Abstract

Acoustic codes assure the intra and interspecific communication of vocal animals. They are composed by a sequence of nominal entities and by magnitude modulation confirming in such a way contemporarily a behavioural and ecological nature. The acoustic codes find evidence in the acoustic niche hypothesis by which species in order to reduce interspecific competition occupy a restricted portion of the available frequencies modulating very precise acoustic cues . Their evolution, like other aspect of biology, is under control of the environmental conditions assuming the more favourable configurations. These nominal entities respond also to the amount of energy by which are emitted allowing to the eavesdropping individuals to range the distance at which a potential competitor is broadcasting a signal. Environmental alterations, especially if of anthropogenic origin, can produce severe consequence of the acoustic codes that in turn may affect the prey–predator balance and the complexity of communities. In fact acoustic codes under an environmental constraint like human noise intrusion can be modified in order to reduce a masking effect, demonstrating their phenological plasticity. The new ecological discipline of soundscape ecology offers the possibility to investigate the nature and the evolution of the acoustic codes in different environmental conditions