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Spectrograms of (a) two Antarctic blue whale calls and (b) one pygmy blue whale “Madagascar” type call, recorded on the hydroacoustic station of the International Monitoring System (spectrogram parameters: FFT 1024 points, 93.75% overlap, Hanning window).
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Blue whales produce intense, stereotypic low frequency calls that are particularly well suited for transmission over long distances. Because these calls vary geographically, they can be used to gain insight into subspecies distribution. In the Southwestern Indian Ocean, acoustic data from a triad of calibrated hydrophones maintained by the Internat...
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Context 1
... glo- bal positioning system clock. Acoustic data for H04S1 and H04S3 were available for the entire recording period; data for H04S2 were available only from May 2003to December 2003 Recordings from the hydrophones included a large vari- ety of sounds including Antarctic blue and pygmy blue whale 'Madagascar type' calls. Antarctic blue whale calls Fig. 2a consist of three tonal units lasting approximately 26 s, and repeated in patterned sequences every 40-50 s over pe- riod extending from a few minutes to hours Ljungblad et al., 1998;Stafford et al., 2004;Rankin et al., 2005;Samaran et al., 2008. The first component is a constant frequency tone centered on 28 Hz followed by a short ...Context 2
... to hours Ljungblad et al., 1998;Stafford et al., 2004;Rankin et al., 2005;Samaran et al., 2008. The first component is a constant frequency tone centered on 28 Hz followed by a short frequency-modulated FM down-sweep from 28 Hz to 20 Hz ending with the third component, a slightly modulated tone 20-18 Hz. Pygmy blue whale 'Madagascar type' calls Fig. 2b consist of two long units repeated in patterned sequences every 90-100 s over a period extending from a few minutes to hours Ljungblad et al., 1998;Samaran et al., 2008 with a 1-2 s 15-28 Hz FM down-sweep that ends with a long 20 s slightly modulated tone. Each component has strong associated ...Similar publications
Humpback whales within the southwestern Indian Ocean undertake annual migrations from summer Antarctic/Southern Ocean feeding grounds towinter breeding grounds in the tropical and sub-tropical coastal waters of Mozambique, Madagascar and the central Mozambique Channel Islands.Little is known of the inter-relationship of humpback whales on each of t...
Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp) are an endangered species found in the So...
There are multiple blue whale acoustic populations found across the Southern Hemisphere. The different subspecies of blue whales feed in separate areas, but during their migration to lower-latitude breeding areas each year, Antarctic blue whales become sympatric with pygmy and Chilean blue whales. Few studies have compared the degree of this overla...
We report two partial skulls of fossil beaked whales (Odontoceti, Ziphiidae) of uncertain age trawled from the sea floor of the sub-Antarctic Indian Ocean (58 to 60 degrees S), representing the southernmost record of the family. The skulls possess diagnostic features of the genus Africanacetus, several specimens of which have been recovered from th...
While visual survey of whales requires substantial means for limited areas, passive acoustic monitoring (PAM) offers larger scale coverage for long periods and less costs. It usually provides information about species behavior, e.g. seasonal movements, but tools are needed to detail the individuals' behavior. From Indian Ocean in a mountainous area...
Citations
... These recordings amounted to the first descriptions of each of these two song types and supported the idea that acoustic monitoring was a robust means of distinguishing between Antarctic and pygmy blue whales. The acoustic data collected on both Antarctic and pygmy blue whale vocalisations Clark and Fowler, 2001;Rankin et al., 2005) paved the way for numerous studies delineating occurrence and habitat usage of blue whales based on PAM and further strengthened the concept of 'acoustic populations' of blue whales (Stafford et al., 2004;McDonald et al., 2006;Samaran et al., 2010a;2010b;. Further, recent surveys that actively used passive acoustics to detect, identify, track, and approach blue whales in the Southern Ocean for photo-identification and biopsy referred to IWC SOWER reports and publications (Clark and Fowler, 2001;Rankin et al., 2005;Gedamke and Robinson, 2010) to select a target research area, develop methods and train field personnel (Miller et al., 2015). The success of the Australian Antarctic Division, Southern Ocean Research Partnership (SORP) 2013 blue whale survey was based on the foundation built by the IWC SOWER cruises Miller et al., 2013a). ...
