Tree bark serves as a tree’s protective outer layer, shielding its delicate inner tissues from environmental stressors and physical harm. Despite its tough exterior, various animals consume tree bark, often for survival or specific nutrients. This consumption can be a natural part of an ecosystem or a sign of potential issues for the tree’s health.
Common Bark-Eating Animals
Many animals, both mammals and insects, consume tree bark, each leaving distinct marks. Deer, for instance, damage trees through antler rubbing or by stripping bark for food, leaving broad, vertical teeth marks. Rabbits and voles typically gnaw on bark at the base of trees, particularly in winter when other food is scarce. Rabbit damage often presents as clean, sharp cuts, while voles leave irregular tooth marks close to the ground, sometimes girdling young trees under snow cover.
Squirrels also strip bark from trunks and branches to access sap or for nesting material. This can result in significant scarring or even “ring-barking,” where the bark is removed entirely around the circumference, potentially killing the tree. Porcupines gnaw on large, irregular patches of bark, often high on the trunk or around roots, particularly during cooler months. Beavers fell trees by gnawing at the base, leaving distinctive 45-degree angle cuts and wood chips. They use the bark for food and the wood for dam construction.
Beyond mammals, insects also target tree bark. Wood borers, which are often the larvae of beetles or moths, tunnel beneath the bark, creating exit holes and sawdust-like frass. Bark beetles, small and cylindrical, create distinct galleries under the bark. Their presence can be identified by sap or pitch oozing from holes, or reddish-brown frass in bark crevices. These insects can disrupt the tree’s vascular system, leading to decline and even death.
Why Animals Consume Bark
Animals consume bark for nutritional needs and survival. The inner layer of bark, the cambium, contains sugars, starches, and other nutrients, making it a valuable food source, particularly in colder months when other vegetation is scarce. Bark also provides hydration for some animals, as certain types contain moisture. Rodents like squirrels, rabbits, and voles gnaw on bark to wear down their continuously growing incisors. Bark consumption, therefore, often occurs out of necessity, helping animals meet their dietary requirements and maintain physical health under various environmental conditions.
Identifying Damage and Protecting Trees
Identifying bark damage requires observing visual cues and injury location. Gnaw marks from rodents typically show parallel grooves from their incisors, while deer antler rubs often leave vertical scrapes and shredded bark, sometimes exposing the underlying wood. Damage at the base of the trunk, particularly under snow, might indicate rabbit or vole activity, whereas higher damage could point to squirrels or porcupines. Sawdust-like material, sap oozing, or small, patterned holes can indicate insect infestations like borers or bark beetles. Looking for nearby animal signs like droppings or tracks can help confirm the culprit.
Protecting trees from bark damage involves preventative measures. Tree guards or wraps can shield young trees from gnawing animals and antler rubs. These barriers should extend above anticipated snow lines and be buried slightly to deter burrowing animals. Fencing can be installed around individual trees or larger areas to exclude deer and other large animals. While repellents exist, their effectiveness can vary and often requires reapplication.