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International Bioacoustics Council
International Bioacoustics Council (IBAC)

XV IBAC Symposium - abstracts

Pavia, Italy, October 24-26, 1996

 

 


TALKS


 

Acoustic biodiversity in tropical cicadas: examples from S.E. Asia.
Matija Gogala

Slovene Museum of Natural History
POB 290, SLO - 61001 Lubljana, Slovenia


It is well known that the singing cicadas show in S.E. Asia very high biodiversity with many species inhabiting the same ecosystem. They have to cope with the problem of sending their acoustic messages in very noisy environment, since many insects, birds, frogs and other animals are emitting sounds at the same place and the same period of the year. Therefore the cicadas have developed there special strategies to cope with the jamming problem. One peculiarity is the evolution of songs with characteristic rhytmic patterns and in many cases even with a high degree of frequency modulation. The second adaptation to the extreme biodiversity is the fixed time of singing. Many cicada species are acoustically active only during a certain species specific time period of the day. Such time window is usually 30 to 60 minutes long. Many species are singing only in the evening or only in the morning hours. Nevertheless, the dawn-dusk species are in Malayan peninsula an exception. Such time sharing between different species is probably not the only reason for "dawn", "dusk" or even "midnight cicadas". This could also be an adaptation to avoid or minimize predation by birds or some other insectivorous animals. It should not be overlooked that many other cicada species there are not limited by a specific time window. Anyway, in the high biodiversity of S.E. Asia it is not difficult to find exceptions or special cases, and this is true also for the singing of cicadas.Therefore, the repertoire of the sound emissions of the S.E. Asian cicadas is challenging for every sound recordist. With a suitable equipment nowadays it is not very difficult to make good documentary recordings there, despite of a high humidity. The main problem is still to see, identify or even catch the singing animals in the dense vegetation, and to find out ethological context of recorded sound emission.



Sound libraries have biodiversity taped.
Richard Ranft

British Library National Sound Archive, 29 Exhibition Road, London SW7 2AS, UK.


Between them, bioacoustic libraries worldwide preserve samples of sounds of most of the vertebrate species that utilise acoustic communication, and many of the most important invertebrates. Their collections have been built up mainly through the contributions of many scientists and recordists and represent many hundreds of thousands of hours of work in the field. They are invaluable especially for comparative studies between individuals, populations and species where it is often impossible for one person to replicate, even in a lifetime of work, the dedicated efforts of so many collectors of sounds.
Example of the uses of sound libraries in biodiversity studies will be given, for example: providing identification tools in fieldwork; documenting biodiversity by sound sampling; analyses of community sound structure and the "acoustic niche" hypothesis; and as clues for taxonomic and phylogenetic analyses.
Sound libraries are gradually improving facilities towards proving remote access to their collections. Preliminary catalogues of two large collections - those of the National Sound Archive in London and of the Borror collection in Ohio - are already accessible on the Internet ( <http://cadensa.bl.uk> and <http://iris.biosci.ohio-state.edu/borror_lab/passerines.html> ) and a small but growing number of Internet sites offer instant access to actual audio samples.


Acoustic localizations of blue whales (Balaenoptera musculus) by fixed arrays and moored autonomous hydrophone arrays.
Kathleen M. Stafford1 , Christopher G. Fox2


1 - CIMRS/PMEL, Newport, OR 97365 U.S.A.
2 - NOAA/PMEL, Newport, OR 97365 U.S.A.

The Pacific Marine Environmental Laboratory (PMEL) of the United States' National Oceanic and Atmospheric Administration (NOAA) has been monitoring and archiving sound recordings from the U.S. Navy's underwater hydrophone arrays since 1991. These data contain many marine mammal calls, including those made by blue whales (Balaenoptera musculus). The call of the blue whale in the northeast Pacific is often sufficiently loud to be detected on more than one array. Matched filtering techniques can expand detection capabilities to additional arrays, allowing blue whale calls to be localized even when they are far from the arrays.In this manner, PMEL has identified regions where blue whales occur seasonally well offshore of the west coast of the U.S.
In order to monitor areas of the world ocean not covered by fixed hydrophone arrays, PMEL has developed autonomous moored hydrophones that have been used to record acoustic energy from both underwater seismic activity as well as that from whale calls. Each mooring package consists of an anchor, an acoustic release, line, hydrophone and data recorder, and a flotation package. The hydrophones are designed to be moored in the SOFAR channel; the titanium case containing the data recorder can withstand pressure to at least 1000 m below sea level. Currently each hydrophone can store up to 2.8 Gb of data; only the sampling frequency and battery life (up to 8 months, depending on sampling frequency) limit the duration of the experiment. The hydrophones are designed to be deployed as an array of independent instruments whose geometry can be determined by the needs of the experimenter in order to localize acoustic sources of interest. Deployment and recovery of each instrument takes as little as one hour depending upon the platform used.
An array of six of these hydrophones was deployed in the NE Pacific in September 1995. One of the goals of this experiment was to compare and "ground truth" locations of calling blue whales from the U.S. Navy's SOSUS data with those detected on the autonomous hydrophones. During the seven day experiment, no blue whales were seen in the area but two blue whales were detected and then tracked acoustically on the hydrophone array. One of these animals was detected on all three available SOSUS arrays. The locations of the blue whale from the two methods are comparable although the location accuracy is more precise on the local array.


Aversive sounds and the harbour porpoise (Phocoena phocoena).
Goodson A. D., Connelly P. R., Lepper P.


Underwater Acoustics Group - Bioacoustics & Sonar
Electronic & Electrical Engineering Department
Loughborough University, LE11 3TU, UK


In the search for an efficient acoustic method of reducing the bycatch of porpoises in bottom-set gillnets the effects of presenting sounds at different frequencies and waveforms have been examined using a rehabilitated, ex-stranded, harbour porpoise as the subject in a 20 x 30 m floating net cage experiment. The animal was available for this study during the last phase of a planned programme of re-adjustment prior to its release.
Low level sounds SL<130 dB re 1Pa at 1m) were presented underwater using a purpose built digital signal synthesiser with three types of output: narrow band tones; wide band frequency sweeps; and click burst sequences which replicated porpoise echolocation signal characteristics. These signals, derived from pre-programmed data stored in EPROM, could be clocked out at different frequencies by binary division of a master clock. This method produce signals with identical waveforms in a series of octave frequency steps when divided down from the 140 kHz maximum frequency. The signals were introduced into the water using 4 simple piezo 'bender' transducers spaced apart at 3 metre intervals starting at a corner of the net cage and extending along the longer 30 m side. Surfacing positions were subsequently extracted from the video camera images which recorded an overhead view of the pool. The animal's behaviour was studied in 20 minute periods, i.e. prior to, during, and after exposure to a sound signal, and the results obtained demonstrate that certain signals caused marked and rapid movement of the animal to parts of the pool away from the transducers whereas other sounds had little or no obvious effect. Surprisingly, this animal's choice of position did not always favour the furthest corner from the transducers. However, a careful analysis of the acoustic sound pressure field shows that the complex pattern of sound caused by the 4 interacting sources produced nulls which the animal was apparently well able to sense and exploit.
This paper demonstrates the complexity of the sound pressure level variations that must be taken into account when working in shallow water conditions especially where constructive and destructive interference can occur between multiple sound sources and with reflecting surfaces.


Comparison of swimbladder and pectoral sounds in Pimelodid, Mochokid and Doradid catfishes.
Friedrich Ladich

Institute of Zoology, University of Vienna, Althanstra▀e 14, 1090 Wien, Austria


Representatives of several tropical catfish families are unusual among teleosts for having evolved two sonic organs: pectoral spines for stridulation and swimbladder drumming muscles. Pectoral mechanisms mainly differ in relative size between pimelodids, mochokids and doradids, whereas swimbladder mechanisms exhibit differences in origin and insertion of the extrinsic muscles. In pimelodids, drumming muscles insert ventrally onto the swimbladder. Mochokids and doradids, however, possess differing elastic spring mechanisms. Differences in vocalizations among families were investigated by comparing sounds produced in distress situations in air and underwater. For each family, fish from two species were hand-held and their sounds recorded.
High frequency broad-band pulsed sounds of similar duration were emitted during abduction of pectoral spines in all three families. Adduction sounds were similar to abduction signals in doradids, shorter and of lower sound pressure in mochokids and totally lacking in pimelodids. Total pectoral sound duration was positively related to relative spine length (normalized for standard length). Simultaneously or successively with pectoral sounds, low frequency harmonic drumming sounds were produced by representatives of two families. Drumming sounds were of similar intensity as stridulation sounds in pimelodids, fainter in doradids, and not present in mochokids. Swimbladder sounds were frequency modulated and the fundamental frequency was similar in pimelodids and doradids..
The ratio of stridulatory to drumming sound amplitude was higher in air than underwater in both doradids and one of the pimelodids. Also, overall duration of pectoral sounds, compared to swimbladder sounds, was longer in air than underwater in one doradid and pimelodid species.
This first comparison of vocalizations within one major teleost order indicates that differences in morphology of swimbladder and pectoral sonic mechanisms result in family-typical patterns of sound production. Furthermore differences in sound production between both media suggest that additionally context- (receiver-) dependent variation in vocalization exists.


