Whales and Bats Have Similar Functional Characteristics of ‘Echolocation’


Bats and sperm whales, which are way different from each other in terms of size and living environments, have similar abilities in using echolocation for hunting, according to Danish researchers.

Echolocation systems are nature's most unique specializations. About 1,100 species of bats and roughly 80 species of toothed whales use this technique, which is 25 percent of all living species of mammals.

Convergent evolution has allowed such different animals to develop the same functional characteristics. The evolution is described as when almost identical features or developments occur in different species.

Researchers from the two Danish universities, Aarhus University and University of Southern Denmark, studied the acoustic properties in both bats and whales in the wild.

"Our studies have shown that the sounds of bats and toothed whales are surprisingly similar," said Annemarie Surlykke, one of the researchers from the University of Southern Denmark, in a news release. "This is due to two things: First, all mammalian ears are developed in quite similar ways, and second--which is the most surprising--the contradicting physical conditions in air and water along with the differences in size of the animals even out the differences that you would expect in the sound frequency."

As bat is far smaller than a whale, its prey is even smaller, which means that a bat needs to produce sound with a very high frequency in order to determine the direction and size of its prey. However, the effect of the higher frequency gets compromised because sound is transported five times slower and the sound waves therefore are five times short in air when compared to water.

The benefit of living in the water than air is the 'acoustic field of vision.' The 'acoustic field of vision' is referred to the area where the animal can see their surroundings using echolocation. Whale's 'acoustic field of vision' is six times larger than the bat's. A sperm whale can echolocate prey up to 500 meters away, while a bat's echolocation distance is only 2-10 meters.

Bats can fly fast and can cover approximately one echolocation distance per second. Therefore, within less than a second, they can detect and catch their prey. On the other hand, whales move more slowly and therefore, have enough time to understand the information from the echoes and to choose their prey more carefully.

This might explain why whales are choosier about their food than bats. Bats lack the time to select their food.

The findings are published in the journal Physiology entitled "Functional Convergence in Bat and Toothed Whale Biosonars".

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