Sitouativnie izmeneniya spektral'noï strouktouri predou-preïdayuzhego ob opasnosti signala stepnogo sourka [Variabilité contextuelle de la structure spectrale du cri d'alarme de la marmotte des steppes. Situation variability of alarm call spectral structure of steppe marmot (Marmota bobac Müller)].

Résumé

Alarm call of steppe marmot consists of a sequence of single notes. We desided, that situation variability in case of increasing danger is expressed by change of notes parameters from the beginning of a vocal sequence to it's end. Five parts of alarm call can be distinguished by expression of their production when observer approaches to marmot. They are the following : 1) initial notes, 2) notes at the middle of sequence, 3) last notes before going into a burrow, 4) notes at the moment of going into a burrow, 5) notes from a burrow. 9 parameters of the notes from different parts of sequence were compared with the help of Mann-Withney statistic. The pause between high-and low-frequecy components, the beginning of fundamental frequency and characteristic of frequency modulation of high-frequency component appeared to be the most stable in different situations while maximum, terminal and dominant frequences of fundamental of high-frequency component and duration of high-and low-frequency components are the most variable. When danger increases the alarm call changes in the following way : maximum terminal and dominant frequencies of high-frequency component decrease as well as it's duration, dominant frequency of low-frequency component decrease, decrease it's duration in the parts of 1, 2, 3 and increase in the parts of 4, 5. Notes in the distinguished parts of alarm call significantly differed from each other.