Use of auditory brainstem response (ABR) for fish auditory sensitivity study.
Hong Y. Yan, Todd N. Kenyon, Friedrich Ladich


School of Biological Sciences, University of Kentucky
101 Morgan Building
Lexington, KY 40506-0225, USA


Traditionally psychoacoustical or electrophysiological methods have been used to study the auditory sensitivity of fishes. No invasive procedures are used in obtaining behavioral audiograms. The training procedures involved are tedious, time consuming and not applicable to every species. Electrophysiological recordings from auditory nerves or endorgans (e.g., microphonics) provide additional ways of auditory sensitivity assessment. Technical difficulties and limited sampling site(s) prevent rapid and complete understanding of fish hearing ability. In an attempt to expedite the fish audition ability research, an auditory brainstem response (ABR) recording protocol is developed to provide measurements of hearing ability of several species of fish. The ABRs represent far field potentials generated by the hearing endorgans, fiber tracts and nuclei of the ascending auditory pathway. Therefore audiograms generated by ABR technique can provide a quick and more complete understanding of fish hearing ability.
Tungsten reference electrode is placed in between nares of fish while the recording electrode is placed on the top of fish head to conduct ABR recording. The fish is immobilized with an injection of Flexedil and a gravity-feed respirator (with aerated water) is used to keep fish alive during the recording. Pure tone bursts (100 Hz to 3 kHz) or click signals are provided through a speaker mounted above the tested animals. A hydrophone is placed adjacent to the ear region of the fish and traces of hydrophone output (i.e., the sound likely perceived by the fish) are used to compare with ABR waves generated by the fish. For comparison purpose fish species used are a hearing specialist (fathead minnow, Pimephales promelas), a generalist (oscar, Astronotus ocellatus) and a labyrinth fish with an accessory hearing enhancing structure (blue gourami, Trichogaster trichopterus). Easy setup of ABR recording devices and commercially available systems (e.g., Tucker-Davis Technologies) facilitate quick ABR measurement of the auditory ability of fishes. This technique can be used to investigate the relationship between acoustic signals generated by sonic fish and their auditory sensitivity.


Eavesdropping in a territorial songbird communication network: preliminary results.
Peter K. McGregor1,2, Torben Dabelsteen2, Jo Holland2

1 - Behaviour & Ecology Research Group, Department of Life Science,
University of Nottingham, Nottingham NG7 2RD, U.K.

2- Department of Population Biology and Centre for Sound Communication, Zoological Institute, University of Copenaghen, Tagensvej 16, DK-2200 Copenaghen N, Denmark.

Bird song is capable of transmission over distances of several territories, therefore signallers and receivers constitute a communication network. Eavesdropping is a type of receiving behaviour that is only possible in communication networks; it is defined as extracting information from interaction between other individuals. Such receiver behaviour has the potential to provide information on relative competitive ability. In the context of territory defence and bird song this means that an individual can, by eavesdropping, use its neighbours as yardsticks against which to judge unknown intruders before having to interact with those intruders.
We used interactive playback with male great tits Parus major to simulate a singing intrusion with a subject's neighbour, we then simulated an intrusion with the subject. Interactive playback was used because it allows the playback stimulus to be varied song by song and therefore we could behave as different types of intruders. We signalled willingness to escalate by overlapping the neighbour's songs and increasing strophe length relative to the neighbour (song type was matched). We signalled unwillingness to escalate by alternating playback and reducing playback strophe length (again, song type was matched).
If subjects had extracted information from the interaction between their neighbour and playback (i.e. if eavesdropping had occurred) we would expect the subject to respond differently to the intruder depending on its apparent willingness to escalate. The first results from such experiments (6 males) show just such a difference. When subjects were subsequently presented with "neutral" interactive playback (same song type as used by the intruder, alternating pattern of singing and matching strophe length) they responded by overlapping song and remaining at some distance to intruders which had signalled willingness to escalate with their neighbours. In contrast, they responded by quickly approaching closely to intruders which had apparently been unwilling to escalate with their neighbours. This difference in response is best interpreted as subjects using information on the fighting ability of the intruder to modify the level of their aggressive response. They rapidly escalated to close-range territory defence with apparently weak opponents, but responded more cautiously to apparently strong opponents.
These results are consistent with eavesdropping and support our contention that such behaviour will be an important feature of receiving in a communication network.


Discrimination of the parental call by the king penguin chick Aptenodytes patagonicus: the "cocktail-party" effect.
Thierry Aubin1, Pierre Jouventin2

1 - NAM-CNRS URA 1491. Universite Paris-Sud. F-91400 Orsay, France.
2 - CEBC-CNRS UPR 4701. Station de Chize. F-79360 Villiers-en-Bois, France.

The king penguin breeds without a nest in colonies of several thousands birds. To beg for food, the chick must recognise the parents in a noisy environment, without using visual and olfactory, only vocal cues. The parental call has to be distinguished from among the calls of other parents and chicks and the display calls of mating pairs. This recognition process is made more difficult not only by these parasitic noises but also by propagation problems due to the parent-chick distance and to the mass screen of birds which together impose a particularly difficult problem of acoustic communication. To study this recognition process, we have quantified some of the problems which the chick must solve. Firstly we described the main characteristics of parental calls. Secondly we measured the ambient noise of the colony in the feeding area. Thirdly, in this area, we studied the propagation of adult calls to analyse the degradation of the signal at different distances, quantifying the effect of the mass body screen by comparison with propagation in an open area. Then, we conducted experiments with chicks, establishing mean and maximum distances of detection of the parental call and testing their ability to detect parental calls in a &laqno; jamming ╗ situation, i.e. among extraneous adult calls. At last, we tested chicks to determine which are the main acoustic parameters involved in the recognition process of the parental call.
Our results demonstrate that the noise in the colony is almost continuous, that it has a high sound pressure level and that the spectrum is occupied by numerous birds at a time. There is total masking effect in terms of frequency and amplitude, increasing the difficulty the chick has in detecting its parents. Nevertheless, the chick can compensate for this effect, since it is able to detect an information-carrying signal whose intensity is below that of a background noise with similar temporal and spectral characteristics. This process of perception against a background noise (i.e. the &laqno; cocktail-party effect) is linked to a coding - decoding of the parental call closely adapted to these particular environmental constraints.


Dialects in Ravens: New aspects of an old problem.
Peter Enggist

Zoological Institute, University of Bern
Arbeitsgruppe Ethologie und Naturschutz Laenggasstr. 27
CH-3012 Bern, Switzerland

Several studies showed that male songbirds react differently to songs of the own, adjacent and foreign dialect. Because reactions to neighbour's and stranger's song of the same dialect were not compared, and because it was not controlled for structural similarities among the tested songs, the interpretation of the differences in reaction remains difficult. It might be that discrimination between alien and foreign dialects is not principally different from the well known discrimination between songs of neighbours and strangers, but might be explained by reacting to differences in structural similarity between the songs. Therefore Falls (1982) speculated that neighbour - stranger discrimination would be weak compared to the discrimination between dialects because dialects are more differing in structure than the vocalisations of neighbours of the same dialect. We tested this hypothesis on ravens (Corvus corax) male repetitive calls. Detailed analysis of the vocal repertoire of 37 resident pairs and the geographic distributions of the call types showed that two repetitive call types of males and two of females separate the study area in two dialect regions. Playback experiments were conducted on males of one of the dialect regions. They reacted differently to neighbour's and stranger's calls of the same dialect, but not differently to calls of the adjacent dialect. Whereas calls of the two dialects are clearly structurally different, neighbour's and stranger's calls within the same dialect are not differing in structural similarity. These results indicate that there is not a tight relationship between signal structure and meaning in the sense that the more differing the signals, the more differing also the reactions, as has been assumed so far. To interpret our results and to get on in our understanding of communication in general, we propose a shift in the point of view from looking at signals and at the reactions on them as properties of individuals alone to one considering them as elements of a relationship between individuals.


Communication in Ravens: Again new aspects of an old problem.
Ueli Pfister

Zoological Institute, University of Bern
Arbeitsgruppe Ethologie und Naturschutz Laenggasstr. 27
CH-3012 Bern, Switzerland

The development of song in most songbirds depends upon learning processes.
Only a few studies revealed the possibility that not only vocalisations might be learned, but also how to use them. We investigated the use of calls in interactions of 21 resident pairs of ravens (Corvus corax) and asked whether the use of calls depends on the call types. In our study area southwards of Bern (Switzerland) we found at 37 resident pairs 81 different call types. The repertoire of an individual male or female raven contains 12 call types in the mean. Therefore the repertoires are only partially overlapping. In an experimental setup we provoked interactions between a free-living and a caged pair. The sequences of calls of the free-living pair were analysed with row-wise matrix correlations and the results depicted with correspondence analysis. We found in all pairs a correlation between the transition matrices of preceding and following calls of the partners which shows that the call behaviour of one individual influences that of the other. Therefore the partners are communicating. Comparing transition matrices of certain call types of different pairs we found in some cases a high correlation between matrices of different call types, in other cases no correlation between matrices of the same call type. Comparing the results of the correspondence analyses among different pairs, we found that the same call types can be differently associated with the calls of the partner, although according to the repertoire composition the same associations would have been possible. This shows that certain pairs may use one and the same call type differently, and different call types the same way. How to use a call is therefore not dependent upon its type or acoustic structure. We conclude that acoustic communication in ravens is based mainly on conventions between the individuals. If not only the vocalisations are learned, but also how to use them in interactions, theoretical concepts of communication, which today assume that meaning relies on signals, have to be extended to include the possibility that the meaning of signals depends on relationships between individuals.


