These beautiful, lonely songs of the deep were captured with bioacoustic technology in the Monterey Bay National Marine Sanctuary from 2015-2021. These recordings have opened up important new perspectives into the challenges these ocean giants encounter. Analysis of these songs led researchers at UC San Diego to conclude that there is a strong connection between whale vocal expression and environmental changes. When marine heat waves increased in frequency and duration, wiping out the whales’ primary food source, their songs disappeared. Researchers from the Monterey Bay Aquarium Research Institute (MBARI) documented this deeply alarming silence with great care. More importantly, it signals deeper issues that demand our attention.
Researchers found a major reduction in the activity of whale song during a period of extreme heat. This egregiously underscores the discomfort these conditions subject whales to. The yearlong survey of public and private vessels that was carried out by the National Oceanic and Atmospheric Administration (NOAA) proved critical to this study. John Ryan and his team matched data from the NOAA survey, which tracked populations of krill, anchovies, and other vital whale prey, to the volume of whale songs recorded by underwater microphones.
Climate change’s role in marine heat waves was emphasized by the researchers. These unprecedented marine heat waves not only elevated ocean temperatures but devastated food supplies for whales. Due to this, whales found it increasingly difficult to feed themselves and their families, resulting in a dramatic decrease in their songs.
“… if it’s harder to gather the food resources it needs to sustain a body that can weigh more than 130 tonnes,” said John Ryan, emphasizing the dire situation faced by these massive creatures.
To get a clearer picture of what caused these dramatic changes, researchers used specialized technology. NOAA and Google AI worked together to create a machine learning model. Our goal with this model is first and foremost to cleanly remove humpback whale songs from the ocean’s natural cacophony. This gaming tech marvel made it possible to study how whales communicate with each other in greater detail and under different environmental conditions.
Aside from listening to the sounds, scientists wanted to gather some physical evidence as well. With crossbows equipped with darts, they captured skin samples from whales to validate changes in their diet. To validate the decreased whale song activity, these samples indicated profound dietary shifts.
As important as acting is, we know the profound importance that singing plays in a whales’ life. In addition to being critical for reproduction, it plays a role in social interactions and foraging. So, a loss of vocal activity is a first warning that something bad is going on in their food web.
“Beyond being beautiful compositions that are wonderful to listen to, these songs are a window into their lives and their resilience through a heat wave as well as their vulnerability,” John Ryan remarked.
Monterey Bay National Marine Sanctuary is famous for its deep feeding grounds for blue, fin, and humpback whales. When food runs out as a result of environmental stressors, even these abundant waters can turn deadly.
“Because they experience these very strong changes in their ecosystem in ways that we can perceive, they are good ecosystem sentinels,” Vanessa ZoBell stated.
The lack of whale song is thus the most dramatic sign that an ecosystem is in trouble.
“We can use sounds like whale song as a metric for understanding biodiversity and ocean health, and if all those sounds go away, it kind of lets us know that a change might be happening in a certain area,” said Vanessa ZoBell.
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