Source levels of killer whale calls: Differences among call types and noise levels.

Abstract

Several studies have reported source levels for a variety of sounds produced by animals. This information can then be used to predict the range over which sounds may be used among individuals in communication networks and how the active space of such signals are affected by anthropogenic sounds. Some studies have also shown that animals readily modify parameters of their acoustic signals in response to changes in background sound levels. For instances, killer whales increased their call source level as vessel noise increased. Killer whale calls are likely used for communication among group members and some are population specific being stereotyped, repeated, and structurally distinct. Call source levels also vary depending on call type, but vocal responses to changes in background sound levels were not taken into account. Data were collected on southern resident killer whales (Orcinus orca) using a hydrophone array in waters surrounding the San Juan Islands, WA over three summers. Differences in call source levels as they relate to differences in call type, call structure, and background sound levels will be presented. Such considerations are necessary to accurately predict the range over which animals communicate and how anthropogenic sound exposure affects their use of sound.