MSGID: 1:317/3 63fed4f6   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Blue whale foraging and reproduction are related to environmental   
   conditions, study shows    
      
     Date:   
         February 28, 2023   
     Source:   
         Oregon State University   
     Summary:   
         A new study of New Zealand blue whales' vocalizations indicates the   
         whales are present year-round in the South Taranaki Bight and their   
         behavior is influenced by environmental conditions in the region.   
      
      
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   FULL STORY   
   ==========================================================================   
   A new study of New Zealand blue whales' vocalizations indicates the   
   whales are present year-round in the South Taranaki Bight and their   
   behavior is influenced by environmental conditions in the region.   
      
      
   ==========================================================================   
   The findings are a significant advancement in researchers' understanding   
   of the habitat use and behavior of this population of blue whales, which   
   Oregon State University researchers first identified as genetically   
   distinct from other blue whale populations less than a decade ago.   
      
   "We went from not knowing 10 years ago whether this was a distinct   
   population to now understanding these whales' ecology and their response   
   to changing environmental conditions," said the study's lead author, Dawn   
   Barlow, a postdoctoral scholar in OSU's Marine Mammal Institute. "These   
   findings can inform conservation management of this blue whale population   
   and their habitat."  The patterns and intensity of the whales' calls   
   and songs over two years showed strong seasonality in their foraging and   
   breeding behavior, and the vocalizations changed based on environmental   
   conditions such as a documented marine heatwave, Barlow said.   
      
   "During the marine heatwave, feeding-related calls were reduced,   
   reflecting poor foraging conditions during that period," Barlow said. "But   
   we also saw changes in vocalizations in the next breeding period,   
   an indication that they put less effort into reproduction following a   
   period of poor feeding conditions."  The study was just published in   
   the journal Ecology and Evolution. Barlow conducted the research as a   
   doctoral student in the Geospatial Ecology of Marine Megafauna Laboratory   
   at Hatfield Marine Science Center in Newport, led by associate professor   
   Leigh Torres, a co-author of the new paper.   
      
   Blue whales are the largest of all whales and are found in all oceans   
   except the Arctic. Their populations were depleted due to commercial   
   whaling in the early 1900s, and today they are listed as endangered   
   under the International Union for Conservation of Nature's Red List of   
   Threatened Species.   
      
   The New Zealand whales' habitat overlaps with a wide range of commercial   
   activities, including oil and gas exploration and extraction, vessel   
   traffic, fisheries, wind energy development and possible seabed mining.   
      
   Torres first hypothesized in 2013 that the South Taranaki Bight, between   
   New Zealand's North and South Islands, was an undocumented blue whale   
   feeding ground. Following comprehensive data collection efforts, and   
   using multiple lines of evidence, Torres, Barlow and colleagues were able   
   to document in 2018 that the population in this region was genetically   
   distinct from other blue whale populations.   
      
   Previous research was primarily based on observations researchers made   
   during visits to the region in the summer months. But the researchers   
   wanted to know more about the whales' behavior during other parts of the   
   year. They placed five hydrophones -- a type of underwater microphone   
   -- that recorded continuously between January 2016 and February 2018,   
   with only brief gaps to retrieve data every six months.   
      
   "Unlike many other baleen whales, this population stays in this region   
   year- round," Barlow said. "That means we can monitor what they are   
   doing from one location. Listening is an effective way to do that."   
   The hydrophone recordings showed that the whales' "D" calls were strongly   
   correlated with oceanographic conditions related to upwelling in the   
   spring and summer. Upwelling is a process where deeper, cooler water is   
   pushed toward the surface; the nutrient-rich water supports aggregations   
   of krill that the blue whales feed on. The whales' D calls were more   
   intense during periods of strong upwelling.   
      
   The recordings also showed that the whales' song vocalizations, which   
   are produced by males and associated with breeding behavior, followed   
   a highly seasonal pattern, with peak intensity in the fall. That timing   
   aligns with past whaling records' estimates of conception, Barlow said.   
      
   The hydrophone evidence of the breeding behavior and the whales'   
   presence in the region year-round can influence the animals' national   
   threat classification status, which impacts management practices, the   
   researchers said.   
      
   Blue whales in New Zealand had been classified as migrant, but as a result   
   of the research by Torres, Barlow and colleagues, the classification of   
   has changed from migrant to data deficient. If the whales are reclassified   
   as a resident population, that could impact management practices, but   
   evidence of breeding in New Zealand is needed for that change to occur,   
   the researchers said.   
      
   "Although no one has actually documented blue whales mating -- it is   
   hard to observe that directly -- the increase in song during the expected   
   time of mating is a strong indication of breeding in New Zealand waters,"   
   Torres said.   
      
   "Our study adds more evidence that these are resident New Zealand blue   
   whales."  Once the researchers were able to make the link between the   
   whales' behavior and their calls, they could then look at the calls and   
   behavior relative to environmental patterns. Specifically, they noted   
   how the whales' foraging and breeding behavior changed during and after   
   a 2016 marine heatwave.   
      
   During the marine heatwave, there were fewer aggregations of krill for   
   the whales to feed on, which the researchers documented in a previous   
   study. The reduction in foraging behavior correlated to less intense D   
   calls during that period, and in the next breeding season, the breeding   
   songs were also less intense.   
      
   The findings raise additional questions about how changing ocean   
   conditions and human activity in the region are impacting the New Zealand   
   blue whale population and reinforce the need for continued monitoring,   
   the researchers said.   
      
   "We have come so far in 10 years in our knowledge of these blue whales   
   -- from not knowing this population existed to now understanding their   
   year-round use of this region for feeding, mating and nursing," Torres   
   said. "New Zealanders should be excited and proud that their country   
   is home to its own unique population of blue whales. We hope our work   
   helps Kiwis manage and protect these whales."  Additional coauthors are   
   Holger Klinck, director of the Cornell University K.   
      
   Lisa Yang Center for Conservation Bioacoustics, who also is affiliated   
   with OSU's Marine Mammal Institute; Dimitri Ponirakis of Cornell;   
   and Trevor Branch of the University of Washington. The Marine Mammal   
   Institute is part of Oregon State's College of Agricultural Sciences.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Dolphins_and_Whales # Marine_Biology # Sea_Life   
                   # Animals # Behavioral_Science # Nature # Fish #   
                   Ecology_Research   
       * RELATED_TERMS   
             o Baleen_whale o Blue_Whale o Right_whale o Whale o Whale_song   
             o Bowhead_Whale o Sperm_Whale o Fin_Whale   
      
   ==========================================================================   
   Story Source: Materials provided by Oregon_State_University. Original   
   written by Michelle Klampe. Note: Content may be edited for style   
   and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Dawn R. Barlow, Holger Klinck, Dimitri Ponirakis, Trevor A. Branch,   
      Leigh   
         G. Torres. Environmental conditions and marine heatwaves influence   
         blue whale foraging and reproductive effort. Ecology and Evolution,   
         2023; 13 (2) DOI: 10.1002/ece3.9770   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230228154516.htm   
      
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