Community Magazine August 2017

AV - ELUL 5777 AUGUST 2017 87 The small brown bat does this by emitting clicks at varying rates. Its cruising rate is ten clicks a second. Because it uses ultrasound, the wavelengths are much shorter, and it can reliably calibrate fine distances, easily navigating amongst bushes and trees and in and out of caves. Naturally, the calibration needed to create the sounds and measure the returning echo would stun a mathematician and is well more advanced than anything man has yet to invent. But the bat doesn’t think much about it – he just clicks away and eats his dinner. If this alone were the level of sophistication of echolocation, it would be well worth our amazement, but that is only the tip of the iceberg. Ten clicks a second is fine for navigating in and out of caves and amongst bushes and trees, but it would never suffice for the hunt. If you have ever tried to catch a housefly with your hand, you know that it’s extremely agile. When being chased by a bat, the fly performs aerial maneuvers that would leave the best stunt pilots jealous. Cut left. Cut right. Dip down. Now up. Stop. Turn. Therefore, to actually catch an insect in mid-flight, the bat must increase the speed of its clicks considerably. In hunting mode, the little brown bat ramps up its rate to as many as 200 clicks a second! For a bat to hunt, track, close in, and catch an insect, it needs to know size, range, and the position of a prey’s flight. It needs to gauge distance, speed, and direction in midair. To do that, many species of bats make use of yet another recently discovered technology. Doppler Effect If you are standing on a street corner as an ambulance approaches you, its siren will sound high-pitched, yet as it passes, the pitch will seemingly drop. This phenomenon, known as the Doppler Effect , is caused by the manner in which sound waves travel. As a wave moves, it has a crest (top) and a trough (bottom). The distance between the crests determines the pitch. A higher note has a shorter distance between each crest. A lower note has a longer distance between each crest. If you are moving towards the source of a sound, the distance between the wave crests will be shortened because you are moving into the oncoming waves. If you are moving away from the source, the distance between the wave crests will increase because you are moving away from the oncoming waves. While the technicalities may not interest you, their applications might. This is essentially the way that police detect speed. By aiming a radar beam at a moving vehicle and measuring the frequency of the beam coming back, a policeman can accurately gauge the speed of the oncoming car. If the car is moving quickly towards the source of the radar, the frequency of the returning beam will be higher. If it’s moving slowly, the frequency will be lower. This is howmany bats maneuver. By constantly sending out streams of hoots, screeches, or chirps and measuring the change in pitch when the sound returns, they are able to track the speed, distance, and direction of a prey. Pretty astonishing, isn’t it?Howadvanced must their brains be that they can detect the most minute changes in pitch and process that new incoming information at the rate of 200 times a second? More Than Just Speed For a bat to navigate without sight, it must do something immensely more complex than measuring speed. It needs to compute direction and movement. It needs to know density, composition, and texture. Is that a leaf or a fly’s wing? Is that a twig or a moth? It must also be able to make fine distinctions. Dry land and a lake might BATS ARE LIKE MINIATURE SPY PLANES, BRISTLING WITH SOPHISTICATED INSTRUMENTATION, AND THEIR BRAINS DELICATELY-TUNED PACKAGES OF MINIATURIZED ELECTRONIC WIZARDRY… German U-boat A U-boat is a type of submarine invented by the Germans for use in World Wars I and II. The initial “U” in U-boat stands for “unterseeboot,” or undersea boat in English. Brown Bat A brown bat will eat up to half a pound of insects a day. Since many of their preferred meals are insects with an aquatic life stage, such as mosquitoes, they prefer to roost near water. Navigation via SONAR Sonar technology sends out sounds and waits for the sounds to bounce off other objects and come back. Remarkably, with sonar, we can interpret vital information, such as exactly how far away enemy submarines are. Unlike humans, however, dolphins have been using this skill, known as biosonar , for millennia.