Subharmonics, biphonations and frequency jumps in the vocalisation of Japanese macaques (Macaca fuscata).
Tobias Riede, GŘnther Tembrock

Humboldt Universitńt Berlin, Fachbereich Biologie, Invalidenstrasse 43, Berlin 10115, Germany

Subharmonics, frequency jumps and biphonations are well described as normal elements of the human vocal repertoire. They were found also in the vocalisation of many other mammals such as the Japanese macaques.
In this work the repertoire of the Japanese macaques was quantitatively analysed for the occurrence of subharmonics, biphonations and frequency jumps. These phenomena are summarised as irregularities. Calls from animals of two established caged groups were recorded, analysed and judged on the existence of irregularities. In the age class up to 1 year irregularities occur on average with a frequency of 18.6% (max. 45%, min. 3.5%; 10 infants; 2000 calls). Adult female vocalisation during the mating season ('solicitation call') contain on average 25% irregularities (max. 32%; min. 15.9%; 6 females; 726 calls). Vocalisations from aggressive encounters (67 calls) contain no irregularities in adult males and females, but some biphonations and frequency jumps have been found in the calls of juveniles. The ratio of the three phenomena shows an individual specific pattern.


Spectrographic analysis of cat vocalisations during the early months of life.
Clotilde Trinchero, Cristina Giacoma, Roberto Ostellino

Dip. di Biologia Animale, UniversitÓ di Torino, V. Accademia Albertina 17, 10123 Torino, Italia.

In a previous study signal emitted by a mother cat and those emitted by the kittens during the first weeks of life were compared. It results that the fundamental frequency of the kitten vocalisation is two or three times the values of fundamental frequency of their mother. The aim of this study is to describe the harmonic structure of the signal, the variation of values of the fundamental frequency during the somatic growth and to study the experimental pattern of Flanagan (1972). The formant frequencies depend, in a complex way, on the dimensions and the shape of the vocal tract.
The contact vocalisations (mews) were elicited removing kittens from the mothers. The vocalisations of four different families of cats were collected and analysed from the second day up until the 7th month of the kitten's lives (total number of kittens=13). Records were collected with an analogic tape recorder (Marantz CP 230) and two digital ones (Aiwa HD-S1 and Casio DA-1); connected microphones were Sennheiser ME88. Vocalisations were analysed with the program Voxys implemented in a IBM compatible computer equipped with a 16 bit Sound Blaster card. The fundamental frequency of each vocalisation is computed obtaining the T0 period by cepstrum analysis in the point of maximum stability of the signal. This is obtained searching the zone of temporal stability during the emission of the sound in three subsequent frequency bands. The formants are obtained by cepstral analysis of the spectrum in the point of maximum stability.
Comparing kittens' mews with those of the mother it is evident that during the early weeks of life, the fundamental frequency (F0) of the kittens' vocalisations is from 2 to 3 times the fundamental frequency of their mother's. For each signal of the kitten the value of F0 decreases as a mean trend with age, while it is constant in each signal of an adult cat. When the kittens are 60 days old the F0 is comparable to their mothers' F0 (the maximum difference recorded is 80 Hz). The ratio among the first three formants is 1:2:3. According to Flanagan's model this ratio indicates that the shape of the vocal tract is similar to a cylinder with aboral extremity open.
The measurements of F0, F1, F2 and F3 allowed to discriminate mother's vocalisations with 100% correctly classified cases (discriminant analysis: Wilks lamda; F=.17. 155, P= 0.000). The vocalisations of 15 days old kittens are correctly classified to their families in percentage varying from 78 to 100%. Similar results are obtained with 30 days old kittens. At 60 days the percentage of correctly classified vocalisations reaches 99%.


Vocalisations of captive black and white ruffed lemur: stability and mother-offspring comparison.
Clotilde Trinchero, Cristina Giacoma, Marco Gamba, Maura Ampollini

Dip. di Biologia Animale, UniversitÓ di Torino, V. Accademia Albertina 17, 10123 Torino, Italia.

The aim of this research is to study the ontogenesis of black and white ruffed lemur (Varecia variegata variegata) vocalisations by comparing the signals emitted by a mother with those emitted by her offsprings in order to estimate the relations between them.
The lemurs live in captivity at "Parco Natura Viva" in Pastrengo (VR- Italy), in a structure consisting of indoor and outdoor sections (cages are respectively of 3.00 x 3.00 m and 5.00 x 5.00 m). The studied group is formed by a pair and their offspring (a young female born in 1994 and one born in 1995; a male born in 1996). The vocalisations of the male (1996) and the female (1995) offsprings were collected and analysed, starting from the first days of life until six and 18 months old.
The vocalisations were recorded by analogical recorder Marantz CP 230, DAT recorders Aiwa HD-S1, Sony TCD-D7, Aiwa PRO HS77; connected microphones were Sennheiser ME88 and ME66, Trevi ME-27, Shure Studio 1.1. Vocalisations were analysed with Macintosh IIci computer using Sound Designer IITM and Canary 1.1.1 programs and IBM compatible computer using Voxys program suitable to provide the formants.
The analysis has been focused on the "mew", a low amplitude call emitted by new-borns as well as adults (Pereira et al. 1988). Preliminary results based on sequential analysis of behaviour preceding and following the "mews" clearly show that the "mews" are always emitted in a relaxed situation or social interaction. The "mews" emitted by the young female are followed by the offspring approaching her mother only in 1.2 % of cases and they elicit mother approaches in 13.0% of analysed sequences.
The full description of sound characteristics is based on the description of spectrogram, spectrum and waveform plates. The tonal call exhibited 15-20 weak harmonic bands and a slow rise in pitch. The mean F0 of the female 1995 regularly decreases from the second day of life up until the 166th day. From that moment until 14 months old varies from 230 to 232 Hz depending on the day. Her mother (5 years old) has a mean F0 of 232+-13. The fundamental frequency and the first formants show the same trend. The mean call length tend to be shorter on the first days of life (range 112-582 msec) and become stable (700-800 msec) before the third month of life. Adult call length varies from 700 to 850 msec length. The amplitude pattern of the first 4 formants show a decreasing trend. The first one exhibits the highest amplitude also in new-borns. The energy distribution of the other formants become stable over the first 5 months of life.


The role of female choice in the evolution of the European green-toad advertisement call.
Sergio Castellano, Cristina Giacoma

Dip. di Biologia Animale, UniversitÓ di Torino, V. Accademia Albertina 17, 10123 Torino, Italia.

In many species of frogs and toads acoustic communication is the most relevant way by which correct syngamy is achieved. In these species females respond phonotactically to the typical stereotyped vocalisations produced by conspecific males. Moreover, many studies have proved that females are able to discriminate among conspecific males and select those uttering the most appealing calls. In the present work we employ the advertisement call of the European green-toad (Bufo viridis) as a model to analyse the role of female choice in the evolution of the acoustic signals. Green toad advertisement calls are described on the basis of four acoustic properties: note and internote duration, pulse-rate and fundamental frequency. Female preferences for these same properties are analysed by means of playback experiments, in which pregnant females have to choose between two synthetic calls that differ in only one of the previously mentioned acoustic properties. The analysis of the within-bout of calling coefficients of variation permits the distinction between highly stereotyped (pulse-rate and fundamental frequency) and highly variable (note and internote duration) acoustic properties of the advertisement calls. Females exhibit patterns of preferences that result in a stabilising or weakly directional selection on stereotyped properties and in a strong directional selection on highly variable (or dynamic) properties of the calls. The observed relationships between signal variability and pattern of female preferences support three hypotheses: 1) different acoustic properties of the signals encode different kinds of biologically significant information; 2) since a high stereotypy of the signals (high redundant information) is known to reduce the risk of communication errors, the high stereotypy of some acoustic properties can be seen as an adaptive character connected to their function of species-specific information encoders; 3) female preferences and the different selective pressures acting upon the acoustic properties of the calls can be seen, together with some developmental constraints, as the most relevant forces in the evolution of the green toad communication system.


First record of the mating call of a burrowing frog from western Madagascar: Scaphiophryne brevis (Boulenger, 1896) (Anura: Microhylidae).
Riccardo Jesu, Giovanni Schimmenti

Acquario di Genova
Area Porto Antico, Ponte Spinola
I - 16128 Genova, Italia

The Anurans of Madagascar include about 170 species grouped in three families: Hyperoliidae, Ranidae and Microhylidae. The endemism rate at species level is around 99%, since only two species belonging to the Ranidae are not endemic to the island.
The subfamily Scaphiophryninae is an endemic taxon of the Microhylidae which has been divided in two genera: Paradoxophyla Blommers-Schl÷sser & Blanc, 1991 (monotypic) and Scaphiophryne Boulenger, 1882 (five species).
Scaphiophryne brevis (Boulenger, 1896) is a very poorly known burrowing frog from western and south-western Madagascar inhabiting dry open habitats, most of them consisting in secondary vegetation types.
During fieldwork carried out in the peak of the rainy season (January 1995) in a coastal area of the west, a group of calling males of Scaphiophryne brevis was observed near shallow temporary ponds in sandy soil located a few dozen metres from the shore within Morondava village. This gave the opportunity of recording for the first time the mating call of this species one century after its description.
The call - recorded at an air temperature around 25 ░C - consists in the monotonous repetition of an inharmonious note lasting 340-350 ms between interval of 400-510 ms. Frequency ranges from 2 to 5.5 kHz.
It may be interesting to compare the call of this species to the one recorded from Scaphiophryne calcarata (Mocquard, 1895), another burrowing frog apparently closely related to Scaphiophryne brevis and found in similar habitats. The mating call of Scaphiophryne calcarata - recorded in Tolagnaro, south-east Madagascar, at 25 ░C - consists in the repetition of a screaming sound which lasts 850-900 ms and is repeated after 2200-2500 ms. Frequency ranges from 3 to 4.3 kHz.