... how loud it is) is needed to estimate detection range and therefore detection probability. Presently there are few source level estimates for Antarctic blue whales (Širović et al., 2007;Samaran et al., 2010b). For Antarctic blue whales there are estimates of detection range based on known sighting locations and calls attributed to those sightings based on DiFAR processing. ...
The International Whaling Commission (IWC) carried out blue whale research within its annual Southern Ocean Whale and Ecosystem Research (SOWER) cruises between 1996 and 2010. Over 700 sonobuoys were deployed to record blue whale vocalisations during 11 Antarctic and three low‐latitude blue whale cruises off Australia, Madagascar and Chile. The recorded acoustic files from Antarctic deployments were collated and reviewed to develop a database of digital acoustic files and the associated deployment station metadata of 7,486 acoustic files from 484 stations. Acoustic files were analysed using the automated detection template and visual verification method. We found a significant difference between the total number of acoustic recording hours (2,481) reported in the associated cruise reports and the currently available number of acoustic recording hours (1,541). Antarctic blue whale vocalisations (9,315 D‐calls and 24,902 Z‐calls) were detected on 4,183 out of the total 7,486 acoustic files. December had the lowest call rates; January and February yielded high call rates. While most sonobuoys (63%) were deployed between 1800hrs and 0600hrs, the majority of calls (62%) were detected during observation periods between 0600hrs and 1800hrs. The difference between the available and reported data is a significant concern. Reconciliation of these and any future IWC acoustic data is strongly recommended.
... These recordings provided the first descriptions of each of these two song types and supported the idea that acoustic monitoring was a robust means of distinguishing between Antarctic and pygmy blue whales. Acoustic data collected on both Antarctic and pygmy blue whale vocalisations Clark and Fowler, 2001;Rankin et al., 2005) paved the way for numerous studies delineating occurrence and habitat usage of blue whales based on passive acoustic monitoring and further strengthened the concept of 'acoustic populations' of blue whales (Stafford et al., 2004;McDonald et al., 2006;Samaran et al., 2010a;2010b;. Recent surveys that actively used passive acoustics to detect, identify, track and approach blue whales in the Southern Ocean for photo-ID and biopsy also used SOWER reports and publications to select a target research area, develop methods and train field personnel (Clark and Fowler, 2001;Rankin et al., 2005;Gedamke and Robinson, 2010;Miller et al., 2015). ...
... The source level of a signal (how loud it is) is needed to estimate detection range and therefore detection probability. Presently there are few source level estimates for Antarctic blue whales (Širović et al., 2007;Samaran et al., 2010b). For Antarctic blue whales, there are estimates of detection range based on known sighting locations and calls attributed to these sightings based on DiFAR processing. ...
The International Whaling Commission (IWC) carried out blue whale research within its annual Southern Ocean Whale and Ecosystem Research (SOWER) cruises between 1996 and 2010. Over 700 sonobuoys were deployed to record blue whale vocalisations during 11 Antarctic and three low‐latitude blue whale cruises off Australia, Madagascar and Chile. The recorded acoustic files from Antarctic deployments were collated and reviewed to develop a database of digital acoustic files and the associated deployment station metadata of 7,486 acoustic files from 484 stations. Acoustic files were analysed using the automated detection template and visual verification method. We found a significant difference between the total number of acoustic recording hours (2,481) reported in the associated cruise reports and the currently available number of acoustic recording hours (1,541). Antarctic blue whale vocalisations (9,315 D‐calls and 24,902 Z‐calls) were detected on 4,183 out of the total 7,486 acoustic files. December had the lowest call rates; January and February yielded high call rates. While most sonobuoys (63%) were deployed between 1800hrs and 0600hrs, the majority of calls (62%) were detected during observation periods between 0600hrs and 1800hrs. The difference between the available and reported data is a significant concern. Reconciliation of these and any future IWC acoustic data is strongly recommended.
