Buchan
Susannah J.
Buchan
Susannah J.
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ArticleSeasonal occurrence of fin whale song off Juan Fernandez, Chile(Inter Research, 2019-06-27) Buchan, Susannah J. ; Gutierrez, Laura ; Balcazar-Cabrera, Naysa ; Stafford, Kathleen M.Fin whales Balaenoptera physalus were the species of baleen whale most widely caught by commercial whaling fleets off the Chilean coast and are globally classified as Endangered. However, very little is known about the present distribution and seasonal movements of fin whales off the coast of Chile. Passive acoustic data collected at the HA03 station of the Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Organization off the Juan Fernandez Archipelago (JFA) between 2007 and 2016 were analyzed. The temporal occurrence of fin whale song was examined using automatic detection via spectrogram cross-correlation of song notes and by calculating the average acoustic power in the frequency bands of fin whale song. Fin whale song off JFA was composed of regular 17 Hz notes associated with high-frequency components at 85 Hz, with singlet phrasing at a dominant primary inter-note interval of 14.4 s and a secondary interval of 30.8 s. There was a clear seasonal pattern in acoustic presence that was consistent across all years: low or no song during the austral summer and a peak in song occurrence in austral winter. A propagation loss model estimated the detection range at this site to be 186 km. Where the fin whales that are heard off JFA spend the summer months remains an open question. Possible locations include the Western Antarctic Peninsula and/or off northern-central mainland Chile. Further studies should be pursued to better understand the distribution and seasonal movements and to support the conservation of this Endangered species.
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ArticleDistribution of blue and sei whale vocalizations, and temperature - salinity characteristics from glider surveys in the Northern Chilean Patagonia mega-estuarine system(Frontiers Media, 2022-10-07) Buchan, Susannah J. ; Gutiérrez, Laura ; Baumgartner, Mark F. ; Stafford, Kathleen M. ; Ramirez, Nadin ; Pizarro, Oscar ; Cifuentes, JoseNorthern Chilean Patagonia is a mega-estuarine system where oceanic waters mix with freshwater inputs in the coastal fjords, channels and gulfs. The aim of this study was to examine the distribution of blue and sei whales with respect to oceanographic conditions of the study area from the estuarine inner sea to the outer ocean. Ocean gliders were used, mounted with a hydrophone to determine acoustic presence of whales (Southeast Pacific and Antarctic blue whale song calls, and blue whales D-calls; sei whale downsweeps and upsweeps), and a temperature and salinity instrument. Four glider deployments were carried out in April 2018 and April-June 2019 navigating a total of 2817 kilometers during 2110 hours. To examine interannual variation, the average percentage of day with presence of calls was compared between years using the adjusted p-values for one-way ANOVA and descriptive statistics. To examine spatial variation between the hourly acoustic presence of blue whales and sei whales and temperature and salinity conditions, Generalized Linear Models (GLMs) were used. Salinities were higher in 2019 compared to 2018. Southeast Pacific blue whales produced song calls throughout the study area in both years, across estuarine and oceanic areas, but percentage of day with presence was higher in 2019 vs 2018. Percentage of day with presence of D-calls was similar between years, but higher in oceanic areas during both study periods. In contrast, the spatial pattern of sei whale acoustic presence was ambiguous and interannual variability was high, suggesting that sei whales preferred estuarine areas in 2018 and oceanic areas in 2019. We discuss possible explanations for observed acoustic presence in relation to foraging behavior and prey distribution.
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ArticleIntraseasonal variation in southeast Pacific blue whale acoustic presence, zooplankton backscatter, and oceanographic variables on a feeding ground in Northern Chilean Patagonia(Elsevier, 2021-11-09) Buchan, Susannah J. ; Pérez-Santos, Iván ; Narváez, Diego ; Castro, Leonardo ; Stafford, Kathleen M. ; Baumgartner, Mark F. ; Valle-Levinson, Arnoldo ; Montero, Paulina ; Gutierrez, Laura ; Rojas, Constanza ; Daneri, Giovanni ; Neira, SergioSeasonal 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.