A bionic sonarhead.
Herbert Peremans, Ashley Walker, John Hallam


Artificial Intelligence Department, University of Edinburgh
Forrest Hill 5, EH1 2QL Edinburgh, UK


We will present a 5 DOF ultrasonic sensorhead that allows the study of different sensor-motor loops in echolocation. The head consists of a neck, allowing for the panning of the head as a whole, a transmitter which is fixed to the head and two independently orientable receivers, one on either side of the transmitter. Each receiver has two DOF allowing for pan and tilt movements around its centre. The generation of the transmit signal, the processing of the received signals as well as the motorcontrol of the sensorhead is executed on a transputer network. To process the received signals we make use of a filterbank modelled on the bat's cochlea. This filterbank consists of a number of bandpass filters logarithmically distributed over the frequency range of interest, currently from 30 kHz to 100 kHz. The shape of these filters and the distribution of their central frequencies can be varied depending on the specific echolocation task being investigated. Next we determine the instantaneous amplitudes of the outputs of these filters by a rectification and low-pass filtering process. We believe that although this is only a crude approximation to the actual processing performed at the cochlear level it nevertheless succeeds in modelling the cochlea's most important characteristics. The outputs of this model are the inputs for the different echolocation tasks we want to study. The head is now being used to investigate what clues are available to a binaural animal while tracking a prey. We also look at the robustness of the different tracking schemes in the presence of clutter. It is clear that the head allows the study of many other mechanisms, especially those involving sensor-motor interaction, important to echolocation. Hence, we argue that bionic devices such as our sensorhead are valuable tools adding to the instrumentarium of those that study echolocation by biological organisms.


Ultrasonic vocalizations during eterosexual encounters in mice.
Mazzacane E., D'Amato F.R.

Istituto di Psicobiologia e Psicofarmacologia, C.N.R., Via Reno 1, 00198 Roma, Italia

Ultrasounds are emitted by mice in different social contexts. The main interest has been devoted to ultrasounds emitted by pups during their development that seem to affect mother-infant relationship. They have been used as a measure of stress that can be easily pharmacologically modulated. Adult mice emit ultrasounds during the first minutes of interaction with a potential sexual partner. Mainly the male seems responsible for these vocalizations and data from the literature suggest that these calls represent a measure of male sexual motivation.
Several experiments have been conducted to verify this hypothesis. NMRI outbread albino mice were tested for ultrasonic emission during the first three minutes of sexual encounters.
Ultrasounds (70 + 5 kHz) were counted by the use of a bat detector (QMC Instruments). Female characteristics (strain, weight, estrous condition) did not seem to affect male ultrasonic emission. Genetic and experiential male's characteristics did not represent variables affecting, from a quantitative point of view, males ultrasonic calls.
We did not find significant correlation between ultrasonic vocalization (UV) and latency of ejaculation nor between male behaviours indicating strong arousal and UV. On the contrary we found a strong inverse relationship between aggressiveness and ultrasonic vocalisation: males with little UV towards females showed more male-male aggressiveness than males with high vocalisations. The amount of ultrasonic calls seemed rather affected by the test cage while not the behaviours: testing the male in the presence of the odour of another male sensibly decreased UV. Moreover, when females were given the opportunity to choose between beddings of males with low and high levels of UV, diestrous females preferred the bedding of high vocalizing males while estrous females did not show clear preference.
All together these data raised doubts about the causal and functional implications related to ultrasonic communication during the first minutes of sexual interaction.


Sonographic characterization of ultrasonic vocalizations emitted by infant laboratory mice.
Igor Branchi, Daniela Santucci, Augusto Vitale, Enrico Alleva

Section of Behavioural Pathophysiology and Section of Comparative Psychology, Laboratorio di Fisiopatologia di Organo e di Sistema, Istituto Superiore di SanitÓ, Viale Regina Elena 299, I-00161 Roma, Italy

Young mice and rats separated from the mother and littermates produce ultrasonic vocalisations during the first two or three weeks of postnatal life. Various conditions such as handling, hypothermia, olfactory or tactile stimulation elicit ultrasonic emission from the immature rodent. These vocalisations are also affected by either changes in social variables or by administration of psychoactives.
Although it is known that pup vocalisation stimulate a prompt expression of maternal behaviours such as nest-building, searching, and retrieving, the communicative role of infant ultrasonic vocalisations is still a matter of investigation. A fine-grained analysis of ultrasonic vocalisations per se, as well as the study of the different contexts in which calls are emitted, may contribute to a better understanding of their possible role in adult-infant intraspecific communication.
Eight-day-old outbred CD-1 mice were isolated from their mother and littermates and randomly exposed to one of the five different experimental conditions, namely: i) odour from the nest; ii) social isolation; iii) low temperature; iv) tactile stimulation; v) odour from a conspecific adult male.
Spectrographic analysis of the structure of the calls revealed that ultrasonic calls by neonatal mice are differently shaped (although conforming to 5 main stereotyped types: constant frequency, modulated frequency, frequency steps, composed, short) and that, when the sound-structure typology and emission frequency interval are considered, the context under which vocalisations are emitted strongly influences type and frequency of call production. Furthermore, the present study helps to better understand the ultrasonic production behaviour of the mouse, increasingly the most common rodent species in biomedical laboratories, and it can be highly adequate for the development of ethological models aimed at teratological or toxicological investigations. Finally, our results may be useful to the evaluation of regulatory guidelines (OCSE, WHO, EU, etc.) using functional endpoints for assessment of early behavioural deficit.


POSTERS


Interactive deterrent devices for fishing nets, designed to reduce small cetacean bycatch.
Goodson A.D., Newborough D. and Woodward B.

Underwater Acoustics Group - Bioacoustics & Sonar
Electronic & Electrical Engineering Department,
Loughborough University, LE11 3TU, UK

The problems of reducing small cetacean bycatch in fishing nets are many and complex and acoustic solutions need to be tailored to suit specific species and net types. Active deterrent devices or alarms have recently been shown to be beneficial in reducing the bycatch of harbour porpoises (Phocoena phocoena) in some carefully monitored trials in North American sink-gillnet fisheries (Kraus et al. 1995). The methodology employed to date is still at an early stage of development, typical devices generate simple 10 kHz tonal pulses from small battery powered packages distributed at intervals along the fishing net. The long term effectiveness of this approach has already been questioned as small cetaceans are known to habituate quite quickly to novel stimuli. A more sophisticated approach is now at the trials stage which uses higher frequency, wideband signals which have been determined to be more aversive to this species (Goodson & Connelly, this meeting). To minimise habituation effects over time such 'beacon alarm' signals need only be transmitted occasionally if the acoustic activity of an approaching echolocating animal can also be detected and used to trigger the device into a transponder type of operation. Such a device has now been designed at Loughborough University and implemented using digital micro-controller technology. As this circuitry is programmable almost any complex waveform can be generated to suit specific applications. The use of a digital micro-controller permits a number of additional features to be implemented in software without a significant increase in the overall component count and, despite the sophistication, the cost per device remains acceptably low.
It may be argued that a silent animal could remain at risk, however, in the context of bottom set nets (sink-gillnets) this should not apply, as the harbour porpoise swimming close to the bottom in deep water is there to forage for prey and hence actively employing its echolocation sense. This interactive approach reduces spurious acoustic emissions which waste battery energy and as most responses are triggered by the approach of an animal at risk of colliding with the net, the deterrent effect is expected to be longer lasting. The alarm response ceases quickly once the animal turns away. Provided that these devices are spaced apart along the net within detection range of each other additional benefit is obtained if they also respond to a neighbour's alarm signal as this will result in a 'ripple-fire' of activity along the net. This linking of emissions provides better orientation information than can be given by simple randomly timed pingers. Interactive devices are also intended for application to large pelagic trawls where the delineation of the net's boundary by such a ripple-fire transmission is expected to give a clearer indication of the extent of the hazard to an animal which may have followed fish into the net. Since triggering can also be stimulated by a ship's echosounder these devices should make the location and recovery of lost nets a relatively simple exercise.