... For song, the source level of 179 dB re 1 μPa at 1 m estimated for pygmy blue whales from the Australian population was used as a proxy (Gavrilov et al., 2011), and the dominant frequency band used was 17-50 Hz. For D calls, the source level was set to 174 dB re 1 μPa at 1 m (Samaran et al., 2010), and the frequency band was 20-100 Hz. Hourly ambient noise levels were considered the 1st percentile levels of the dominant frequency band for each call type. ...
Animal behavior is motivated by the fundamental need to feed and reproduce, and these behaviors can be inferred from spatiotemporal variations in biological signals such as vocalizations. Yet, linking foraging and reproductive effort to environmental drivers can be challenging for wide‐ranging predator species. Blue whales are acoustically active marine predators that produce two distinct vocalizations: song and D calls. We examined environmental correlates of these vocalizations using continuous recordings from five hydrophones in the South Taranaki Bight region of Aotearoa New Zealand to investigate call behavior relative to ocean conditions and infer life history patterns. D calls were strongly correlated with oceanographic drivers of upwelling in spring and summer, indicating associations with foraging effort. In contrast, song displayed a highly seasonal pattern with peak intensity in fall, which aligned with the timing of conception inferred from whaling records. Finally, during a marine heatwave, reduced foraging (inferred from D calls) was followed by lower reproductive effort (inferred from song intensity). Our work links animal behavior and oceanography to provide insights into species life history and investigate the impacts of environmental change. We examine environmental correlates of blue whale vocalization patterns in Aotearoa New Zealand. Our results demonstrate the vulnerability of marine predator populations to marine heatwaves due to the links between environmental factors that control prey availability, foraging effort, and reproductive effort.
... Fin whales in the Southern Ocean are also known to produce distinctive stereotyped song in the form of regularly repeated 20 Hz pulses (Širović et al., 2009;Buchan et al., 2019) as well as FM downswept calls, hereafter referred to as 40 Hz calls (Širović et al., 2006Gedamke and Robinson, 2010;Miller et al., 2021a). For both ABWs and Southern Ocean fin whales, knowledge of source level is limited to only song calls, and this knowledge comes from a small number of calls, produced by an even smaller number of individuals (Širović et al., 2007;Samaran et al., 2010b;Bouffaut et al., 2021). While all populations of blue whales are known to produce D-calls, there are only three studies that present estimates of SL, and each of these for only a small number of calls all in the Northern Hemisphere (Thode et al., 2000;Berchok et al., 2006;Akamatsu et al., 2014). ...
The source levels, SL, of Antarctic blue and fin whale calls were estimated using acoustic recordings collected from directional sonobuoys deployed during an Antarctic voyage in 2019. Antarctic blue whale call types included stereotyped song and downswept frequency-modulated calls, often, respectively, referred to as Z-calls (comprising song units-A, B, and C) and D-calls. Fin whale calls included 20 Hz pulses and 40 Hz downswept calls. Source levels were obtained by measuring received levels (RL) and modelling transmission losses (TL) for each detection. Estimates of SL were sensitive to the parameters used in TL models, particularly the seafloor geoacoustic properties and depth of the calling whale. For our best estimate of TL and whale-depth, mean SL in dB re 1 μPa ± 1 standard deviation ranged between 188–191 ± 6–8 dB for blue whale call types and 189–192 ± 6 dB for fin whale call types. These estimates of SL are the first from the Southern Hemisphere for D-calls and 40 Hz downsweeps, and the largest sample size to-date for Antarctic blue whale song. Knowledge of source levels is essential for estimating the detection range and communication space of these calls and will enable more accurate comparisons of detections of these sounds from sonobuoy surveys and across international long-term monitoring networks.
... For this coastal study site, detection range was estimated at between 2.75 km and 15.3 km for song calls and 1.4 to 6 km for D-calls. Detection range for D-calls was smaller given the lower source levels and higher frequencies of D-calls (Berchok et al., 2006;Samaran et al., 2010aSamaran et al., , 2010b. These values are considerably less than those reported for the open ocean (e.g. ...
... These values are considerably less than those reported for the open ocean (e.g. Samaran et al., 2010aSamaran et al., , 2010b. The mooring was in a small basin with a land mass nearby and subsurface bathymetric rises that constrained how far away a low-frequency whale call could be heard (Fig. 1a). ...
