Acoustically Derived Estimate of the Size Distribution for a Sample of Sperm Whales (Physeter catodon) 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