Underwater acoustic recording of cetaceans made by the Italian Navy.
Gianni Pavan1,3, Marco Priano1, Michele Manghi1, Pamela Nascetti2, Andrea Perazzi2

1 - Centro Interdisciplinare di Bioacustica e Ricerche Ambientali, UniversitÓ degli Studi di Pavia
Via Taramelli 24, 27100 Pavia, Italia.
2 - Istituto di Anatomia Comparata, UniversitÓ di Genova, Italia
3 - Dipartimento di Urbanistica, Istituto Universitario di Architettura di Venezia, Italia

Within the frame of the European Nature Conservation Year 1995, the Italian Navy set up a cooperative research program with Universities and other institutions to give logistic support and to apply its technologies to the study and protection of the marine environment. The project includes a research program on cetacean acoustics, mainly dealing with the sperm whale Physeter macrocephalus, to unveil and monitor its seasonal movements and behaviour. The Italian Navy surface vessels crews have been trained to visually recognize them in order to fill sighting schedules. Besides, personnel working on submarines and maritime patrol aircraft has been trained in identifying biological sounds recorded during ASW (Anti Submarine Warfare) operations.
ASW techniques proved to be successful in finding and recording cetaceans; unclassified sound recordings made independently by the Navy, with surface vessels, submarines and sonobuoys, have been provided to the Cetacean Sound Library of the Centro Interdisciplinare di Bioacustica e Ricerche Ambientali.
The research continued in 1996 mainly with the collection of recordings from sonobuoys deployed while performing ASW patrolling activities.
To date, several valuable recordings have been collected from elusive species like the sperm whale and pilot whale. Several recordings of sperm whale codas typical of the Mediterranean Sea (/// / pattern) have been collected, including new "short" codas with the same distinctive pattern.
Whenever possible, species identification of vocalizing animals was made by comparing sounds with those available in the Cetacean Sound Library.


Acoustic behaviour of a Bottlenose Dolphin (Tursiops truncatus) mother-calf pair in captivity: technical aspects in data collection and analysis.
Guido Gnone1, Gianni Pavan2,5, Stefania Manca3, Carla Benoldi4, Barbara Bonsignori4, Michele Manghi2

1 - Acquario di Genova, Area Porto Antico, Ponte Spinola, 16128 Genova, Italia
2 - Centro Interdisciplinare di Bioacustica e Ricerche Ambientali, UniversitÓ di Pavia, Italia
3 - Istituto di Zoologia, UniversitÓ di Genova, Italia
4 - Istituto di Zoologia, UniversitÓ di Milano, Italia
5 - Dipartimento di Urbanistica, Istituto Universitario di Architettura di Venezia, Italia

For one year, starting on September 5th 1994, the behaviour of a captive new born bottlenose dolphin (Tursiops truncatus) and its mother was monitored through both video and acoustic recordings.
The main objective of such research was to study the behavioural evolution of the two during the first year of the calf's life. Attention was focused on acoustic behaviour and its use in relation to the contexts.
In order to be able capture any possible correlation, the acoustic signals were analysed with a PC based DSP Workstation developed at the University of Pavia and the resulting real-time spectrographic analyses were superimposed on the live video recordings.
The poster will present all the technical elements used in developing such method for collection and analysis of the video and acoustic signal. Problems related to such system and suggestions for a better output will also be part of the presentation.


Analysis of long clicking sequences of Sperm whales (Physeter macrocephalus).
Gianni Pavan1,2, Marco Priano1, Michele Manghi1, Claudio Fossati1

1 - Centro Interdisciplinare di Bioacustica e Ricerche Ambientali, UniversitÓ degli Studi di Pavia
Via Taramelli 24, 27100 Pavia, Italia.
2 - Dipartimento di Urbanistica, Istituto Universitario di Architettura di Venezia, Italia

In June 1995, a 12 days research cruise was organized in the Ligurian and North Thyrrenian Sea to record cetacean sounds with the towed array of the University of Pavia. The cruise has been supported by the Italian Navy within the ENCY 95 (European Nature Conservation Year) activities.
The hydrophone was towed for 111 hours (out of 12 cruising days) at speeds up to 14 km/h; listening stations were held on a 24h schedule for at least 10 min every half an hour. One sperm whale was detected and located. It was heard at night and acoustically tracked for the following 8 hours. Within this period, the whale was sighted at the surface 5 times while 8 complete dives were continuously recorded on DAT tapes (about 6 hours of recording). The recordings are now archived at the Cetacean Sound Library held at the Centro.
New methods of sound analysis were developed to make the analysis of such long recordings easier and to give compact pictures of whole dives. Our real-time analysis software was modified with new procedures able to 1) automatically detect and count clicks, 2) measure and save inter-click intervals, 3) save a packed representations of the click sequences and display autocorrelograms to show the evolution of interclick intervals over long periods of time.
The analysis of the recordings shows that all the recorded dives were characterized by a typical and constant clicking pattern at their beginning. The duration of the acoustical emission, measured from the first click to the last click of each dive, was on average 27 minutes 30 seconds while the silence related to the surfacing was on average 13 minutes and 11 seconds.


Sound production and reproductive behaviour in the Armoured Catfish Corydoras paleatus (Callichthyidae).
Inge Pruzskinszky, Friedrich Ladich

Institute of Zoology, University of Vienna, Althanstra▀e 14, 1090 Wien, Austria

Sound production during courtship, dyadic encounters and in distress situations was investigated in C. paleatus. Fish emitted broad-band stridulation sounds made up of several pulses. Each sound corresponds to the abduction of one pectoral spine. The sonic mechanism was developed in all individuals. Males, however, had relatively longer pectoral spines (standardized to body length) than juveniles or females.
Several males, which are usually smaller than females, court with one gravid female at the same time. Courting males emitted trains of sounds averaging 1250 ms in duration. During spawning one male clasped the female's barbels with his pectoral spine and inseminated almost all eggs. DNA-fingerprinting revealed, however, that a few eggs were fertilized by nearby males. Males did not behave aggressively towards each other during courting or dyadic encounters. During dyadic encounters males emitted shorter duration trains of sounds (mean: 850 ms) than during courtship.
Single stridulation sounds were emitted in distress situations, when fish were hand-held in air. Contrary to courtship and encounter sounds, distress calls were produced by both sexes and were also recorded from juveniles. Dominant frequency of sounds was negatively correlated to body weight. Sound duration was positively correlated to relative size of pectoral spines.
This description of acoustical behaviour in corydoradine catfish reveals striking differences to the second callichthyid subfamily (Callichthyinae), where vocalization was observed during territorial behaviour in males and aggressive behaviour in both sexes (Mayr, 1987).


Ontogeny of Agonistic Behaviour and Vocalization in the Croaking Gourami, Trichopsis vittata (Teleostei).
Silvia M. Henglmueller, Friedrich Ladich


Institute of Zoology, University of Vienna, Althanstrasse 14
1090 Vienna, Austria

The development of agonistic behaviour and vocalization in the croaking gourami was studied from hatching to four months of age, by which time fish became sexually mature. Initial interactions started when fry were 11 days old and consisted of Approach and Flight in a feeding context. More complex threat patterns appeared during dyadic encounters as fish grew older. Lateral Display (spreading of median fins in a lateral position) first occurred during the third week, Circling shortly afterwards and Pectoral fin beating when fish were seven weeks old. Rapid pectoral fin beating was first accompanied by sound emission at eight weeks. Initially, croaking sounds were built up of a series of single pulses, each one produced by one pectoral fin. Later single-pulses gave way to double-pulsed bursts. Mean number of single and double pulses increased from 4.4 to 6.0 per croak and mean pulse period from 27 to 35 ms from initial sound production until maturity. Furthermore sound pressure increased significantly with growth of fish. Dominant frequency of croaks decreased from 3600 to 1500 Hz with increasing size (15 - 37 mm standard length). After vocalization was established Frontal Display, Mouth Biting and Appeasement Behaviour occurred at the age of ten weeks. The development of agonistic behaviour is mainly age and not size dependent in croaking gouramis, although growth-rates differed widely. Unlike behavioural patterns sound characteristics were clearly correlated with body size.
To our knowledge this is the first study investigating ontogeny of vocalization in fish. Results in T. vittata demonstrate that sound production develops simultaneously with agonistic behaviour patterns and thus independently of sexual maturation.


Startle response level of Japanese anchovy Engraulis japonicus to underwater pure tone signals.
T.Akamatsu,Y.Matsusita,Y.Hatakeyama, Y.Inoue


National Research Institute of Fisheries Engineering,
Hasaki, Kashima, Ibaraki, 314-04 Japan


Reactions of Japanese anchovies Engraulis japonicus to 100 to 700 Hz underwater pure tone signals were observed. A mean body length of the anchovies was 11 cm and a mean weight was 10 g. Seven hundred fish were kept in a net enclosure which was 2 m in diameter and 1.5 m in depth.
The anchovies ordinarily swam in a circle at almost same speed in the net enclosure.
The startle response behavior was defined as follows: more than a half of the fish changed their behavior just after the sound projection , for example, the acceleration of the swimming speed, dispertion or condensation of fish group. When no or few anchovies changed their ordinary behavior, it was defined as no response.
The up/down staircase method was used to determine the threshold level of the startle response. The sound pressure level ranged from 130 to 160 dB and was changed by 5 dB step.The startle response levels were 154.5 dB at 100 Hz, 153.3 dB at 200 Hz, 146.8 dB at 300 Hz and 153.8 dB at 500 Hz. The 700 Hz signal did not affect the fish behavior up to 158 dB.