Seasonal variation in the acoustic presence of blue whale calls has been widely reported for feeding grounds worldwide, however variation over the submonthly scale (several days to <1 month) has been examined to a much lesser extent. This study combines passive acoustic, hydroacoustic, and in situ oceanographic observations collected at a mooring in the Corcovado Gulf, Northern Chilean Patagonia, from January 2016-February 2017, to examine the temporal variation in blue whale acoustic occurrence and prey backscatter over seasonal and submonthly scales. Time series data for a) Southeast Pacific blue whale song calls and D-calls, b) zooplankton backscatter, c) tidal amplitude, and d) meridional and zonal wind stress were examined visually for seasonal trends. To examine submonthly timescales over the summer feeding season (January-June), wavelet transforms and wavelet coherence were applied; generalized linear models (GLM) were also applied. There was a 3-month lag between the seasonal onsets of high zooplankton backscatter (October) and blue whale acoustic presence (January), and an almost immediate drop in blue whale acoustic presence with the seasonal decrease of backscatter (June). This may be due to the use of memory by animals when timing their arrival on the feeding ground, but the timing of their departure may be related to detection of low prey availability. Over the summer feeding season, blue whale acoustic presence was strongly associated with zooplankton backscatter (GLM coefficient p<<0.0001). Song calls followed a seasonal cycle, but D-calls appeared to respond to short term variations in environmental conditions over submonthly scales. Results suggest that spring tides may increase prey aggregation and/or transport into the Corcovado Gulf, leading to increased blue whale acoustic presence over 15-day or 30-day cycles; and short-lived events of increased wind stress with periodicities of 2-8 days and 16-30 days, may also contribute to the aggregation of prey. We discuss the strengths and limitations of coupling passive and active acoustic data to examine drivers of blue whale distribution.
... SL estimates require (1) calibrated data, (2) information on the source-receiver range, and (3) a sufficiently representative propagation model. Ranges to vocalizing marine mammals have primarily been estimated from sightings (Cummings and Thompson, 1971), time difference of arrival, and hyperbolic intercepts from multiple widespread sensors (Charif et al., 2002;Gavrilov et al., 2011;Samaran et al., 2010b), time delays and bearings (McDonald et al., 2001), combination of multipath with time of arrival analysis (Weirathmueller et al., 2013) or time difference of arrivals ( Sirović et al., 2007), and beamforming (Wang et al., 2016). The three-component vector-sensor and hydrophone of a single Ocean Bottom Seismometer (OBS) can also be used for range estimation (Matias and Harris, 2015). ...
... The estimated value for Unit A exactly matches a previous estimate of Sirović et al. (2007) from the western Antarctic Peninsula in the same frequency band and is also close to the values obtained for BW off the coast of California (McDonald et al., 2001;Thode et al., 2000) and Chile (Cummings and Thompson, 1971). A later estimate of ABW SL by Samaran et al. (2010b) was measured on the entire call frequency band and found values ' 10 dB lower in the western Indian Ocean. Several possible reasons were proposed to explain the differences: frequency band differences, inter-individual variations, or changes in the behavioral context (Samaran et al., 2010b). ...
... A later estimate of ABW SL by Samaran et al. (2010b) was measured on the entire call frequency band and found values ' 10 dB lower in the western Indian Ocean. Several possible reasons were proposed to explain the differences: frequency band differences, inter-individual variations, or changes in the behavioral context (Samaran et al., 2010b). However, another possible explanation could be that none of the previously mentioned methods considered the interference from the surface-reflected wave, except in Thode et al. (2000), where the acoustic field was comprehensively estimated in a shallow-water environment. ...
