Age-depended alarm behaviour and response to alarm call in bobac marmots (Marmota bobac Mull.) [Comportement d’alarme dépendant de l’âge et réponse au cri d’alarme chez les marmottes bobac]

Résumé

Play-back experiments were carried out in 1986-1988 in "Strel'tzovskaya steppe" Reserve (Ukraina). Tape-recordings of adult-variation of alarm call and juvenile one were broadcasted in natural population. Bobac marmots' alarm signal represents the sequence of sounds with intersound intervals up to severals, and every sound consists of the low and high-frequency components. The latter has higher dominant frequency and longer duration in juveniles signal. We made two model variants of signal, consisting of 3 times repeated sound of adult and juvenile marmots, respectively. Marmots' responses were assessed by 5 chosen types of postures. Playback experiments have shown significant differences in responses of adult animals and juveniles: the latter alerted strongly, with shorter latent period, but they quicker resumed normal activity. And all marmots responded twice often to adult-variant. Moreover, alerting to juvenile-variant was significantly shorter. The results have shown that marmots can distinct signal age-variants. Juvenile marmots, having higher acoustic activity and reactivity on the whole, use to call to nondangerous objects, thus, it seems the benefit for marmots to pay less attention to juveniles' alarm calls