Whales have developed an impressive strategy to evade predators

The ocean is a world of sound. Beneath the surface, marine life relies on calls, clicks, and songs to navigate, communicate, and survive. For baleen whales, singing songs is essential, but it also comes with risks.

Killer whales, their primary natural predators, are intelligent and highly skilled hunters. Yet, despite their sharp senses, some baleen whales manage to avoid their attacks.

New research from the University of Washington sheds light on a fascinating survival strategy. Some baleen whales call at frequencies so deep that killer whales cannot hear them.

This unique adaptation influences everything from migration to mating, revealing how fear shapes the behavior of these giants of the sea.

Fight or flight dilemma of whales

Baleen whales, known for their filter-feeding systems, differ from their toothed relatives in behavior and survival strategies.

Unlike dolphins or sperm whales, which often live in large, social pods, many baleen whale species lead more solitary lives. When faced with an attack, they must decide whether to fight or flee.

Some species, like humpbacks and gray whales, choose to stand their ground. They rely on their maneuverability and group defense to deter predators. Others, like blue and fin whales, opt for speed, escaping into the vastness of the open ocean.

This divide between fight and flight species plays a crucial role in shaping their lifestyles, habitats, and even the way they sing.

Mystery of whale songs

Whale songs are among the most haunting and complex sounds in nature. Scientists have long studied these vocalizations to understand their purpose.

While it is well known that whales use songs to attract mates and communicate across great distances, one question remained: why don’t killer whales track these calls to hunt them down?

The answer lies in frequency. Killer whales have a hearing range that starts at 100 hertz, meaning they cannot detect sounds below this threshold.

Some baleen whales, particularly those in the flight category, have adapted by producing ultra-low-frequency calls that remain completely undetectable to their predators. These deep-voiced species include blue, fin, sei, Bryde’s, and minke whales.

How songs help whales hide

Trevor Branch, professor of aquatic and fishery sciences at the University of Washington, led a study analyzing the relationship between whale songs and predation risk.

The research combined existing knowledge of killer whale hearing with studies on baleen whale vocalizations. By modeling how sound moves through the ocean, Professor Branch was able to determine which species remain acoustically hidden.

It turns out that the calls of flight species rarely travel more than a kilometer before fading. This means that even if killer whales could hear them, they would still be difficult to track.

Meanwhile, the fight species – right, bowhead, gray, and humpback whales – produce higher-frequency calls that can be detected from much greater distances.

Whales survival strategy hidden in songs

The idea that baleen whales rely on fight or flight responses is not new, but the role of sound in their survival adds a new layer of understanding. Could these deep songs serve as a defense mechanism?

This concept, known as “acoustic crypsis,” suggests that some whales evolved to sing in a way that keeps them hidden from predators.

“But these super-loud songs could expose them and their mates to killer whale attack. And this is where acoustic crypsis comes in: singing at low frequencies that are impossible, or very difficult, for killer whales to hear,” Branch said.

This survival strategy highlights how even the most massive creatures on Earth must adapt to threats. By calling at deep frequencies, flight species can continue their essential communication while reducing the risk of drawing unwanted attention.

How habitat influences defense

The fight-or-flight divide among baleen whales also affects where they live. Fight species tend to migrate and give birth in coastal areas.

These shallow waters provide some protection, as they allow group defense strategies to work more effectively. Their slow-swimming bodies may make them vulnerable, but their ability to maneuver quickly gives them an edge when fending off an attack.

In contrast, flight species thrive in the open ocean. Their sleek, powerful bodies allow them to escape quickly when danger approaches.

These whales spread out over vast distances, making it harder for killer whales to find them. Their survival depends on speed and silence rather than confrontation.

Trade-offs in feeding and mating

Choosing where to live comes with trade-offs. Coastal waters offer some protection from predators, but they also provide less food. Fight species must compete for limited resources, while flight species, living in more isolated open waters, have access to greater food supplies.

However, mating presents the opposite challenge. It is much easier for fight species to find partners when gathered in the same location.

Flight species, scattered across thousands of miles, must rely on their songs to attract mates. This explains why their calls are long and repetitive, increasing the chances of being heard over vast distances.

Role of fear in whale behavior

The findings of this research suggest that fear plays a significant role in shaping whale behavior. Every aspect of their lives, from where they breed to how they communicate, is influenced by the threat of predation.

“It just never occurred to me that some whales sing low to avoid killer whales, but the more I looked at this, the more I realized that every aspect of their behavior is influenced by the fear of predation,” said Professor Branch.

This hidden war of sound beneath the waves highlights how even the ocean’s largest creatures must navigate the dangers of their world. By understanding songs of whales, scientists continue to uncover the secrets of survival in the deep.

The study is published in the journal Marine Mammal Science.

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