Silbo

The Silbo gomero ("Gomeran whistle") is a form of whistled speech practiced by by inhabitants of La Gomera to communicate across the creeks. Invented by the original inhabitants of the island, the Guanches, Silbo was adopted by the Spanish settlers in the 16th century and survived after the extinction of the Guanches. When this unique medium of communication was about to die out early in the 21st century, the local government required all children to study it in school.

The language has 4 vowels and 4 consonants and more than 4000 words can be expressed.