Bats' sonar system 'louder' than home fire alarms, rock concerts

Washington, Apr 30 : If you thought rock concerts were deafening, wait till you hear these bats. According to new measurements, bats using sound to find their way in the dark boom louder than home fire alarms and rock concerts.

Researchers Annemarie Surlykke from the Institute of Biology, SDU, Denmark, and her colleague, Elisabeth Kalko, from the University of Ulm, Germany, studied the echolocation behavior in 11 species of insect-eating tropical bats from Panama.

The researchers used microphone arrays and photographic methods to reconstruct flight paths of the bats in the field when these nocturnal hunters find and capture their insect prey in air using their sonar system.

The research team took this information as a base to estimate the emitted sound intensity and found that bats emit exceptionally loud sounds exceeding 140 dB SPL, which is the highest level reported so far for any animal in air.

For comparison, the level at a loud rock concert is 115-120 dB and for humans, the threshold of pain is around 120 dB.

Bats emit their echolocation calls at ultrasonic frequencies, i.e. above the human hearing range.

This is necessary to get echoes from small insects, but the drawback of high frequencies is that they do not carry far in air as they are attenuated faster than low frequencies.

By estimating detection range for typical insect prey, Surlykke and Kalko conclude that these extreme intensities are essential for the bats as they serve to counteract attenuation.

The study is published in PLoS ONE.

ANI