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Abstract
Across mammalian species, comparable morphological and physiological constraints in
the production of airborne vocalisations are suggested to lead to commonalities in
the vocal conveyance of acoustic features to specific attributes of callers, such
as arousal and individual identity. To explore this hypothesis we examined intra-
and interindividual acoustic variation in chatter calls of tree shrews (Tupaia belangeri).
The calls were induced experimentally by a disturbance paradigm and related to two
defined arousal states of a subject. The arousal state of an animal was primarily
operationalised by the habituation of the subject to a new environment and additionally
determined by behavioural indicators of stress in tree shrews (tail-position and piloerection).
We investigated whether the arousal state and indexical features of the caller, namely
individual identity and sex, are conveyed acoustically. Frame-by-frame videographic
and multiparametric sound analyses revealed that arousal and identity, but not sex
of a caller reliably predicted spectral-temporal variation in sound structure. Furthermore,
there was no effect of age or body weight on individual-specific acoustic features.
Similar results in another call type of tree shrews and comparable findings in other
mammalian lineages provide evidence that comparable physiological and morphological
constraints in the production of airborne vocalisations across mammals lead to commonalities
in acoustic features conveying arousal and identity, respectively.