Echolocation click characteristics of two fish-eating killer whale populations

Acoustic disturbance has been identified as a threat to the survival of the endangered Southern Resident killer whale (SRKW) population whose critical habitat in the Salish Sea overlaps with busy commercial shipping lanes and popular recreational boating areas. Vessel noise has the potential to mask important sounds used by the whales for navigating, communicating, and foraging. To investigate the impact on foraging, acoustic characteristics of the whales’ echolocation clicks must be known. We collected data on SRKW in the wild using a 2 × 2 m2 23-hydrophone array deployed at short ranges (<500 m). We also acquired data on a neighboring population of Northern Resident killer whales (NRKW), whose numbers are increasing. Comparable results were obtained for most parameters between the two populations. Average peak-to-peak apparent source levels were 203 and 196 dB re 1 μPa at 1 m for SRKW and NRKW, respectively. The two populations had similar mean centroid and peak frequencies ranging between 26–29 kHz and 19–21 kHz, respectively. However, root-mean-square bandwidths differed significantly between the populations, with averages of 52 and 39 kHz for SRKWs and NRKWs, respectively. These results will be used to investigate masking potential under varying ambient noise conditions.