal control. However, normal infants show a considerable amount of voiceless and partially voiced cries (Lenti Boero et al. 1998, Perceptual & Motor Skills 86, 1123-1140), while infants affected by severe pathologies such as congenital hypothyroidism (Lenti Boero et al. 2000: J. Child Neurology 15, 603-608) and CNS lesions induced by neonatal asphyxia, emit a lesser amount of voiceless and partially voiced cries than normal controls. In this presentation we examine this issue, both from a physioacoustic and an evolutionary perspective and suggest that disphonation might be due to different causes and that in normal infants it might have had an important evolutionary role in calling the attention of a distant care-giver.

In human speech, temporal features have only secondary importance but it seem likely they play a much more important part in avian communication. The different physiology of birds results in many short discrete sounds separated by clear silences. We have used this structure of bird vocalisations as the basis of a number of small linked computer programs. First, and acting as the foundation of all the others, is a program to recognise sound from silence, using amplitude threshold and two glitch filters all easily variable. The times of onset of each sound and silence are stored in a second file that can either be opened in a spreadsheet or accessed for further processing. The initial use of this program was to measure the pulse rates in the fast and slow parts of nightjar churring to allow recognition of individual birds. This program was then expanded to draw 'temporal spectra' of songs (i.e. the relative frequencies of notes of different lengths) and used to explore the temporal differences between the songs of closely related species. The latest development is more ambitious. Each 'note' in a simple song, identified by the first program, is characterised by a few simple time and frequency variables, e.g. note length, frequency mean, slope, curve and complexity. The goal, which is still a long way off, would be to look for sequences using the same type of analysis tools as those developed for word and grammar recognition. However, initial tests with chaffinch song look promising.

The subjects of this study are nine Humboldt penguins Spheniscus humboldti kept in captivity at the Genoa Aquarium. The ecstatic display is an acoustic behaviour performed both by males and females and its function is not well defined. It was described as an attracting call given by unpaired males toward unattached females or as a territorial display of males. Observations collected over about two years of study have given information about the distribution of this behaviour: males vocalise much more than females and the acoustic activity is higher in the afternoon, when penguins are in or near the nest. The ecstatic display is composed of short initial inspirations, from one to four loud emissions, a final inspiration and, sometimes, a very short emission after last inspiration. Researchers are able to distinguish each individual through its characteristic acoustic patterns ' that enable individual recognition. The following parameters were measured: number of initial inspirations, length of each emission, length of gaps between two emissions, .number of emissions, presence/absence of final inspiration, presence/absence of final short emission, pattern of distribution of dominant frequencies of emissions. Most of these parameters are statistically different between individuals.

To test a new method of quantitatively analysing complex animal communication systems, we applied information theory concepts to the notes repertoire combined with temporal parameters of the Rufous-bellied Thrush Turdus rufiventris song. Like most Turdus thrushes, Rufous-bellied Thrushes are remarkable for their long, varied and melodious songs. For the analysis of the species repertoire, we used recordings of 44 individuals from 24 localities covering its full geographical range. We measured the repertoire size, note duration and rhythm (frequency of note utterance), and combined these parameters with the Shannon entropy values calculated for each individual. Although individuals maintain species-specific recognition capacity, we found a large variation between their song parameters and show that information theory can be useful to analyse large and varied animal vocal repertoires. In order to reduce the heterogeneity of our sample and elucidate the breath of the observed variation, we used mathematical tools based on information theory to create an index integrating the values of entropy and rhythmicity of the individual songs. To define the structure and organisation of this species song, values of the conditioned entropy were analysed to establish individual sequences and results were synthesised using cluster analysis. Although its song characteristics challenge human understanding of animal communication, the Rufous-bellied Thrush recognises itself as a species and successfully establishes intra-specific communication and all necessary biological functions. Our application of information theory to the structure and organisation of Turdus rufiventris song allows the identification of the chaotic behaviour of this communication signal, opening the way for further analysis which could demonstrate more clearly the function and codification of complex sound communication systems.

Among the various animals using acoustic signals for their communication needs, man and other primates are not the only ones who developed complex signals. We will show, with examples taken from the Brazilian fauna and recordings deposited into the Arquivo Sonoro Neotropical-ASN at the Campinas State University-UNICAMP, that different strategies exist for acoustic communication. Complex repertoires are found in species with complex social relationships. This is the case in some crickets (Endocous itatibensis, for example) and amphibians, like Hyla minuta, with sophisticated territorial and courting behaviour. In birds, the size and complexity of the repertoire is related to their social organisation and reaches a peak in gregarious jays (like Cyanocorax caeruleus) and anis (especially Guira guira). The "functional song'', that is the acoustic communication signals assuming the primordial function of species-specific recognition, expresses two opposite tendencies: the simplest unequivocal signal or the most varied one. The first solution is the most efficient if the signal is not degraded during its transmission, as are the double drumstrokes of the large Campephilus woodpeckers and the pure and unmodulated single whistle of some tinamous, doves, or owls like Glaucidium minutissimum. The other communication strategy consists in increasing the complexity of the signal, ensuring its reception through high redundancy and low monotony. It also permits the coding of populational and even individual identification cues, but must retain the specificity. Such a strategy is possible only by learning and some measure of interaction and creativity. Besides dialects, made of various parts, songs may show individual variations by different means: unique but stereotyped combination of sound elements as in Volatinia jacarina, multiplicity of fixed song types as in Cyclarhis gujanensis, versatility of the emission of different phrases (Cistothorus platensis) or notes (Turdus rufiventris, Augastes lumachellus). The song of the Humpback Whale Megaptera novaeangliae is a dialect combining a very long phrase with a largely predictable sequence. Versatility is increased by imitations as in the song of Turdus lawrencei. The challenge is to measure these diverse types of complexity.