Bats start out with shorter-rate chirps, increasing their frequency as they approach their prey and leading to a hypersonic pulse called the 'terminal buzz'. A group of scientists investigated how bats produced this buzz. They also wanted to determine whether the upper buzz limit is a function of how quickly the bats can hear the return signals that bounce off their prey, or whether it's because of the bats' own call-producing abilities.
They set up a chamber with 12 microphones and recorded the activities of five different free-flying Daubenton's bats, little bats found in woodland areas from Britain to Japan. The bats hunted mealworms that were suspended in the chamber. The animals' chirp rate was so rapid that the researchers knew they couldn't be using normal skeletal muscle.
They attached the bats' vocal muscles to a motor and a force monitor, and stimulated the muscles to flex. The researchers monitored how long it took a muscle to twitch, and determined the muscles were able to contract and relax at frequencies up to 180 Hz and, in one case, up to 200 Hz.
They also noticed that echoes from individual calls ended before the start of the next call, so the bats don't confuse themselves. But a bat could theoretically produce calls at a greater frequency than 200 Hz - up to 400 Hz before echo interference would become a problem. The reason they don't? The superfast muscles are only so fast.
The muscle performance is said to be equated to a car engine. As quoted from a researchers: "It can be tuned to be efficient, or tuned to be powerful depending on what you want it to do."
These laryngeal muscles contract at a rate 20 times that of the fastest human eye muscles, and about 100 times faster than typical skeletal muscles, the researchers say.
Previously, scientists thought these ridiculously quick muscle contractions were only found in the sound-producing organs of rattlesnakes and some types of fish. This suggests that these special muscles are more common than previously thought.
Source:
Elemans, C. P. H., A. F. Mead, et al. (2011). "Superfast Muscles Set Maximum Call Rate in Echolocating Bats." Science 333(6051): 1885-1888 %R 1810.1126/science.1207309.
You had me at "Terminal Buzz".
ReplyDeleteSounds like the way forward re: cloned super soldiers must involve gene splicing with bats. Alternatively, Oz could spend some research money and end up winning gold every time in Olympic sprinting contests. As a track person yourself, what do you think of half-bat competition?
Terminal buzzes pop up in other places too (a terminal buzz is the noise a bat makes right before eating something!). I read a paper last year which talks about the effects of radar on the feeding habits of bats: it turns out that bats don't like to be near large radar installations.
ReplyDeletePeople think that this is due to thermal expansion of certain components of the inner ear as a result of absorption of pulsed EMR. Interestingly, humans are also supposed to be able to `hear' microwaves in the same way (apparently during WWII radar technicians noticed popping noises when near the antennae).
I'll put up some slides on this sometime soon.
I recall a documentary I once watched where they compared different muscle types in terms of their ability to move quickly (humans of different ancestries and cheetahs were compared). Since cheetahs already weigh quite a bit less than humans (on Earth), I think that it might not be possible to transfer the high frequency of muscle contractions to humans and retain the necessary load bearing requirements of human movement.
ReplyDeleteJosh H