Toxicants
A pelleted 0.31% strychnine bait is available for control of mountain beavers. Recent field tests in Washington and Oregon, however, showed marginal efficacy in late winter. Pelleted bait is placed by hand inside main burrows, using about five baits each in 10 burrow openings in each system. The registered label allows 1/2 to 1 1/2 pounds of bait per acre (0.6 to 1.7 kg/ha). The bait formulation contains waterproofing binders that tolerate wet burrow conditions.
Regulations related to toxicants change regularly. Be sure to obtain the latest information to maintain legal and safe toxicant application. Toxicants pose risks to nontargets, so be sure of all legalities before using any control method no matter where you reside.
Experimental zinc phosphide-treated apple bait was poorly accepted by mountain beavers and was potentially hazardous to bait handlers. The treated bait was readily eaten by black-tailed deer (Odocoileus hemionus columbianus) and could present a hazard.
Baiting is severely restricted in areas frequented by endangered species such as northern spotted owls (Strix occidentalis caurina) and bald eagles (Haliaeetus leucocephalus).
Fumigants
Fumigants are generally ineffective because of the open, well-ventilated structure of the mountain beaver burrow systems. Aluminum phosphide that was activated when mountain beavers pulled pellets attached to vegetation into the nest area was only partially effective. The use of carbon monoxide gas cartridges and carbon monoxide gas have been unsuccessful in controlling mountain beavers. No fumigants are registered for mountain beaver control. The use of smoke bombs or similar material is effective in locating the numerous openings in a mountain beaver burrow system.
Resources: (online)
Mountain Beavers
