The best human sopranos sing impressively high notes, but they cannot match the clear-winged woolly bat, which a new study has just determined produces the world's highest pitched call.
This bat and its Malaysian relatives also tie many other bats for being the world's fastest "talkers," since they all emit repeating echolocation calls at a rate of up to one vocalization every 5 milliseconds, according to the study, published in the latest issue of the Royal Society Biology Letters.
"A soprano singer might reach the A (note), which is 1.76 kilohertz," co-author Bjorn Siemers told Discovery News. "Our bats attained mean starting frequencies of 235 kilohertz and a maximum of 250, so it is safe to say that the bats produce tones that are 120 times higher than those of a human female singer."
Siemers, research leader of the Sensory Ecology Group at the Max Planck Institute for Ornithology, said the bats reach notes that are 8 octaves higher than what the best human sopranos can produce. The bats can also "sweep through a frequency range of up to 170 kilohertz," moving from lower to higher notes, "while a human singer produces a glissando through less than 2 kilohertz at most."
For the study, Siemers and his colleagues studied several species of bats in the Kerivoulinae and Murininae subfamilies at Kuala Lompat Research Station, Krau Wildlife Reserve, Peninsular Malaysia. Mealworms were tantalizingly hung from a string in a large screened-off tent to which the bats were added.
The scientists then recorded, and later computer analyzed, the echolocation calls emitted by the bats in response to the dangling mealworms. These are tonal calls that create an echo. When the echo returns to the hunting bat, the predator can glean information about the size, location and more of prey.
As the bats approached the mealworms, they produced repeated calls every 17 milliseconds. Closer to the kill, these calls increased to one every 5 milliseconds, known as the "buzz" moment. Unlike other bats and trilling birds, the clear-winged woolly bat and its relatives did not switch to a more narrow-band call as they got to this super-fast calling level.
Secret mammal singers"Somehow they overcame this trade off that keeps other bats and birds from calling fast and broadband," Siemers said.
These incredibly high-pitched and fast-paced calls enable the bats to track bugs and other prey in the dense rainforest understory.
"The high frequencies make the bats' sonar beam very focused and short-ranged," he said. "This may help the bats to scan the foliage bit by bit and to 'concentrate' on a small spot where prey is, while 'fading out/suppressing' too much distracting background echoes from the vegetation."
He added that the many different frequencies contained in the call could aid the bats in distinguishing insects and spiders from leaves and twigs because with such fine-tuned echolocation, each probably looks different. In terms of function, it would be like a person shining a light on a bug in the darkness, and then flashing the beam right over the bug to obtain more detailed information.
While bugs seemingly wouldn't have a chance, given the bats' precision, a separate study led by the University of Bristol's James Windmill determined that many insects adjust their hearing in response to bat echolocation calls. For example, Windmill and his team discovered that the yellow underwing "moth cleverly tunes its ear to enhance its detection of bats."
Siemers reminds that the record-breaking bat is classified as near threatened on the World Conservation Union's Red List. One of the greatest threats is deforestation to allow for palm oil — added to margarine, baked goods, lipstick, detergent and more — plus other agriculture crops.
To help combat this problem, the Roundtable for Sustainable Palm Oil has created a certification process where manufacturers agree to obtain the coveted oil from sustainable sources. Conservationists also continue to monitor bat populations.
© 2012 Discovery Channel