Sound of Silence: A Warning for Blue Whales

There’s a startling shift happening off California’s coast, where the iconic song of the Blue Whale has lessened, raising alarms among scientists. They believe this change points to deeper ecological issues.

Over the past six years, researchers have closely monitored the sounds made by three whale species—the Blue, Fin, and Humpback Whales—in California’s North Pacific Ocean ecosystem.

Using a submarine hydrophone, the study recorded these structured whale songs, aiming to understand their role in foraging and the implications for the ecosystem. This research was shared in a February publication, highlighting some troubling patterns since 2017: there’s been a noticeable decline in song detection for both the Blue and Fin Whales.

The recordings began back in 2015, just as an extensive ocean heat wave was taking hold. This unusual warming event started in 2013, with vast pools of warm water shifting from places like the Bering Sea and Gulf of Alaska to the U.S. west coast.

At the same time, California’s current ecosystem experienced a significant increase in harmful algal blooms, leading to the highest levels of marine mammal poisoning ever reported, including to whales.

By 2016, waters were recorded at about 4.5 degrees above average, affecting nearly 2,000 miles of the Pacific.

This heat wave fostered conditions ripe for harmful algal blooms, which devastated krill populations—essential food for Blue Whales—resulting in quieter waters and reduced whale songs.

“Imagine trying to sing when you’re starving,” mused John Ryan, a biological oceanographer and co-author of the report. “They were clearly distracted, just trying to find food.” Ryan referred to the situation as unprecedented, calling it “the most extensive marine mammal crisis ever documented.”

During the study, Blue Whale vocalizations plummeted by 40%.

Research indicated that, by 2019, Blue Whales needed to search larger areas to find krill, which were sparse in their usual spots.

These enormous mammals rely strictly on krill, whereas their Humpback counterparts have a more varied diet, including both krill and fish.

Interestingly, the heat wave didn’t seem to disrupt fish populations, as there was a rise in detected Humpback songs.

Over the six years, small whale species have seen their vocal presence increase from 34% to 76%.

As concerns grow over the quieting of the oceans, scientists are eager to learn about long-term impacts caused by this heat anomaly, which has reportedly tripled in frequency since the 1940s.

“These ocean heat waves can drastically affect entire ecosystems,” said Kelly Benoit Bird, a marine biologist. “If whales can’t find food over the vast expanse of the West Coast, that could lead to significant repercussions.”

More time spent foraging means less energy for reproduction, potentially resulting in dwindling Blue Whale populations.

“Understanding where these whales are and what they’re doing reveals important insights into ecological health,” noted ecologist Dawn Barlow. “The implications of the blob highlight just how lasting these impacts can be.”

“Research shows that climate change is indeed affecting our oceans,” she added.