High-frequency modulated signals of killer whales (Orcinus orca) in the North Pacific

Abstract

Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6–36.1 kHz and median duration ranged from 50–163 ms. Source levels were 185–193 dB peak-to-peak re: 1 μPa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Uncommon, lowfrequency FM sounds with a fundamental of 50-270 Hz lasting 0.1-2.8 s were reported from Iceland [222]. Killer whales also produce high-frequency FM sounds with a fundamental of 16-75 kHz and source levels of 185-193 dB re 1 µPa pp @ 1 m [212,215,217]. CW tones are rare (3-5 kHz, 0.37 ± 0.08 s; [208]).…”

“…Their sounds have been studied in coastal British Columbia, Canada, and Washington State, USA [201][202][203][204][205][206][207][208][209][210], in California [211], in other areas of the North Pacific, including Russia [212][213][214][215][216], in the North Atlantic off Norway and Iceland [217,218], in Antarctica [219,220] and south-western Australia [16]. A geographic comparison of North Atlantic and North Pacific killer whale sound frequencies was recently published [221].…”

Geographic variation in the time‐frequency characteristics of high‐frequency whistles produced by killer whales (Orcinus orca)

“…To compare whistles produced in the Northeast Atlantic with those produced by killer whales in the North Pacific, we analyzed high-frequency whistles described by Simonis et al (2012). The recordings were collected at sampling rates of 192 or 200 kHz from either a ship-based hydrophone array or a high-frequency acoustic recording package (HARP) and were scanned for high-frequency whistles through the use of Long-Term Spectral Averages (LTSAs; Wiggins and Hildebrand 2007).…”

“…High-frequency whistles ranging up to 75 kHz were first reported from herringeating Northeast Atlantic killer whales (Samarra et al 2010). High-frequency whistles have since been described from killer whale recordings made in the North Pacific (referred to as "high-frequency modulated signals" and "ultrasonic whistles"; Simonis et al 2012, Filatova et al 2012) and in the Antarctic (Trickey et al 2014), indicating that this is a widespread sound type produced by several populations, although they do not appear to be ubiquitous (Samarra et al 2010, Filatova et al 2012). In the North Pacific, whistles were consistently downsweeps and, in some cases, highly stereotyped (Filatova et al 2012, Simonis et al 2012).…”

“…High-frequency whistles have since been described from killer whale recordings made in the North Pacific (referred to as "high-frequency modulated signals" and "ultrasonic whistles"; Simonis et al 2012, Filatova et al 2012) and in the Antarctic (Trickey et al 2014), indicating that this is a widespread sound type produced by several populations, although they do not appear to be ubiquitous (Samarra et al 2010, Filatova et al 2012). In the North Pacific, whistles were consistently downsweeps and, in some cases, highly stereotyped (Filatova et al 2012, Simonis et al 2012). Here, we analyze qualitatively and quantitatively the variation in time-frequency contours of high-frequency whistles recorded from herring-eating killer whales in Norway and Iceland, and compare them to stereotyped high-frequency whistles recorded in the North Pacific.…”