Whales are famous for their songs. But scientists have discovered that, for some whales, those songs may also help them survive. A University of Washington researcher has found that some baleen whales, including blue, fin and minke whales, have evolved to sing at such low frequencies that killer whales, their only natural predator, cannot hear them. Scientists refer to this behavior as acoustic crypsis. This means that these whales make themselves difficult for predators to detect by using sounds that killer whales cannot hear. The discovery gives scientists new understanding of why some whales sing the way they do and shows that the risk of being hunted may have affected the way they communicate.
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What is sound camouflage and what did the study reveal about the blue whale
The study, titled “Most ‘flying’ baleen whale species, unlike ‘fighting’ species, are acoustically mysterious to killer whales”, was published in the journal Marine Mammal Science. It was led by Trevor Branch, professor of aquatic and fisheries sciences at the University of Washington.For the study, Branch reviewed aquarium experiments that measured the hearing range of killer whales. They also examined the sounds of all baleen whale populations and studied how sound travels through the ocean. This helped them find out which whale calls killer whales are actually able to hear.The results showed that killer whales cannot hear sounds below 100 hertz (Hz). They can only hear loud sounds below 1,500 Hz. Branch found that the sounds of “flying” whale species, which flee when attacked, typically cannot be heard by killer whales from more than a kilometer away.Acoustic crypsis is a behavior that helps animals avoid detection by predators. In simple terms, these whales are not singing more quietly. They are singing at frequencies that killer whales cannot hear, making it almost impossible for their predators to detect them through sound.
Fight and flight whales use different survival strategies
The study divided baleen whales into two groups: the fighting species and the flying species. Fighting species are slower moving but more mobile. They protect their calves by gathering in shallow coastal waters in winter and defending themselves if attacked. Flying species are fast swimmers. Instead of fighting, they flee when they detect danger and spend the winter spreading out into the deep, open oceans.The flying group includes blue, fin, sei, Bryde’s and minke whales. The fighting group includes the right, bowhead, gray and humpback whales. The two groups also communicate in different ways. Fighting species produce more complex songs to compete with other whales in a group. Flying species sing loud, simple songs that can travel long distances to attract females.The blue whale is one of the best examples. They are the loudest animals on Earth and can produce sounds of approximately 180 decibels. Although their calls are extremely loud, they are at such low frequencies that killer whales cannot hear them.
What does this discovery tell scientists
The study also helps explain how these whales evolved. They chose not to sing at lower frequencies. Over millions of years, natural selection favored whales whose low-frequency calls were less likely to be heard by killer whales. Those whales were more likely to survive and have young, passing this trait on to future generations.Killer whales live in every ocean and hunt many different types of animals, from small fish to the largest whales. For flying species that spend most of their time alone in deep, open water, remaining hidden through sound is an important way to reduce the risk of attack. Studies show that fear of predators has helped shape one of the most advanced communication systems in the animal world.