Acoustic analysis of alarm calls of the European ground squirrel (Spermophilus citellus) and the Taurus ground squirrel (S. taurensis) (Mammalia: Sciuridae)
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.