Ultrasonic Vocalisations of the Bavarian Pine Vole: Preliminary Evidence for a Diverse Ultrasonic Repertoire

Abstract Objective The Bavarian pine vole ( Microtus bavaricus ) is a critically endangered rodent endemic to the Northern Alps and among Europe’s rarest mammals. Little is known about its biology or behaviour. This study provides a preliminary description of its ultrasonic vocalisations (USVs). Results Recordings from three opposite-sex pairs of adult pine voles at Alpenzoo Innsbruck-Tirol, Austria, indicate a diverse USV repertoire. USV frequency contours and features resembled those of other rodent species. The introduction of a male intruder into an established (resident) pair’s territory increased the occurrence of discontinuous USVs, suggesting a potential heightened arousal in the individuals. Using K-means clustering on five acoustic features, we identified nine USV clusters. Three appeared to be specific to the intruder context (established pair exposed to a male intruder) and differed significantly in acoustic structure from the remaining clusters. This preliminary characterisation of the Bavarian pine vole’s USV behaviour provides the first acoustic baseline for a species on the brink of extinction, opening avenues for conservation-relevant research.