The present work draws on folk zoonymy studies in the framework of geolinguistics. It is mainly inspired by the results of two ongoing research projects, namely the Atlas Linguarum Europae (ALE) and the Atlas Linguistique Roman (ALiR), which focus on motivational aspects of folk zoonymy. All animal designations analysed here have been collected during fieldwork on Modern Greek varieties on the island of Lesbos. The analysis of these lexical data is based on the approach by Guiraud (1986 [1967]), according to whom semantic motivation plays a fundamental role in the denomination process, as well as in lexical evolution. We try to prove that the denomination process is influenced, on the one hand, by the nature of designated entities (or at least by their representation in speakers' mind), and on the other hand, by cultural aspects. We mainly address issues in diatopic lexical variation. In the first place, we describe lexical data collected in Lesbos; we then attempt to shade light on motivational aspects underlying designations; finally, we adopt a comparative approach to establish a relation between data from Lesbos and those of other Greek and European varieties with the aim of contributing to the development of a motivational typology of the European folk zoonyms.