The latest study on New Zealand’s blue whale population highlights the species’ behavior and how it is influenced by environmental conditions.
The study, published in the journal Ecology and Evolution, shows that blue whales in New Zealand’s South Taranaki Bight are present year-round, with strong seasonality in their foraging and breeding behavior, which is affected by changing environmental conditions.
The research was conducted by Dawn Barlow, a postdoctoral scholar at Oregon State University’s Marine Mammal Institute, and her colleagues.
They found that the whales’ vocalizations indicate that their foraging and reproductive behaviors are linked to environmental factors such as upwelling, a process where deeper, cooler water is pushed toward the surface and nutrient-rich water supports aggregations of krill that the blue whales feed on.
The study also showed that the whales’ vocalizations changed during and after a 2016 marine heatwave. During the heatwave, there were fewer aggregations of krill for the whales to feed on, and this correlated with a reduction in foraging behavior and less intense vocalizations.
The next breeding season’s songs were also less intense, indicating that the whales put less effort into reproduction following a period of poor feeding conditions.
These findings can inform conservation management of this blue whale population and their habitat. Blue whales are the largest of all whales and were severely 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.
Thus, this study highlights the need for continued monitoring to understand how changing ocean conditions and human activity in the region are impacting the New Zealand blue whale population.
The researchers used 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.
The recordings showed that the whales’ “D” calls were strongly correlated with oceanographic conditions related to upwelling in the spring and summer, and the whales’ song vocalizations followed a highly seasonal pattern, with peak intensity in the fall. That timing aligns with past whaling records’ estimates of conception.
This study adds more evidence that these are resident New Zealand blue whales, and the researchers hope that their work helps Kiwis manage and protect these whales.
Blue whales in New Zealand had been classified as migrant, but the classification 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.
This study provides valuable insights into the behavior of New Zealand’s blue whale population, indicating that their foraging and reproductive behaviors are linked to environmental factors such as upwelling, and it highlights the need for continued monitoring and conservation efforts.
As individuals, we can also do our part by reducing our carbon footprint, supporting conservation efforts, and raising awareness about the importance of protecting these magnificent creatures.
This article by Nicholas Vincent was first published by OneGreenPlanet on 3 March 2023.
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