Acoustic analysis of some characteristics of red deer roaring

Different strategies have been adopted to track and monitor red deer (Cervus elaphus) populations according to different habitats and ecosystems. The population census techniques usually carried out are time consuming and involve lot of manpower. A method that relies on individual animal signs like acoustic indices could be useful to support the wildlife management, since vocalisations can encode and transmit a variety of biologically significant information. The present study considered 460 roars recorded from 14 adult deers, from five to eight years old. Recordings were performed in five different locations of northern-central Italy. The acoustic spectrum of each roar was analysed in order to extract its main features, namely: the fundamental frequency (F0), the peak frequency (PF), the sound length (SL) and 24 frequency bins of 174.3 Hz, representing the sound distribution between 50 and 4233.2 Hz (F1 to F24). Statistical analyses showed that individuality and age of animals were significant on F0 (P<0.001), PF (P<0.001) and SL (P<0.001). Results also showed a correlation among the 24 F-variables of roars emitted by deer of similar age (r>0.90; P<0.001), indicating that age could influence the spectral features of roaring. The roaring frequency variables appear to be indicators of the individuality of male deer, even if the strong influence of age on the emitted sounds could compromise the reliability of the method over long periods of time.