This text describes and analyzes the expansion of fauna and flora lexicon in Sao Tome and Principe's vernacular Portuguese. The consolidation of Portuguese as a vehicular language allows us to observe how the socio-cultural changes in the last fifty years have triggered different changes in the lexicon in this multilingual environment. Here, we use the perceptual similarity model, which is the most appropriate approach for this language contact situation since Santomeans, or other ethnic group members, whether bilingual or not, are mainly responsible for incorporating loanwords in vernacular Portuguese. Once dominant, the Santome language is now spoken by less than a third of the population. However, it enjoys the prerogative of having been the ancestral language responsible for naming the local fauna and flora. For this reason, it has prestige in these areas with bilingual, passive, and monolingual speakers. The data reveal three strategies used in the incorporation of loanwords: nativization, translation, and hybridism.