Bats: Honkin' with Brevirostris
Aerosmith's lead screamer Steven Tyler has nothing on Cormura brevirostris. It's a species of fruit bat that lives in Panama. European biologists studying bats' version of sonar – used to find food – have discovered that these bats can chirp at rock-concert levels. No stacks of Marshall amplifiers needed.
The scientists studied fruit bats spanning 11 species and found that they generated sounds that routinely reached between 122 and 134 decibels (dB) at distances of some 4 inches from their mouths. One species, which hunts over water, reached sound levels of 140 dB. In comparison, sound at rock concerts pumps out at 115 to 120 dB. The bats' levels are significantly higher than previous studies suggested. The pitch is far above the range of human hearing. But high-pitched sounds fade faster with distance than low-pitched sounds. That's why the bats must give their pings such punch: the higher the pitch, the higher the volume needed to detect prey at roughly similar distances, the team found. The team notes that as the bats closed in on their prey, they lowered the volume.
The research group, led by University of Southern Denmark biologist Annemarie Surlykke, used an array of microphones and cameras to identify the bats, determine the distance between the bats and the mikes, and calculate the up-close decibel level. The results appear in this week's issue of the Public Library of Science – Biology.