Repellants are not effective in reducing culvert problems, but may be used to protect riparian areas. Effective repellants render a plant less attractive to foraging animals. The likelihood that a particular plant will be eaten depends on its own palatability and the availability and desirability of alternative foods. Although beavers tend to avoid plants treated with predator odors, during studies beavers have damaged some of the treated trees.

Beavers readily gnawed through trees treated with deer repellants (Deer Away–Big Game Repellent Powder, Thiuram, and Ro-Pel; NWRC unpublished data). Beaver also chewed branches treated with 100 times the recommended concentration of hot sauce (capsaicin). These studies suggest that the usefulness of commonly available repellants is probably limited.

Chemical repellants did reduce damage when they were applied directly to foliage consumed by beavers. Beavers clipped substantially fewer cottonwood and willow seedlings treated with Deer Away—Big Game Repellent Powder and Plantskydd than they untreated seedlings. These products are among the most effective repellants to reduce deer browsing. These products are not registered for beaver. Future label restrictions may restrict the application of chemical repellants in riparian zones.

Textural repellants (for instance, paint with sand) may offer an alternative. During tests, cottonwood stems that were painted with a textural repellant were damaged less than stems that were not. A few treated trees were cut and others were stripped of bark, but untreated stems or stems painted with untreated paint were damaged severely during this 2-Repellantsweek trial. Eight of ten beavers completely avoided stems treated with 30-millimeter sand, and gnawing by the other two beavers was very limited. Painting cottonwood stems in this study did not adversely affect the vigor of the stems. Buds sprouted through the paint and new foliage appeared.

Another approach to reducing damage is to convince beavers that unoccupied sites are occupied. During tests, unoccupied sites treated with a mixture of beaver castoreum anal gland secretion were colonized less often than untreated sites. This study indicated that dispersing beaver probably avoid areas with odors indicating they are occupied. However, the feasibility of using such an approach in the field is largely unknown. No product on the market is effective in deterring beaver from settling unoccupied sites. Beavers did not reduce their use of treated areas during experiments with deer repellants.

Although chemical repellants may deter beavers from clipping seedlings and textural repellants may reduce gnawing, site considerations will determine whether these techniques can be used. Plants such as willow that are preferred by beavers are more difficult to protect than plants that are not preferred, such as cascara.

After certain plants have been treated, an animal's foraging choices will depend on the size of the area being protected and the percentage of plants that have been treated relative to all the plants in the beaver's territory. Beavers in sparsely occupied wetlands can expand their territory, but beavers in densely populated areas or in areas with drier climates may not have that option. Competition with other beavers may cause beavers to be less selective in their choice of foods, rendering repellants less effective.