Further investigation determined the frog actively opens and closes two narrow channels known as the Eustachian tubes, which connect the pharynx (part of the neck and throat) to the left and right middle ears. When open, the tubes couple the frog's left and right ears, making them sensitive to audible sounds from all directions. When closed, their ability to pick up ultrasonic frequencies kicks in. "We said, 'Woah! This is bizarre!'" Feng recalled. "In all textbooks on sound communication and hearing in frogs, it is plainly stated that the Eustachian tubes are permanently open!" The ability to tune into specific frequencies at will isn't the frog's only claim to animal fame. It also possesses recessed ears instead of ones that, like those of most other creatures, are located on the body's surface. It additionally can localize sound with astonishing precision. With an error of less than 1 percent, males of this species leap directly toward calling, wooing females. This level of accuracy has never before been observed in frogs. "On the one hand, I am surprised that any frog can open and close the Eustachian tubes," Carl Gerhardt, professor of biological sciences at the University of Missouri, told Discovery News. "But on the other hand, I am not too surprised that this frog does it because it is also the first to be shown to have ultrasonic hearing and calls with ultrasonic components." The frog's unique hearing system is already being used as a model for "intelligent" hearing aids that can spatially separate sounds, process them the way that human brains do, and boost sound signals of interest, such as differentiating background noise from that of a desired conversation. Related Links: Discovery News blog: Born Animal How Stuff Works: Are frogs on the brink of extinction? |
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