Bathymetric map of Palmyra Atoll, with positions of HARPs indicated by stars and beaked whale sightings indicated by filled circles. Top right inset shows approximate location of Palmyra Atoll. Data courtesy of NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center and the Pacific Islands Benthic Habitat Mapping Center, SOEST, University of Hawaii. Coastline data courtesy of National Geophysical Data Center, NOAA Satellite and Information Service, WVS Coastline Database. Plotting with GMT by Paul Wessel and Walter H. F. Smith.
Surfacing sequence mother-calf pair of Mesoplodon sp. at Palmyra Atoll.
Typical upsweep FM pulse recorded on the HARP at Palmyra Atoll. It represents the sum of 303 aligned pulses; all with a signal-to-noise ratio between 29 and 30 dB. (A) Waveform with normalized amplitude versus time, (B) spectrogram (Hann window, 40-point FFT, 98% overlap) with frequency versus time, and (C) spectra (Hann window, 256-point FFT) with normalized amplitude versus frequency. The continuous line represents the FM pulse; the dashed line shows the preceding noise floor.
FM pulse echolocation signals recorded on HARP at Palmyra Atoll. (A) Lower (dark gray) and upper (light gray) limits of −10 dB frequency versus received level with mean value and standard deviation of groups with 2 dB bin width, line of best fit. (B) Pulse duration versus received level with mean value and standard deviation of groups with 2 dB bin width, line of best fit. Box around 150 and 160 dB received level indicates data used for parameter calculations in Table I. Data basis for (A) and (B) were 7833 pulses. [(C) and (D)] Histogram of bimodally distributed inter-pulse interval with (C) showing the dominant first peak and (D) the smaller second peak. Black line indicates fit of Gaussian mixture model, two mixtures.
FM pulse echolocation sequences with (A) single and shorter inter-pulse intervals (mean 225 ms) and (B) double inter-pulse intervals (mean 430 ms).
Typical buzz click recorded at Palmyra Atoll. It represents the sum of 48 aligned clicks; all with a signal-to-noise ratio larger than 20 dB. (A) Waveform with normalized amplitude versus time, (B) spectrogram (Hann window, 40-point FFT, 98% overlap) with frequency versus time, and (C) spectra (Hann window, 256-point FFT) with normalized amplitude over frequency. The continuous line represents the buzz click; the dashed line shows the preceding noise floor.
[(A) and (B)] Change from regular pulses to clicks of buzzes in two sequences with shortening of inter-pulse intervals (open circles) before the buzz clicks to a minimum of 26 ms (A) and 24 ms (B) followed by inter-click intervals (points) between 10 and 4 ms. After the buzz there was a pause of 708 ms (A) and 499 ms (B) before echolocation pulses were resumed. (C) Detail of buzz inter-click intervals (points) versus time of sequence A (black) and B (gray). Lines in the beginning and end indicate long inter-pulse intervals.
Averaged power spectra for four beaked whale species ( beaked whale, beaked whale, ’ beaked whale, beaked whale HARP, beaked whale array); data and graph adapted from Gillespie et al., 2009.
Signal parameters of FM pulses and buzz clicks with received levels between 150 and 160 dB re (pp) for HARP recordings (FM pulses: , , inter-pulse interval ; buzz clicks: , inter-click interval ). FM pulses with a received level between 130 and 160 dB re (pp) for array recording (, pulse , inter-pulse interval ); of sequences, of signals. Inter-pulse intervals for HARP are given as mean and standard deviation .
Comparison of FM pulse parameters of beaked whales.
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