Source levels and communication-range models for harp seal (Pagophilus groenlandicus) underwater calls in the Gulf of St. Lawrence, Canada

• Published in: Canadian Journal of Zoology
• Main Authors: Rossong, M. A., Terhune, J. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2009
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Canada; Harp Seal; Pagophilus groenlandicus
• Online Access: http://dx.doi.org/10.1139/z09-048; http://www.nrcresearchpress.com/doi/full-xml/10.1139/Z09-048; http://www.nrcresearchpress.com/doi/pdf/10.1139/Z09-048

Harp seals ( Pagophilus groenlandicus (Erxleben, 1777)) produce underwater call types during the breeding season that are thought to be important for reproductive behaviours and herd formation. Underwater calls were recorded in the Gulf of St. Lawrence, Canada, in March 2007. A four hydrophone array system determined the locations of nearby calling seals and call source levels (amplitudes at 1 m from the seal). Source levels ranged from 103 to 180 dB re 1 µPa-m and mean values per call type ranged from 129 to 151 dB re 1 µPa-m with considerable overlap between call types. Short-range sound transmission losses under the ice were variable. Theoretical communication-range models were constructed under quiet (0 sea state, transmission-loss pattern of 20 log range) and noisy (herd noise, transmission-loss patterns of 15, 17.5, or 20 log range) conditions. Monte Carlo models for the calls for a quiet sea indicated median distances of 0.5–5.5 km (maximum 80 km). Communication distances in the presence of other calling seals dropped to 0.03–0.5 km (maximum 15 km) for dB loss = 20 log range but were longer under different spreading-loss patterns. Communication ranges are significantly influenced by call source levels, background noise, and in situ sound transmission patterns.