FACTORS AFFECTING ACOUSTIC VARIATION IN BARBARY-MACAQUE (MACACA-SYLVANUS) DISTURBANCE CALLS

Semi-free-ranging Barbary macaques (Macaca sylvanus) were observed to utter distinctive calls after disturbances in the surroundings (e.g. p resence of a predator, occurrence of some unusual phenomenon). These c alls differed from calls given in other contexts. Most of these calls were uttered in a serial manner, some of which lasted as long as the c orresponding context. The aim of this study was to determine the objec t-related specificity of calls and variation of acoustic parameters wi thin a call series. The analysis revealed that acoustic features of ca lls varied among contexts. Within one apparently homogeneous context, both temporal and frequency characteristics shifted gradually. Further more, the disturbance calls clearly differed between individuals. To e xamine the disturbance calls' meaning, playback experiments were condu cted in which alarm calls and disturbance calls were presented. After playback of an alarm call, subjects typically showed an escape respons e, whereas, in response to disturbance calls, they most often scanned the surroundings. Juvenile animals generally showed stronger responses than adults.