Whistled languages are found around the world, but they are rare. A casual listen might suggest little more than a basic code with a modest vocabulary, but whistled languages are rich and complex surrogate languages seemingly capable of expressing just about anything that can be said in the languages from which they derive.
Whistled languages transpose some of the phonetic features of their source languages. Silbo Gomero, based on Spanish, is one of the better known. It is used on La Gomera, a small island of the Canaries with many hills, woods and ravines – terrain well suited to whistles. ‘Silbadores’ can transmit news and other intelligible information over distances of several kilometres.
A silbador whistling down a Gomeran hill
For centuries, Silbo Gomero has served social, practical, and ceremonial functions. Its origins are uncertain, but it is thought to have come from north Africa. Where other whistled languages of the Canaries have died out, Silbo Gomero enjoys a protected status with UNESCO and was recently added to the island’s school curriculum.
Ramón Trujillo, who wrote a book about the Gomeran whistle, said it “has the basic structure of a natural language and serves as its substitute” (translator: Jeff Brent). This point is echoed by Meyer and Gautheron, whose “Whistled speech and whistled languages” (PDF) tells us the whistle is “a vehicle for articulated language in the true sense of the word”.
Their paper is a very useful introduction, offering a concise overview of where and why whistled languages arise, how they work, their phonological features, and so on:
Whistled languages have naturally developed in response to the necessity for humans to communicate in conditions of relative isolation (distance, night, noise) and specific activities (social information, shepherding, hunting or fishing, courtship, shamanism). Therefore, they are mostly related to places with mountains or dense forests. Southern China, Papua New Guinea, the Amazon forest, subsaharan Africa, Mexico, and Europe encompass most of these locations.
The ability to use a whistled language is passed down through countless generations as part of a particular region’s oral culture. The whistling, though perplexing to outsiders, is taught, used, and experienced as a natural language by its adepts. Even at a neural level,
areas of the brain normally associated with spoken-language function are also activated in proficient whistlers, but not in controls, when they are listening to Silbo Gomero (Carreiras et al., 2005).
Another fMRI study showed that Silbo Gomero
activates left posterior temporal and inferior frontal regions in persons familiar with the use of this speech surrogate. . . . For subjects unfamiliar with Silbo, language regions are not activated. Our results provided further evidence for the flexibility of the human capacity for language to process a wide variety of signal forms.
Non-profit research association The World Whistles has a website offering audio samples of various whistled languages, along with a wide range of publications. The whistles sound so much like birdsong that I was unsurprised to find an anecdote on Linguist List that “some of the commonly used silbo introductions have been picked up and repeated by birds”.
This page from SIL in Mexico transcribes a whistled conversation about oranges and coffee plants in Sochiapam Chinantec.
Updates:
The BBC reports on Silbo Gomero’s revival.
Julien Meyer has a useful article at Scientific American on the status of whistled speech and what it tells us about the human brain.
Finally two videos: a short cheerful clip about Silbo Gomero, from Busuu.com:
And UNESCO’s 10-minute film, which is well worth a look:
Posted by Stan Carey 
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