Some mammalian and avian species alter their vocal communication signals to reduce masking by background noises (including conspecific calls). A preliminary study suggested that Weddell seals (Leptonychotes weddellii) increase the durations of some underwater call types when overlapped by another calling seal. The present study examined the durations and overlapping sequences of Weddell seal calls recorded in Eastern Antarctica. The calling rate, call type (13 major categories), total duration, numbers of elements per call, and overlapping order of 100-200 consecutive calls per recording location were measured. In response to increased conspecific calling rates, the call durations and numbers of elements (within repeated-element call types) did not change or became shorter. Calls that were not overlapped were 3.8 plus or minus 6.1 s long, the first call in a series of overlapped calls was 14.4 plus or minus 15.7 s and subsequent calls in an overlapping series were 6.5 plus or minus 10.3 s. The mean durations of non-overlapped and overlapped calls matched random distributions. Weddell seals do not appear to be adjusting the durations or timing of their calls to purposefully avoid masking each others' calls. The longer a call is, the more likely it is to overlap another call by chance. An implication of this is that Weddell seals may not have the behavioural flexibility to reduce masking by altering the temporal aspects of their calls or calling behaviours as background noises (natural and from shipping) increase.

Recordings were made of adult male and female Weddell seals on the ice during the breeding seasons of 1990 and 1997. The recordings were made near Davis, Antarctica in the Vestfold Hills. The vocalisations made with both the mouth and nostrils closed were classified into call types. These call types are also produced by the seals when underwater. The call classifications were based on those described by Thomas, J.A. and Kuechle,, V.B. (1982, J. Acoust. Soc. Amer. 72: 1730-1738) and Pahl, B.C., Terhune, J.M. and Burton, H.R. (1997, Aus. J. Zool. 45: 171-187). Nineteen call types were identified. Of these, males made 18 and females made 15. Trills are only made by males and it is likely that a stepped ascending whistle is only made by females. A roar and mew are also potential male-only call types. The data suggest that the Trill vocalisations can be used to indicate the presence of males. This will be useful when recording underwater where the calling seals cannot be observed directly. A description of the types of calls made by Weddell Seals is listed below. SymbolNameDescription OToneConstant-frequency, predominantly sinusoidal call. LGrowlConstant-frequency, broad bandwidth, long call. QWhoopConstant-frequency call with a terminal upsweep. SSqueakBrief call with constant frequency or rising frequency and an irregular waveform. WAWhistle AscendingAscending frequency, sinusoidal waveform. TCTrill Constant-FrequencyNarrow bandwidth trill with a constant-frequency beginning, sinusoidal or frequency-modulated waveform. TTrillNarrow to broad bandwidth, containing a frequency downsweep, greater than 2 seconds. WDWhistle DescendingDescending frequency, sinusoidal waveform (less than 2 seconds). MMewAbruptly descending frequency followed by a long constant-frequency ending. CChugAbruptly descending frequency followed by a brief constant-frequency ending. GGuttural Glug (Grunt)Descending-frequency call that was lower than a Chug and had a brief duration. WAGWhistle Ascending - GruntBrief Ascending Whistle followed by a Guttural Glug (Grunt), the two types alternate in a regular pattern. KKnockAbrupt, brief-duration broadband sound

The underwater and in-air recordings were used to derive a technique to classify the call types. The in-air recordings demonstrated that both males and females vocalise and often a single seal will string up to 6 call types together in a variety of orders. No 'Trills' were heard by males or females on the ice. The seals lengthened the duration of multiple-element calls when they were 'interrupted' by another calling seal. This suggests that the seals are listening for the calls of conspecifics while they themselves are calling. A pilot project indicated that almost none of the calls are completely masked by other calling seals. The recordings are being used (in association with recordings obtained in later years) to address other aspects of Weddell seal vocal communication. See the link below for public details on this project.

This dataset contains digitized passive acoustic recordings from a hydrophone connected to an autonomous recording device both moored near the sea-floor in the Southern Ocean. Recordings were digitised at a sample rate of 500 Hz and were continuous over the period of operation. The intended purpose of these recordings was to collect baseline data on the acoustic environment (i.e. underwater sound fields). Underwater sounds that were recorded include sounds generated by Antarctic sea ice, marine mammals, and man-made sounds from ships and geo-acoustic surveys. Marine mammal sounds include calls from blue, fin, humpback, and minke whales. The hydrophone was deployed on a mooring on the Kerguelen Plateau.

This dataset contains digitized passive acoustic recordings from a hydrophone connected to an autonomous recording device both moored near the sea-floor in the Southern Ocean. Recordings were digitised at a sample rate of 500 Hz and were continuous over the period of operation. The intended purpose of these recordings was to collect baseline data on the acoustic environment (i.e. underwater sound fields). Underwater sounds that were recorded include sounds generated by Antarctic sea ice, marine mammals, and man-made sounds from ships and geo-acoustic surveys. Marine mammal sounds include calls from blue, fin, humpback, and minke whales. The hydrophone was deployed on a mooring on the Kerguelen Plateau in 2006.

