Acoustic cues of caller identity and affect intensity in communication calls of tree shrews (Tupaia belangeri)
Comparative studies on the vocalisation of humans and animals have shown that structural and temporal variations in communication sounds serve several functions, such as to reliably transmit the affective state and individuality of the sender. These variations within a call type are named acoustic cues and are ghoutght to be important factors in the communication process of social living animals. In the present study, we have examined attention calls of tree shrews (Tupaia belangeri) for acoustic cues conveying the affective state and/or individuality of the sender. Any general physiological activation of the nervous system in a tree shrew leads to defined changes in its behavioural patterns. When aroused, it raises its tail/ruffles its tail hair and sometimes utters attention calls (von Holst, 1977). Tree shrews utter these calls in their natural habitat, when they are confronted with new environmental stimuli (Emmons, 2000).