Porcupines are herbivores eating many plants, consuming the inner tree
bark, twigs, and leaves with preferences for ponderosa pine, aspen, willow
and cottonwood. However, practically all species of trees in their range
are eaten. Porcupine damage to cottonwood trees along Montana's streams
and rivers has at times been serious. In addition, porcupines produce significant
damage to fruits, vegetables, corn, alfalfa and small grains. Damage to
forest plantings, ornamental plants and orchards can be significant when
a porkie gets started on them. Extensive girdling of trees in a given area
often occurs when porcupines congregate around good winter denning sites.
Porcupines have a strong attraction to salt from sweat left on tool
handles, canoe paddles, gloves, pack straps, horse harness, etc. The resins
in plywood also have a great appeal for porcupines and they have been known
to destroy siding on cabins, sheds, containers and signs. Car tires and even
hoses have been attractive to porcupines supposedly for the mineral content.
Most porcupine damage occurs in winter when woody plants become the staple of
the diet. Porcupines damage plants by girdling, basal gnawing, or branch
clipping which often reduces tree diameter growth. However, their preference for
mistletoe is an asset.
