Individual identity of alarm calls in wild-living Brandt's voles (Lasiopodomys brandtii).

We investigated acoustic variation responsible for the individuality of alarm calls produced by 50 Brandt's voles Lasiopodomys brandtii derived from 50 different wild-living colonies. For the first time, we described the calling pattern of Brandt's voles, producing a long series of short alarm calls with short inter-call intervals. The alarm calls displayed four different contours of fundamental frequency but were nevertheless strongly individually distinct within a series of 50 successive alarm calls per caller (2500 analyzed alarm calls). The average value of correct assignment of alarm calls to individuals with discriminant function analysis was 15 times higher than the value expected by chance and was robust, not decreasing with cross-validation. We discuss that the highly individualistic alarm calls provide a basis for individual recognition of callers by colony members. At the same time, heterogeneity of call contours makes the long call series less monotonous, potentially preventing habituation and promoting alertness of conspecific call recipients.