A weather-resistant housing (1 a, 1 b) provides a chamber (1 b) containing an acoustic generator. An acoustic outlet (2) is located, in use, to direct an acoustic signal into air of the animal tunnel/burrow system rather than into ground/soil. The acoustic outlet may be an acoustic tube that extends along a tunnel of a subterranean tunnel system of the species to be deterred so as to form part of that tunnel. The device may be powered by a battery (10). A part of the device that extends above the ground may support a solar panel (5). The acoustic signal represents one or more deterrent communication calls of the species to be deterred. In the case of a water vole or mole, the acoustic signal represents one or more of a distance regulating or territorial call and a defensive call. Two such communication calls may be artificially paired to form the acoustic signal.