Repeatability and effects of temperature and individual size on components of the breeding sounds emitted by males Padogobius martensii (Pisces, Gobiidae).
Marco Lugli

Dipartimento di Biologia Evolutiva e Funzionale, Viale delle Scienze, UniversitÓ di Parma, 43100 Parma, Italy

Repeatability, that is the intra-class correlation coefficient (Sokal & Rohlf, 1981), describes the degree to which variation within individuals contributes to the total variation in a group of individuals. In this study the repeatability for several parameters of the tonal and the drumming sounds emitted by breeding males of Padogobius martensii was measured to examine (1) which parameters of the sounds were more repeatable (i.e., stereotyped), (2) the contribution of temperature and male size to between-male variation in sound parameters, and (3) the potentiality for individual assessment/recognition by acoustical means in this species.
Sounds were collected from single bouts of calling by 16 males differing in body size and water temperature. All the sound parameters examined showed a remarkable inter-male variability. Water temperature explained most of between-male variation in the properties of the tonal sound, while body size was the main factor explaining the between-male variation in the properties of the drumming sound. After temperature control, however, the two types of sound showed a similar pattern of variation in the acoustic properties. Parameters of the tonal sound were less repeatable than their counterparts in the drumming sound. In general, high repeatability in a sound parameter was associated with a larger contribution of male size to the between-male variation in that property (after correction for temperature). Because of higher repeatability and stronger relationship with male size, the drumming sound appears to be adapted to convey information about the quality of the emitter (assessment signal).


Sound production with an abdominal "tymbal" organ in a noctuid moth, Pseudoips fagana.
Niels Skals, Annemarie Surlykke, Hanne S°rensen

Centre for Sound Communication, Inst. of Biology
Odense University, Campusvej 55, DK -5230 Odense M, Denmark


Hearing in moths has evolved to enable them to detect and evade echolocating bats. Thus most moths are silent. Among Arctiidae click production with tymbal organs on the metathoracic episternites is fairly common, but in most species this is also part of the interaction with bats. However, a few moth species produce sound and use their hearing for intraspecific communication. Generally, the noctuid species described so far produce sound by some kind of stridulatory mechanism often involving the wings and legs. Here we describe quite another mechanism of sound production in the male noctuid moth Pseudoips fagana (FABRICIUS) of the subfamily Chloephorinae, involving a ventral "tymbal" organ centrally on the ventral part of the basal abdominal segment. P. fagana, the green silver line, is common in northern Europe. The sound production has been observed while the moths fly around the tree tops in the dusk. The clicks sound like electric sparks to the human ear and may be heard at several meters distance. We recorded clicks from males in stationary flight in the lab. The moths would only click while flying in place. We elicited the clicks by very intense ultrasonic sound pulses. The moths produce short series of clicks each lasting around 0.3 to 0.4 ms with maximum sound energy around 30 kHz. The sound pressure level was intense, 119 dB SPL at 2 cm. The sound producing organ is buried deeply in a groove, but may be observed if the moth is placed ventral side up and the abdomen is bend dorsally. The hearing of P. fagana was measured by recording extracellularly from the auditory nerve. Both males and females were most sensitive around 30 kHz with a threshold of about 35 dB SPL, thus matched to the spectrum of the sounds. There are no behavioural observations on these moths, but we believe it most likely that the sounds are part of the sexual display.

Research supported by the Danish National Research Foundation.


Acoustic emission in Megatrupes cavicollis (Bates 1887) (Coleoptera, Geotrupinae).
C. Palestrini, M. Luzzatto, A. Roggero, M. Zunino


Dip. di Biologia Animale, UniversitÓ di Torino, V. Accademia Albertina 17, 10123 Torino, Italia.

The genus Megatrupes Zunino 1984 is up to now represented by two species, M. cavicollis (Bates 1887) and M. fisheri (Howden 1987), both distributed between the Wesyern Sierra Madre and the Sistema VolcÓnico Transversal, in Mexico.
The aim of our research is to analyze the sound produced by M. cavicollis through two distinct apparatuses - thoraco-elytral and coxo-abdominal. The individuals examined were collected during the summer 1987 at the Reserva de la Biosfera "La Michilia", Durango, Mexico.
Signals were recorded, acquired and analyzed through the program Signalyze 3.12. Each emission is constituted of a disyllabic chirp, with two distinct subunits separated by a pause. This is a standard situation among the Geotrupinae.
Seven variables concerning duration and frequencies of the chiro have been analyzed. The sexual dimorphism, as regard the morpho-anatomy, does not appear at the acoustic one.
Both apparatuses contribute to the sound production. Nevertheless, the coxo-abdominal apparatus seems to be more effective than the thoraco-elytral. Individuals deprived of the elytra emitted stridulations very similar to those usually produced by individuals not experimentally constrained, whereas individuals deprived of their hind legs emitted very thin, unrecognizable sounds.
Although statistical analyses of frequencies and duration show significant differences among individuals, males and females do not appear to be separated into two distinguishable clusters.


New data on the acoustic communication in two mediterranean grasshoppers (Orthoptera, Acrididae).
M.E. Clemente, M.D. Garcia, J.J.Presa

Department of Animal Biology (Zoology). Faculty of Biology.
Espinardo Campus. University of Murcia. 30100 Murcia. Spain.


New data on the sound produced by Sphingonotus coerulans corsicus Chopard, 1923 and Truxalis nasuta (Linneo, 1758) are given. Oscillograms of both sounds are provided for the first time, as well as their physical characteristics and other aspects of the communication between specimens.
For both species sound seems to be a territorial and sexual cue; they have not been observed singing when isolated, as other Acrididae, but always when they are close to or in contact with other individuals.
The song of Truxalis nasuta consists of isolated echemes composed of 7 - 29 syllables lasting about 0,234 seconds. The syllable repetition rate is about 2,2 syllables/sec.
The main frequency of emission is between 1 and 10 kHz, with the main peak at 5 kHz.
For Sphingonotus coerulans corsicus two different songs have been recorded, one for a territorial behaviour and other for a courtship one.
The territorial song consists of isolated syllables lasting about 0,350 seconds with the main frequency between 4 and 8 kHz, with a peak at 7 kHz.
The courtship song consists of a syllable produced by the movement of hind legs followed by several microsyllables produced by light movements of hind legs. The syllable lasts about 0,670 seconds. Sometimes, after the sounds referred before, the specimens produce a new syllable, always shorter than the first, and more microsyllables, but always fewer than before. The frequency of this song lays between 3 and 5 kHz, with the main peak at 3 kHz.
* This communication has been partially supported by the D.G.I.C.Y.T. grant number
PB89-0448 of the Spanish Governement.


Stridulation in four ants species of the genus Messor: ultrasonic emission and description of their stridulatory apparata (Hymenoptera, Formicidae).
Priano M.1, Pavan G.1,4, Mori A.2, Grasso D.2 , Le Moli F.2, Giovannotti M.3, Fanfani A.3

1 - Centro Interdisciplinare di Bioacustica e Ricerche Ambientali, UniversitÓ degli Studi di Pavia
Via Taramelli 24, 27100 Pavia, Italy.
2 - Dipartimento di Biologia Evolutiva e Funzionale, UniversitÓ degli Studi di Parma, Italy.
3 - Dipartimento di Biologia Animale e dell'Uomo, UniversitÓ degli Studi "La Sapienza", Roma, Italy.
4 - Dipartimento di Urbanistica, Istituto Universitario di Architettura di Venezia, Italy

The aim of this work is to amplify the knowledge of acoustic communication in ants. Four myrmicinae species belonging to the genus Messor (i.e M. capitatus, M. minor, M. structor and M. wasmanni) were tested.
Some Messor species have already been the object of a preliminary study only on workers (Schillinger and Baroni Urbani, 1985) but in our work the ultrasonic emission of specimens belonging to the castes of queens, males and workers (minor and major) were recorded.
Ultrasonic signals were acquired using a Bruel & Kjaer 2231 with a B&K 4135 transducer (frequency response up to 100 kHz) and a bat detector Ultra Sound Advice S-25.
Signals were fed into an amplifier with anti-aliasing low-pass filter to be digitally recorded and analyzed on a PC-based Digital Signal Processing Workstation. Sampling frequencies up 200000 s/sec allowed the recording up to 87.5 kHz. The ants were held with a pincer and the microphon was kept at a distance of approx. 1 cm.
The description and measurements of stridulatory apparata were made by means of S.E.M. (Scannig Electron Microscope Cambridge S 250 TP) analysis on the same specimens used for recordings.
In all the individuals investigated, a stridulatory organ occurs in the position regarded as typical of Formicidae: the plectrum on the hind margin of the third abdominal tergite and the file of pars stridens on the pretergite of the fourth.
The file is made up of very regular parallel cuticular ridges and, in all the individual examined, extends for almost the whole length of the pretergite itself stopping at a very short distance from the anterior margin of the pretergite. The pars stridens shows very sharp margins. Posteriorly, some long bristles occur in proximity of the margins.
The hind margin of the third abdominal tergite shows, in its very central part, a tickening connected with the scraper. This tickening makes the scraping action of the tergal margin more effective conferring rigidity upon this region.
For each species it is possible to describe a common general pattern of structure and operation of the organ producing sounds and ultrasonic emission which is always of values in maximum frequency higher than 41 kHz.
Playback tests are in progress in order to clear up the biological role and significance of the acoustic signalling for the survival of the colony of these species.


