Bark‐stripping by Grey squirrels (Sciurus carolinensis)

Abstract

To investigate why Grey squirrels strip bark from young trees, squirrel populations and tree quality were studied at 30 English Midland woods. In young beech and sycamore woodlands, the area of bark which Grey squirrels stripped from each tree was strongly related to the phloem width (volume per unit area) of the tree, and not to the phloem sugar content. Variation in bark‐stripping between woods was strongly related to average phloem widths in each plantation. The extent of bark‐stripping also correlated with juvenile squirrel density, but only in years with relatively little squirrel breeding. There was a tendency for damage to recur in previously damaged areas, in a pattern suggesting that squirrels had learned the habit. The results indicate that bark‐stripping can be initiated by young squirrels, perhaps through agonistic gnawing or exploratory feeding, or by older squirrels which have learned the habit, but that severe damage occurs only where the tree phloem is suitable.