USDA National Wildlife Research Center Symposia


Date of this Version

August 1995


Nonlethal electroshocking devices have been developed at the Denver Wildlife Research Center for repelling aquatic mammals and birds from selected areas. These devices are augmented with infrared motion sensors to turn on the apparatus only when warm-blooded animals are present, thereby conserving electrical energy and allowing battery operation. Electronic safety controls are incorporated to prevent animals from being over-exposed or repeatedly exposed to the electrical fields. The technical basis for this equipment is based upon research originally reported in the electrofishing literature. Obviously, any animal immersed in water is highly susceptible to electrical shock, but permanent injury can be avoided by controlling the intensity of the electrical energy. As the intensity of the electrical field is increased, the severity of the electrical shock experienced by an animal is known to progress through several stages including mild initiation, extreme agitation, electronarcosis (an unconscious state), tetany (characterized by muscular rigidity), and death. Fortunately, with proper engineering, in-water electroshocking apparatus can be designed to limit the degree of electrical shock to the desired threshold. Additionally, controlled studies with fish provide evidence that there is a predictable relationship between the intensity of the electrical shock and the magnitude of the electrical power transferred from the water into the fish. By applying this electrical model and measuring the electrical conductivity of the water, it should be possible to predict the level of electrical power density required in the water to elicit a particular electroshock response.