Repetition patterns in Weddell seal (Leptonychotes weddellii) underwater multiple element calls
Digital audio tape (DAT) recordings of Weddell seal underwater vocalisations were obtained near Weddell seal breeding groups during the 1997 breeding season. These recordings were made off the Eastern Antarctic coastline near two Australian Antarctic stations. Eight recordings (three from the same l...
| Summary: | Digital audio tape (DAT) recordings of Weddell seal underwater vocalisations were obtained near Weddell seal breeding groups during the 1997 breeding season. These recordings were made off the Eastern Antarctic coastline near two Australian Antarctic stations. Eight recordings (three from the same location) were made near Casey during 21 October - 30 November and seven recordings (each at a different location) were made near Davis during 8 November - 1 December, for a total of 15 recordings made at 12 locations. The recordings were made during a period of 24 h light, near groups of females with pups on the ice. The number, sex and age of the vocalising seals could not be determined, nor was it possible to determine the proximity of the seals to the hydrophone. Each recording lasted 1-2 hours. At each recording site, one hole was drilled through the sea-ice and the hydrophone was lowered approximately 2 m below the ice. Sony TCD-D3 DAT recorders (frequency response 0.002-20kHz plus or minus 1 dB) were used to make the recordings. At Casey, an ITC 6050C hydrophone (frequency response 0.002-30 kHz plus or minus 1 dB), with a built in preamplifier was connected to the Sony DAT recorder. At Davis, a Bruel and Kjaer 8100 hydrophone equipped with a Bruel and Kjaer 2635 charge preamplifier (frequency response 0.002-30 kHz plus or minus 1 dB) was used. Many vocalisations produced by Weddell seals (Leptonychotes weddellii) are made up of repeated individual distinct sounds (elements). Patterning of multiple element calls was examined during the breeding season at Casey and Davis, Antarctica. Element and interval durations were measured from 405 calls all greater than 3 elements in length. The duration of the calls (22 plus or minus 16.6s) did not seem to vary with an increasing number of elements (F4.404 = 1.83, p = 0.122) because element and interval durations decreased as the number of elements within a call increased. Underwater vocalisations showed seven distinct timing patterns of increasing, decreasing, or constant element and interval durations throughout the calls. One call type occurred with six rhythm patterns, although the majority exhibited only two rhythms. Some call types also displayed steady frequency changes as they progressed. Weddell seal multiple element calls are rhythmically repeated and thus the durations of the elements and intervals within a call occur in a regular manner. Rhythmical repetition used during vocal communication likely enhances the probability of a call being detected and has important implications for the extent to which the seals can successfully transmit information over long distances and during times of high level background noise. See other metadata records and datasets associated with ASAC project 2122 (ASAC_2122) for further information. The fields in this dataset are: Tape/Site/File Filename Call Type Total Number of Elements Attribute Frequency Time Casey Davis |
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