This dataset contains digitized passive acoustic recordings from a hydrophone connected to an autonomous recording device both moored near the sea-floor in the Southern Ocean. Recordings were digitised at a sample rate of 500 Hz and were continuous over the period of operation. The intended purpose of these recordings was to collect baseline data on the acoustic environment (i.e. underwater sound fields). Underwater sounds that were recorded include sounds generated by Antarctic sea ice, marine mammals, and man-made sounds from ships and geo-acoustic surveys. Marine mammal sounds include calls from blue, fin, humpback, and minke whales. The data were collected in 2006 from a hydrophone deployed on a mooring in the Prydz Bay area.

This dataset contains digitized passive acoustic recordings from a hydrophone connected to an autonomous recording device both moored near the sea-floor in the Southern Ocean. Recordings were digitised at a sample rate of 500 Hz and were continuous over the period of operation. The intended purpose of these recordings was to collect baseline data on the acoustic environment (i.e. underwater sound fields). Underwater sounds that were recorded include sounds generated by Antarctic sea ice, marine mammals, and man-made sounds from ships and geo-acoustic surveys. Marine mammal sounds include calls from blue, fin, humpback, and minke whales.

This dataset contains digitized passive acoustic recordings from a hydrophone connected to an autonomous recording device both moored near the sea-floor in the Southern Ocean. Recordings were digitised at a sample rate of 500 Hz and were continuous over the period of operation. The intended purpose of these recordings was to collect baseline data on the acoustic environment (i.e. underwater sound fields). Underwater sounds that were recorded include sounds generated by Antarctic sea ice, marine mammals, and man-made sounds from ships and geo-acoustic surveys. Marine mammal sounds include calls from blue, fin, humpback, and minke whales. The data were collected in 2005 from a hydrophone deployed on a mooring in the Prydz Bay area.

The date are of the highest amplitudes across the frequency range of Weddell seal tonal trills (an underwater call made by males). Each column presents the results of a frequency amplitude measure that is relative to the highest amplitude of that trill, independent of the frequency at which that amplitude occurs. This removes the influence of the overall amplitude of the call which is influence of the distance the sea was from the hydrophone when the recording was made. Four trill patterns were identified (A - D) and a number of trills not included in the analyses are classed as type X. The X call types were excluded because the original recording was later found to be overloaded or partly masked by ice noises or the calls of another seal. Analysis details are included in the accompanying manuscript. The accompanying Excel file contain the frequency amplitude measurements of individual trills at two location groups: the Aurora Truning location at the anchorage location of the Aurora Australis near Davis and the other group is a number of breeding groups in the Vestfold Hills. Variable A is the frequency in Hz, Variables B to DH at the Aurora Turning location and B to BY at the Davis locations are data from individual trills. Rows 2 or 3 indicate the four Trill patterns, A, B, C or D, with an X designation for trills that were not included in the analyses due to limited frequency ranges or overloading of the original recordings (that was discovered later in the analyses). ssize or samplesize is the number of trills that were at each frequency bin.

During the winter and spring of 2000 and 2002, underwater calls of Weddell seals were recorded near Mawson. The goal was to determine if some call types were only given during the spring breeding season. The calls were classified into 10 broad types and the proportional usage of each was determined from May to December. All call types were present throughout the study period and during periods of darkness and light and at high, medium or low calling rates. Taken from the abstract of the referenced paper: Proportional underwater call type usage by Weddell seals (Leptonychotes weddellii (Lesson, 1826)) near Mawson, Antarctica, investigated the hypothesis that certain call types function specifically in breeding behaviour. Recordings were collected at various sites in 2000 and 2002 from June to December. Twenty-four hour recordings were collected in 2002 at two sites. One hundred consecutive calls from each of 248 recordings were classified into one of ten common call types. Time to 100 calls provided the calling rate. The study period was divided into four periods representing initial sea-ice formation, pre-pupping, pupping, and mating. Calling rate and light-dark differences were also examined. No presence-absence differences were observed for any of the call types with season. The largest difference between nonbreeding and breeding situations was an increase from 32.2% to 38.1% for descending whistles (F[3,244] = 4.483, p = 0.004). Trills gradually increased from 1.8% to 7.3% toward the mating period (F[3,244] = 30.932, p less than 0.001). The proportion of trills, chugs, descending whistles, and other call types also varied with calling rate and light-dark conditions. Some pre-reproductive behaviours may occur in winter, but no call types of Weddell seals function solely in the breeding season.