The Vocal Repertoire of Adult Tree Shrews (Tupaia Belangeri)

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Abstract
The adult vocal repertoire of T. belangeri consists of 8 distinct sounds which are organized into a graded system. Within the repertoire 4 basic acoustic structures have been distinguished which can be associated with one of the following functional categories: contact, aggression, defence, attention and alarm; Elements repeated continually at short regular intercall intervals showing narrow frequency band spectra occur during courtship and mating in males; Elements of short duration with harmonic spectra, low fundamentals and often low frequency noise components signal alarm which consequently focuses other individuals' attention on the sender or the external stimulus; Elements of irregular repetition rate showing broadband harmonic spectra of highly variable duration and frequency modulation are associated with the vocalizers defensive behavior; Elements with noisy spectra over a wide frequency range parallel aggressive behavior by the vocalizer which is often intensified with visual threat display. The findings of the present study are compared and discussed with data from literature referring to tupaia vocalizations. A comparison with the call system of insectivores and prosimians revealed similarities as well as divergencies. Presence of many similarities regarding the basic structural patterning of contact, aggressive and defensive vocalizations in the three orders indicates a certain conservatism in these sounds. Propagation of alarm calls in tree shrews which lacks in insectivores appears to be a more recent evolutionary development in mammals with the highest degree of elaboration in primates. The adult vocal repertoire of T. belangeri consists of 8 distinct sounds which are organized into a graded system. Within the repertoire 4 basic acoustic structures have been distinguished which can be associated with one of the following functional categories: contact, aggression, defence, attention and alarm; Elements repeated continually at short regular intercall intervals showing narrow frequency band spectra occur during courtship and mating in males; Elements of short duration with harmonic spectra, low fundamentals and often low frequency noise components signal alarm which consequently focuses other individuals' attention on the sender or the external stimulus; Elements of irregular repetition rate showing broadband harmonic spectra of highly variable duration and frequency modulation are associated with the vocalizers defensive behavior; Elements with noisy spectra over a wide frequency range parallel aggressive behavior by the vocalizer which is often intensified with visual threat display. The findings of the present study are compared and discussed with data from literature referring to tupaia vocalizations. A comparison with the call system of insectivores and prosimians revealed similarities as well as divergencies. Presence of many similarities regarding the basic structural patterning of contact, aggressive and defensive vocalizations in the three orders indicates a certain conservatism in these sounds. Propagation of alarm calls in tree shrews which lacks in insectivores appears to be a more recent evolutionary development in mammals with the highest degree of elaboration in primates.

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