FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Porcupines and Squirrels
Figure 301. Figure 301. Porcupine chew through the bark and feed on the cambium.

Although squirrels and porcupines have a variable diet during the growing season, in the winter they chew through the outer bark of branches or boles and feed on cambium. Coniferous trees are preferred. Squirrels target smaller branches and often target dwarf mistletoe infested limbs. Porcupine injury can be locally damaging because the animal tends to stay in a small area, girdling and killing the tops of many trees. Since porcupine populations tend to fluctuate, trees often form new leaders and grow to maturity.

Figure 301b. Figure 301b. Squirrels more often chew on branches and select those infested with dwarf mistletoe..