Devices To Frighten Beavers
Animals generally avoid areas that appear threatening. In remote areas, beavers may be hard to see unless noise and movement are kept to a minimum, but beavers in urban areas may frequent lakes even when people are active along the shore. Visual displays or noises that alarm the animal will discourage its visits. Although animals are generally wary of unfamiliar sounds or sights, they become less wary with time unless the noise or vision is paired with negative reinforcement. Most devices used to frighten beavers (such as artificial lights, propane cannons, or cracker shells) rarely work for more than a few days or a week.
The possibility that wildlife will become accustomed to devices intended to frighten them can be minimized by installing or operating the devices only when they are needed the most. It is important to begin using these devices immediately after the onset of damage. Established movements and behaviors are much more difficult to disrupt than behaviors that are just forming. Devices that operate sporadically or are activated by an animal's presence are more effective than permanent or routine displays.
Visual displays combined with noisemakers generally are more effective than either technique would be if implemented alone. For example, sirens and strobe lights activated at irregular intervals are likely to be more effective than a constant visual display or loud noises emitted at fixed intervals.
Supplementing these techniques with other measures occasionally can increase their effectiveness. For example, beavers will grow accustomed to noise from a radio next to a break in a dam and will ignore it over time, but if someone occasionally jumps out from behind the dam when a beaver approaches, the radio will do a better job of frightening the beaver.
Several commercial devices can be used to frighten beavers. When these devices are combined with homemade devices, endless combinations are possible. One such device can be created by attaching a Critter Gitter (AMTEK, San Diego, CA) on each side of a 4- by 4-inch post that is 12 inches long. The Critter Gitters are attached a couple of inches from the bottom of the post and a flashing light (Enhancer Model EH/ST-1) is attached just above each Critter Gitter. A 2-inch hole bored through the core of the post allows the device to be installed over a metal T-post. The device is then secured to a flotation platform that keeps the motion detectors a few centimeters above the water level.
Trials showed that this device did deter beavers, but not for extended periods. Anecdotal evidence suggests that the device may discourage beavers from repairing dams for a few days if it is installed in a stream channel after a dam has been breached. Those few days might allow the pond to drain temporarily.
Several respondents said they had tried using a white flag attached to a post near the entrance to a culvert or a white bed sheet stretched across the stream channel at the entrance of the culvert. One respondent had success with this method. Another respondent placed a white flag at a culvert entrance after demolishing a beaver dam. The dam was rebuilt within weeks. The second time the dam was demolished, the road maintenance crew found the white flag inside the dam.
