Spanish whistling networks
A fascinating subject, but seldom studied by linguists is speech surrogates. They are communication systems that replace the use of speech by other sounds, sometimes made with musical instruments, like drums or, in this case, by means of whistles.
Whistle language has been observed between some ancient Central and South American tribes and also in some of the South Pacific Islands (I don't know much about these other surrogates, so any further information is welcome).
However, it was also a living system of communication in the Island of la Gomera, in the Canary Islands (Spain). This island is almost covered with ravines and cliffs, so movements and communication through the island can be very complicated.
Nevertheless the inhabitants developed a whistled speech system, that helped them to avoid ravines. The idea is very simple: they simmulate the patterns of tone and rythm in spoken language, so == with some practice == they can have long conversations about almost any topic. Therefore, it is not a simple system of signals to say "here, danger" or something like that, but a real surrogate language: Spanish spoken with whistles instead of phonetic sounds.
The name of this surrogate is "silbo canario" (zeel- bo ka-na-reeo) or just "silbo", which in Spanish is the name to designate a very high whistle.
Unfortunately, this old language may disappear soon: the local government tries to save it, as it is a very interesting cultural phenomenon unique in the island, but it is not an easy task, when one considers strong competitors, like cellular phones. Also, it is not considered "fashionable" between young people.
David Casacuberta (firstname.lastname@example.org)