And other strange sounds
Sounds accompany many kinds of activities. The buzz of a mosquito in the bedroom comes to mind; and then there is the clashing of horns of mountain sheep in combat, the chewing of food, the knock on the door, sounds in courtship, territorial claims in birds, monkeys and other animals. etc. Come to think of it there aren’t really terribly many animals that are totally silent; worms perhaps and, with very few exceptions, spiders, but certainly not fish.
Sounds can carry important information and then serve as signals, which influence another individual’s behaviour and that alone is an exciting field of research. However, the methods by which the sounds are produced are equally interesting. Humans and other mammals have a larynx, consisting of 2 vocal cords vibrating in the voice box as air passes by. Quick vibrations as well as short vocal cords create higher pitch; the reverse causes lower pitch. Cats have an extra pair of so-called false vocal cords, which can be activated in purring.
Birds, even the champion singers amongst them, do not have a larynx at all, but an organ called a “syrinx”, which allows them to produce sounds which in terms of pitch composition are far more complex than sounds from a larynx. The famous Mongolian “throat-singing” comes close to syrinx-generated sounds in that two different pitches can simultaneously be heard, but the sound generation method is of course not the same. There are some cave-inhabiting oil birds, e.g., in Trinidad, which can produce cries outside the range of an adult’s human hearing, but not reaching the high frequencies used by bats or some dolphins and whales (children can hear much higher pitch than adults, who year after year tend to lose about 400 Hz as my children reminded me by calling me “deaf” for not hearing the high-pitched sounds of grasshoppers during one of our summer strolls in northern Finland).
With the exception of large fruit bats known as Flying Foxes, bats emit and direct their sounds from the nostrils rather than the mouth. Using echolocation and ultrasound (which only to humans, but not them is “ultra”), they can then fly, feed, and chew in total darkness. Dolphins literally appear to blow their noses when they emit their sounds (which can reach 200 kHz, but for a human singer 2 kHz is already a very high note). Another group of ultrasound producers, grasshoppers strike their wings with a leg like a violin player would use a bow across the strings and crickets rub one wing with the other: they stridulate. Some fish grunt, using muscles to squeeze the swimbladder; rock lobsters can communicate by grinding their mandibular teeth or by moving their antennal bases over a small washboard like structure on the carapace while singing cicadas, whose females are mostly silent, employ a sort of cymbal percussion, in which a stiff membrane is rapidly clicked in and out to produce deafeningly loud sounds.
Methods of sound production in the animal world are fascinatingly diverse and sometimes outright peculiar (doesn’t the “ringing ear” actually emit sound?). Topping it all, however, is probably the small death-watch beetle, a timber borer, whose message to a mate consists of audible and sometimes outright disturbing taps (as the novelist Edgar Allan Poe knew only too well!). Whether or not it is out of frustration, impatience or lack of a voice, the beetle produces these taps by knocking its head against the wood!
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2017.
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