FN Archimer Export Format
PT J
TI Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean
BT 
AF LEROY, Emmanuelle C
   ROYER, Jean-Yves
   BONNEL, Julien
   SAMARAN, Flore
AS 1:1,2;2:1,2;3:3;4:4;
FF 1:;2:;3:;4:;
C1 Univ Brest, Plouzane, France.
   CNRS, Lab Geosci Ocean, IUEM, Plouzane, France.
   Woods Hole Oceanog Inst, Falmouth, MA USA.
   ENSTA Bretagne, UMR CNRS 6285, Lab STICC, Brest, France.
C2 UBO, FRANCE
   CNRS, FRANCE
   WHOI, USA
   ENSTA BRETAGNE, FRANCE
UM LGO
IF 3.235
TC 31
UR https://archimer.ifremer.fr/doc/00516/62730/67109.pdf
LA English
DT Article
CR DEFLO-HYDRO
   OHA-SIS-BIO - OBSERVATOIRE HYDROACOUSTIQUE
   VT 109 / OHA-SIS-BIO-1
BO Marion Dufresne
DE ;large baleen whales;blue whale calls;frequency shifts;frequency decrease;ambient noise;bioacoustics
AB In the past decades, in the context of a changing ocean submitted to an increasing human activity, a progressive decrease in the frequencies (pitch) of blue whale vocalizations has been observed worldwide. Its causes, of natural or anthropogenic nature, are still unclear. Based on 7years of continuous acoustic recordings at widespread sites in the southern Indian Ocean, we show that this observation stands for five populations of large whales. The frequency of selected units of vocalizations of fin, Antarctic, and pygmy blue whales has steadily decreased at a rate of a few tenths of hertz per year since 2002. In addition to this interannual frequency decrease, blue whale vocalizations display seasonal frequency shifts. We show that these intra-annual shifts correlate with seasonal changes in the ambient noise near their call frequency. This ambient noise level, in turn, shows a strong correlation with the seasonal presence of icebergs, which are one of the main sources of oceanic noise in the Southern Hemisphere. Although cause-and-effect relationships are difficult to ascertain, wide-ranging changes in the acoustic environment seem to have a strong impact on the vocal behavior of large baleen whales. Seasonal frequency shifts may be due to short-term changes in the ambient noise, and the interannual frequency decline to long-term changes in the acoustic properties of the ocean and/or in postwhaling changes in whale abundances. Plain Language Summary In the past decades, a progressive decrease in the frequencies of blue whale vocalizations is observed worldwide. Its causes,of natural or anthropogenic nature, are unclear. Based on 7years of widespread acoustic records in the southern Indian Ocean, we show that the call frequency of five populations of large baleen whales decreases at a constant rate of tenths of hertz per year. We also found that seasonal shifts in the whale call frequency follow seasonal changes in the ambient noise in the same frequency band. Wide-ranging changes in the acoustic environment have thus a strong impact on the vocal behavior of large whales in the short term, but, paradoxically, not in the long term. 
PY 2018
PD NOV
SO Journal Of Geophysical Research-oceans
SN 2169-9275
PU Amer Geophysical Union
VL 123
IS 11
UT 000453907000048
BP 8568
EP 8580
DI 10.1029/2018JC014352
ID 62730
ER

EF