Acoustic characteristics of northern and southern resident killer whale echolocation clicks

• Main Author: Lawson, Jack
• Other Authors: Dosso, Stanley Edward
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: resident killer whale; echolocation; Killer Whale; Orca; Orcinus orca; Killer whale
• Online Access: http://hdl.handle.net/1828/13387

Resident killer whales (Orcinus orca) in the Salish Sea use echolocation clicks to hunt for Chinook salmon, their preferred prey. An increase in underwater anthro- pogenic noise in recent decades has been identified as a threat to their survival due to auditory masking effects on these signals. Studies quantifying the effects of anthro- pogenic noise on echolocation signals have yet to be carried out due to a data gap for echolocation acoustic characteristics. In particular, to date, only one study has reported click characteristics for northern resident killer whales, and no results have been reported for southern residents. This thesis reports on acoustic recordings of resident killer whale echolocation clicks gathered over two summers in several loca- tions around Vancouver Island, and spectral and temporal characteristics extracted from them. Acoustic characteristics are reported separately for southern and north- ern resident killer whales based on 708 clicks from 19 click trains and 1277 clicks from 16 click trains, respectively. Results are further categorized into click type (slow, fast, and buzz clicks) based on inter-click interval, an indicator of foraging phase. Results show no differences in acoustic characteristics between the northern and southern killer whales, suggesting echolocation clicks do not vary between these subspecies. No significant differences are noted between slow- and fast-click characteristics, while buzz clicks appear to have some significant differences in characteristics from the oth- ers. Apparent source level values for northern and southern killer whales vary between 179-221 dB re 1 μPa at 1 m and 192-220 dB re 1 μPa at 1 m, respectively, based on the largest amplitude click from each click train (assumed to be directed towards the recording array). The values reported in this thesis will be used in subsequent noise modelling studies to quantify the effects of anthropogenic noise on resident killer whale ability to hunt for prey via echolocation signals. Graduate