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Passive acoustic monitoring of the temporal variability of odontocete tonal sounds from a long-term marine observatory.

Lin TH, Yu HY, Chen CF, Chou LS - PLoS ONE (2015)

Bottom Line: The seasonal variation of whistle usage involved the previous three parameters, in addition to the diversity of whistle clusters.Our results indicated that the species and behavioral composition of the local odontocete community may vary among seasonal and diurnal cycles.The current monitoring platform facilitates the evaluation of whistle usage based on group behavior and provides feature vectors for species and behavioral classification in future studies.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ecology and Evolutionary Biology, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (R.O.C.).

ABSTRACT
The developments of marine observatories and automatic sound detection algorithms have facilitated the long-term monitoring of multiple species of odontocetes. Although classification remains difficult, information on tonal sound in odontocetes (i.e., toothed whales, including dolphins and porpoises) can provide insights into the species composition and group behavior of these species. However, the approach to measure whistle contour parameters for detecting the variability of odontocete vocal behavior may be biased when the signal-to-noise ratio is low. Thus, methods for analyzing the whistle usage of an entire group are necessary. In this study, a local-max detector was used to detect burst pulses and representative frequencies of whistles within 4.5-48 kHz. Whistle contours were extracted and classified using an unsupervised method. Whistle characteristics and usage pattern were quantified based on the distribution of representative frequencies and the composition of whistle repertoires. Based on the one year recordings collected from the Marine Cable Hosted Observatory off northeastern Taiwan, odontocete burst pulses and whistles were primarily detected during the nighttime, especially after sunset. Whistle usage during the nighttime was more complex, and whistles with higher frequency were mainly detected during summer and fall. According to the multivariate analysis, the diurnal variation of whistle usage was primarily related to the change of mode frequency, diversity of representative frequency, and sequence complexity. The seasonal variation of whistle usage involved the previous three parameters, in addition to the diversity of whistle clusters. Our results indicated that the species and behavioral composition of the local odontocete community may vary among seasonal and diurnal cycles. The current monitoring platform facilitates the evaluation of whistle usage based on group behavior and provides feature vectors for species and behavioral classification in future studies.

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Location of the marine cable hosted observatory.The MACHO is connected with a land station at Toucheng Town through a 45-km-long submarine cable (dashed line).
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pone.0123943.g001: Location of the marine cable hosted observatory.The MACHO is connected with a land station at Toucheng Town through a 45-km-long submarine cable (dashed line).

Mentions: In this study, the acoustic recordings were collected from the Marine Cable Hosted Observatory (MACHO). The access of MACHO recordings was permitted by the Central Weather Bureau of Taiwan (R.O.C.). Recordings are archived in the Geophysical Database Management System (http://gdms.cwb.gov.tw/index.php). The MACHO (N24°33.0’ E122°07.9’) is located on the seafloor of the Ilan Ridge, off Suao Town (Fig 1). A hydrophone (model TC-4032; Reson, Slangerup, Denmark; receiving sensitivity, –164 dB re 1 V/μPa; preamplifier gain, 10 dB; and frequency response, 10 Hz—80 kHz ± 2.5 dB) is bottom mounted at a water depth of 277 m. The recordings were collected continuously with a sampling frequency of 384 kHz and saved in the waveform audio format every 30 s. The continuous recording resulted in 64.5 GB of data per day. The acoustic monitoring system of the MACHO has a consistent systematic noise in the 3–4.5 kHz range; therefore, only the 4.5–48 kHz range was processed to prevent the influence of noise.


Passive acoustic monitoring of the temporal variability of odontocete tonal sounds from a long-term marine observatory.

Lin TH, Yu HY, Chen CF, Chou LS - PLoS ONE (2015)

Location of the marine cable hosted observatory.The MACHO is connected with a land station at Toucheng Town through a 45-km-long submarine cable (dashed line).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4414466&req=5

pone.0123943.g001: Location of the marine cable hosted observatory.The MACHO is connected with a land station at Toucheng Town through a 45-km-long submarine cable (dashed line).
Mentions: In this study, the acoustic recordings were collected from the Marine Cable Hosted Observatory (MACHO). The access of MACHO recordings was permitted by the Central Weather Bureau of Taiwan (R.O.C.). Recordings are archived in the Geophysical Database Management System (http://gdms.cwb.gov.tw/index.php). The MACHO (N24°33.0’ E122°07.9’) is located on the seafloor of the Ilan Ridge, off Suao Town (Fig 1). A hydrophone (model TC-4032; Reson, Slangerup, Denmark; receiving sensitivity, –164 dB re 1 V/μPa; preamplifier gain, 10 dB; and frequency response, 10 Hz—80 kHz ± 2.5 dB) is bottom mounted at a water depth of 277 m. The recordings were collected continuously with a sampling frequency of 384 kHz and saved in the waveform audio format every 30 s. The continuous recording resulted in 64.5 GB of data per day. The acoustic monitoring system of the MACHO has a consistent systematic noise in the 3–4.5 kHz range; therefore, only the 4.5–48 kHz range was processed to prevent the influence of noise.

Bottom Line: The seasonal variation of whistle usage involved the previous three parameters, in addition to the diversity of whistle clusters.Our results indicated that the species and behavioral composition of the local odontocete community may vary among seasonal and diurnal cycles.The current monitoring platform facilitates the evaluation of whistle usage based on group behavior and provides feature vectors for species and behavioral classification in future studies.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ecology and Evolutionary Biology, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (R.O.C.).

ABSTRACT
The developments of marine observatories and automatic sound detection algorithms have facilitated the long-term monitoring of multiple species of odontocetes. Although classification remains difficult, information on tonal sound in odontocetes (i.e., toothed whales, including dolphins and porpoises) can provide insights into the species composition and group behavior of these species. However, the approach to measure whistle contour parameters for detecting the variability of odontocete vocal behavior may be biased when the signal-to-noise ratio is low. Thus, methods for analyzing the whistle usage of an entire group are necessary. In this study, a local-max detector was used to detect burst pulses and representative frequencies of whistles within 4.5-48 kHz. Whistle contours were extracted and classified using an unsupervised method. Whistle characteristics and usage pattern were quantified based on the distribution of representative frequencies and the composition of whistle repertoires. Based on the one year recordings collected from the Marine Cable Hosted Observatory off northeastern Taiwan, odontocete burst pulses and whistles were primarily detected during the nighttime, especially after sunset. Whistle usage during the nighttime was more complex, and whistles with higher frequency were mainly detected during summer and fall. According to the multivariate analysis, the diurnal variation of whistle usage was primarily related to the change of mode frequency, diversity of representative frequency, and sequence complexity. The seasonal variation of whistle usage involved the previous three parameters, in addition to the diversity of whistle clusters. Our results indicated that the species and behavioral composition of the local odontocete community may vary among seasonal and diurnal cycles. The current monitoring platform facilitates the evaluation of whistle usage based on group behavior and provides feature vectors for species and behavioral classification in future studies.

Show MeSH