Have you ever had the chance to hear a whale sing? These enormous animals do not merely convey messages—they sing strong, harmonious songs that echoes across the seas. Humpback whales sing in various octaves, threading their voices together into beautiful music. Blue whales and fin whales contribute low base notes, which turn the seas into a colossal symphony.

But songs of whales are not only harmonious music. Scientists found that the sounds can tell us a great deal about what is going on in the ocean and how it is changing. A new study, released in PLOS One, identified that the manner in which whales sing is very much related to the availability of food.

The connection between whale song and food 

Researchers tracked whale songs in the eastern North Pacific, along the California coast, over a period of more than six years. It is an important feeding ground for whales prior to their journey to warmer seas to give birth. Because whales consume so little during their prolonged migration, they need to pack away enough energy from their time spent feeding to carry them through.

The research centered on three species: blue whales, humpback whales, and fin whales. They feed on krill and fish but in various manners. Blue whales feed solely on krill, whereas humpback whales feed on both krill and small fish such as anchovies. The supply of these foods varies annually, and scientists wished to determine whether that influenced how frequently whales sang.

Researchers used an underwater microphone, known as a hydrophone, to capture whale songs. The equipment, part of the Monterey Accelerated Research System, helped them to hear whales miles away. But hearing only the songs wasn't sufficient—there was a need for additional clues.

Therefore, they paired sound recordings with other research techniques, such as photo identification of individual humpback whales using a citizen science project known as Happy whale. They also examined the whales' diet by analyzing their skin samples and tracked how much krill and fish were present annually.

The research began in 2015, a year when a marine heatwave created a lack of food. That was when the whales sang the least. As the sea resumed normal and the amount of food improved, whale songs grew stronger and more abundant.

Humpbacks, especially, sang more as the northern anchovy population rose to an all-time high of 50 years. Examining their skin proved that they had changed their diet to more fish. While blue whales, who only feed on krill, suffered as krill declined and they sang less. Their skin samples indicated that they had to go further than ever before to search for food.

This study shows that listening to whale songs can help scientists understand how marine life adapts to environmental changes. Humpback whales proved to be especially resilient because they can switch their diet when necessary, making them better equipped to survive changing conditions.

Learning about these patterns is key to predicting the response of marine ecosystems to long-term alterations created by nature as well as by human beings. Through collaborative effort—scientists, independent research organizations, and government organizations—the experts will keep discovering the ocean's secrets and safeguard these awe-inspiring animals.

(This article is based on "Whales sing when they’ve had a good meal – new research," originally published in The Conversation)

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