Damage to Structures
Porcupines destroy siding on cabins when seeking plywood resins.
Damage to Landscapes and Crops
Clipped twigs on fresh snow, tracks, and gnawings on trees are useful means of damage identification. Trees are often deformed from partial girdling. Porcupines clip twigs and branches that fall to the ground or onto snow and often provide food for deer and other mammals. The considerable secondary effects of their feeding come from exposing the tree sapwood to attack by disease, insects, and birds. This exposure is important to many species of wildlife because diseased or hollow trees provide shelter and nest sites.
Porcupines occasionally will cause considerable losses by damaging fruits, sweet corn, alfalfa, and small grains. They chew on hand tools and other wood objects while seeking salt.
Damage to Livestock and Animals
When a porcupine quill is lodged into skin, it will work its way further into animal tissue. This is because quills have tiny barbs that help the quills keep moving in deeper. Quills may carry bacteria, causing infections. Porcupines offer a considerable threat to dogs, which never seem to learn to avoid them. Domestic stock occasionally will nuzzle a porcupine and may be fatally injured if quills are not removed promptly.