Whistled speech in a non tonal language consists of the natural emulation of vocalic and consonantal qualities in a simple modulated whistled signal. This special speech register represents a natural telecommunication system that enables high levels of sentence intelligibility by trained speakers. It is not directly intelligible to naïve listeners. Yet, it is easily learned by speakers of the language that is being whistled, as attested by current efforts of revitalization of whistled Spanish in the Canary Islands. To understand better the relation between whistled and spoken speech perception, we looked here at how Spanish native speakers knowing nothing about whistled speech categorized four Spanish whistled vowels. The results show that naïve participants were able to categorize these vowels, although not as accurately as a native whistler.