Apparatus and methods are disclosed for deterring marine animals such as seals and other marine-dwelling animals from mounting or hauling out onto a marine vessel or structure. In one embodiment, the device comprises a base support member for attachment of the device to a structure to be protected. The base support member includes a stand-off block member and associated irritating, non-fixed/rotating element attached thereto. When large animals such as seals mount on a structure where the deterrent device is installed, the preferably blunted corners of the rotating element cause discomfort to the animal by creating pressure points on the skin or blubber of the animal as they brush by or step on the device. The non-fixed/rotating element preferably can turn or otherwise release the animal as it moves away from the discomfort. Thus, the invention preferably irritates these nuisance animals sufficiently to make them move from that area, while minimizing or eliminating the risk of harm to the animal. Methods are disclosed for deterring animals from getting into and/or staying in selected/protected areas, as well as other methods such as ways of attaching the device to surface to be protected in order to deter animals from getting onto that surface.
