Sitouationie izmeneziya spektral'noï strouktouri predoupreïdakzhego ob opasmosti signala stepnixh sourkov [Variabilité contextuelle de la structure spectrale du signal d'alarme de marmotte. Contextual variety of spectral structure in marmot's alarm call].

Résumé

In marmot species the contextual variety of alarm call is mainly based on changing intersounds intervals : intervals become shorter upon extreming danger (Nikolskii, 1984). However, contextual informaition can be transmitted simultaneously by changing the other signal parameters, ex. spectral structure of particular sounds, as it was shown in californian ground squirrels (Owings et. al., 1986). Field observations of Marmota bobac alert behaviour revealed, that in sudden danger marmots emitted a few calls composed of the pure tones, rithmically disorganized and sounded like whistles but the following sounds became "repetitions" and rithmical, and and more identical. "Nonrepetitions" and some modified first sounds are typical for the begining of alert reaction. It seems that particular warning of danger is communicated with the use of the single nonrepetitious sound, which evoke immediate recipient reaction (usually, running to the shelter). The following sounds, more similar and monotonous, form the continuous series and probably serve to maintain neighbour vigilance. Field observations showed, that the first sounds evoked a very violent alert, but then recipients returned to their previous activities even when the vocalizer continued its alarm call, monitoring statical disturber. Sometimes the marmot continue calling for nearly an hour without any responses of surrounders. But any new motion of the disturbing object evoke nonrepetitious sound (or sounds) again, as in the first moments of alert. This sound makes immediate panic. I have made type recording of the first sounds of Marmota bobacalarm call in different sudden danger situations (running towards marmot man, roe deer, dog, fox, hares and cattle were mobbed only by this-year young). The tape recordings were analized on a sonograph, and it was shown, that first sounds were higher in frequency, longer in duration and had no low frequency component, if compare with following serial sounds. Revealed spectral differs are repeated steadily in the calls both of adults and juvenils. In play-back experiments marmots responsed differenty to non repetitious and serial sound, played one by one in couple invaried turn. I have not found any specifity of calls, evoked by sudden different cause (man, roe, fox, hare). Variety in rythmical struture fully depended on the speed of approaching and the size of the intruder. Sonogrammes : ai-the 20th, a2-the ist sounds in adult's alarm call. See the sonogrammes in Russian (p.21)