Through-ice communication by Weddell seals may not be practicable

Brief description

Possible communication between territorial male Weddell seals (Leptonychotes weddellii) under the ice with females on the ice was investigated. In-air and underwater recordings of underwater calls were made at three locations near Davis, Antarctica. Most underwater calls were not detectable in air, often because of wind noise. In-air call amplitudes of detectable calls ranged from 32-74 dB re. 20 microPa at 86 Hz down to 4-38 dB re. 20 microPa at 3.6 kHz. Most of these would be audible to humans. Only 26 of 582 amplitude measurements (from 230 calls) ranged from 5 dB to a maximum of 15 dB above the minimum harbour-seal (Phoca vitulina) in-air detection threshold. Seals on the ice could likely hear a few very loud underwater calls but only if the caller was nearby and there were no wind noises. The low detectability of underwater calls in air likely precludes effective communication between underwater seals and those on the ice.

See other metadata records and datasets associated with ASAC project 2122 (ASAC_2122) for further information.

The fields in this dataset are:

Column A: G = grunt, T = trill, CT = constant freq. trill, O = tone, C = chug, AW = ascending whistle, DW = descending whistle, L = growl, R - roar

Column B: frequency (Hz)

Column C: underwater call level NOTE dB re 20 uPa

Column D: in-air call level dB re 20 uPa

Column E: in-air background noise level at this frequency dB re 20 uPa

Column F: water - air difference dB

Column G: location, 1-3, see paper for code

Column H: seal in-air threshold dB re 20 uPa

Column I: human in-air threshold dB re 20 uPa

Column J: seal in-air threshold at this frequency dB re 20 uPa

Lineage

Progress Code: completed

Statement: Recordings were made on an opportunistic basis on 1 and 8 December 1997 at 68.5699S, 77.9266E. This site was 1.55 km from the shoreline at Davis Station, eastern Antarctica. The water depth was 23m. The 2-m-thick-land-fast sea ice in the recording area had previously been broken up and refrozen following the arrival of the R.S.V. Aurora Australis during the station resupply 2 months earlier. There were at least five adult Weddell seals (two of each sex and one whose sex was unknown) using breathing ad haul-out holes in the area. Simultaneous in-air and underwater recordings of underwater vocalisations were made in three locations, each with different ice conditions: (1) refrozen large blocks of ice with 30cm of snow, (2) a refrozen lead with 10cm of snow and 10cm of ice, and (3) 7-month-old sea ice, 2m thick with a thin layer of snow. Each recording location was adjacent to a breathing hole maintained by the seals.

For more information, see the referenced paper.