New Vocal Organ Discovered In Koalas Explains The Tiny Animals’ Elephant-Like Mating Call
Male koalas are diminutive in size, but give off extremely low pitched mating calls — a sound about 20 times lower than it should be. This low, rumbling bellow appears rather incongruous. Scientists have now found out how these sleepy marsupials are able to produce low-pitched voice. They have actually evolved a vocal organ that lets them perform this unusual feat.
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Under normal circumstances, koalas should have high pitched voices because there is a direct correlation between size and the pitch produced by them. An animal's vocal chords could range from small to large depending on the mass of their bodies. According to the findings reported in the journal Current Biology the secret to koala's low pitch voice is a specialized sound producing organ, never seen before in any land dwelling mammal. The organ is located in larynx, outside the voice box. "We have discovered that koalas possess an extra pair of vocal folds that are located outside the larynx, where the oral and nasal cavities connect," said Benjamin Charlton of the University of Sussex. The scientists have shown that these additional vocal folds are used effectively by koalas to produce extremely low-pitched mating calls.
The koalas give off a continuous series of sounds on exhalation and inhalation that could be compared to a donkey's braying, according to Charlton. Explaining further, Charlton claimed that when a koala inhales, its bellow resembles the sound somewhat like snoring while the exhalation appears to sound like belching. "They are actually quite loud," Charlton said.
The low pitched voice of koala is surprising because this pitch is typical of an animal as huge as an elephant. Smaller species give calls at higher frequencies than larger ones because dimensions of the laryngeal vocal folds normally constrain the lowest frequency that an animal can generate. The koalas, however, do not encounter this constraint as they have vocal folds in a different and unusual location, just above the larynx at the junction between the oral and nasal cavities.
"To our knowledge, the only other example of a specialized sound-producing organ in mammals that is independent of the larynx are the phonic lips that toothed whales use to generate echolocation clicks," Charlton said.
The uniqueness of this study stems from the fact that this is the first evidence that shows than an organ other than larynx is discovered to produce sound in terrestrial mammal. Charlton and his colleagues will continue to study further looking closely at the other animals to see whether this vocal adaptation is unique to koalas.
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