Vocalization structure and its possible function in the Brown-headed parrot Poicephalus cryptoxanthus.
Vincenzo Venuto, Renato Massa

Dipartimento di Scienze dell'Ambiente e del Territorio
UniversitÓ degli Studi di Milano
Via Emanueli 15, 20126 Milano, Italia


Today there is evidence that parrot vocalizations and even parrot mimicry are highly functional. In addition, there are also data suggesting that parrots may be able to use assemblages of short sounds, normally used in a given context, to built up more complex vocalizations that may be used in a different context.
To investigate this possibility, we studied vocalizations and associated behavioural patterns of the Brown-headed parrot (Poicephalus cryptoxanthus), a South-East African species, kept in pairs in captivity at our African Parrot Centre of the University of Milan. By analyzing a total of 12 hours of records by mean of the "Canary" program of Cornell Laboratory of Ornithology, we recognized seven main types of calls that may be separated in the following groups: a) short antagonistic calls associated with an imminent attack or a warning to disperse, b) nestling's calls mainly consisting in food begging, c) sexual interactions, that is courtship, duetting, preening and courtship-feeding. The latter are also the longest and most complicated calls. They are composed of a total of 10-13 syllabes that may be assembled in different notes that, in turn, may be further assembled in a song that may consequently be highly variable and may even last for 78 seconds. These long and complicated songs are usually uttered as a duet by the members of a pair probably to consolidate the ties between male and female. These findings further support the hypothesis that some parrots may maintain their monogamic pair-bond through the performance of a pair specific courtship song that, in some species, such as the African grey, may also include the mimicry of heterospecific sounds.


Song repertoire variability in the reed bunting Emberiza schoeniclus.
Giuliano Matessi1, Alessandro Grapputo1, Andrea Pilastro2, Guglielmo Marin1

1 - Dipartimento di Biologia, via Trieste, 75 - 35121 Padova
2 - I.N.F.S., via CÓ Fornacetta, 9 - 400064 Ozzano E. (BO)

The Reed bunting (Emberiza schoeniclus) is a passerine belonging to the family Emberizidae, subfamily Emberizinae, largely spread in the Paleartic region, mainly in marshes and reedbeds. This species includes several forms, grouped in three main subspecies: E. s. schoeniclus, intermedia and pyrrhuloides. These differ slightly in size and colour and highly in bill shape and size. A high intraspecific polymorphism for bill size is rather uncommon in passerines; it has been shown that this variation is genetically determined and often involves an extension of the trophic niche.
We analised the genetic and morphologic variation within and among populations of E. s. schoeniclus ( the small bill, migrant form, that breeds in central Europe and marginally in north Italy) and E. s. intermedia ( the large bill, mainly resident form, that breeds in several locations throughout Italy). During winter the subspecies are simpatric in northern Italy. The separation in bill morphology was reflected in a separation in genetic variability. We are intersted in finding the forces that could maintain this separation. One could be a difference in song repertoires. Models of cultural evolution, similar to genetic models, can be used to explain the formation and stability of local dialects. Morphological, genetic and cultural evolution can be compared to explain this species' population structure. We recorded songs from individuals of the two subspecies breeding in two different localities in northern Italy. The songs were translated into sonograms and these were compared over a range of variables. A catalogue of syllable types was built grouping the syllables according to qualitative sonogram similarity. The songs of the two subspecies were significantly different in bout length and average number of repeated sillables. We built a syllable sequence distance matrix, using the catalogue to count the number of shared syllable types, and performed cluster analysis, but this did not to separate the two populations. We intend to spread the analysis to other populations in Europe, characterize songs with more detail, use quantitative methods to create the syllable type catalogue and refine the syllable sequence analysis in order to build a cultural evolution model.


The measurement of hierarchy of the Canary (Serinus canaria) in the laboratory.
L. Luisanti Fitri, I. BÚme, and M.Kreutzer


Laboratoire de Psychophysiologie et d'Ethologie,
Universite de Paris X, CNRS URA 2214,
200 Avenue de la Republique
92001 Nanterre Cedex, France


Recently, it is demonstrated that female canaries (Serinus canaria) elicit high levels of sexual display to a special song phrase of a male fullsong. This song phrase is called as "phrase A". However, this special song phrase is not commonly existed in the repertoires of male canaries. This preferential response of female canary to song "phrase A" might be considered as one of the cue to be indicative of male quality. We made a test to find an adeguate method of measuring hierarchy within a mixture flock of ten individually marked males. Among these flock members only five males have been known to have this song "phrase A" within their repertoires. Other phenotypic that correlates to male quality such as body weight, wing length and tarus length were also examined in the test. The role of hierarchy was assessed by dyadic interation among flock members in gaining access to resources provided inside the aviary. These resources were food and bathtub box which were established at different high level. We found that interaction among flockmates were manifest differently at the feeder and the bathtub. Phenotypic appearances tended to have positive correlations with the higher ranking birds at the feeder. More information is needed to get the evidence that song "phrase A" in relation to male quality may explain the formation of hierarchy in the canary.


Methodological considerations on the acoustic signal analysis for two species of bats (Chiroptera Vespertilionidae).
C. Zmarich1, E. Vernier2, F. Ferrero1

1 - Centro di Studio per le Ricerche di Fonetica (CNR), via Anghinoni 10, 35121 Padova, Italia.
2 - Dipartimento di Biologia dell'Universitˆ di Padova, Padova (freelance)
Private office: via delle Palme 20/1, 35137 Padova, Italia

Ultrasonic emissions of bats (Mammalis Chiroptera) consist of either social calls or echolocation pulses. As to the latter, every bat species exploits peculiar morphological features in the time and frequency domain, thereby making them distinguishable by their unique echolocation pattern.
In this study, the echolocation pulses of two species of vespertilionid bats have been recorded twice, first in laboratory and then in a natural environment. The signals of adult specimens of Pipistrellus kuhlii and Hypsugo savii are analysed and described. These species, which are quite common in Italy, are externally similar and have antropic habits, covering a very much similar ecological role. Their distinction is normally based on areal spreading, physical size and morphology, and acoustic classification criteria. The latter criterion is often used in field recording conditions after heterodyning conversion has made the ultrasonic pulses audible to the human ear.
The ultrasonic sounds were checked and detected with a Pettersson Ultrasound Detector D-100 connected to a Schlumemberger magnetic recorder Euromag 1. The recording rate was set to 38 cm/s. As for the laboratory recording conditions, the specimens were recorded while flying inside a 7x4x3 m room. A wide band microphone was set at 1.5 metres from the floor near the central point of the longest wall. As for the field conditions, specimens flying under or near street lamps (P. kuhlii) or over little private gardens in complete darkness/poor light (H. savii) were recorded.
In order to apply DSP analysis to the recorded signals, the magnetic tape was played at 4.75 cm/s, making exploitation of the nominal 8 kHz spectrographic standard range possible. In this way duration is extended and frequency is lowered by the same 8-fold factor (the virtual interval of 1 kHz thus corresponding to a real interval of 8 kHz). Spectrographic analysis was performed with the DSP Sonagraph 5500 and CSL 4300 software by KayElemetrics Corp. Measurements for time and frequency were taken through power spectra obtained by positioning the cursor on the waveform at the initial, central and final part of each single signal. Measurements of emission rates were taken simply by counting the occurrences of the homogeneous signal units per second.
Some methodological suggestions are made regarding the best way to perform spectrographic analysis on signals that differ for general shape (quasi-constant frequency vs downward frequency modulation) and duration (short vs long). A general difference between the lab and field conditions is the relative greatest length of the signals in the latter. Based on measurement values, it is possible to compare the two species only for the lab recordings, because the signals recorded in the field are different for the different species (QCF for H.savii and DFM for P.kuhlii). The DFM signals of the two species both begin at 70 kHz but end at 45 kHz for H. savii and 35 kHz for P.kuhlii. Furthermore, the signals of P.kuhlii have greater amplitude, more steep slope and occur in more rapid succession than those of P. savii.


Acoustic communication and related behaviour of captive otters (Lutra lutra).
Claudio Gnoli, Claudio Prigioni, Paola Polotti


Dipartimento di Biologia Animale, UniversitÓ di Pavia, Piazza Botta 9
27100 Pavia, Italy.


A male, a female, two juveniles and two cubs of European otter (Lutra lutra) were filmed in a large enclosure during a period of 8 months. For each episode of acoustic communication, data were collected on uttered sounds, involved individuals, and their distance, postures, and behaviour before, during, and after vocalizing. Eight different sounds were considered, according to the inventory referred by Rogoschik (Wiss. Beitr. Univ. Halle, 37(1989): 213-221). Associations between the recorded parameters were evaluated by an association index.
Male and female vocalized frequently towards the cubs and human beings, and cubs towards the female. Senders and addressees resulted inequally distributed for the different sounds. Vocalizations occurred preferentially on land and along the banks. Most frequent behavioural contexts were parental contacts (between the female and the cubs), contacts with human beings and playing activity; on the other hand, vocalizations rarely occurred while fishing, moving, feeding and marking.
Hiss and snort were uttered when an animal approached the addressee, from a distance of a few meters; they were often accompanied with a typical arcuated head movement. Moan was a threat sound, uttered while keeping the body motionless and fixing its eyes on the addressee. Chuckle, chuckle-chitter, chitter and squeal were mostly uttered at very short distances; although they all show a similar "staccato" acoustic structure, only the chuckle was uttered in social contexts, while the other ones were associated with increasing aggressive excitement. Whistle was uttered usually in very long sequences, at long distances; its main function seems to be keeping an acoustic contact between individuals, in particular cubs and their mother; however, sometimes it was uttered by juveniles together with chitter and other agonistic sounds. This shows that the communicative system of the species is quite complex.


Physical and functional features of vocalization in youngs of Macaca nemestrina.
A preliminary study.

