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The usage of vocalisations by beluga whales Delphinapterus leucas during group-resting and sexual behaviour [abstract]

R. A. Belikov and V. M. Bel'kovich (2002). The usage of vocalisations by beluga whales Delphinapterus leucas during group-resting and sexual behaviour [abstract]. Bioacoustics, Volume 13 (2): 200

 

Abstract: 

Acoustical communication plays one of the crucial roles in functioning of white whale reproductive gathering. However its mechanisms have not been clearly understood so far. This study was conducted during the summer season in 1999 at a beluga reproductive gathering off cape Beluzjy, Great Solovetsky Island, the White Sea. The sound recordings were made using a Sony MZ-R55 MD-recorder with frequency response from 20 to 20,000 Hz ± 3 dB. Processing and analysis of the acoustical stream were conducted using Cool Edit Pro 1.0 software. Two behavioural situations were analysed (83 minutes, 2771 signals): group-resting (24 min., 958 signals) and sexual behaviour (59 min., 1813 signals). The average vocalisation rate during group-resting was 39.4 signals/min and 5.3 signals per whale/min. The following proportions of the main types of vocalisations were: "squeak'' (24%), "U'' (19%), "whistles'' (11%), "vowels'' (7%), "chirrup'' (6.6%), "scream'' (6.2%), "bleating'' (6%), "creak'' (5.9). During sexual behaviour, the mean vocalisation rate was 30.7 signals/min and 1.7 signals per whale/min; these values are significantly lower than the statistical means 53.7 signals/min and 3.6 signals per whale/ min. The following types of signals predominated during sexual behaviour: "squeak'' (24.4%), "vowels'' (10.8%), "chirrup'' (10%), "bleating" (8.6%), "whistles'' (6.5%), "creak" (5.6%). Thus it was found that during sexual behaviour the average number of signal/min decreased and group composition and structure of the main types of vocalisation were changed due to a decrease in proportions of "U", "scream'' and "whistles'' types of vocalisations. Time analysis showed that an intensification of the sexual interactions was accompanied by decreases in total signal production. The bursts (peaks) of vocal activity preceded behavioural peaks rather than accompanied them. Thus, our results confirmed the important role of the sound communication to maintain group unity and co-ordinate activities of beluga whales.