Acoustical analysis of underwater vocalizations from crabeater seals, Lobodon carcinophagus.

摘要

Underwater vocalizations of packice crabeater seals (Lobodon carcinophagus) were recorded by Jeanette A. Thomas off the western side of the Antarctic Peninsula during the austral breeding season in November of 1978. The recordings were made by dropping an ANS 57 sonobuoy off a ship into the ocean to a depth of 15.3 meters or from an iceberg using an Interoceans R130 hydrophone. All recordings were made on a Nagra III reel-to-reel recorder at 7.5 cm/sec, with a frequency response of 20 Hz -- 20 kHz +/- 2 dB and digitized by the Bioacoustics Laboratory at the Cornell Laboratory of Ornithology. A total of 908 seconds of underwater acoustic data and 315 vocalizations were recorded in November of 1978.;Recordings collected in 2007 were made by a diver, David Cothran, using a Sony TRV-900 digital video camcorder housed in a Light and Motion Bluefin water-proof housing at a sampling rate of 16-bit with a linear frequency response up to 48 kHz. A total of 20 seconds of underwater acoustic data and 18 vocalizations were recorded in February 2007.;One common vocalization was identified during the breeding season, November 1978 recordings. This was the long groan, which represented 94.6% of the entire underwater acoustic repertoire. Four rare underwater vocalizations were identified in recordings made during the non-breeding season. They were the short groan, whistle, screech, and grunt.;For the first time, the acoustic characteristics of the loan groans and four rare vocalizations were examined spectrographically and parameters of frequency and time are reported herein. Long groans showed little frequency or temporal variation. All of the rare vocalizations had an average duration approximately half of the duration of the long groan with varying dominant frequencies.;Because the long groan was only observed in the breeding season recordings, the function of this vocalization is suspected to be an aggressive acoustic sound used to deter rival males in the area. The purpose of the four rare vocalizations is unclear due to the small sample size. Further research must be conducted to adequately expand the underwater acoustic repertoire of the crabeater seal.