LAUSR

Abstract The present study provides the first detailed sound-analysis-based description of the male calling song and male–female duet of Isophya fatrensis Chládek, an endemic bush-cricket species known from Veľká Fatra, Kremnické vrchy, Nízke Tatry and Poľana Mountains in Slovak Western Carpathians. The male calling song consists of a long sequence of syllable groups, each composed of 2–10 syllables. Intersyllable interval tends to decrease within each syllable group. In response to the male calling song, females emit short acoustic replies during the intervals between the syllable-groups of the male song. Results of a generalized linear regression model calculated between male syllable duration and the relative timing of female response suggest that the beginning of the last syllable of the male syllable groups function as a marker for female response timing. The oscillographic pattern of male song is superficially similar to that of I. harzi, but the timing of female response is sharply different in the two species. These results confirm the validity of the specific status of Isophya fatrensis and can aid reliable identification of specimens.