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A new study has found that blue whales vocalize less when underfed, and vocalize more when sustenance is in abundance. Researchers analyzed whale sounds off the coast of California across a six-year timespan and detected an upturn in their singing following a marine heatwave — despite assertions in numerous publications that blue whales are falling silent.
Whales possess diverse forms of vocal communication, yet solely males are known to sing. There’s substantiation that males employ their songs to lure females and relate to other males, according to study conductor John Ryan, a biological oceanographer from the Monterey Bay Aquarium Research Institute in California. “It’s a fundamental aspect of how they perceive their surroundings and relate to each other,” he stated to Live Science.
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“We’re able to spot one of these whales if we’re nearby and at the surface, and it’s on the surface, but that requires close proximity,” Ryan specified. “Conversely, should one of those whales be situated anywhere inside a zone measuring thousands of square kilometers surrounding our hydrophone, we are able to pick up their sound.”
In February, Ryan alongside his group of associates released a report in the periodical PLOS One, employing hydrophones, or underwater microphones, to capture vocalizations from blue (Balaenoptera musculus), humpback (Megaptera novaeangliae) and fin whales (Balaenoptera physalus) located in the Monterey Bay National Marine Sanctuary. Subsequently, the team juxtaposed the sound-related figures with fishery records procured by the National Oceanic and Atmospheric Administration (NOAA). What the scientists determined was that whale melodies vary dependent upon food accessibility, with fewer songs emitted when nourishment was hard to come by.
The research initiative launched in 2015, coinciding with the height of a disruptive marine heatwave remembered as “the blob”. This climatic occurrence disordered the underwater habitat, thus causing starvation in whales. Consequently, researchers chronicled a nadir in whale song throughout the year 2015. Contrarily, as water temperatures lowered and the marine ecosystems slowly revived, whale sounds returned to their typical levels.
In July, National Geographic reported that blue whales are becoming silent, a claim subsequently echoed in various media outlets referencing the February publication. Nevertheless, even with year-over-year shifts in the quantity of whale songs documented in the analysis, recordings of all three whale types revealed increased singing by the study’s closure versus its commencement. That is to say, the whales were in fact not going silent at all; the levels were climbing — or at the least, better heard following the heatwave.
The rate of blue whale singing presented a considerable climb from 2015 to 2018, a plunge from 2018 to 2020, and an additional rise in 2021. This vocal pattern coincided with peaks and nadirs in the abundance of their principal nourishment, krill. It is thought by researchers that during times of limited food supplies, the whales find themselves short of energy to devote to their singing.
Researchers documented heightened singing activity from humpback whales and blue whales following the crest of the marine heatwave of 2015 (year 1).
“Notably, blue whales are prey-specific. Hence they must expand the range of their search when their sole diet is less available,” Ryan clarified. “We might expect these creatures will have reduced capacity to engage in auxiliary habits as they dedicate extended time and vital energy to nourishment.”
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Chemical examination of whale tissue samples confirmed that blue whales cast their nets wider and combed the seas more thoroughly for krill in times of scarcity. On the other hand, humpback whales diversified their diet, shifting between krill and seafood such as anchovies and sardines, contingent on their local prevalence. As a result, their species alone documented consistent upticks in singing frequency throughout the entire half-decade, according to the research.
“In the context of shifting food sources across the six-year assessment, humpback whales demonstrated improved hardiness as opposed to blue whales,” Ryan said. “This is ascribable to the humpback whales’ knack for versatile sustenance, permitting them to subsist on different varieties of organisms,” he went on to state.
Humpback whales increased their singing activity progressively throughout the 6-year duration of the study.
Findings from the study correlated with the conclusions from a 2023 report appearing in the journal Ecology and Evolution. That report documented a fall in selected blue whale signals off the coast of New Zealand coinciding with regional marine heatwaves spanning the summers of 2016 and 2018. Both reports underline the detrimental impacts marine heatwaves have on whales.
Instances of extreme marine heatwaves have increased threefold over the past 80 years, with subsequent widespread heatwaves occurring during 2023 and 2024. The recent investigation into whale sound covered archival data concluding in June 2021, and therefore it remains unclear what has taken place afterwards. Despite this, even with the globe’s seas steadily warming as a result of climate change, whales off the California coast have not “stopped singing.”
Ryan remarked that his team is presently analyzing figures collected beyond the study’s end date. In response to questions surrounding a fall in blue whale sounds since 2021, he simply answered, “Nope.”
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Modern blue whale populations number fewer members than their pre-commercial hunting figures from the beginning of the 20th century. Post-hunting bans, the numbers are steadily increasing, according to NOAA, even with the latest figures being several years old.
A summary from NOAA’s recent Pacific marine animal stock estimation notes there are roughly 1,898 blue whales inside the eastern North Pacific habitat — the precise group that Ryan monitored off California. However, the reference point in question is sourced from figures acquired in 2018. As per a 2018 assessment issued by the IUCN Red List of Threatened Species, estimates place the global count between 5,000 and 15,000 adult blue whales.
Editor’s note: Clarification has been added to this report, underscoring that analyses of whale tissue confirmed the species widening their search for krill as their foundational food, not that they simply continued to feed on krill.
Patrick PesterSocial Links NavigationTrending News Writer
Patrick Pester serves as Live Science’s trending news contributor. His published works extend across other scientific online platforms, such as BBC Science Focus and Scientific American. Patrick transitioned into journalism following initial years working at zoos and for conservation efforts. He earned the Master’s Excellence Scholarship which supported his studies at Cardiff University, where he concluded a master’s degree focused on international journalism. Additional education includes a second master’s degree obtained at Middlesex University London in biodiversity, evolution, and practical conservation. When unengaged with the news cycle, Patrick explores trading routes relating to human remains.
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