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The vocal repertoire of many delphinid odontocetes includes narrowband tonal whistles used mainly for communication. The aim of this study was to describe the whistle repertoire of short-beaked common dolphins, Delphinus delphis, recorded in the Celtic Sea between May and August 2005. The 1835 whistles recorded were classified into six broad categories and 30 sub-types, of which simple upsweeps and downsweeps were the most common. Furthermore, the parameters duration, inflections, steps and various frequency variables were measured. The whistles covered a frequency span from 3.56 kHz to 23.51 kHz and had durations between 0.05 and 2.02 seconds. Whistle parameters varied with behavioural context, group size and between encounters. The whistle repertoire of Celtic Sea common dolphins was compared to that of D. delphis from the Western Approaches of the English Channel, recorded during a survey between January and March 2004. The relative abundances of the broad whistle types did not differ between the two locations, but most whistle parameters were significantly different: almost all frequency variables measured were significantly higher in English Channel whistles. This may indicate some degree of population structuring of short-beaked common dolphins around Britain. Alternatively, the common dolphins in the English Channel may have shifted the frequencies of their vocalizations up to avoid masking by low-frequency ambient noise produced by high levels of vessel traffic in this area. [ABSTRACT FROM PUBLISHER]

Sperm whale social distribution was investigated in the Mediterranean Sea, using data collected during summer surveys from 1997 to 2002. Variations in the size of sperm whale schools/underwater aggregations were assessed using both visual and acoustic data. Individual body lengths were estimated acoustically, using the click inter-pulse intervals. Regional comparisons were undertaken, taking the 41° parallel as a north/south boundary. In the southern region, schools of up to seven sperm whales were sighted and calves were relatively frequent. The animals ranged between 8·6 m and 13·1 m long. In the northern region, school sizes were significantly smaller, with a maximum of three whales sighted at the surface. However, the acoustic survey showed that sperm whales form loose aggregations of up to five animals in certain areas. Whales detected in the north were 12·6 m long on average, and the body size range was relatively small. This summer survey demonstrated a segregation of males, in the north, from larger schools including calves, which seemed to be confined to the southern region. [ABSTRACT FROM PUBLISHER]

Six juvenile sperm whales were observed visually and acoustically in the confined waters of Scapa Flow, Orkney Islands during March 1993. General visual behaviours observed included slow travelling, head-outs, logging and side fluking but there were no observations of tail fluking within the confines of Scapa Flow. Recordings of the whales' vocalizations through hydrophones revealed a remarkably wide repertoire including clicks, rapid clicks, gunshots, chirrups, creaks, short trumpets, pips, squeals and clangs. Selected examples of these sounds were digitized and analysed as spectrograms. Clicks, rapid clicks, gunshots and clangs all showed a characteristic impulsive broadband signature. Chirrups, short trumpets and creaks were composed of rapid sequences of broadband impulses, although creaks were invariably faint and were difficult to illustrate well. Chirrups, short trumpets and clangs showed strong spectral peaks and pips were particularly unusual sounds with impulsive narrowband signatures composed of harmonically spaced peaks. Squeals exhibited prolonged, narrowband swept frequency signatures often with slight oscillation. All types of vocalization with the exception of clangs were heard from sperm whales during pure observation, minimum disturbance encounters in the field. Two attempts were made to remove the whales from Scapa Flow, the first being an enticement operation to lure the whales to open water with the use of underwater playback of sounds of socializing female sperm whales and the second a shepherding operation to drive the whales with a flotilla of vessels. The enticement operation was unsuccessful but the shepherding operation was successful, although the whales showed considerable reluctance to navigate a narrow channel to the open sea. During the shepherding operation there was a distinct change in the nature of the whales' vocalizations, with clangs predominating over other forms. [ABSTRACT FROM PUBLISHER]

Passive acoustic monitoring of common dolphins was conducted across a survey area of 1000 n.m.2 (nautical miles) off the west Wales coast during the months September, October, November and December 1995. Dolphin presence and distribution was assessed by a system of percentage acoustic contact. Results were compared with those from a seismic/dolphin survey during the same months of the previous year, and across the same survey area. Distributions of common dolphins within the survey area showed similar trends for both years, with a marked decrease in dolphin contacts between September and October of both years. These observations suggest offshore migration of common dolphin populations at the time of year. Sea surface temperature distribution across the entire region was visualized during two survey periods using infrared satellite imagery. It is hypothesized from these observations that offshore migration of common dolphins coincides with a break-up of the Celtic Sea Front, a distinct oceanographic feature which crosses the survey area. [ABSTRACT FROM PUBLISHER]

Common dolphin, Delphinus delphis (bairdi), were monitored acoustically across a survey area of 2747 km2 during a three month period before, during and after an oil industry two dimensional (2D) seismic reflection survey. Over 900 h of audio survey data were collected and analysed, along with GPS positional data, to reveal trends in presence and distribution of animals. The presence of dolphins was determined from vocalization events on the survey recordings. Dolphin presence was assessed by a system of percentage acoustic contact. This was highest before and after the seismic survey, with common dolphins showing a clear south-westerly skew within the survey area and a probable south-westerly migration of animals between September and December. Acoustic contact with dolphins during the seismic survey also showed a south-westerly skew within the survey area, although percentages were lower. Monitoring during the period of seismic activity was restricted to the immediate vicinity (1–2 km) of the seismic vessel, so percentage contact most likely reflects the response of dolphins to such immediate activity. The overall result suggests an avoidance reaction by common dolphins to air gun emissions, although certain observations suggest tolerance to these sounds outside a 1 km radius of the guns. [ABSTRACT FROM PUBLISHER]