Rigamonti, M. M.1, Prato Previde, E.2, Poli, M.D.2

1 - Centro di Primatologia HSR, via Olgettina 60, 20132 Milano, Italia.
2 - Istituto di Psicologia della Facoltˆ Medica, Universitˆ degli Studi di Milano, Via T. Pini 1, 20134 Milano, Italia

The period immediately following birth appears to be particularly well suited to study the developmental similarities in vocal communication between man and other primates. Vocalisations performed by non-human primates during their first year of life are therefore particularly important in a comparative and evolutionary perspective, as they allow interesting comparisons with studies on human linguistic development. However this topic has received little attention.
We studied the functional relationships, in a social colony of pig-tailed macaques (Macaca nemestrina), between the maternal response to the search of physical contact by the young and the physical structure of the vocalisations produced by the latter. The research was performed on three mother-young dyads, audio-recording the vocalisations produced by the young and by the adults and video-recording mother-young interactions. Our results allow a description of some of the physical characteristics of the vocalisations produced by the young during spontaneous interactions with their mothers; furthermore they suggest the existence of different structural or syntactical categories and suggest a relationship between maternal behavior and vocalisation patterns.


Preliminary analysis of wolf vocalizations recorded in the wild in Italy.
Lorenza Mauri, Marco Apollonio, Ettore Centofanti


Dipartimento di Scienze del Comportamento Animale e dell'Uomo
Via Volta 6, 56126 Pisa, Italy.

During censuses of wolves, performed with the wolf-howling tecnique, in the Foreste Casentinesi National Park, we recorded answers of wolf packs and isolated individuals.
Most difficulties were caused by the distance between wolves and the recording equipe. The aim of this preliminar analysis was to verify if it was possible, in the wild, to distinguish by mean of sonagraph analysis:
a) adults from pups; b) the number of individuals of each pack; c) different adult individuals from each others.
A first distinction is possible thanks to the different frequency range of adults and pups vocalisations. The substantial overlapping of different vocalisations makes the second aim difficult, but it is possible to determine a minimum number of individuals. The third aim is difficult to reach because only few vocalisations of each individual can be collected.


Ultrasound and mating behaviour in the field voles, Microtus agrestis.
Marie-juliette Mandelli, G.D.Sales

Life Sciences Dept., King's college London, UK.


Field voles are common in Britain and across Europe where they may show regular fluctuations in population every 3-4 years. In some countries they are pests of agriculture and particularly of forestry. These voles are induced ovulators and while their reproductive physiology is fairly well understood, little is known of their reproductive behaviour and especially of their acoustic communication. The present study has shown that in heterosexual encounters adult voles emit ultrasonic calls during a range of behaviours as it had been found in several other rodents. For example, male mice of different strains are known to emit 70 kHz - ultrasonic vocalizations as part of their courtship behaviour and rats, emit 50 kHz pulses.
In Microtus agrestis, the nature of the calls varies particularly in the amount of frequency modulations. The frequency ranges from 20 kHz to 80 kHz with an average at 35-40 kHz, the male seems to be the main emitter.
In heterosexual encounters between sexually na´ve animals both sexes call, but calling appears to be modified by sexual and parental experience, as sexually experienced males emit longer and wider calls than sexually na´ve males, and sexually experienced females do not emit any ultrasonic pulses when presented with an anaesthetised male (also sexually experienced) as sexually na´ve female do. The environment in which the animals meet also effects ultrasound emission: the calls emitted by pairs in the male's home cage were longer and of broader-bandwidth than those emitted in the home cage of the female. The effect, on the emission of ultrasonic pulses, of sexual and parental experience as well as the effect of different environments will be illustrated. The relationship between calls and the different types of behaviour and the effect of these calls on the recipients are currently being investigated.


Analysis of ultrasound using AVISOFT-sonagraph software.
Raimund Specht

Haupstr. 52, D-13158 Berlin, Germany

There are two methods of ultrasound acquisition and analysis with PC's:
The first and most straightforward solution is a special data acquisition board with a sampling frequency high enough to capture the entire bandwidth of the signals to be analysed. This requires to take the computer into the field if you have to do field research. The best choice would be a PCMCIA data acquisition card for portable notebook PC's. Unfortunately the devices available on the market still have limited sampling frequencies of approximately 100 kHz. This allows a usable bandwidth of less than 50kHz which is not sufficient for all kinds of ultrasound. The data streams generated by these data acquisition boards can be stored on hard-disk and can then be read by the Avisoft-SONAGRAPH software using one of its user-defined import formats.
The alternative method is the usage of a digital time-expansion bat-detector to transform the ultrasound into low frequency sound which can be processed by conventional audio equipment. These transformed sounds can be stored on standard tape recorders and can be transferred into the computer using a common sound-card. In this case the transformed ultrasound is treated like any other audio signal. In order to get the original scaling of waveforms, spectra and sonagram displays the time-expansion factor used on the bat-detector can be specified in the Avisoft-SONAGRAPH software.
Conventional bat-detectors using heterodyne or frequency division technology are not suited for spectral analysis on a computer. These devices could only be used to get an idea of the time structure of the signals.


Ultrasound acquisition and analysis. Comparison of current methods.
Pavan G.1,2, Manghi M.1

1 - Centro Interdisciplinare di Bioacustica e Ricerche Ambientali, UniversitÓ degli Studi di Pavia
Via Taramelli 24, 27100 Pavia, Italia.
2 - Dipartimento di Urbanistica, Istituto Universitario di Architettura di Venezia, Italia

Instrumentation recorders designed to record ultrasounds are very expensive and not well suited for field use; thus, cheaper devices to detect and possibly record ultrasound were developed for field research, mainly to study echolocation in bats.
These are called bat detectors. Basically they employ three methods for making ultrasounds more manageable: heterodyne conversion, frequency count-down, and time-expansion. Only the last method allow the complete recording of all the features of the ultrasonic signals. It is based on the digital recording with a high enough sampling rate (typically ranging among 300 and 400 ksamples/sec) and on the subsequent playback at a reduced sample rate to fall ultrasonic frequencies within the range of conventional audio recorders.
This procedure doesn't allow long recordings. Better suited to long recordings is the digital acquisition on a PC and several acquisition boards on the market allow for this.
We developed a PC based Digital Signal Processing Workstation (DSPW), based on a Microstar DAP 2400E/6 acquisition board, to allow recording and playback of acoustic signals up to 150 kHz with a resolution of 12 bits (72 dB dynamic range). The actually available Pentium CPUs allow, together with highly optimized custom made software, to analyze and display spectrograms in real-time up to 150 kHz while performing hard-disk recording and other data analysis and logging tasks. A sharp anti-aliasing filter is required to prevent aliasing.
When sampling at 312.5 ks/sec a 2 GB hard disk allows the continuous recording of up to 56 minutes.
This instrumentation is very useful in laboratory experiments to monitor the ultrasonic activities of the research subjects and to optimize the instrumental setup (minimization of noise sources, microphone placement). Also it allows to immediately evaluate the results of an experiment instead of waiting for later analyses on the recordings.
Special analysis procedures allow to log data in real-time (onset, offset, freq. tracking) and to produce reports about the monitored signals.


Real-time spectrographic analysis with Sound Blaster sound boards.
Gianni Pavan1,3, Ethan Brodsky2

1 - Centro Interdisciplinare di Bioacustica e Ricerche Ambientali, UniversitÓ degli Studi di Pavia
Via Taramelli 24, 27100 Pavia, Italia.
2 - 4010 Cherokee Dr., Madison, WI 53711, USA
3 - Dipartimento di Urbanistica, Istituto Universitario di Architettura di Venezia, Italia

Spectrographic display of animal sounds has been widely used since the first analogical analysis instruments were developed for military acoustic research. However, until recently, the high cost of the specialized hardware necessary for this type of analysis made it inaccessible to most researchers. The recent development of digital signal processing techniques and high-speed hardware at relatively low-cost has made the real-time visualization of acoustic signals an every-day invaluable tool for bioacoustic research and education.
A new version of the DSPW software already described in previous reports has now been developed to use Creative
TM Sound Blaster and compatible boards. The software strictly requires 16 bit sound boards (Sound Blaster 16, Sound Blaster 32 and true compatibles, including those based on the Vibra 16 chipset); it is DOS based and uses a high DMA channel (4-7) to perform continuous gap-free transfer of samples from the board to the computer memory. Since several notebooks now incorporate Sound Blaster compatible sound devices, this software opens new perspectives in field applications.
The software is a powerful display and analysis tools. Depending on the CPU speed (a Pentium is recommended), overlap and zero-padding can be performed in real-time to get smooth time-frequencies plots up to 44.1 ks/sec. Both spectrogram and cepstrogram can be computed in real-time. Three basic real-time display modes are available: horizontal display with envelope (wrap around or scrolling display), four strips scrolling display, vertical scrolling display.
Even if cheap sound boards seem to be adequate for music and games, some problems are still to be solved when analyzing sounds: signal to noise ratio, bit resolution, frequency response, anti-aliasing filters, available sampling frequencies (most boards allow sampling rates ranging from 5 ks/s to 44.1 ks/s) and sampling frequency accuracy change depending on the sound board model. Thus, a great care must be used when using digitizing devices which are not designed for great accuracy. Before to start using a particular sound device, a series of tests must be made. For this purpose, a collection of freeware utilities have been developed by Philip van Baren to check the real performances of Sound Blaster boards.
A freeware version of the real-time software will be soon available on the net.

Web references
G.Pavan, http://www.unipv.it/webcib/
E.Brodsky, http://www.pobox.com/~ebrodsky/
P.vanBaren, http://bul.eecs.umich.edu/~phillipv/signal/

 


 

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