Damage to Structures
Floods and falling trees pose severe risks to structures. Low-grade streams (less than 3% slope) with culverts or constricted areas are at highest risk for dam-building and flooding. Highways may flood because of ponds created by beavers, dams of may be destroyed by burrowing in banks, and train derailments may be caused by continued flooding of train tracks and trestles. Residential developments have been threatened by flooding, and thousands of acres of cropland and commercial forests have been flooded by beavers. Ditches, drain pipes, and culverts can get plugged so that they must be cleared and replaced. Bridges have been destroyed due to dam-building activity of beavers.
Damage to Livestock and Pets
Beavers generally are not a threat to livestock or pets. Beavers in urban areas may become habituated to humans and may be aggressive if approached.
Damage to Landscapes
Beavers damage gardens and landscapes through flooding and removal of plants. Valuable ornamental trees may be at risk near ponds or streams inhabited by beavers.
Beaver ponds can provide short-term benefits to trout and other fish, but long-term negative impacts to streams are a concern. High-class trout streams are threatened by beavers due to increased sedimentation, water temperature, acidity, and decreased dissolved oxygen.
Health and Safety Concerns
Beavers infected with rabies, which is very uncommon, may attack people. Beavers are hosts to several ectoparasites and internal parasites, including nematodes, trematodes, and coccidia. Beavers contaminate water with Giardia lamblia, a pathogenic intestinal parasite that causes intestinal problems in humans. Trappers should avoid splashing water in their face, and carefully wash their hands before eating or smoking. Anyone that develops severe abdominal cramps or persistent diarrhea working with beavers should consult medical personnel. Tularemia has been reported in beavers from Canada and the northern US. Trappers should wear rubber gloves when skinning or eviscerating beaver carcasses.
Floods undermine roads and interfere with septic systems. Bank dens cause the collapse of banks along farm and shoreline properties. Falling trees pose threats to structures, power lines, and people.
Beaver trappers should use caution when working in and around water. Drowning and hypothermia are serious threats whenever water work is necessary. Use extreme caution, particularly when walking on ice.