Two unit analysis of Sri Lankan pygmy blue whale song over a decade

J.L.M.O. and S.L.N. were funded by the Office of Naval Research (Award No. N000141110619). D.V.H. was funded by the Office of Naval Research (Award No. N000141612364). Sri Lankan pygmy blue whale song consists of three repeated units: (1) low frequency pulsive unit, (2) frequency modulated (FM) upsw...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America
Main Authors: Miksis-Olds, Jennifer L., Nieukirk, Sharon L., Harris, Danielle V.
Other Authors: University of St Andrews.School of Mathematics and Statistics, University of St Andrews.Sea Mammal Research Unit, University of St Andrews.Centre for Research into Ecological & Environmental Modelling
Format: Article in Journal/Newspaper
Language:English
Published: 2019
Subjects:
Sri Lankan pygmy blue whale
Song
Ambient sound
Selection
QH301 Biology
3rd-DAS
QH301
Indian
Lombard
Blue whale
Online Access:https://hdl.handle.net/10023/17689
https://doi.org/10.1121/1.5084269
Description
Summary:J.L.M.O. and S.L.N. were funded by the Office of Naval Research (Award No. N000141110619). D.V.H. was funded by the Office of Naval Research (Award No. N000141612364). Sri Lankan pygmy blue whale song consists of three repeated units: (1) low frequency pulsive unit, (2) frequency modulated (FM) upsweep, and (3) long tonal downsweep. The Unit 2 FM unit has up to three visible upsweeps with energy concentrated at approximately 40, 50, and 60 Hz, while the Unit 3 (∼100 Hz) tonal downsweep is the most distinct unit lasting 20–30 s. Spectral characteristics of the Units 2 and 3 song elements, along with ocean sound levels, were analyzed in the Indian Ocean from 2002 to 2013. The peak frequency of the tonal Unit 3 calls decreased from approximately 106.5 to 100.7 Hz over a decade corresponding to a 5.4% decrease. Over the same time period, the frequency content of the Unit 2 upsweeps did not change as dramatically with only a 3.1% change. Ambient sound levels in the vocalization bands did not exhibit equivalent patterns in amplitude trends. Analysis showed no increase in the ambient sound or compensated peak amplitude levels of the tonal downsweeps, eliminating the presence of a Lombard effect. Here it is proposed that each song unit may convey different information and thus may be responding to different selective pressures. Peer reviewed

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