Comparison of echolocation clicks from geographically sympatric killer whales and long-finned pilot whales

The source characteristics of biosonar signals from sympatric killer whales and long-finned pilot whales in a Norwegian fjord were compared. A total of 137 pilot whale and more than 2000 killer whale echolocation clicks were recorded using a linear four-hydrophone array. Of these, 20 pilot whale clicks and 28 killer whale clicks were categorized as being recorded on-axis. The clicks of pilot whales had a mean apparent source level of 196 dB re 1 mu Pa pp and those of killer whales 203 dB re 1 mu Pa pp. The duration of pilot whale clicks was significantly shorter (23 mu s, S.E. - 1.3) and the centroid frequency significantly higher (55 kHz, S.E. = 2.1) than killer whale clicks (duration: 41 mu s, S.E. = 2.6; centroid frequency: 32 kHz, S.E. = 1.5). The rate of increase in the accumulated energy as a function of time also differed between clicks from the two species. The differences in duration, frequency, and energy distribution may have a potential to allow for the distinction between pilot and killer whale clicks when using automated detection routines for acoustic monitoring. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3583499]