The source level (SL) and vocalizing source depth (SD) of individuals from two blue whale (BW) subspecies, an Antarctic blue whale (Balaenoptera musculus intermedia; ABW) and a Madagascar pygmy blue whale (Balaenoptera musculus brevicauda; MPBW) are estimated from a single bottom-mounted hydrophone in the western Indian Ocean. Stereotyped units (male) are automatically detected and the range is estimated from the time delay between the direct and lowest-order multiply-reflected acoustic paths (multipath-ranging). Allowing for geometric spreading and the Lloyd's mirror effect (range-, depth-, and frequency-dependent) SL and SD are estimated by minimizing the SL variance over a series of units from the same individual over time (and hence also range). The average estimated SL of 188.5 ± 2.1 dB re 1 μ Pa measured between [25–30] Hz for the ABW and 176.8 ± 1.8 dB re. 1 μ Pa measured between [22–27] Hz for the MPBW agree with values published for other geographical areas. Units were vocalized at estimated depths of 25.0 ± 3.7 and 32.7 ± 5.7 m for the ABW Unit A and C and, ≃ 20 m for the MPBW. The measurements show that these BW calls series are stereotyped in frequency, amplitude, and depth.
... The Indian Ocean has an incredible diversity of blue whale acoustic populations [6][7][8][9][10][11] . Until very recently, there were four recognized blue whale populations from two subspecies: the Antarctic blue whale (B. ...
... The Indian Ocean has an incredible diversity of blue whale acoustic populations [6][7][8][9][10][11] . Until very recently, there were four recognized blue whale populations from two subspecies: the Antarctic blue whale (B. ...
... The Indian Ocean has an incredible diversity of blue whale acoustic populations [6][7][8][9][10][11] . Until very recently, there were four recognized blue whale populations from two subspecies: the Antarctic blue whale (B. ...
Blue whales were brought to the edge of extinction by commercial whaling in the twentieth century and their recovery rate in the Southern Hemisphere has been slow; they remain endangered. Blue whales, although the largest animals on Earth, are difficult to study in the Southern Hemisphere, thus their population structure, distribution and migration remain poorly known. Fortunately, blue whales produce powerful and stereotyped songs, which prove an effective clue for monitoring their different ‘acoustic populations.’ The DGD-Chagos song has been previously reported in the central Indian Ocean. A comparison of this song with the pygmy blue and Omura’s whale songs shows that the Chagos song are likely produced by a distinct previously unknown pygmy blue whale population. These songs are a large part of the underwater soundscape in the tropical Indian Ocean and have been so for nearly two decades. Seasonal differences in song detections among our six recording sites suggest that the Chagos whales migrate from the eastern to western central Indian Ocean, around the Chagos Archipelago, then further east, up to the north of Western Australia, and possibly further north, as far as Sri Lanka. The Indian Ocean holds a greater diversity of blue whale populations than thought previously.
... www.nature.com/scientificreports/ the World Ocean Atlas (WOA2009), bathymetry was extracted at a 1-arc minute resolution from the ETOPO1 dataset 56 , and geo-acoustic parameters for fine sand 57,58 (grain size phi = 3) were used in the propagation model. The source depth (depth of the calling whale) was set to 5 m below the surface, the source level of the calls was set to 174 dB 59 . D calls were simulated at varying distances along 8 radials centered on the hydrophone, and detection range was estimated given the ambient noise levels recorded at the hydrophone. ...
Understanding relationships between physical drivers and biological response is central to advancing ecological knowledge. Wind is the physical forcing mechanism in coastal upwelling systems, however lags between wind input and biological responses are seldom quantified for marine predators. Lags were examined between wind at an upwelling source, decreased temperatures along the upwelling plume's trajectory, and blue whale occurrence in New Zealand's South Taranaki Bight region (STB). Wind speed and sea surface temperature (SST) were extracted for austral spring-summer months between 2009 and 2019. A hydrophone recorded blue whale vocalizations October 2016-March 2017. Timeseries cross-correlation analyses were conducted between wind speed, SST at different locations along the upwelling plume, and blue whale downswept vocalizations (D calls). Results document increasing lag times (0-2 weeks) between wind speed and SST consistent with the spatial progression of upwelling, culminating with increased D call density at the distal end of the plume three weeks after increased wind speeds at the upwelling source. Lag between wind events and blue whale aggregations (n = 34 aggregations 2013-2019) was 2.09 ± 0.43 weeks. Variation in lag was significantly related to the amount of wind over the preceding 30 days, which likely influences stratification. This study enhances knowledge of physical-biological coupling in upwelling ecosystems and enables improved forecasting of species distribution patterns for dynamic management.
