Bats and whales use similar biosonar for hunting

Despite the difference in their size, with one weighing 50 tons and the other weight just a few grams, bats and whales share a similar story.

ANI| Updated: Oct 30, 2013, 11:03 AM IST

Washington: Despite the difference in their size, with one weighing 50 tons and the other weight just a few grams, bats and whales share a similar story.

They both have developed the ability to use echolocation - a biological sonar - for hunting.

Now, Danish researchers show that the biosonar of toothed whales and bats share surprisingly many similarities - even though they live in very different environments and vary extremely in size.

Echolocation systems are one of Nature`s extremely successful specializations.

About 1,100 species of bats and roughly 80 species of toothed whales use the technique - this is 25 percent of all living species of mammals.

But why have such different animals as whales and bats both developed the same technique?

The reason cannot be found in kinship, as bats and whales are no closer related to each other than all other mammals descended from the same land vertebrates for 200 million years ago.

The answer lies in convergent evolution - when almost identical features or developments happen in different species. Through evolution both bats and toothed whales have developed the same functional characteristics.

Researchers from the two Danish universities, Aarhus University and University of Southern Denmark, have now studied the acoustic properties of the technique behind echolocation in bats and whales in the wild.

Previous studies of their abilities to locate and catch prey have primarily been based on laboratory tests, and the studies in the wild now provide a much more realistic picture of how the animals use echolocation.

"Our studies have shown that the sounds of bats and toothed whales are surprisingly similar. 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", Professor Annemarie Surlykke from University of Southern Denmark said.

As a bat is much smaller than a whale and its prey is accordingly smaller, it needs to produce sounds with a very high frequency in order to achieve the same capacity to determine direction and size of its prey.

However, the effect of the higher frequency will be partially cancelled out by the fact that the sound is transported five times as slowly and that the sound waves therefore are five times as short in air as in water.

The researchers conclude that bats and toothed whales produce signals for echolocation in the same frequency range, from 10 to 200 kHz.

The studies have been published in the scientific magazine Physiology entitled `Functional Convergence in Bat and Toothed Whale Biosonars`.