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Alarm calls of the European Spermophilus citellus (EGS), Taurus S. taurensis (TGS) and Anatolian S. xanthoprymnus (AGS) ground squirrels share the same basic structure. They are tonal sounds consisting primarily of two different elements. The first element, often produced without the second element, has limited frequency modulation, while the second element is more frequency modulated. The present study examined whether this frequency-modulated element enhances the individual distinctiveness of calls, allowing calls to be ascribed with greater confidence to individual callers of the three species. Cross-validated discriminant function analysis (DFA) based on five acoustic parameters of the first element successfully classified calls to correct individuals (EGS: 90%, TGS: 98%, AGS: 96%). Cross-validated DFA based on five acoustic parameters of the second element was also successful in classifications (EGS: 88%, TGS: 86%, AGS: 96%), though discrimination of callers based on parameters of the second versus first element was the same for the AGS, lower for the EGS and significantly lower for the TGS. Cross-validated DFA based on five acoustic parameters of two-element calls also successfully classified calls to correct individuals (EGS: 93%, TGS: 98%, AGS: 97%), though did not improve the extent to which calls could be classified to individuals beyond that based on the first element alone. Thus, the second element does not enhance the individual distinctiveness of calls, but may convey other information such as the location of the caller. [ABSTRACT FROM AUTHOR]

Abstract: In comparison to some other species of ground squirrels, little is known about alarm calls of the European ground squirrel Spermophilus citellus, occurring in some parts of Central Europe and the Balkans, and essentially nothing is known about alarm calls of the Taurus ground squirrel S. taurensis, recently described from a small area in Taurus Mountains in southern Anatolia, Turkey. In this study, we performed a detailed analysis, description and comparison of alarm calls in these closely related species. We recorded 20 free-living individuals (10 per species) spontaneously vocalizing toward human in their natural colonies, and analyzed a total of 600 alarm calls (30 per individual). In both species, alarm calls in this context are tonal sounds usually consisting of two different elements. There is almost no frequency modulation in the first element, while the second element is highly modulated in frequency. In spite of the similar basic structure, the calls of each species differed significantly in most of temporal and spectral parameters. Our results support the assumption that vocalizations in sciurids are useful features supporting species identification. The potential factors that might be important in shaping the acoustic structure of alarm calls in S. citellus and S. taurensis remain a fruitful area for future research. [Copyright &y& Elsevier]