Analysis of the vocalizations of Orcinus orca in response to anthropogenic noise

Abstract

Underwater noise created by vessel traffic in the world's oceans may be detrimental to marine life that relies on acoustic senses for survival. An analytical study was completed which examined changes in vocal behavior of subpod A36, killer whales (Orcinus orca) that reside off Vancouver Island. The average call rate of each call type was calculated from the recordings, and call rates were found to significantly decrease in the presence of vessel noise. Structural characteristics of specific call types such as differences in frequency, duration, and harmonics were also examined and statistically compared with and without boat noise. Differences found include a decreased number of harmonics in the N5 call, and a more peaked distribution of the average frequency of the first harmonic of the N4 call when associated with vessel noise. The significance of the result relative to the possible disturbance of these killer whales is uncertain