(Color online) Study area with Baird's beaked whale encounters from Southwest Fisheries Science Center combined visual and acoustic surveys (stars) and acoustic encounters from autonomous HARPs (dots).
(Color online) Peak frequency distribution of echolocation signals for HARP (A) and towed array data (B). GMM with five mixtures (line) fitted to the HARP peak frequency histogram. Echolocation signals within the first three mixtures were assigned to subsets 1–3, respectively, and those within the last two to subset 4.
Peak frequency distribution of echolocation signals in ten individual HARP encounters (site, date, time, and n number of echolocation signals given). GMM with five mixtures fitted (line) to the peak frequency histogram, probability of fit was omitted, and only dominant fits are shown to simplify graphs.
(Color online) Description of echolocation signals extracted from towed array recordings split into four subsets (I–IV). (A) Concatenated spectrograms with signals sorted by peak frequency. (B) Spectra with mean signal (solid line) and mean noise before signal (dashed line). (C) Two signal examples with waveform (normalized amplitude, top) and spectrogram [144 points discrete Fourier transform (DFT), 98% overlap, bottom].
(Color online) Description of echolocation signals extracted from HARP recordings split into four subsets (I–IV). (A) Concatenated spectrograms with signals sorted by peak frequency. (B) Spectra with mean signal (solid line) and mean noise before signal (dashed line). (C) Two signal examples with waveform (normalized amplitude, top) and spectrogram (60 points DFT, 98% overlap, bottom). (D) Histogram of inter-pulse/inter-click interval.
(Color online) Long-term spectral average (LTSA) of three representative acoustic encounters of Baird's beaked whale on HARP recordings. Different signal types were notable in the LTSA with variable proportions of FM pulses versus clicks in each encounter. Distinct banding pattern was apparent in all three examples.
(Color online) Example acoustic encounter showing an LTSA (top) and two echolocation sequences (bottom, spectrogram and time series) within the same encounter. Echolocation clicks associated with a certain subset are indicated by subset numbers (1–3).
(Color online) Two example burst pulse sequences of up to 15 s duration from HARP recordings. All signals were of the FM pulse type. Inter-pulse intervals ranged from slow 30–60 ms to fast 5–10 ms.
(Color online) Whistles of Baird's beaked whales with fundamental frequencies between 4 and 12 kHz and up to three harmonics from HARP recordings.
(Color online) Mean spectra of Baird's beaked whale (bold black, Bb) in comparison to Blainville's (Md), Cuvier's (Zc), and Stejneger's (Ms) beaked whales (left). While these species have overlapping geographic distributions, their echolocation signals are species-specific allowing passive acoustic monitoring to be used for population assessment. Mean spectra of the four Baird's beaked whale subsets (s1–s4, right) indicate variability in the relative use of the consistent spectral peaks. The mean spectrum (bold, right) retains the relevant spectral features of all subsets (s1–s4, right), and emphasizes consistent spectral peaks, despite varying peak signal level, independent of subset or signal type.
Baird's beaked whale acoustic encounters for towed-array data.
Baird's beaked whale acoustic encounters for autonomous HARP data.
Analysis settings for towed array and autonomous HARP data.
Signal characteristics for four subsets of Baird's beaked whale signals with splits based on multi-modal peak frequency distribution in HARP data for both towed array and autonomous HARP data. Number (n) of echolocation signals in subset, median, and 10%–90% percentiles of distribution in subset are presented.
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