Acoustically Derived Estimate of the Size Distribution for a Sample of Sperm Whales (<i>Physeter catodon</i>) in the Western North Atlantic

Abstract

Acoustic determination of sperm whale length based on measurement of the interpulse interval (IPI) of the characteristic multipulse sound click was used on a sample of 4000 clicks in 193 click series recorded in the North Atlantic. The analysis of IPI could be done with reasonable reproducibility using a minimum of equipment: a tape recorder, filter, and oscilloscope. Criteria were developed to choose suitable clicks for analysis. In the click sample, 11% met the criteria for analysis, and were contained in 41 click series, of which 22 had a unique IPI. The IPIs in the 41 series ranged between 1.6 and 8.0 ms, and corresponded to a predicted size range of 7–22 m. This is consistent for the size range reported for the western North Atlantic.Key words: bioacoustics, sperm whale, Physeter catodon, size determination, click, interpulse interval