How blue whales try to escape their only animal enemies
Killer whales are the only natural enemies of large whales. However, they use special tactics to evade their opponents despite their loud behaviour.
Sword whales are skilful predators from which even the largest living animals on earth are not safe: They attack and even kill blue whales and other baleen whales. But to avoid attracting attention in the first place, these large whales use a special tactic: they sing particularly loudly, but also very low - in frequency ranges below 100 hertz, in which the killer whales can no longer perceive anything. This is the conclusion drawn by scientists led by Trevor Branch from the University of Washington based on experiments with killer whales in aquariums and data from the wild.
Branch and co. divided the baleen whales into two groups: Fighting and flight animals. The former include, for example, northern right whales, grey whales and humpback whales, some of which gather in large numbers in shallower waters to mate and give birth to their offspring. Although they swim slower than their relatives and have more compact bodies, they are more manoeuvrable and defend themselves together when killer whales attack. At the same time, they communicate with songs above 1500 hertz, which the orcas can easily hear.
The opposite is true for the second group, the flight animals such as blue, fin and minke whales. They have rather slender, streamlined bodies, swim relatively fast and stay at sea, where they can flee in all directions. They usually travel alone or in small groups, which makes them easier to attack. To avoid putting themselves in danger, they sing particularly low, which killer whales can no longer detect over distances of more than one kilometre. At the same time, these large whales have to sing very loudly to attract the attention of mating partners over long distances. Blue whale songs can reach up to 188 decibels and travel several hundred kilometres.
In contrast to their fighting relatives, these large whales have less complex and repetitive songs, which they also emit over longer periods of time. This allows the males to be heard and ultimately found by as many females as possible. The loudest sounds of the blue whales are in the frequency range below 80 Hertz, which killer whales can only hear at close range. Then it becomes dangerous even for the giants.
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