Bark stripping is a common issue involving the removal of a tree’s protective outer layer, which can expose underlying tissues and potentially harm its health. Multiple animal species contribute to this damage, each with distinct behaviors and motivations. Understanding which creatures are responsible helps assess the impact on trees and consider protective measures.
Animals That Strip Bark
Many animals strip bark from trees, including rodents and larger mammals. Rodents like fox and eastern gray squirrels commonly strip bark from trunks and branches, often targeting younger trees or horizontal branches. Voles, small mouse-like rodents, chew bark low on the trunk, especially under snow cover. Porcupines strip bark higher in trees, focusing on trunks and branches. Beavers, primarily aquatic, can strip bark from trees up to their standing height, often less than six feet.
Larger animals also cause bark damage. Deer, particularly bucks, rub their antlers, scraping and shredding bark from trunks and branches, often impacting smaller saplings. Black bears strip bark to access inner tree layers. This behavior is observed in various tree species and can occur from the base of the tree up to several feet high. Rabbits commonly girdle the lower portion of young, smooth-barked tree trunks.
Reasons for Bark Stripping
Animals strip bark for behavioral and nutritional reasons. A primary motivation is seeking food, particularly the nutritious inner bark (cambium or phloem). This inner layer contains sugars and nutrients, serving as a food source, especially during winter months when other vegetation is scarce. Bears, for instance, feed on sugary sapwood beneath the bark, especially in spring.
For rodents like squirrels, porcupines, and voles, gnawing on bark helps wear down their continuously growing incisor teeth. This gnawing also provides minerals, such as calcium, important for bone growth. Deer rub their antlers on trees for territorial marking and to remove velvet, especially during the fall breeding season. Some animals, like certain birds, may also strip bark for nesting material.
Clues to Identify the Animal
Identifying the animal responsible for bark stripping involves examining the damage characteristics and surrounding evidence. The height of the damage provides a significant clue: rabbits and voles typically cause damage low to the ground, often beneath the snowline. Deer antler rubs usually occur between one and six feet high, depending on the deer’s size. Bear damage can range from the base of the trunk up to several feet, sometimes as high as 10 to 16 feet if they climb. Porcupine damage is frequently found high in the tree canopy, but can also extend down the trunk.
The type of marks left on the tree also aids identification. Rodents, including squirrels, voles, and porcupines, leave distinct gnaw marks from their incisors. Porcupine gnaw marks are typically wider (around 5mm), while squirrel marks are smaller (about 1/16-inch wide). Deer antler rubs create vertical scrapes and shredded bark. Bears leave vertical tooth and claw marks on the exposed wood after stripping bark. Other evidence, such as scat, tracks, or hair near the damaged tree, can further pinpoint the culprit. The time of year the damage occurs can also be indicative, as some animals, like deer, are more active in bark stripping during specific seasons, such as fall for antler rubbing or winter for feeding when food is scarce.