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Biomagnetism
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Waves
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Infrasonic Waves
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Species: Aves Strigiformes Tytonidae Tyto alba (Barn Owl) Species
distinctions: Barn Owl: Physics Application: The Barn owl is notorious for possessing the ability to navigate and direct itself through complete darkness with sensitive hearing. It is a quiet bird of prey which utilizes echolocation to catch prey in the dark, where the facial discs that distinguish it from other owls allows sounds to be localized with which the bird can pinpoint a precise location of movement and its direction. Species: Mammalia Insectivora Soricidae Sorex minutus (Pygmy Shrew) Species distinctions: Pygmy Shrew: Physics Application: This shrew is tiny and emits small cries as it moves through its home tunnels in search of food, cries which are perceived by the human ear as weak squeaks like that of a mouse. However, the cries consist of not only an audible component but an ultrasonic component which may allow the shrews to find their way through the darkness of the tunnels and located movement, where the ultrasonic waves are emitted and reflect off that which will become their prey. Species: Noctilio leporinus (Fish-eating Bat) Species
distinctions: Known for its
upper lip which is divided into harelip and folds of skin under the lower
lip, which resembles the muzzle of a bulldog. Nostrils project beyond the
lips and lacks noseleaves (folds of skin above the nose). Their diet
consists of fish and has fur of reddish-brown only around the shoulder,
head, and the middle of the back. Physics Application: During the day, the bat rests in rock clefts or hollow trees and may be found by following their unpleasant odour, but at dusk, the bats catch their prey: mostly seawater or freshwater fish, which they catch in the company of pelicans, or crickets, flying ants, and beetles. Before echolocation became a known system, it was believed that the fish-eating bats randomly trailed their claws and caught fish by chance but it was demonstrated later that the bats may use echolocation to locate fish and catch them. However, there was still a problem: the ultrasonic cries would almost entirely reflect off the water surface: only 0.1% of sound would penetrate the water and any sound that reached the fish would be subjected to a 99.9% loss as it switched mediums. Also, the waves would reflect off fish only if they had an air-filled swim-bladder, as flesh offers resistence to sound like water, which would provide no noticeable echo. It was, however, shown that the bats catch fish which break the water’s surface to catch for or otherwise, which explains why the bats fish with pelicans: the pelicans cause the fish to panic and break the surface, a point at which the bats catch them to feed.
Anemaw [Animal Electromagnetism and Waves] © Elizabeth Gerrow 2002 . |
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