A researcher from the University of Washington has found that some baleen whales avoid attracting deadly predators through an usual process known as 'acoustic crypsis'.
Whales are well-known for their complex songs, which are often used for mating, navigation and hunting, but some baleen whales have adjusted their song to avoid attracting killer whales.
Killer whales are the only natural predator of baleen whales – and when attacked, baleen whales will go into fight or flight mode.
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The whales, which are often classified as a 'flight' species, such as blue, Bryde and minke, were discovered to sing at a lower frequency than those classed as a 'fight' species. This is an example of acoustic crypsis: a behavioural adaptation to reduce detection by eavesdroppers, such as predators.
Trevor Branch, professor of aquatic and fishery sciences at the UW, published his findings in Marine Mammal Science. He conducted a review of aquarium experiments on killer whales' hearing ranges, reviewed the source frequency and source level of populations of all baleen whales, and combined these with knowledge of how sounds move through the ocean, to predict which whale populations can be easily heard by killer whales.
The research found that the calls of the flight species generally can't be heard more than 1km away by killer whales – unlike the calls of the fight species.
“These super-loud songs could expose them and their mates to killer whale attack. This is where acoustic crypsis comes in: singing at low frequencies that are impossible, or very difficult, for killer whales to hear,” Branch said.
“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 realised that every aspect of their behavior is influenced by the fear of predation," he continued.
While blue whales are the loudest animal in the world, at a deafening 180 decibels, the frequency of their songs enable them to avoid attracting trouble.
Main image: Getty
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