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ArticleVisual and passive acoustic observations of blue whale trios from two distinct populations(Wiley, 2019-09-03) Schall, Elena ; Di Iorio, Lucia ; Berchok, Catherine L. ; Filún, Diego ; Bedriñana-Romano, Luis ; Buchan, Susannah J. ; Van Opzeeland, Ilse ; Sears, Richard ; Hucke-Gaete, RodrigoBlue whale populations from both hemispheres are thought to undertake annual migrations between high latitude feeding grounds and low latitude breeding grounds (Mackintosh, 1966). For individuals of some populations these predetermined movements to and from wintering areas where calving occurs have been confirmed through photo‐identification, satellite‐tracking, and passive acoustic monitoring (Burtenshaw et al., 2004; Mate, Lagerquist, & Calambokidis, 1999; Sears & Perrin, 2002; Stafford, Nieukirk, & Fox, 1999a). However, for many blue whale populations no clear migratory behavior has been reported and locations of respective breeding grounds remain unclear (e.g., Hucke‐Gaete, Osman, Moreno, Findlay, & Ljungblad, 2004; Samaran et al., 2013; Stafford, Chapp, Bohnenstiel, & Tolstoy, 2011; Thomisch et al., 2016). On feeding grounds in the Gulf of St. Lawrence and along the coast of California, blue whales have been observed to form female–male pairs during summer, which can remain stable up to over several weeks, with the number of pairs increasing towards the end of summer (Sears & Perrin, 2002; Calambokidis, unpublished data;1 RS, unpublished data). These pairs are sometimes joined by a second male, forming a blue whale trio, which often is observed to engage in surface active behaviors lasting several minutes (Sears & Perrin, 2002; RS, unpublished data). The formation of blue whale trios is probably related to reproductive competition between male escorts and female choice (RS, unpublished data). Blue whale males produce population‐specific songs likely functioning as reproductive advertisement (Edds‐Walton, 1997; Oleson et al. 2007a; Stafford, Fox, & Clark, 1998). Several studies have reported song year‐round in low‐, mid‐, and high‐latitude waters, frequently with high song production rates during summer on the feeding grounds (e.g., Barlow et al., 2018; Buchan, Stafford, & Hucke‐Gaete, 2015; Samaran, Adam, & Guinett, 2010; Širović et al., 2004; Stafford, Nieukirk, & Fox, 1999b; Thomisch et al., 2016). Therefore, breeding activities in blue whales may be more opportunistic, i.e., not restricted to the breeding season or to a specific habitat.
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ArticleInter-annual decrease in pulse rate and peak frequency of Southeast Pacific blue whale song types(Nature Research, 2020-05-15) Malige, Franck ; Patris, Julie ; Buchan, Susannah J. ; Stafford, Kathleen M. ; Shabangu, Fannie ; Findlay, Ken ; Hucke-Gaete, Rodrigo ; Neira, Sergio ; Clark, Christopher W. ; Glotin, HervéA decrease in the frequency of two southeast Pacific blue whale song types was examined over decades, using acoustic data from several different sources in the eastern Pacific Ocean ranging between the Equator and Chilean Patagonia. The pulse rate of the song units as well as their peak frequency were measured using two different methods (summed auto-correlation and Fourier transform). The sources of error associated with each measurement were assessed. There was a linear decline in both parameters for the more common song type (southeast Pacific song type n.2) between 1997 to 2017. An abbreviated analysis, also showed a frequency decline in the scarcer southeast Pacific song type n.1 between 1970 to 2014, revealing that both song types are declining at similar rates. We discussed the use of measuring both pulse rate and peak frequency to examine the frequency decline. Finally, a comparison of the rates of frequency decline with other song types reported in the literature and a discussion on the reasons of the frequency shift are presented.