Monitoring southern resident killer whale behavior on the outer coast of Washington using passive acoustics.

Abstract

Killer whales produce population-specific pulsed calls, and remote acoustic monitoring has been utilized to better assess the seasonal distribution and movements of southern resident killer whales (SRKWs) in the coastal waters of Washington State due to the many factors that limit visual sightings. In 2008 and 2009, Ecological Acoustic Recorders (EARs) were deployed at four locations spanning the Washington coast. The EARs were duty cycled to record for 30 s at 5- and 7-min intervals providing additional information about length of detections and acoustic behavior. SRKW were detected at all four locations. 26 of the 48 SRKW detections had sufficient data for analysis of acoustic behavior, and detections ranged in duration from a few minutes to one 24-h period. For each recording, we classified the presence, absence, and rates of various killer whale sounds to determine how they differed spatially and temporally. These preliminary data will be compared to multiple studies whose findings have demonstrated how the acoustic behavior of piscivorous killer whales differs among activity states: resting, socializing, foraging and traveling. These differences can provide information necessary to help identify important foraging areas and times on the outer coast in the absence of visual sightings.