A comparative analysis of the alarm call frequency in different age rodent groups

Alarm calls of juvenile and adult groups of Spermophilus pygmaeus, Marmota bobak, Rhombomys opimus, and Microtus brandti were recorded under natural conditions. The spectral analysis showed that the fundamental and dominant frequencies of alarm calls in juveniles were higher than those in adults. The results obtained support the general opinion represented in literature that sounds of juvenile and thus, smaller animals have a higher frequency than those in adults. The results obtained are opposite to the conclusions of Matrosova et al. (2005), whose publication showed the absence of significant differences in frequency of alarm calls in the both age groups of Spermophilus suslicus. The authors assume that this phenomenon may be due to enhancing anti-noise characteristics of the alarm calls transmitting to long distances.