“…An alternative is the deployment of devices (acoustic or optical) in which the task is to warn animals against approaching danger. For most mammal species, audible signals are of greater stimulatory significance than visual ones (e.g., Zieliń ski et al, 1991Zieliń ski et al, , 1995Werka et al, 2004). In turn, either animals fail to react to artificial emitted sounds, or the effectiveness of the latter appears to be short lived (Woronecki, 1988;Curtis et al, 1995;Putman, 1997;Belant et al, 1998;Ujvári et al, 2004;Edgar et al, 2007).…”